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Carvia-Hermoso C, Cuéllar V, Bernabéu-Roda LM, van Dillewijn P, Soto MJ. Sinorhizobium meliloti GR4 Produces Chromosomal- and pSymA-Encoded Type IVc Pili That Influence the Interaction with Alfalfa Plants. PLANTS (BASEL, SWITZERLAND) 2024; 13:628. [PMID: 38475474 DOI: 10.3390/plants13050628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 02/09/2024] [Accepted: 02/23/2024] [Indexed: 03/14/2024]
Abstract
Type IVc Pili (T4cP), also known as Tad or Flp pili, are long thin microbial filaments that are made up of small-sized pilins. These appendages serve different functions in bacteria, including attachment, biofilm formation, surface sensing, motility, and host colonization. Despite their relevant role in diverse microbial lifestyles, knowledge about T4cP in bacteria that establish symbiosis with legumes, collectively referred to as rhizobia, is still limited. Sinorhizobium meliloti contains two clusters of T4cP-related genes: flp-1 and flp-2, which are located on the chromosome and the pSymA megaplasmid, respectively. Bundle-forming pili associated with flp-1 are involved in the competitive nodulation of alfalfa plants, but the role of flp-2 remains elusive. In this work, we have performed a comprehensive bioinformatic analysis of T4cP genes in the highly competitive S. meliloti GR4 strain and investigated the role of its flp clusters in pilus biogenesis, motility, and in the interaction with alfalfa. Single and double flp-cluster mutants were constructed on the wild-type genetic background as well as in a flagellaless derivative strain. Our data demonstrate that both chromosomal and pSymA flp clusters are functional in pili biogenesis and contribute to surface translocation and nodule formation efficiency in GR4. In this strain, the presence of flp-1 in the absence of flp-2 reduces the competitiveness for nodule occupation.
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Affiliation(s)
- Cristina Carvia-Hermoso
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain
| | - Virginia Cuéllar
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain
| | - Lydia M Bernabéu-Roda
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain
| | - Pieter van Dillewijn
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain
| | - María J Soto
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain
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García-Tomsig NI, Guedes-García SK, Jiménez-Zurdo JI. A Workflow for the Functional Characterization of Noncoding RNAs in Legume Symbiotic Bacteria. Methods Mol Biol 2024; 2751:179-203. [PMID: 38265717 DOI: 10.1007/978-1-0716-3617-6_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2024]
Abstract
Computational comparative genomics and, later, high-throughput transcriptome profiling (RNAseq) have uncovered a plethora of small noncoding RNA species (sRNAs) with potential regulatory roles in bacteria. A large fraction of sRNAs are differentially regulated in response to different biotic and abiotic stimuli and have the ability to fine-tune posttranscriptional reprogramming of gene expression through protein-assisted antisense interactions with trans-encoded target mRNAs. However, this level of gene regulation is still understudied in most non-model bacteria. Here, we compile experimental methods to detect expression, determine 5'/3'-ends, assess transcriptional regulation, generate mutants, and validate candidate target mRNAs of trans-acting sRNAs (trans-sRNAs) identified in the nitrogen-fixing α-rhizobium Sinorhizobium meliloti. The workflow, molecular tools, and methods are suited to investigate the function of newly identified base-pairing trans-sRNAs in phylogenetically related α-rhizobia.
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Affiliation(s)
- Natalia I García-Tomsig
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - Sabina K Guedes-García
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - José I Jiménez-Zurdo
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain.
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García-Tomsig NI, García-Rodriguez FM, Guedes-García SK, Millán V, Becker A, Robledo M, Jiménez-Zurdo JI. A double-negative feedback loop between NtrBC and a small RNA rewires nitrogen metabolism in legume symbionts. mBio 2023; 14:e0200323. [PMID: 37850753 PMCID: PMC10746234 DOI: 10.1128/mbio.02003-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 09/05/2023] [Indexed: 10/19/2023] Open
Abstract
The nitrogen (N) status transduced via the NtrBC two-component system is a major signaling cue in the root nodule endosymbiosis of diazotrophic rhizobia with legumes. NtrBC is upregulated in the N-limiting rhizosphere environment at the onset of nodulation but silenced in nodules to favor the assimilation of the fixed N into plant biomass. We reported that the trans-acting sRNA NfeR1 (Nodule Formation Efficiency RNA) broadly influences the symbiotic performance of the α-rhizobium Sinorhizobium meliloti. Here, we show that NfeR1 is indeed an N-responsive sRNA that fine-tunes NtrBC output during the symbiotic transition. Biochemical and genetic approaches unveiled that NtrC and the LysR-type symbiotic regulator LsrB bind at distinct nearby sites in the NfeR1 promoter, acting antagonistically as repressor and activator of transcription, respectively. This complex transcriptional control specifies peak NfeR1 steady-state levels in N-starved and endosymbiotic bacteria. Furthermore, NfeR1 base pairs the translation initiation region of the histidine kinase coding mRNA ntrB, causing a decrease in both NtrB and NtrC abundance as assessed by double-plasmid genetic assays. In the context of endogenous regulation, NfeR1-mediated ntrBC silencing most likely amends the effective strength of the known operon autorepression exerted by NtrC. Accordingly, a lack of NfeR1 shifts the wild-type NtrBC output, restraining the fitness of free-living rhizobia under N stress and plant growth upon nodulation. The mixed NtrBC-NfeR1 double-negative feedback loop is thus an unprecedented adaptive network motif that helps α-rhizobia adjust N metabolism to the demands of an efficient symbiosis with legume plants. IMPORTANCE Root nodule endosymbioses between diazotrophic rhizobia and legumes provide the largest input of combined N to the biosphere, thus representing an alternative to harmful chemical fertilizers for sustainable crop production. Rhizobia have evolved intricate strategies to coordinate N assimilation for their own benefit with N2 fixation to sustain plant growth. The rhizobial N status is transduced by the NtrBC two-component system, the seemingly ubiquitous form of N signal transduction in Proteobacteria. Here, we show that the regulatory sRNA NfeR1 (nodule formation efficiency RNA) of the alfalfa symbiont Sinorhizobium meliloti is transcribed from a complex promoter repressed by NtrC in a N-dependent manner and feedback silences ntrBC by complementary base-pairing. These findings unveil a more prominent role of NtrC as a transcriptional repressor than hitherto anticipated and a novel RNA-based mechanism for NtrBC regulation. The NtrBC-NfeR1 double-negative feedback loop accurately rewires symbiotic S. meliloti N metabolism and is likely conserved in α-rhizobia.
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Affiliation(s)
- Natalia I. García-Tomsig
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - Fernando M. García-Rodriguez
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - Sabina K. Guedes-García
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - Vicenta Millán
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - Anke Becker
- Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, Marburg, Germany
| | - Marta Robledo
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - José I. Jiménez-Zurdo
- Structure, Dynamics and Function of Rhizobacterial Genomes (RhizoRNA Lab), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
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Zehentner B, Scherer S, Neuhaus K. Non-canonical transcriptional start sites in E. coli O157:H7 EDL933 are regulated and appear in surprisingly high numbers. BMC Microbiol 2023; 23:243. [PMID: 37653502 PMCID: PMC10469882 DOI: 10.1186/s12866-023-02988-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 08/21/2023] [Indexed: 09/02/2023] Open
Abstract
Analysis of genome wide transcription start sites (TSSs) revealed an unexpected complexity since not only canonical TSS of annotated genes are recognized by RNA polymerase. Non-canonical TSS were detected antisense to, or within, annotated genes as well new intergenic (orphan) TSS, not associated with known genes. Previously, it was hypothesized that many such signals represent noise or pervasive transcription, not associated with a biological function. Here, a modified Cappable-seq protocol allows determining the primary transcriptome of the enterohemorrhagic E. coli O157:H7 EDL933 (EHEC). We used four different growth media, both in exponential and stationary growth phase, replicated each thrice. This yielded 19,975 EHEC canonical and non-canonical TSS, which reproducibly occurring in three biological replicates. This questions the hypothesis of experimental noise or pervasive transcription. Accordingly, conserved promoter motifs were found upstream indicating proper TSSs. More than 50% of 5,567 canonical and between 32% and 47% of 10,355 non-canonical TSS were differentially expressed in different media and growth phases, providing evidence for a potential biological function also of non-canonical TSS. Thus, reproducible and environmentally regulated expression suggests that a substantial number of the non-canonical TSSs may be of unknown function rather than being the result of noise or pervasive transcription.
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Affiliation(s)
- Barbara Zehentner
- Chair for Microbial Ecology, TUM School of Life Sciences, Department of Molecular Life Sciences, Technical University of Munich, Freising, Germany
| | - Siegfried Scherer
- Chair for Microbial Ecology, TUM School of Life Sciences, Department of Molecular Life Sciences, Technical University of Munich, Freising, Germany
- ZIEL - Institute for Food & Health, Technical University of Munich, Freising, Germany
| | - Klaus Neuhaus
- ZIEL - Institute for Food & Health, Technical University of Munich, Freising, Germany.
- Core Facility Microbiome, ZIEL - Institute for Food & Health, Technical University of Munich, Freising, Germany.
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Waldburger L, Thompson MG, Weisberg AJ, Lee N, Chang JH, Keasling JD, Shih PM. Transcriptome architecture of the three main lineages of agrobacteria. mSystems 2023; 8:e0033323. [PMID: 37477440 PMCID: PMC10469942 DOI: 10.1128/msystems.00333-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 06/15/2023] [Indexed: 07/22/2023] Open
Abstract
Agrobacteria are a diverse, polyphyletic group of prokaryotes with multipartite genomes capable of transferring DNA into the genomes of host plants, making them an essential tool in plant biotechnology. Despite their utility in plant transformation, genome-wide transcriptional regulation is not well understood across the three main lineages of agrobacteria. Transcription start sites (TSSs) are a necessary component of gene expression and regulation. In this study, we used differential RNA-seq and a TSS identification algorithm optimized on manually annotated TSS, then validated with existing TSS to identify thousands of TSS with nucleotide resolution for representatives of each lineage. We extend upon the 356 TSSs previously reported in Agrobacterium fabrum C58 by identifying 1,916 TSSs. In addition, we completed genomes and phenotyping of Rhizobium rhizogenes C16/80 and Allorhizobium vitis T60/94, identifying 2,650 and 2,432 TSSs, respectively. Parameter optimization was crucial for an accurate, high-resolution view of genome and transcriptional dynamics, highlighting the importance of algorithm optimization in genome-wide TSS identification and genomics at large. The optimized algorithm reduced the number of TSSs identified internal and antisense to the coding sequence on average by 90.5% and 91.9%, respectively. Comparison of TSS conservation between orthologs of the three lineages revealed differences in cell cycle regulation of ctrA as well as divergence of transcriptional regulation of chemotaxis-related genes when grown in conditions that simulate the plant environment. These results provide a framework to elucidate the mechanistic basis and evolution of pathology across the three main lineages of agrobacteria. IMPORTANCE Transcription start sites (TSSs) are fundamental for understanding gene expression and regulation. Agrobacteria, a group of prokaryotes with the ability to transfer DNA into the genomes of host plants, are widely used in plant biotechnology. However, the genome-wide transcriptional regulation of agrobacteria is not well understood, especially in less-studied lineages. Differential RNA-seq and an optimized algorithm enabled identification of thousands of TSSs with nucleotide resolution for representatives of each lineage. The results of this study provide a framework for elucidating the mechanistic basis and evolution of pathology across the three main lineages of agrobacteria. The optimized algorithm also highlights the importance of parameter optimization in genome-wide TSS identification and genomics at large.
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Affiliation(s)
- Lucas Waldburger
- Department of Bioengineering, University of California, Berkeley, California, USA
- Joint BioEnergy Institute, Emeryville, California, USA
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Mitchell G. Thompson
- Joint BioEnergy Institute, Emeryville, California, USA
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Alexandra J. Weisberg
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA
| | - Namil Lee
- Joint BioEnergy Institute, Emeryville, California, USA
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California, USA
| | - Jeff H. Chang
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA
| | - Jay D. Keasling
- Joint BioEnergy Institute, Emeryville, California, USA
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California, USA
- Institute for Quantitative Biosciences, University of California, Berkeley, California, USA
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kongens Lyngby, Denmark
- Center for Synthetic Biochemistry, Institute for Synthetic Biology, Shenzhen Institutes for Advanced Technologies, Shenzhen, China
| | - Patrick M. Shih
- Joint BioEnergy Institute, Emeryville, California, USA
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
- Department of Plant and Microbial Biology, University of California, Berkeley, California, USA
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6
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Adaikpoh BI, Romanowski SB, Eustáquio AS. Understanding Autologous Spliceostatin Transcriptional Regulation to Derive Parts for Heterologous Expression in a Burkholderia Bacterial Host. ACS Synth Biol 2023; 12:1952-1960. [PMID: 37338297 PMCID: PMC10527236 DOI: 10.1021/acssynbio.3c00228] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
Burkholderia β-Proteobacteria are emerging sources of natural products. We are interested in developing Burkholderia sp. FERM BP-3421 into a synthetic biology chassis to facilitate natural product discovery. FERM BP-3421 produces autologous spliceostatins on gram per liter scale. We reasoned that transcription factors and promoters that regulate spliceostatin biosynthesis would provide valuable parts for heterologous expression. Herein we demonstrate that fr9A encodes a pathway-specific transcriptional activator of spliceostatin biosynthesis. In-frame deletion of fr9A abolished spliceostatin production, which was restored by genetic complementation. Using transcriptomics and green fluorescent protein (GFP) reporter assays, we identified four fr9 promoters, three of which are activated by LuxR-type regulator Fr9A. We then constructed an Fr9A-regulated promoter system that was compared to benchmarks and effectively applied for GFP and capistruin lasso peptide expression in an optimized host background. Our findings enrich the genetic toolbox for optimizing heterologous expression and promoting the discovery and development of natural products from Burkholderia bacteria.
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Affiliation(s)
- Barbara I. Adaikpoh
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois, 60607, United States
- Center for Biomolecular Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois 60607, United States
| | - Sean B. Romanowski
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois, 60607, United States
- Center for Biomolecular Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois 60607, United States
| | - Alessandra S. Eustáquio
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois, 60607, United States
- Center for Biomolecular Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois 60607, United States
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Brito-Santana P, Duque-Pedraza JJ, Bernabéu-Roda LM, Carvia-Hermoso C, Cuéllar V, Fuentes-Romero F, Acosta-Jurado S, Vinardell JM, Soto MJ. Sinorhizobium meliloti DnaJ Is Required for Surface Motility, Stress Tolerance, and for Efficient Nodulation and Symbiotic Nitrogen Fixation. Int J Mol Sci 2023; 24:ijms24065848. [PMID: 36982921 PMCID: PMC10055731 DOI: 10.3390/ijms24065848] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 03/14/2023] [Accepted: 03/17/2023] [Indexed: 03/30/2023] Open
Abstract
Bacterial surface motility is a complex microbial trait that contributes to host colonization. However, the knowledge about regulatory mechanisms that control surface translocation in rhizobia and their role in the establishment of symbiosis with legumes is still limited. Recently, 2-tridecanone (2-TDC) was identified as an infochemical in bacteria that hampers microbial colonization of plants. In the alfalfa symbiont Sinorhizobium meliloti, 2-TDC promotes a mode of surface motility that is mostly independent of flagella. To understand the mechanism of action of 2-TDC in S. meliloti and unveil genes putatively involved in plant colonization, Tn5 transposants derived from a flagellaless strain that were impaired in 2-TDC-induced surface spreading were isolated and genetically characterized. In one of the mutants, the gene coding for the chaperone DnaJ was inactivated. Characterization of this transposant and newly obtained flagella-minus and flagella-plus dnaJ deletion mutants revealed that DnaJ is essential for surface translocation, while it plays a minor role in swimming motility. DnaJ loss-of-function reduces salt and oxidative stress tolerance in S. meliloti and hinders the establishment of efficient symbiosis by affecting nodule formation efficiency, cellular infection, and nitrogen fixation. Intriguingly, the lack of DnaJ causes more severe defects in a flagellaless background. This work highlights the role of DnaJ in the free-living and symbiotic lifestyles of S. meliloti.
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Affiliation(s)
- Paula Brito-Santana
- Estación Experimental del Zaidín, CSIC, Department of Biotechnology and Environmental Protection, 18008 Granada, Spain
| | - Julián J Duque-Pedraza
- Estación Experimental del Zaidín, CSIC, Department of Biotechnology and Environmental Protection, 18008 Granada, Spain
| | - Lydia M Bernabéu-Roda
- Estación Experimental del Zaidín, CSIC, Department of Biotechnology and Environmental Protection, 18008 Granada, Spain
| | - Cristina Carvia-Hermoso
- Estación Experimental del Zaidín, CSIC, Department of Biotechnology and Environmental Protection, 18008 Granada, Spain
| | - Virginia Cuéllar
- Estación Experimental del Zaidín, CSIC, Department of Biotechnology and Environmental Protection, 18008 Granada, Spain
| | - Francisco Fuentes-Romero
- Facultad de Biología, Departamento de Microbiología, Universidad de Sevilla, 41012 Sevilla, Spain
| | - Sebastián Acosta-Jurado
- Centro Andaluz de Biología del Desarrollo, CSIC, Junta de Andalucía, Departamento de Biología Molecular e Ingeniería Bioquímica, Universidad Pablo de Olavide, 41013 Seville, Spain
| | - José-María Vinardell
- Facultad de Biología, Departamento de Microbiología, Universidad de Sevilla, 41012 Sevilla, Spain
| | - María J Soto
- Estación Experimental del Zaidín, CSIC, Department of Biotechnology and Environmental Protection, 18008 Granada, Spain
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Bensig EO, Valadez-Cano C, Kuang Z, Freire IR, Reyes-Prieto A, MacLellan SR. The two-component regulatory system CenK–CenR regulates expression of a previously uncharacterized protein required for salinity and oxidative stress tolerance in Sinorhizobium meliloti. Front Microbiol 2022; 13:1020932. [PMID: 36246272 PMCID: PMC9561847 DOI: 10.3389/fmicb.2022.1020932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 09/16/2022] [Indexed: 11/24/2022] Open
Abstract
Genes of unknown function constitute a considerable fraction of most bacterial genomes. In a Tn5-based search for stress response genes in the nitrogen-fixing facultative endosymbiont Sinorhizobium (Ensifer) meliloti, we identified a previously uncharacterized gene required for growth on solid media with increased NaCl concentrations. The encoded protein carries a predicted thioredoxin fold and deletion of the gene also results in increased sensitivity to hydrogen peroxide and cumene hydroperoxide. We have designated the gene srlA (stress resistance locus A) based on these phenotypes. A deletion mutant yields phenotypic revertants on high salt medium and genome sequencing revealed that all revertants carry a mutation in genes homologous to either cenK or cenR. srlA promoter activity is abolished in these revertant host backgrounds and in a strain carrying a deletion in cenK. We also observed that the srlA promoter is autoregulated, displaying low activity in a wildtype (wt) host background and high activity in the srl deletion mutant background. The srlA promoter includes a conserved inverted repeat directly upstream of the predicted −35 subsequence. A mutational analysis demonstrated that the site is required for the high promoter activity in the srlA deletion background. Electromobility shift assays using purified wildtype CenR response regulator and a D55E phosphomimetic derivative suggest this protein acts as a likely Class II activator by binding promoter DNA. These results document the first identified CenK–CenR regulon member in S. meliloti and demonstrate this two-component regulatory system and gene srlA influences cellular growth and persistence under certain stress-inducing conditions.
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Affiliation(s)
- Eukene O. Bensig
- Department of Biology and Environmental Science, University of the Philippines Cebu, Cebu City, Philippines
| | | | - ZiYu Kuang
- Department of Biology, University of New Brunswick, Fredericton, NB, Canada
| | - Isabela R. Freire
- Department of Biology, University of New Brunswick, Fredericton, NB, Canada
| | | | - Shawn R. MacLellan
- Department of Biology, University of New Brunswick, Fredericton, NB, Canada
- *Correspondence: Shawn R. MacLellan,
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Genome-Wide Transcription Start Sites Mapping in Methylorubrum Grown with Dichloromethane and Methanol. Microorganisms 2022; 10:microorganisms10071301. [PMID: 35889020 PMCID: PMC9320726 DOI: 10.3390/microorganisms10071301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 06/17/2022] [Accepted: 06/22/2022] [Indexed: 02/04/2023] Open
Abstract
Dichloromethane (DCM, methylene chloride) is a toxic halogenated volatile organic compound massively used for industrial applications, and consequently often detected in the environment as a major pollutant. DCM biotransformation suggests a sustainable decontamination strategy of polluted sites. Among methylotrophic bacteria able to use DCM as a sole source of carbon and energy for growth, Methylorubrum extorquens DM4 is a longstanding reference strain. Here, the primary 5′-ends of transcripts were obtained using a differential RNA-seq (dRNA-seq) approach to provide the first transcription start site (TSS) genome-wide landscape of a methylotroph using DCM or methanol. In total, 7231 putative TSSs were annotated and classified with respect to their localization to coding sequences (CDSs). TSSs on the opposite strand of CDS (antisense TSS) account for 31% of all identified TSSs. One-third of the detected TSSs were located at a distance to the start codon inferior to 250 nt (average of 84 nt) with 7% of leaderless mRNA. Taken together, the global TSS map for bacterial growth using DCM or methanol will facilitate future studies in which transcriptional regulation is crucial, and efficient DCM removal at polluted sites is limited by regulatory processes.
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Transcription Regulation of Cell Cycle Regulatory Genes Mediated by NtrX to Affect Sinorhizobium meliloti Cell Division. Genes (Basel) 2022; 13:genes13061066. [PMID: 35741828 PMCID: PMC9223101 DOI: 10.3390/genes13061066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 04/25/2022] [Accepted: 04/26/2022] [Indexed: 12/10/2022] Open
Abstract
The cell division of the alfalfa symbiont, Sinorhizobium meliloti, is dictated by a cell cycle regulatory pathway containing the key transcription factors CtrA, GcrA, and DnaA. In this study, we found that NtrX, one of the regulators of nitrogen metabolism, can directly regulate the expression of ctrA, gcrA, and dnaA from the cell cycle pathway. Three sets of S. meliloti ntrX mutants showed similar cell division defects, such as slow growth, abnormal morphology of some cells, and delayed DNA synthesis. Transcription of ctrA and gcrA was upregulated, whereas the transcription of dnaA and ftsZ1 was downregulated in the insertion mutant and the strain of Sm1021 expressing ntrXD53E. Correspondingly, the inducible transcription of ntrX activates the expression of dnaA and ftsZ1, but represses ctrA and gcrA in the depletion strain. The expression levels of CtrA and GcrA were confirmed by Western blotting. The transcription regulation of these genes requires phosphorylation of the conserved 53rd aspartate in the NtrX protein that binds directly to the promoter regions of ctrA, gcrA, dnaA, and ftsZ1 by recognizing the characteristic sequence CAAN2-5TTG. Our findings suggest that NtrX affects S. meliloti cell division by regulating the transcription of the key cell cycle regulatory genes.
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11
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The zinc-finger bearing xenogeneic silencer MucR in α-proteobacteria balances adaptation and regulatory integrity. THE ISME JOURNAL 2022; 16:738-749. [PMID: 34584215 PMCID: PMC8857273 DOI: 10.1038/s41396-021-01118-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Revised: 09/07/2021] [Accepted: 09/10/2021] [Indexed: 02/08/2023]
Abstract
Foreign AT-rich genes drive bacterial adaptation to new niches while challenging the existing regulation network. Here we report that MucR, a conserved regulator in α-proteobacteria, balances adaptation and regulatory integrity in Sinorhizobium fredii, a facultative microsymbiont of legumes. Chromatin immunoprecipitation sequencing coupled with transcriptomic data reveal that average transcription levels of both target and non-target genes, under free-living and symbiotic conditions, increase with their conservation levels. Targets involved in environmental adaptation and symbiosis belong to genus or species core and can be repressed or activated by MucR in a condition-dependent manner, implying regulatory integrations. However, most targets are enriched in strain-specific genes of lower expression levels and higher AT%. Within each conservation levels, targets have higher AT% and average transcription levels than non-target genes and can be further up-regulated in the mucR mutant. This is consistent with higher AT% of spacers between -35 and -10 elements of promoters for target genes, which enhances transcription. The MucR recruitment level linearly increases with AT% and the number of a flexible pattern (with periodic repeats of Ts) of target sequences. Collectively, MucR directly represses AT-rich foreign genes with predisposed high transcription potential while progressive erosions of its target sites facilitate regulatory integrations of foreign genes.
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Identification of a Novel Pyruvyltransferase Using 13C Solid-State Nuclear Magnetic Resonance To Analyze Rhizobial Exopolysaccharides. J Bacteriol 2021; 203:e0040321. [PMID: 34606371 DOI: 10.1128/jb.00403-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The alphaproteobacterium Sinorhizobium meliloti secretes two acidic exopolysaccharides (EPSs), succinoglycan (EPSI) and galactoglucan (EPSII), which differentially enable it to adapt to a changing environment. Succinoglycan is essential for invasion of plant hosts and, thus, for the formation of nitrogen-fixing root nodules. Galactoglucan is critical for population-based behaviors such as swarming and biofilm formation and can facilitate invasion in the absence of succinoglycan on some host plants. The biosynthesis of galactoglucan is not as completely understood as that of succinoglycan. We devised a pipeline to identify putative pyruvyltransferase and acetyltransferase genes, construct genomic deletions in strains engineered to produce either succinoglycan or galactoglucan, and analyze EPS from mutant bacterial strains. EPS samples were examined by 13C cross-polarization magic-angle spinning (CPMAS) solid-state nuclear magnetic resonance (NMR). CPMAS NMR is uniquely suited to defining chemical composition in complex samples and enables the detection and quantification of distinct EPS functional groups. Galactoglucan was isolated from mutant strains with deletions in five candidate acyl/acetyltransferase genes (exoZ, exoH, SMb20810, SMb21188, and SMa1016) and a putative pyruvyltransferase (wgaE or SMb21322). Most samples were similar in composition to wild-type EPSII by CPMAS NMR analysis. However, galactoglucan produced from a strain lacking wgaE exhibited a significant reduction in pyruvylation. Pyruvylation was restored through the ectopic expression of plasmid-borne wgaE. Our work has thus identified WgaE as a galactoglucan pyruvyltransferase. This exemplifies how the systematic combination of genetic analyses and solid-state NMR detection is a rapid means to identify genes responsible for modification of rhizobial exopolysaccharides. IMPORTANCE Nitrogen-fixing bacteria are crucial for geochemical cycles and global nitrogen nutrition. Symbioses between legumes and rhizobial bacteria establish root nodules, where bacteria convert dinitrogen to ammonia for plant utilization. Secreted exopolysaccharides (EPSs) produced by Sinorhizobium meliloti (succinoglycan and galactoglucan) play important roles in soil and plant environments. The biosynthesis of galactoglucan is not as well characterized as that of succinoglycan. We employed solid-state nuclear magnetic resonance (NMR) to examine intact EPS from wild-type and mutant S. meliloti strains. NMR analysis of EPS isolated from a wgaE gene mutant revealed a novel pyruvyltransferase that modifies galactoglucan. Few EPS pyruvyltransferases have been characterized. Our work provides insight into the biosynthesis of an important S. meliloti EPS and expands the knowledge of enzymes that modify polysaccharides.
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Evguenieva-Hackenberg E. Riboregulation in bacteria: From general principles to novel mechanisms of the trp attenuator and its sRNA and peptide products. WILEY INTERDISCIPLINARY REVIEWS-RNA 2021; 13:e1696. [PMID: 34651439 DOI: 10.1002/wrna.1696] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/25/2021] [Accepted: 09/10/2021] [Indexed: 12/26/2022]
Abstract
Gene expression strategies ensuring bacterial survival and competitiveness rely on cis- and trans-acting RNA-regulators (riboregulators). Among the cis-acting riboregulators are transcriptional and translational attenuators, and antisense RNAs (asRNAs). The trans-acting riboregulators are small RNAs (sRNAs) that bind proteins or base pairs with other RNAs. This classification is artificial since some regulatory RNAs act both in cis and in trans, or function in addition as small mRNAs. A prominent example is the archetypical, ribosome-dependent attenuator of tryptophan (Trp) biosynthesis genes. It responds by transcription attenuation to two signals, Trp availability and inhibition of translation, and gives rise to two trans-acting products, the attenuator sRNA rnTrpL and the leader peptide peTrpL. In Escherichia coli, rnTrpL links Trp availability to initiation of chromosome replication and in Sinorhizobium meliloti, it coordinates regulation of split tryptophan biosynthesis operons. Furthermore, in S. meliloti, peTrpL is involved in mRNA destabilization in response to antibiotic exposure. It forms two types of asRNA-containing, antibiotic-dependent ribonucleoprotein complexes (ARNPs), one of them changing the target specificity of rnTrpL. The posttranscriptional role of peTrpL indicates two emerging paradigms: (1) sRNA reprograming by small molecules and (2) direct involvement of antibiotics in regulatory RNPs. They broaden our view on RNA-based mechanisms and may inspire new approaches for studying, detecting, and using antibacterial compounds. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Small Molecule-RNA Interactions RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs.
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Post-Transcriptional Control in the Regulation of Polyhydroxyalkanoates Synthesis. Life (Basel) 2021; 11:life11080853. [PMID: 34440597 PMCID: PMC8401924 DOI: 10.3390/life11080853] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 08/15/2021] [Accepted: 08/18/2021] [Indexed: 01/08/2023] Open
Abstract
The large production of non-degradable petrol-based plastics has become a major global issue due to its environmental pollution. Biopolymers produced by microorganisms such as polyhydroxyalkanoates (PHAs) are gaining potential as a sustainable alternative, but the high cost associated with their industrial production has been a limiting factor. Post-transcriptional regulation is a key step to control gene expression in changing environments and has been reported to play a major role in numerous cellular processes. However, limited reports are available concerning the regulation of PHA accumulation in bacteria, and many essential regulatory factors still need to be identified. Here, we review studies where the synthesis of PHA has been reported to be regulated at the post-transcriptional level, and we analyze the RNA-mediated networks involved. Finally, we discuss the forthcoming research on riboregulation, synthetic, and metabolic engineering which could lead to improved strategies for PHAs synthesis in industrial production, thereby reducing the costs currently associated with this procedure.
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Abstract
Bioinformatic analysis showed previously that a majority of promoters in the photoheterotrophic alphaproteobacterium Rhodobacter sphaeroides lack the thymine at the last position of the -10 element (-7T), a base that is very highly conserved in promoters in bacteria other than alphaproteobacteria. The absence of -7T was correlated with low promoter activity using purified R. sphaeroides RNA polymerase (RNAP), but the transcription factor CarD compensated by activating almost all promoters lacking -7T tested in vitro, including rRNA promoters. Here, we show that a previously uncharacterized R. sphaeroides promoter, the promoter for carD itself, has high basal activity relative to other tested R. sphaeroides promoters despite lacking -7T, and its activity is inhibited rather than activated by CarD. This high basal activity is dependent on a consensus-extended -10 element (TGn) and specific features in the spacer immediately upstream of the extended -10 element. CarD negatively autoregulates its own promoter by producing abortive transcripts, limiting promoter escape, and reducing full-length mRNA synthesis. This mechanism of negative regulation differs from that employed by classical repressors, in which the transcription factor competes with RNA polymerase for binding to the promoter, and with the mechanism of negative regulation used by transcription factors like DksA/ppGpp and TraR that allosterically inhibit the rate of open complex formation. IMPORTANCE R. sphaeroides CarD activates many promoters by binding directly to RNAP and DNA just upstream of the -10 element. In contrast, we show here that CarD inhibits its own promoter using the same interactions with RNAP and DNA used for activation. Inhibition results from increasing abortive transcript formation, thereby decreasing promoter escape and full-length RNA synthesis. We propose that the combined interactions of RNAP with CarD, with the extended -10 element and with features in the adjacent -10/-35 spacer DNA, stabilize the promoter complex, reducing promoter clearance. These findings support previous predictions that the effects of CarD on transcription can be either positive or negative, depending on the kinetic properties of the specific promoter.
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Robledo M, García-Tomsig NI, Matia-González AM, García-Rodríguez FM, Jiménez-Zurdo JI. Synthetase of the methyl donor S-adenosylmethionine from nitrogen-fixing α-rhizobia can bind functionally diverse RNA species. RNA Biol 2021; 18:1111-1123. [PMID: 33043803 PMCID: PMC8244774 DOI: 10.1080/15476286.2020.1829365] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Function of bacterial small non-coding RNAs (sRNAs) and overall RNA metabolism is largely shaped by a vast diversity of RNA-protein interactions. However, in non-model bacteria with defined non-coding transcriptomes the sRNA interactome remains almost unexplored. We used affinity chromatography to capture proteins associated in vivo with MS2-tagged trans-sRNAs that regulate nutrient uptake (AbcR2 and NfeR1) and cell cycle (EcpR1) mRNAs by antisense-based translational inhibition in the nitrogen-fixing α-rhizobia Sinorhizobium meliloti. The three proteomes were rather distinct, with that of EcpR1 particularly enriched in cell cycle-related enzymes, whilst sharing several transcription/translation-related proteins recurrently identified associated with sRNAs. Strikingly, MetK, the synthetase of the major methyl donor S-adenosylmethionine, was reliably recovered as a binding partner of the three sRNAs, which reciprocally co-immunoprecipitated with a FLAG-tagged MetK variant. Induced (over)expression of the trans-sRNAs and MetK depletion did not influence canonical riboregulatory traits, `for example, protein titration or sRNA stability, respectively. An in vitro filter assay confirmed binding of AbcR2, NfeR1 and EcpR1 to MetK and further revealed interaction of the protein with other non-coding and coding transcripts but not with the 5S rRNA. These findings uncover a broad specificity for RNA binding as an unprecedented feature of this housekeeping prokaryotic enzyme.
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MESH Headings
- Gene Expression Regulation, Bacterial
- Methionine Adenosyltransferase/genetics
- Methionine Adenosyltransferase/metabolism
- Nitrogen Fixation/physiology
- Plant Root Nodulation/physiology
- Plants/microbiology
- Protein Binding
- Protein Interaction Mapping
- RNA, Bacterial/classification
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Messenger/classification
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Small Untranslated/classification
- RNA, Small Untranslated/genetics
- RNA, Small Untranslated/metabolism
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- S-Adenosylmethionine/metabolism
- Sinorhizobium meliloti/enzymology
- Sinorhizobium meliloti/genetics
- Symbiosis/physiology
- Transcriptome
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Affiliation(s)
- Marta Robledo
- Structure, Dynamics and Function of Rhizobacterial Genomes (Grupo de Ecología Genética de la Rizosfera), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - Natalia I. García-Tomsig
- Structure, Dynamics and Function of Rhizobacterial Genomes (Grupo de Ecología Genética de la Rizosfera), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - Ana M. Matia-González
- Department of Microbial and Cellular Sciences, School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
| | - Fernando M. García-Rodríguez
- Structure, Dynamics and Function of Rhizobacterial Genomes (Grupo de Ecología Genética de la Rizosfera), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
| | - José I. Jiménez-Zurdo
- Structure, Dynamics and Function of Rhizobacterial Genomes (Grupo de Ecología Genética de la Rizosfera), Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain
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Leitner M, Bishop C, Asgari S. Transcriptional Response of Wolbachia to Dengue Virus Infection in Cells of the Mosquito Aedes aegypti. mSphere 2021; 6:e0043321. [PMID: 34190587 PMCID: PMC8265661 DOI: 10.1128/msphere.00433-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 06/07/2021] [Indexed: 11/20/2022] Open
Abstract
Aedes aegypti transmits one of the most significant mosquito-borne viruses, dengue virus (DENV). The absence of effective vaccines and clinical treatments and the emergence of insecticide resistance in A. aegypti necessitate novel vector control strategies. A new approach uses the endosymbiotic bacterium Wolbachia pipientis to reduce the spread of arboviruses. However, the Wolbachia-mediated antiviral mechanism is not well understood. To shed light on this mechanism, we investigated an unexplored aspect of Wolbachia-virus-mosquito interaction. We used RNA sequencing to examine the transcriptional response of Wolbachia to DENV infection in A. aegypti Aag2 cells transinfected with the wAlbB strain of Wolbachia. Our results suggest that genes encoding an endoribonuclease (RNase HI), a regulator of sigma 70-dependent gene transcription (6S RNA), essential cellular, transmembrane, and stress response functions and primary type I and IV secretion systems were upregulated, while a number of transport and binding proteins of Wolbachia, ribosome structure, and elongation factor-associated genes were downregulated due to DENV infection. Furthermore, bacterial retrotransposon, transposable, and phage-related elements were found among the up- and downregulated genes. We show that Wolbachia elicits a transcriptional response to virus infection and identify differentially expressed Wolbachia genes mostly at the early stages of virus infection. These findings highlight Wolbachia's ability to alter its gene expression in response to DENV infection of the host cell. IMPORTANCE Aedes aegypti is a vector of several pathogenic viruses, including dengue, Zika, chikungunya, and yellow fever viruses, which are of importance to human health. Wolbachia is an endosymbiotic bacterium currently used in transinfected mosquitoes to suppress replication and transmission of dengue viruses. However, the mechanism of Wolbachia-mediated virus inhibition is not fully understood. While several studies have shown mosquitoes' transcriptional responses to dengue virus infection, none have investigated these responses in Wolbachia, which may provide clues to the inhibition mechanism. Our results suggest changes in the expression of a number of functionally important Wolbachia genes upon dengue virus infection, including those involved in stress responses, providing insights into the endosymbiont's reaction to virus infection.
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Affiliation(s)
- Michael Leitner
- Australian Infectious Disease Research Centre, School of Biological Sciences, The University of Queensland, Brisbane, Australia
| | - Cameron Bishop
- Australian Infectious Disease Research Centre, School of Biological Sciences, The University of Queensland, Brisbane, Australia
| | - Sassan Asgari
- Australian Infectious Disease Research Centre, School of Biological Sciences, The University of Queensland, Brisbane, Australia
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Melior H, Li S, Stötzel M, Maaß S, Schütz R, Azarderakhsh S, Shevkoplias A, Barth-Weber S, Baumgardt K, Ziebuhr J, Förstner KU, Chervontseva Z, Becher D, Evguenieva-Hackenberg E. Reprograming of sRNA target specificity by the leader peptide peTrpL in response to antibiotic exposure. Nucleic Acids Res 2021; 49:2894-2915. [PMID: 33619526 PMCID: PMC7968998 DOI: 10.1093/nar/gkab093] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 01/31/2021] [Accepted: 02/19/2021] [Indexed: 11/13/2022] Open
Abstract
Trans-acting regulatory RNAs have the capacity to base pair with more mRNAs than generally detected under defined conditions, raising the possibility that sRNA target specificities vary depending on the specific metabolic or environmental conditions. In Sinorhizobium meliloti, the sRNA rnTrpL is derived from a tryptophan (Trp) transcription attenuator located upstream of the Trp biosynthesis gene trpE(G). The sRNA rnTrpL contains a small ORF, trpL, encoding the 14-aa leader peptide peTrpL. If Trp is available, efficient trpL translation causes transcription termination and liberation of rnTrpL, which subsequently acts to downregulate the trpDC operon, while peTrpL is known to have a Trp-independent role in posttranscriptional regulation of antibiotic resistance mechanisms. Here, we show that tetracycline (Tc) causes rnTrpL accumulation independently of Trp availability. In the presence of Tc, rnTrpL and peTrpL act collectively to destabilize rplUrpmA mRNA encoding ribosomal proteins L21 and L27. The three molecules, rnTrpL, peTrpL, and rplUrpmA mRNA, form an antibiotic-dependent ribonucleoprotein complex (ARNP). In vitro reconstitution of this ARNP in the presence of competing trpD and rplU transcripts revealed that peTrpL and Tc cause a shift of rnTrpL specificity towards rplU, suggesting that sRNA target prioritization may be readjusted in response to changing environmental conditions.
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Affiliation(s)
- Hendrik Melior
- Institute of Microbiology and Molecular Biology, University of Giessen, 35392 Giessen, Germany
| | - Siqi Li
- Institute of Microbiology and Molecular Biology, University of Giessen, 35392 Giessen, Germany
| | - Maximilian Stötzel
- Institute of Microbiology and Molecular Biology, University of Giessen, 35392 Giessen, Germany
| | - Sandra Maaß
- Institute of Microbiology, University of Greifswald, 17489 Greifswald, Germany
| | - Rubina Schütz
- Institute of Microbiology and Molecular Biology, University of Giessen, 35392 Giessen, Germany
| | - Saina Azarderakhsh
- Institute of Microbiology and Molecular Biology, University of Giessen, 35392 Giessen, Germany
| | - Aleksei Shevkoplias
- Faculty of Biology and Biotechnology, Higher School of Economics, 117312 Moscow, Russia.,Institute for Information Transmission Problems (the Kharkevich Institute, RAS), 127051 Moscow, Russia
| | - Susanne Barth-Weber
- Institute of Microbiology and Molecular Biology, University of Giessen, 35392 Giessen, Germany
| | - Kathrin Baumgardt
- Institute of Microbiology and Molecular Biology, University of Giessen, 35392 Giessen, Germany
| | - John Ziebuhr
- Institute of Medical Virology, University of Giessen, 35392 Giessen, Germany
| | - Konrad U Förstner
- Data Science and Services, ZB MED - Information Centre for Life Sciences, 50931 Cologne, Germany
| | - Zoe Chervontseva
- Institute for Information Transmission Problems (the Kharkevich Institute, RAS), 127051 Moscow, Russia
| | - Dörte Becher
- Institute of Microbiology, University of Greifswald, 17489 Greifswald, Germany
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Pervasive RNA Regulation of Metabolism Enhances the Root Colonization Ability of Nitrogen-Fixing Symbiotic α-Rhizobia. mBio 2021; 13:e0357621. [PMID: 35164560 PMCID: PMC8844928 DOI: 10.1128/mbio.03576-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The rhizosphere and rhizoplane are nutrient-rich but selective environments for the root microbiome. Here, we deciphered a posttranscriptional network regulated by the homologous trans-small RNAs (sRNAs) AbcR1 and AbcR2, which rewire the metabolism of the nitrogen-fixing α-rhizobium Sinorhizobium meliloti during preinfection stages of symbiosis with its legume host alfalfa. The LysR-type regulator LsrB, which transduces the cell redox state, is indispensable for AbcR1 expression in actively dividing bacteria, whereas the stress-induced transcription of AbcR2 depends on the alternative σ factor RpoH1. MS2 affinity purification coupled with RNA sequencing unveiled exceptionally large and overlapping AbcR1/2 mRNA interactomes, jointly representing ⁓6% of the S. meliloti protein-coding genes. Most mRNAs encode transport/metabolic proteins whose translation is silenced by base pairing to two distinct anti-Shine Dalgarno motifs that function independently in both sRNAs. A metabolic model-aided analysis of the targetomes predicted changes in AbcR1/2 expression driven by shifts in carbon/nitrogen sources, which were confirmed experimentally. Low AbcR1/2 levels in some defined media anticipated overexpression growth phenotypes linked to the silencing of specific mRNAs. As a proof of principle, we confirmed AbcR1/2-mediated downregulation of the l-amino acid AapQ permease. AbcR1/2 interactomes are well represented in rhizosphere-related S. meliloti transcriptomic signatures. Remarkably, a lack of AbcR1 specifically compromised the ability of S. meliloti to colonize the root rhizoplane. The AbcR1 regulon likely ranks the utilization of available substrates to optimize metabolism, thus conferring on S. meliloti an advantage for efficient rhizosphere/rhizoplane colonization. AbcR1 regulation is predicted to be conserved in related α-rhizobia, which opens unprecedented possibilities for engineering highly competitive biofertilizers. IMPORTANCE Nitrogen-fixing root nodule symbioses between rhizobia and legume plants provide more than half of the combined nitrogen incorporated annually into terrestrial ecosystems, rendering plant growth independent of environmentally unfriendly chemical fertilizers. The success of symbiosis depends primarily on the capacity of rhizobia to establish competitive populations in soil and rhizosphere environments. Here, we provide insights into the regulation and architecture of an extensive RNA posttranscriptional network that fine-tunes the metabolism of the alfalfa symbiont S. meliloti, thereby enhancing the ability of this beneficial bacterium to colonize nutrient-rich but extremely selective niches, such as the rhizosphere of its host plant. This pervasive RNA regulation of metabolism is a major adaptive mechanism, predicted to operate in diverse rhizobial species. Because RNA regulation relies on modifiable base-pairing interactions, our findings open unexplored avenues for engineering the legumes rhizobiome within sustainable agricultural practices.
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Albicoro FJ, Draghi WO, Martini MC, Salas ME, Torres Tejerizo GA, Lozano MJ, López JL, Vacca C, Cafiero JH, Pistorio M, Bednarz H, Meier D, Lagares A, Niehaus K, Becker A, Del Papa MF. The two-component system ActJK is involved in acid stress tolerance and symbiosis in Sinorhizobium meliloti. J Biotechnol 2021; 329:80-91. [PMID: 33539896 DOI: 10.1016/j.jbiotec.2021.01.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 12/31/2020] [Accepted: 01/08/2021] [Indexed: 01/25/2023]
Abstract
The nitrogen-fixing α-proteobacterium Sinorhizobium meliloti genome codifies at least 50 response regulator (RR) proteins mediating different and, in many cases, unknown processes. RR-mutant library screening allowed us to identify genes potentially implicated in survival to acid conditions. actJ mutation resulted in a strain with reduced growth rate under mildly acidic conditions as well as a lower capacity to tolerate a sudden shift to lethal acidic conditions compared with the parental strain. Mutation of the downstream gene actK, which encodes for a histidine kinase, showed a similar phenotype in acidic environments suggesting a functional two-component system. Interestingly, even though nodulation kinetics, quantity, and macroscopic morphology of Medicago sativa nodules were not affected in actJ and actK mutants, ActK was required to express the wild-type nitrogen fixation phenotype and ActJK was necessary for full bacteroid development and nodule occupancy. The actJK regulatory system presented here provides insights into an evolutionary process in rhizobium adaptation to acidic environments and suggests that actJK-controlled functions are crucial for optimal symbiosis development.
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Affiliation(s)
- Francisco J Albicoro
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Walter O Draghi
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - María C Martini
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - María E Salas
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - G A Torres Tejerizo
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Mauricio J Lozano
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - José L López
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Carolina Vacca
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Juan H Cafiero
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Mariano Pistorio
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Hanna Bednarz
- CeBiTec, Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany
| | - Doreen Meier
- CeBiTec, Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany; LOEWE Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, Marburg, Germany
| | - Antonio Lagares
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Karsten Niehaus
- CeBiTec, Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany
| | - Anke Becker
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, Marburg, Germany; Faculty of Biology, Philipps-Universität Marburg, Marburg, Germany
| | - M F Del Papa
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina.
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Henry KK, Ross W, Myers KS, Lemmer KC, Vera JM, Landick R, Donohue TJ, Gourse RL. A majority of Rhodobacter sphaeroides promoters lack a crucial RNA polymerase recognition feature, enabling coordinated transcription activation. Proc Natl Acad Sci U S A 2020; 117:29658-29668. [PMID: 33168725 PMCID: PMC7703639 DOI: 10.1073/pnas.2010087117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Using an in vitro transcription system with purified RNA polymerase (RNAP) to investigate rRNA synthesis in the photoheterotrophic α-proteobacterium Rhodobacter sphaeroides, we identified a surprising feature of promoters recognized by the major holoenzyme. Transcription from R. sphaeroides rRNA promoters was unexpectedly weak, correlating with absence of -7T, the very highly conserved thymine found at the last position in -10 elements of promoters in most bacterial species. Thymine substitutions for adenine at position -7 in the three rRNA promoters strongly increased intrinsic promoter activity, indicating that R. sphaeroides RNAP can utilize -7T when present. rRNA promoters were activated by purified R. sphaeroides CarD, a transcription factor found in many bacterial species but not in β- and γ-proteobacteria. Overall, CarD increased the activity of 15 of 16 native R. sphaeroides promoters tested in vitro that lacked -7T, whereas it had no effect on three of the four native promoters that contained -7T. Genome-wide bioinformatic analysis of promoters from R. sphaeroides and two other α-proteobacterial species indicated that 30 to 43% contained -7T, whereas 90 to 99% of promoters from non-α-proteobacteria contained -7T. Thus, promoters lacking -7T appear to be widespread in α-proteobacteria and may have evolved away from consensus to enable their coordinated regulation by transcription factors like CarD. We observed a strong reduction in R. sphaeroides CarD levels when cells enter stationary phase, suggesting that reduced activation by CarD may contribute to inhibition of rRNA transcription when cells enter stationary phase, the stage of growth when bacterial ribosome synthesis declines.
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Affiliation(s)
- Kemardo K Henry
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706
| | - Wilma Ross
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706;
| | - Kevin S Myers
- Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI 53726
| | - Kimberly C Lemmer
- Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI 53726
| | - Jessica M Vera
- Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI 53726
| | - Robert Landick
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706
- Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI 53726
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Timothy J Donohue
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706
- Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI 53726
| | - Richard L Gourse
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706;
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22
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Cervantes-Rivera R, Puhar A. Whole-genome Identification of Transcriptional Start Sites by Differential RNA-seq in Bacteria. Bio Protoc 2020; 10:e3757. [PMID: 33659416 PMCID: PMC7842792 DOI: 10.21769/bioprotoc.3757] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/25/2020] [Accepted: 07/23/2020] [Indexed: 11/02/2022] Open
Abstract
Gene transcription in bacteria often starts some nucleotides upstream of the start codon. Identifying the specific Transcriptional Start Site (TSS) is essential for genetic manipulation, as in many cases upstream of the start codon there are sequence elements that are involved in gene expression regulation. Taken into account the classical gene structure, we are able to identify two kinds of transcriptional start site: primary and secondary. A primary transcriptional start site is located some nucleotides upstream of the translational start site, while a secondary transcriptional start site is located within the gene encoding sequence. Here, we present a step by step protocol for genome-wide transcriptional start sites determination by differential RNA-sequencing (dRNA-seq) using the enteric pathogen Shigella flexneri serotype 5a strain M90T as model. However, this method can be employed in any other bacterial species of choice. In the first steps, total RNA is purified from bacterial cultures using the hot phenol method. Ribosomal RNA (rRNA) is specifically depleted via hybridization probes using a commercial kit. A 5'-monophosphate-dependent exonuclease (TEX)-treated RNA library enriched in primary transcripts is then prepared for comparison with a library that has not undergone TEX-treatment, followed by ligation of an RNA linker adaptor of known sequence allowing the determination of TSS with single nucleotide precision. Finally, the RNA is processed for Illumina sequencing library preparation and sequenced as purchased service. TSS are identified by in-house bioinformatic analysis. Our protocol is cost-effective as it minimizes the use of commercial kits and employs freely available software.
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Affiliation(s)
- Ramón Cervantes-Rivera
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Sweden
- Umeå Centre for Microbial Research (UCMR), Umeå University, 90 187 Umeå, Sweden
- Department of Molecular Biology, Umeå University, 90 187 Umeå, Sweden
| | - Andrea Puhar
- The Laboratory for Molecular Infection Medicine Sweden (MIMS), Sweden
- Umeå Centre for Microbial Research (UCMR), Umeå University, 90 187 Umeå, Sweden
- Department of Molecular Biology, Umeå University, 90 187 Umeå, Sweden
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23
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Melior H, Maaß S, Li S, Förstner KU, Azarderakhsh S, Varadarajan AR, Stötzel M, Elhossary M, Barth-Weber S, Ahrens CH, Becher D, Evguenieva-Hackenberg E. The Leader Peptide peTrpL Forms Antibiotic-Containing Ribonucleoprotein Complexes for Posttranscriptional Regulation of Multiresistance Genes. mBio 2020; 11:e01027-20. [PMID: 32546623 PMCID: PMC7298713 DOI: 10.1128/mbio.01027-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 05/07/2020] [Indexed: 11/20/2022] Open
Abstract
Bacterial ribosome-dependent attenuators are widespread posttranscriptional regulators. They harbor small upstream open reading frames (uORFs) encoding leader peptides, for which no functions in trans are known yet. In the plant symbiont Sinorhizobium meliloti, the tryptophan biosynthesis gene trpE(G) is preceded by the uORF trpL and is regulated by transcription attenuation according to tryptophan availability. However, trpLE(G) transcription is initiated independently of the tryptophan level in S. meliloti, thereby ensuring a largely tryptophan-independent production of the leader peptide peTrpL. Here, we provide evidence for a tryptophan-independent role of peTrpL in trans We found that peTrpL increases the resistance toward tetracycline, erythromycin, chloramphenicol, and the flavonoid genistein, which are substrates of the major multidrug efflux pump SmeAB. Coimmunoprecipitation with a FLAG-peTrpL suggested smeR mRNA, which encodes the transcription repressor of smeABR, as a peptide target. Indeed, upon antibiotic exposure, smeR mRNA was destabilized and smeA stabilized in a peTrpL-dependent manner, showing that peTrpL acts in the differential regulation of smeABR Furthermore, smeR mRNA was coimmunoprecipitated with peTrpL in antibiotic-dependent ribonucleoprotein (ARNP) complexes, which, in addition, contained an antibiotic-induced antisense RNA complementary to smeRIn vitro ARNP reconstitution revealed that the above-mentioned antibiotics and genistein directly support complex formation. A specific region of the antisense RNA was identified as a seed region for ARNP assembly in vitro Altogether, our data show that peTrpL is involved in a mechanism for direct utilization of antimicrobial compounds in posttranscriptional regulation of multiresistance genes. Importantly, this role of peTrpL in resistance is conserved in other AlphaproteobacteriaIMPORTANCE Leader peptides encoded by transcription attenuators are widespread small proteins that are considered nonfunctional in trans We found that the leader peptide peTrpL of the soil-dwelling plant symbiont Sinorhizobium meliloti is required for differential, posttranscriptional regulation of a multidrug resistance operon upon antibiotic exposure. Multiresistance achieved by efflux of different antimicrobial compounds ensures survival and competitiveness in nature and is important from both evolutionary and medical points of view. We show that the leader peptide forms antibiotic- and flavonoid-dependent ribonucleoprotein complexes (ARNPs) for destabilization of smeR mRNA encoding the transcription repressor of the major multidrug resistance operon. The seed region for ARNP assembly was localized in an antisense RNA, whose transcription is induced by antimicrobial compounds. The discovery of ARNP complexes as new players in multiresistance regulation opens new perspectives in understanding bacterial physiology and evolution and potentially provides new targets for antibacterial control.
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Affiliation(s)
- Hendrik Melior
- Institute of Microbiology and Molecular Biology, University of Giessen, Giessen, Germany
| | - Sandra Maaß
- Institute of Microbiology, University of Greifswald, Greifswald, Germany
| | - Siqi Li
- Institute of Microbiology and Molecular Biology, University of Giessen, Giessen, Germany
| | - Konrad U Förstner
- ZB MED-Information Centre for Life Sciences, University of Cologne, Cologne, Germany
| | - Saina Azarderakhsh
- Institute of Microbiology and Molecular Biology, University of Giessen, Giessen, Germany
| | | | - Maximilian Stötzel
- Institute of Microbiology and Molecular Biology, University of Giessen, Giessen, Germany
| | - Muhammad Elhossary
- ZB MED-Information Centre for Life Sciences, University of Cologne, Cologne, Germany
| | - Susanne Barth-Weber
- Institute of Microbiology and Molecular Biology, University of Giessen, Giessen, Germany
| | - Christian H Ahrens
- Agroscope & SIB Swiss Institute of Bioinformatics, Wädenswil, Switzerland
| | - Dörte Becher
- Institute of Microbiology, University of Greifswald, Greifswald, Germany
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24
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Flores-Tinoco CE, Tschan F, Fuhrer T, Margot C, Sauer U, Christen M, Christen B. Co-catabolism of arginine and succinate drives symbiotic nitrogen fixation. Mol Syst Biol 2020; 16:e9419. [PMID: 32490601 PMCID: PMC7268258 DOI: 10.15252/msb.20199419] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 04/13/2020] [Accepted: 04/21/2020] [Indexed: 12/22/2022] Open
Abstract
Biological nitrogen fixation emerging from the symbiosis between bacteria and crop plants holds promise to increase the sustainability of agriculture. One of the biggest hurdles for the engineering of nitrogen-fixing organisms is an incomplete knowledge of metabolic interactions between microbe and plant. In contrast to the previously assumed supply of only succinate, we describe here the CATCH-N cycle as a novel metabolic pathway that co-catabolizes plant-provided arginine and succinate to drive the energy-demanding process of symbiotic nitrogen fixation in endosymbiotic rhizobia. Using systems biology, isotope labeling studies and transposon sequencing in conjunction with biochemical characterization, we uncovered highly redundant network components of the CATCH-N cycle including transaminases that interlink the co-catabolism of arginine and succinate. The CATCH-N cycle uses N2 as an additional sink for reductant and therefore delivers up to 25% higher yields of nitrogen than classical arginine catabolism-two alanines and three ammonium ions are secreted for each input of arginine and succinate. We argue that the CATCH-N cycle has evolved as part of a synergistic interaction to sustain bacterial metabolism in the microoxic and highly acid environment of symbiosomes. Thus, the CATCH-N cycle entangles the metabolism of both partners to promote symbiosis. Our results provide a theoretical framework and metabolic blueprint for the rational design of plants and plant-associated organisms with new properties to improve nitrogen fixation.
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Affiliation(s)
| | - Flavia Tschan
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Tobias Fuhrer
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Céline Margot
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Uwe Sauer
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Matthias Christen
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
| | - Beat Christen
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland
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25
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Greffe VRG, Michiels J. Desiccation-induced cell damage in bacteria and the relevance for inoculant production. Appl Microbiol Biotechnol 2020; 104:3757-3770. [PMID: 32170388 DOI: 10.1007/s00253-020-10501-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 02/18/2020] [Accepted: 02/26/2020] [Indexed: 12/21/2022]
Abstract
Plant growth-promoting bacteria show great potential for use in agriculture although efficient application remains challenging to achieve. Cells often lose viability during inoculant production and application, jeopardizing the efficacy of the inoculant. Since desiccation has been documented to be the primary stress factor affecting the decrease in survival, obtaining xerotolerance in plant growth-promoting bacteria is appealing. The molecular damage that occurs by drying bacteria has been broadly investigated, although a complete view is still lacking due to the complex nature of the process. Mechanic, structural, and metabolic changes that occur as a result of water depletion may potentially afflict lethal damage to membranes, DNA, and proteins. Bacteria respond to these harsh conditions by increasing production of exopolysaccharides, changing composition of the membrane, improving the stability of proteins, reducing oxidative stress, and repairing DNA damage. This review provides insight into the complex nature of desiccation stress in bacteria in order to facilitate strategic choices to improve survival and shelf life of newly developed inoculants. KEY POINTS: Desiccation-induced damage affects most major macromolecules in bacteria. Most bacteria are not xerotolerant despite multiple endogenous adaption mechanisms. Sensitivity to drying severely hampers inoculant quality.
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Affiliation(s)
- Vincent Robert Guy Greffe
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium.,VIB Center for Microbiology, Flanders Institute for Biotechnology, Leuven, Belgium
| | - Jan Michiels
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium. .,VIB Center for Microbiology, Flanders Institute for Biotechnology, Leuven, Belgium.
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26
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Structure of a Core Promoter in Bifidobacterium longum NCC2705. J Bacteriol 2020; 202:JB.00540-19. [PMID: 31964699 DOI: 10.1128/jb.00540-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 01/14/2020] [Indexed: 01/04/2023] Open
Abstract
Bacterial promoters consist of core sequence motifs termed -35 and -10 boxes. The consensus motifs are TTGACA and TATAAT, respectively, which were identified from leading investigations on Escherichia coli However, the consensus sequences are not likely to fit genetically divergent bacteria. The sigma factor of the genus Bifidobacterium has a characteristic polar domain in the N terminus, suggesting the possibility of specific promoter recognition. We reevaluated the structure of Bifidobacterium longum NCC2705 promoters and compared them to other bacteria. Transcriptional start sites (TSSs) of the B. longum NCC2705 strain were identified using transcriptome sequencing (RNA-Seq) analysis to extract promoter regions. Conserved motifs of a bifidobacterial promoter were determined using regions upstream of TSSs and a hidden Markov model. As a result, consensus motifs of the -35 and -10 boxes were TTGTGC and TACAAT, respectively. To assess each base of both motifs, we constructed 37 plasmids based on pKO403-TPCTcon, including the hup promoter connected with a chloramphenicol acetyltransferase as a reporter gene. This reporter assay showed two optimal motifs of the -35 and -10 boxes, namely, TTGNNN and TANNNT, respectively. We further analyzed spacer lengths between the -35 and -10 boxes via a bioinformatics approach. The spacer lengths predominant in bacteria have been generally reported to be approximately 17 bp. In contrast, the predominant spacer lengths in the genus Bifidobacterium and related species were 11 bp, in addition to 17 bp. A reporter assay to assess the spacer lengths indicated that the 11-bp spacer length produced unusually high activity.IMPORTANCE The structures of sigma factors vary among bacterial strains, indicating that recognition rules may also vary. Therefore, we investigated the promoter structure of Bifidobacterium longum NCC2705 using a bioinformatics approach and wet analyses. The most frequent and optimal motifs were similar to other bacterial consensus motifs. The optimal spacer length between the two boxes was reported to be 17 bp. It is widely applied to a bioinformatics approach for other bacteria. Unexpectedly, conserved spacer lengths were 11 bp as well as 17 bp in the genus Bifidobacterium Moreover, the sigma factor of the genus Bifidobacterium has a characteristic domain in the N terminus which may contribute to the additional functions. Hence, it would be valuable to reevaluate the promoter in other organisms.
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27
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Riboregulation in Nitrogen-Fixing Endosymbiotic Bacteria. Microorganisms 2020; 8:microorganisms8030384. [PMID: 32164262 PMCID: PMC7143759 DOI: 10.3390/microorganisms8030384] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 03/04/2020] [Accepted: 03/05/2020] [Indexed: 01/21/2023] Open
Abstract
Small non-coding RNAs (sRNAs) are ubiquitous components of bacterial adaptive regulatory networks underlying stress responses and chronic intracellular infection of eukaryotic hosts. Thus, sRNA-mediated regulation of gene expression is expected to play a major role in the establishment of mutualistic root nodule endosymbiosis between nitrogen-fixing rhizobia and legume plants. However, knowledge about this level of genetic regulation in this group of plant-interacting bacteria is still rather scarce. Here, we review insights into the rhizobial non-coding transcriptome and sRNA-mediated post-transcriptional regulation of symbiotic relevant traits such as nutrient uptake, cell cycle, quorum sensing, or nodule development. We provide details about the transcriptional control and protein-assisted activity mechanisms of the functionally characterized sRNAs involved in these processes. Finally, we discuss the forthcoming research on riboregulation in legume symbionts.
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28
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Melior H, Li S, Madhugiri R, Stötzel M, Azarderakhsh S, Barth-Weber S, Baumgardt K, Ziebuhr J, Evguenieva-Hackenberg E. Transcription attenuation-derived small RNA rnTrpL regulates tryptophan biosynthesis gene expression in trans. Nucleic Acids Res 2020; 47:6396-6410. [PMID: 30993322 PMCID: PMC6614838 DOI: 10.1093/nar/gkz274] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 03/01/2019] [Accepted: 04/12/2019] [Indexed: 01/06/2023] Open
Abstract
Ribosome-mediated transcription attenuation is a basic posttranscriptional regulation mechanism in bacteria. Liberated attenuator RNAs arising in this process are generally considered nonfunctional. In Sinorhizobium meliloti, the tryptophan (Trp) biosynthesis genes are organized into three operons, trpE(G), ppiD-trpDC-moaC-moeA, and trpFBA-accD-folC, of which only the first one, trpE(G), contains a short ORF (trpL) in the 5′-UTR and is regulated by transcription attenuation. Under conditions of Trp sufficiency, transcription is terminated between trpL and trpE(G), and a small attenuator RNA, rnTrpL, is produced. Here, we show that rnTrpL base-pairs with trpD and destabilizes the polycistronic trpDC mRNA, indicating rnTrpL-mediated downregulation of the trpDC operon in trans. Although all three trp operons are regulated in response to Trp availability, only in the two operons trpE(G) and trpDC the Trp-mediated regulation is controlled by rnTrpL. Together, our data show that the trp attenuator coordinates trpE(G) and trpDC expression posttranscriptionally by two fundamentally different mechanisms: ribosome-mediated transcription attenuation in cis and base-pairing in trans. Also, we present evidence that rnTrpL-mediated regulation of trpDC genes expression in trans is conserved in Agrobacterium and Bradyrhizobium, suggesting that the small attenuator RNAs may have additional conserved functions in the control of bacterial gene expression.
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Affiliation(s)
- Hendrik Melior
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - Siqi Li
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - Ramakanth Madhugiri
- Institute of Medical Virology, Justus Liebig University, Giessen, 35392, Germany
| | - Maximilian Stötzel
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - Saina Azarderakhsh
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - Susanne Barth-Weber
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - Kathrin Baumgardt
- Institute of Microbiology and Molecular Biology, Justus Liebig University, Giessen, 35392, Germany
| | - John Ziebuhr
- Institute of Medical Virology, Justus Liebig University, Giessen, 35392, Germany
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29
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Leonard S, Meyer S, Lacour S, Nasser W, Hommais F, Reverchon S. APERO: a genome-wide approach for identifying bacterial small RNAs from RNA-Seq data. Nucleic Acids Res 2019; 47:e88. [PMID: 31147705 PMCID: PMC6735904 DOI: 10.1093/nar/gkz485] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 05/06/2019] [Accepted: 05/20/2019] [Indexed: 12/02/2022] Open
Abstract
Small non-coding RNAs (sRNAs) regulate numerous cellular processes in all domains of life. Several approaches have been developed to identify them from RNA-seq data, which are efficient for eukaryotic sRNAs but remain inaccurate for the longer and highly structured bacterial sRNAs. We present APERO, a new algorithm to detect small transcripts from paired-end bacterial RNA-seq data. In contrast to previous approaches that start from the read coverage distribution, APERO analyzes boundaries of individual sequenced fragments to infer the 5′ and 3′ ends of all transcripts. Since sRNAs are about the same size as individual fragments (50–350 nucleotides), this algorithm provides a significantly higher accuracy and robustness, e.g., with respect to spontaneous internal breaking sites. To demonstrate this improvement, we develop a comparative assessment on datasets from Escherichia coli and Salmonella enterica, based on experimentally validated sRNAs. We also identify the small transcript repertoire of Dickeya dadantii including putative intergenic RNAs, 5′ UTR or 3′ UTR-derived RNA products and antisense RNAs. Comparisons to annotations as well as RACE-PCR experimental data confirm the precision of the detected transcripts. Altogether, APERO outperforms all existing methods in terms of sRNA detection and boundary precision, which is crucial for comprehensive genome annotations. It is freely available as an open source R package on https://github.com/Simon-Leonard/APERO
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Affiliation(s)
- Simon Leonard
- Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation, Pathogénie, 11 avenue Jean Capelle, F-69621 Villeurbanne, France
| | - Sam Meyer
- Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation, Pathogénie, 11 avenue Jean Capelle, F-69621 Villeurbanne, France
| | - Stephan Lacour
- Univ. Grenoble Alpes, CNRS, Inria, LiPhy (UMR5588), 38000 Grenoble, France
| | - William Nasser
- Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation, Pathogénie, 11 avenue Jean Capelle, F-69621 Villeurbanne, France
| | - Florence Hommais
- Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation, Pathogénie, 11 avenue Jean Capelle, F-69621 Villeurbanne, France
| | - Sylvie Reverchon
- Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation, Pathogénie, 11 avenue Jean Capelle, F-69621 Villeurbanne, France
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30
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Becerra-Rivera VA, Bergström E, Thomas-Oates J, Dunn MF. Polyamines are required for normal growth in Sinorhizobium meliloti. MICROBIOLOGY-SGM 2019; 164:600-613. [PMID: 29619919 DOI: 10.1099/mic.0.000615] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Polyamines (PAs) are ubiquitous polycations derived from basic l-amino acids whose physiological roles are still being defined. Their biosynthesis and functions in nitrogen-fixing rhizobia such as Sinorhizobium meliloti have not been extensively investigated. Thin layer chromatographic and mass spectrometric analyses showed that S. meliloti Rm8530 produces the PAs, putrescine (Put), spermidine (Spd) and homospermidine (HSpd), in their free forms and norspermidine (NSpd) in a form bound to macromolecules. The S. meliloti genome encodes two putative ornithine decarboxylases (ODC) for Put synthesis. Activity assays with the purified enzymes showed that ODC2 (SMc02983) decarboxylates both ornithine and lysine. ODC1 (SMa0680) decarboxylates only ornithine. An odc1 mutant was similar to the wild-type in ODC activity, PA production and growth. In comparison to the wild-type, an odc2 mutant had 45 % as much ODC activity and its growth rates were reduced by 42, 14 and 44 % under non-stress, salt stress or acid stress conditions, respectively. The odc2 mutant produced only trace levels of Put, Spd and HSpd. Wild-type phenotypes were restored when the mutant was grown in cultures supplemented with 1 mM Put or Spd or when the odc2 gene was introduced in trans. odc2 gene expression was increased under acid stress and reduced under salt stress and with exogenous Put or Spd. An odc1 odc2 double mutant had phenotypes similar to the odc2 mutant. These results indicate that ODC2 is the major enzyme for Put synthesis in S. meliloti and that PAs are required for normal growth in vitro.
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Affiliation(s)
- Victor A Becerra-Rivera
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Ed Bergström
- Centre of Excellence in Mass Spectrometry and Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| | - Jane Thomas-Oates
- Centre of Excellence in Mass Spectrometry and Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| | - Michael F Dunn
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
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31
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Baena I, Pérez-Mendoza D, Sauviac L, Francesch K, Martín M, Rivilla R, Bonilla I, Bruand C, Sanjuán J, Lloret J. A partner-switching system controls activation of mixed-linkage β-glucan synthesis by c-di-GMP in Sinorhizobium meliloti. Environ Microbiol 2019; 21:3379-3391. [PMID: 30963697 DOI: 10.1111/1462-2920.14624] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 04/06/2019] [Indexed: 11/29/2022]
Abstract
Sinorhizobium meliloti synthesizes a linear mixed-linkage (1 → 3)(1 → 4)-β-d-glucan (ML β-glucan, MLG) in response to high levels of cyclic diguanylate (c-di-GMP). Two proteins BgsA and BgsB are required for MLG synthesis, BgsA being the glucan synthase which is activated upon c-di-GMP binding to its C-terminal domain. Here we report that the product of bgrR (SMb20447) is a diguanylate cyclase (DGC) that provides c-di-GMP for the synthesis of MLG by BgsA. bgrR is the first gene of a hexacistronic bgrRSTUWV operon, likely encoding a partner-switching regulatory network where BgrR is the final target. Using different approaches, we have determined that the products of genes bgrU (containing a putative PP2C serine phosphatase domain) and bgrW (with predicted kinase effector domain), modulate the phosphorylation status and the activity of the STAS domain protein BgrV. We propose that unphosphorylated BgrV inhibits BgrR DGC activity, perhaps through direct protein-protein interactions as established for other partner switchers. A bgrRSTUWV operon coexists with MLG structural bgsBA genes in many rhizobial genomes but is also present in some MLG non-producers, suggesting a role of this partner-switching system in other processes besides MLG biosynthesis.
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Affiliation(s)
- Irene Baena
- Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain
| | - Daniel Pérez-Mendoza
- Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Laurent Sauviac
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Kevin Francesch
- Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain
| | - Marta Martín
- Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain
| | - Rafael Rivilla
- Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain
| | - Ildefonso Bonilla
- Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain
| | - Claude Bruand
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Juan Sanjuán
- Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Javier Lloret
- Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain
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Dupuy P, Sauviac L, Bruand C. Stress-inducible NHEJ in bacteria: function in DNA repair and acquisition of heterologous DNA. Nucleic Acids Res 2019; 47:1335-1349. [PMID: 30517704 PMCID: PMC6379672 DOI: 10.1093/nar/gky1212] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 11/16/2018] [Accepted: 11/22/2018] [Indexed: 12/16/2022] Open
Abstract
DNA double-strand breaks (DSB) in bacteria can be repaired by non-homologous end-joining (NHEJ), a two-component system relying on Ku and LigD. While performing a genetic characterization of NHEJ in Sinorhizobium meliloti, a representative of bacterial species encoding several Ku and LigD orthologues, we found that at least two distinct functional NHEJ repair pathways co-exist: one is dependent on Ku2 and LigD2, while the other depends on Ku3, Ku4 and LigD4. Whereas Ku2 likely acts as canonical bacterial Ku homodimers, genetic evidences suggest that Ku3-Ku4 form eukaryotic-like heterodimers. Strikingly, we found that the efficiency of both NHEJ systems increases under stress conditions, including heat and nutrient starvation. We found that this stimulation results from the transcriptional up-regulation of the ku and/or ligD genes, and that some of these genes are controlled by the general stress response regulator RpoE2. Finally, we provided evidence that NHEJ not only repairs DSBs, but can also capture heterologous DNA fragments into genomic breaks. Our data therefore suggest that NHEJ could participate to horizontal gene transfer from distantly related species, bypassing the need of homology to integrate exogenous DNA. This supports the hypothesis that NHEJ contributes to evolution and adaptation of bacteria under adverse environmental conditions.
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Affiliation(s)
- Pierre Dupuy
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Laurent Sauviac
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Claude Bruand
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
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McIntosh M, Serrania J, Lacanna E. A novel LuxR-type solo of Sinorhizobium meliloti, NurR, is regulated by the chromosome replication coordinator, DnaA and activates quorum sensing. Mol Microbiol 2019; 112:678-698. [PMID: 31124196 DOI: 10.1111/mmi.14312] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2019] [Indexed: 12/16/2022]
Abstract
The genome of Sinorhizobium meliloti, a model for studying plant-bacteria symbiosis, contains eight genes coding for LuxR-like proteins. Two of these, SinR and ExpR, are essential for quorum sensing (QS). Roles and regulation surrounding the others are mostly unknown. Here, we reveal the DNA recognition sequence and regulon of the LuxR-like protein SMc00877. Unlike ExpR, which uses the long-chain acyl homoserine lactones (AHLs) as inducers, SMc00877 functioned independently of AHLs and was even functional in Escherichia coli. A target of SMc00877 is SinR, the major regulator of AHL production in S. meliloti. Disruption of SMc00877 decreased AHL production. A weaker production of AHLs resulted in smaller microcolonies, starting from single cells, and delayed AHL-dependent regulation. SMc00877 was expressed only in growing cells in the presence of replete nutrients. Therefore, we renamed it NurR (nutrient sensitive LuxR-like regulator). We traced this nutrient-sensitive expression to transcription control by the DNA replication initiation factor, DnaA, which is essential for growth. These results indicate that NurR has a role in modulating the threshold of QS activation according to growth. We propose growth behavior as an additional prerequisite to population density for the activation of QS in S. meliloti.
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Affiliation(s)
- Matthew McIntosh
- LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, Marburg, 35043, Germany.,Faculty of Biology, Philipps-Universität Marburg, Marburg, 35043, Germany.,Institut für Mikrobiologie und Molekularbiologie, Universität Giessen, Heinrich-Buff-Ring 26-32, Giessen, 35392, Germany
| | - Javier Serrania
- LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, Marburg, 35043, Germany.,Faculty of Biology, Philipps-Universität Marburg, Marburg, 35043, Germany
| | - Egidio Lacanna
- LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, Marburg, 35043, Germany.,Faculty of Biology, Philipps-Universität Marburg, Marburg, 35043, Germany
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Tan YJC, Zhao C, Nasreen M, O'Rourke L, Dhouib R, Roberts L, Wan Y, Beatson SA, Kappler U. Control of Bacterial Sulfite Detoxification by Conserved and Species-Specific Regulatory Circuits. Front Microbiol 2019; 10:960. [PMID: 31139157 PMCID: PMC6527743 DOI: 10.3389/fmicb.2019.00960] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Accepted: 04/16/2019] [Indexed: 11/15/2022] Open
Abstract
Although sulfite, a by-product of the degradation of many sulfur compounds, is highly reactive and can cause damage to DNA, proteins and lipids, comparatively little is known about the regulation of sulfite-oxidizing enzyme (SOEs) expression. Here we have investigated the regulation of SOE-encoding genes in two species of α-Proteobacteria, Sinorhizobium meliloti and Starkeya novella, that degrade organo- and inorganic sulfur compounds, respectively, and contain unrelated types of SOEs that show different expression patterns. Our work revealed that in both cases, the molecular signal that triggers SOE gene expression is sulfite, and strong up-regulation depends on the presence of a sulfite-responsive, cognate Extracytoplasmic function (ECF) sigma factor, making sulfite oxidation a bacterial stress response. An additional RpoE1-like ECF sigma factor was also involved in the regulation, but was activated by different molecular signals, taurine (Sm) and tetrathionate (Sn), respectively, targeted different gene promoters, and also differed in the magnitude of the response generated. We therefore propose that RpoE1 is a secondary, species-specific regulator of SOE gene expression rather than a general, conserved regulatory circuit. Sulfite produced by major dissimilatory processes appeared to be the trigger for SOE gene expression in both species, as we were unable to find evidence for an increase of SOE activity in stationary growth phase. The basic regulation of bacterial sulfite oxidation by cognate ECF sigma factors is likely to be applicable to three groups of alpha and beta-Proteobacteria in which we identified similar SOE operon structures.
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Affiliation(s)
- Yi Jie Chelsea Tan
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia
| | - Chengzhi Zhao
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia
| | - Marufa Nasreen
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia
| | - Leo O'Rourke
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia
| | - Rabeb Dhouib
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia
| | - Leah Roberts
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia
| | - Ying Wan
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia
| | - Scott A Beatson
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia
| | - Ulrike Kappler
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia
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Fernández N, Cabrera JJ, Varadarajan AR, Lutz S, Ledermann R, Roschitzki B, Eberl L, Bedmar EJ, Fischer HM, Pessi G, Ahrens CH, Mesa S. An Integrated Systems Approach Unveils New Aspects of Microoxia-Mediated Regulation in Bradyrhizobium diazoefficiens. Front Microbiol 2019; 10:924. [PMID: 31134003 PMCID: PMC6515984 DOI: 10.3389/fmicb.2019.00924] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 04/11/2019] [Indexed: 01/31/2023] Open
Abstract
The adaptation of rhizobia from the free-living state in soil to the endosymbiotic state comprises several physiological changes in order to cope with the extremely low oxygen availability (microoxia) within nodules. To uncover cellular functions required for bacterial adaptation to microoxia directly at the protein level, we applied a systems biology approach on the key rhizobial model and soybean endosymbiont Bradyrhizobium diazoefficiens USDA 110 (formerly B. japonicum USDA 110). As a first step, the complete genome of B. diazoefficiens 110spc4, the model strain used in most prior functional genomics studies, was sequenced revealing a deletion of a ~202 kb fragment harboring 223 genes and several additional differences, compared to strain USDA 110. Importantly, the deletion strain showed no significantly different phenotype during symbiosis with several host plants, reinforcing the value of previous OMICS studies. We next performed shotgun proteomics and detected 2,900 and 2,826 proteins in oxically and microoxically grown cells, respectively, largely expanding our knowledge about the inventory of rhizobial proteins expressed in microoxia. A set of 62 proteins was significantly induced under microoxic conditions, including the two nitrogenase subunits NifDK, the nitrogenase reductase NifH, and several subunits of the high-affinity terminal cbb3 oxidase (FixNOQP) required for bacterial respiration inside nodules. Integration with the previously defined microoxia-induced transcriptome uncovered a set of 639 genes or proteins uniquely expressed in microoxia. Finally, besides providing proteogenomic evidence for novelties, we also identified proteins with a regulation similar to that of FixK2: transcript levels of these protein-coding genes were significantly induced, while the corresponding protein abundance remained unchanged or was down-regulated. This suggested that, apart from fixK2, additional B. diazoefficiens genes might be under microoxia-specific post-transcriptional control. This hypothesis was indeed confirmed for several targets (HemA, HemB, and ClpA) by immunoblot analysis.
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Affiliation(s)
- Noemí Fernández
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Juan J Cabrera
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Adithi R Varadarajan
- Agroscope, Research Group Molecular Diagnostics, Genomics and Bioinformatics and Swiss Institute of Bioinformatics, Wädenswil, Switzerland.,Department of Health Sciences and Technology, Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Stefanie Lutz
- Agroscope, Research Group Molecular Diagnostics, Genomics and Bioinformatics and Swiss Institute of Bioinformatics, Wädenswil, Switzerland
| | | | - Bernd Roschitzki
- Functional Genomics Center Zurich, ETH & UZH Zurich, Zurich, Switzerland
| | - Leo Eberl
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Eulogio J Bedmar
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | | | - Gabriella Pessi
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Christian H Ahrens
- Agroscope, Research Group Molecular Diagnostics, Genomics and Bioinformatics and Swiss Institute of Bioinformatics, Wädenswil, Switzerland
| | - Socorro Mesa
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
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Comparative Transcriptomic Profiling of Yersinia enterocolitica O:3 and O:8 Reveals Major Expression Differences of Fitness- and Virulence-Relevant Genes Indicating Ecological Separation. mSystems 2019; 4:mSystems00239-18. [PMID: 31020044 PMCID: PMC6478967 DOI: 10.1128/msystems.00239-18] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 02/27/2019] [Indexed: 01/16/2023] Open
Abstract
Yersinia enterocolitica is a major diarrheal pathogen and is associated with a large range of gut-associated diseases. Members of this species have evolved into different phylogroups with genotypic variations. We performed the first characterization of the Y. enterocolitica transcriptional landscape and tracked the consequences of the genomic variations between two different pathogenic phylogroups by comparing their RNA repertoire, promoter usage, and expression profiles under four different virulence-relevant conditions. Our analysis revealed major differences in the transcriptional outputs of the closely related strains, pointing to an ecological separation in which one is more adapted to an environmental lifestyle and the other to a mostly mammal-associated lifestyle. Moreover, a variety of pathoadaptive alterations, including alterations in acid resistance genes, colonization factors, and toxins, were identified which affect virulence and host specificity. This illustrates that comparative transcriptomics is an excellent approach to discover differences in the functional output from closely related genomes affecting niche adaptation and virulence, which cannot be directly inferred from DNA sequences. Yersinia enterocolitica is a zoonotic pathogen and an important cause of bacterial gastrointestinal infections in humans. Large-scale population genomic analyses revealed genetic and phenotypic diversity of this bacterial species, but little is known about the differences in the transcriptome organization, small RNA (sRNA) repertoire, and transcriptional output. Here, we present the first comparative high-resolution transcriptome analysis of Y. enterocolitica strains representing highly pathogenic phylogroup 2 (serotype O:8) and moderately pathogenic phylogroup 3 (serotype O:3) grown under four infection-relevant conditions. Our transcriptome sequencing (RNA-seq) approach revealed 1,299 and 1,076 transcriptional start sites and identified strain-specific sRNAs that could contribute to differential regulation among the phylogroups. Comparative transcriptomics further uncovered major gene expression differences, in particular, in the temperature-responsive regulon. Multiple virulence-relevant genes are differentially regulated between the two strains, supporting an ecological separation of phylogroups with certain niche-adapted properties. Strong upregulation of the ystA enterotoxin gene in combination with constitutive high expression of cell invasion factor InvA further showed that the toxicity of recent outbreak O:3 strains has increased. Overall, our report provides new insights into the specific transcriptome organization of phylogroups 2 and 3 and reveals gene expression differences contributing to the substantial phenotypic differences that exist between the lineages. IMPORTANCEYersinia enterocolitica is a major diarrheal pathogen and is associated with a large range of gut-associated diseases. Members of this species have evolved into different phylogroups with genotypic variations. We performed the first characterization of the Y. enterocolitica transcriptional landscape and tracked the consequences of the genomic variations between two different pathogenic phylogroups by comparing their RNA repertoire, promoter usage, and expression profiles under four different virulence-relevant conditions. Our analysis revealed major differences in the transcriptional outputs of the closely related strains, pointing to an ecological separation in which one is more adapted to an environmental lifestyle and the other to a mostly mammal-associated lifestyle. Moreover, a variety of pathoadaptive alterations, including alterations in acid resistance genes, colonization factors, and toxins, were identified which affect virulence and host specificity. This illustrates that comparative transcriptomics is an excellent approach to discover differences in the functional output from closely related genomes affecting niche adaptation and virulence, which cannot be directly inferred from DNA sequences.
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37
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Martini MC, Zhou Y, Sun H, Shell SS. Defining the Transcriptional and Post-transcriptional Landscapes of Mycobacterium smegmatis in Aerobic Growth and Hypoxia. Front Microbiol 2019; 10:591. [PMID: 30984135 PMCID: PMC6448022 DOI: 10.3389/fmicb.2019.00591] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 03/08/2019] [Indexed: 12/13/2022] Open
Abstract
The ability of Mycobacterium tuberculosis to infect, proliferate, and survive during long periods in the human lungs largely depends on the rigorous control of gene expression. Transcriptome-wide analyses are key to understanding gene regulation on a global scale. Here, we combine 5′-end-directed libraries with RNAseq expression libraries to gain insight into the transcriptome organization and post-transcriptional mRNA cleavage landscape in mycobacteria during log phase growth and under hypoxia, a physiologically relevant stress condition. Using the model organism Mycobacterium smegmatis, we identified 6,090 transcription start sites (TSSs) with high confidence during log phase growth, of which 67% were categorized as primary TSSs for annotated genes, and the remaining were classified as internal, antisense, or orphan, according to their genomic context. Interestingly, over 25% of the RNA transcripts lack a leader sequence, and of the coding sequences that do have leaders, 53% lack a strong consensus Shine-Dalgarno site. This indicates that like M. tuberculosis, M. smegmatis can initiate translation through multiple mechanisms. Our approach also allowed us to identify over 3,000 RNA cleavage sites, which occur at a novel sequence motif. To our knowledge, this represents the first report of a transcriptome-wide RNA cleavage site map in mycobacteria. The cleavage sites show a positional bias toward mRNA regulatory regions, highlighting the importance of post-transcriptional regulation in gene expression. We show that in low oxygen, a condition associated with the host environment during infection, mycobacteria change their transcriptomic profiles and endonucleolytic RNA cleavage is markedly reduced, suggesting a mechanistic explanation for previous reports of increased mRNA half-lives in response to stress. In addition, a number of TSSs were triggered in hypoxia, 56 of which contain the binding motif for the sigma factor SigF in their promoter regions. This suggests that SigF makes direct contributions to transcriptomic remodeling in hypoxia-challenged mycobacteria. Taken together, our data provide a foundation for further study of both transcriptional and posttranscriptional regulation in mycobacteria.
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Affiliation(s)
- M Carla Martini
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Ying Zhou
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Huaming Sun
- Program in Bioinformatics and Computational Biology, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Scarlet S Shell
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, United States.,Program in Bioinformatics and Computational Biology, Worcester Polytechnic Institute, Worcester, MA, United States
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Characterization of the Sinorhizobium meliloti HslUV and ClpXP Protease Systems in Free-Living and Symbiotic States. J Bacteriol 2019; 201:JB.00498-18. [PMID: 30670545 DOI: 10.1128/jb.00498-18] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 01/15/2019] [Indexed: 12/15/2022] Open
Abstract
Symbiotic nitrogen fixation (SNF) in the interaction between the soil bacteria Sinorhizobium meliloti and legume plant Medicago sativa is carried out in specialized root organs called nodules. During nodule development, each symbiont must drastically alter their proteins, transcripts, and metabolites in order to support nitrogen fixation. Moreover, bacteria within the nodules are under stress, including challenges by plant antimicrobial peptides, low pH, limited oxygen availability, and strongly reducing conditions, all of which challenge proteome integrity. S. meliloti stress adaptation, proteome remodeling, and quality control are controlled in part by the large oligomeric protease complexes HslUV and ClpXP1. To improve understanding of the roles of S. meliloti HslUV and ClpXP1 under free-living conditions and in symbiosis with M. sativa, we generated ΔhslU, ΔhslV, ΔhslUV, and ΔclpP1 knockout mutants. The shoot dry weight of M. sativa plants inoculated with each deletion mutant was significantly reduced, suggesting a role in symbiosis. Further, slower free-living growth of the ΔhslUV and ΔclpP1 mutants suggests that HslUV and ClpP1 were involved in adapting to heat stress, the while ΔhslU and ΔclpP1 mutants were sensitive to kanamycin. All deletion mutants produced less exopolysaccharide and succinoglycan, as shown by replicate spot plating and calcofluor binding. We also generated endogenous C-terminal enhanced green fluorescent protein (eGFP) fusions to HslU, HslV, ClpX, and ClpP1 in S. meliloti Using anti-eGFP antibodies, native coimmunoprecipitation experiments with proteins from free-living and nodule tissues were performed and analyzed by mass spectrometry. The results suggest that HslUV and ClpXP were closely associated with ribosomal and proteome quality control proteins, and they identified several novel putative protein-protein interactions.IMPORTANCE Symbiotic nitrogen fixation (SNF) is the primary means by which biologically available nitrogen enters the biosphere, and it is therefore a critical component of the global nitrogen cycle and modern agriculture. SNF is the result of highly coordinated interactions between legume plants and soil bacteria collectively referred to as rhizobia, e.g., Medicago sativa and S. meliloti, respectively. Accomplishing SNF requires significant proteome changes in both organisms to create a microaerobic environment suitable for high-level bacterial nitrogenase activity. The bacterial protease systems HslUV and ClpXP are important in proteome quality control, in metabolic remodeling, and in adapting to stress. This work shows that S. meliloti HslUV and ClpXP are involved in SNF, in exopolysaccharide production, and in free-living stress adaptation.
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39
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Herrou J, Willett JW, Fiebig A, Varesio LM, Czyż DM, Cheng JX, Ultee E, Briegel A, Bigelow L, Babnigg G, Kim Y, Crosson S. Periplasmic protein EipA determines envelope stress resistance and virulence in Brucella abortus. Mol Microbiol 2019; 111:637-661. [PMID: 30536925 DOI: 10.1111/mmi.14178] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/30/2018] [Indexed: 12/17/2022]
Abstract
Molecular components of the Brucella abortus cell envelope play a major role in its ability to infect, colonize and survive inside mammalian host cells. In this study, we have defined a role for a conserved gene of unknown function in B. abortus envelope stress resistance and infection. Expression of this gene, which we name eipA, is directly activated by the essential cell cycle regulator, CtrA. eipA encodes a soluble periplasmic protein that adopts an unusual eight-stranded β-barrel fold. Deletion of eipA attenuates replication and survival in macrophage and mouse infection models, and results in sensitivity to treatments that compromise the cell envelope integrity. Transposon disruption of genes required for LPS O-polysaccharide biosynthesis is synthetically lethal with eipA deletion. This genetic connection between O-polysaccharide and eipA is corroborated by our discovery that eipA is essential in Brucella ovis, a naturally rough species that harbors mutations in several genes required for O-polysaccharide production. Conditional depletion of eipA expression in B. ovis results in a cell chaining phenotype, providing evidence that eipA directly or indirectly influences cell division in Brucella. We conclude that EipA is a molecular determinant of Brucella virulence that functions to maintain cell envelope integrity and influences cell division.
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Affiliation(s)
- Julien Herrou
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Jonathan W Willett
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Aretha Fiebig
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Lydia M Varesio
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Daniel M Czyż
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL, USA
| | - Jason X Cheng
- Department of Pathology, The University of Chicago, Chicago, IL, USA
| | - Eveline Ultee
- Department of Biology, Universiteit Leiden, Leiden, Netherlands
| | - Ariane Briegel
- Department of Biology, Universiteit Leiden, Leiden, Netherlands
| | - Lance Bigelow
- Biosciences Division, Argonne National Laboratory, Argonne, IL, USA
| | - Gyorgy Babnigg
- Biosciences Division, Argonne National Laboratory, Argonne, IL, USA
| | - Youngchang Kim
- Biosciences Division, Argonne National Laboratory, Argonne, IL, USA
| | - Sean Crosson
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
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40
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Thomet M, Trautwetter A, Ermel G, Blanco C. Characterization of HicAB toxin-antitoxin module of Sinorhizobium meliloti. BMC Microbiol 2019; 19:10. [PMID: 30630415 PMCID: PMC6327479 DOI: 10.1186/s12866-018-1382-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Accepted: 12/26/2018] [Indexed: 02/06/2023] Open
Abstract
Background Toxin-antitoxin (TA) systems are little genetic units generally composed of two genes encoding antitoxin and toxin. These systems are known to be involved in many functions that can lead to growth arrest and cell death. Among the different types of TA systems, the type II gathers together systems where the antitoxin directly binds and inhibits the toxin. Among these type II TA systems, the HicAB module is widely distributed in free-living Bacteria and Archaea and the toxin HicA functions via RNA binding and cleavage. The genome of the symbiotic Sinorhizobium meliloti encodes numerous TA systems and only a few of them are functional. Among the predicted TA systems, there is one homologous to HicAB modules. Results In this study, we characterize the HicAB toxin-antitoxin module of S. meliloti. The production of the HicA of S. meliloti in Escherichia coli cells abolishes growth and decreases cell viability. We show that expression of the HicB of S. meliloti counteracts HicA toxicity. The results of double hybrid assays and co-purification experiments allow demonstrating the interaction of HicB with the toxin HicA. Purified HicA, but not HicAB complex, is able to degrade ribosomal RNA in vitro. The analysis of separated domains of HicB protein permits us to define the antitoxin activity and the operator-binding domain. Conclusions This study points out the first characterization of the HicAB system of the symbiotic S. meliloti whereas HicA is a toxin with ribonuclease activity and HicB has two domains: the COOH-terminal one that binds the operator and the NH2-terminal one that inhibits the toxin. Electronic supplementary material The online version of this article (10.1186/s12866-018-1382-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Manon Thomet
- Ribosome, bacteria and stress Team, Univ. Rennes, CNRS, Institut de Génétique et de Développement de Rennes (IGDR), UMR6290, F35000, Rennes, France
| | - Annie Trautwetter
- Ribosome, bacteria and stress Team, Univ. Rennes, CNRS, Institut de Génétique et de Développement de Rennes (IGDR), UMR6290, F35000, Rennes, France
| | - Gwennola Ermel
- Ribosome, bacteria and stress Team, Univ. Rennes, CNRS, Institut de Génétique et de Développement de Rennes (IGDR), UMR6290, F35000, Rennes, France.
| | - Carlos Blanco
- Ribosome, bacteria and stress Team, Univ. Rennes, CNRS, Institut de Génétique et de Développement de Rennes (IGDR), UMR6290, F35000, Rennes, France
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41
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Abstract
High-throughput transcriptome profiling (RNAseq) has uncovered large and heterogeneous populations of small noncoding RNA species (sRNAs) with potential regulatory roles in bacteria. A large fraction of sRNAs are differentially regulated and rely on protein-assisted antisense interactions to trans-encoded target mRNAs to fine-tune posttranscriptional reprogramming of gene expression in response to external cues. However, annotation and function of sRNAs are still largely overlooked in nonmodel bacteria with complex lifestyles. Here, we describe experimental protocols successfully applied for the accurate annotation, expression profiling and target mRNA identification of trans-acting sRNAs in the nitrogen-fixing α-rhizobium Sinorhizobium meliloti. The protocols presented here can be similarly applied for the characterization of trans-sRNAs in genetically tractable α-proteobacteria of agronomical or clinical relevance interacting with eukaryotic hosts.
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Plágaro AH, Pearman PB, Kaberdin VR. Defining the transcription landscape of the Gram-negative marine bacterium Vibrio harveyi. Genomics 2018; 111:1547-1556. [PMID: 30423347 DOI: 10.1016/j.ygeno.2018.10.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 09/13/2018] [Accepted: 10/23/2018] [Indexed: 12/13/2022]
Abstract
Vibrio harveyi is a Gram-negative pathogenic bacterium ubiquitously present in natural aquatic systems. Although environmental adaptability in V. harveyi may be enabled by profound reprogramming of gene expression previously observed during responses to starvation, suboptimal temperatures and other stress factors, the key characteristics of V. harveyi transcripts and operons, such as their boundaries and size as well as location of small RNA genes, remain largely unknown. To reveal the main features of the V. harveyi transcriptome, total RNA of this organism was analyzed by differential RNA sequencing (dRNA-seq). Analysis of the dRNA-seq data made it possible to define the primary transcriptome of V. harveyi along with cis-acting regulatory elements (riboswitches and leader sequences) and new genes. The latter encode a number of putative polypeptides and new phylogenetically conserved antisense RNAs potentially involved in the post-transcriptional control of gene expression.
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Affiliation(s)
- Ander Hernández Plágaro
- Department of Immunology, Microbiology and Parasitology, University of the Basque Country UPV/EHU, 48940 Leioa, Spain.
| | - Peter B Pearman
- Department of Plant Biology and Ecology, University of the Basque Country UPV/EHU, 48940 Leioa, Spain; IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013 Bilbao, Spain
| | - Vladimir R Kaberdin
- Department of Immunology, Microbiology and Parasitology, University of the Basque Country UPV/EHU, 48940 Leioa, Spain; IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013 Bilbao, Spain; Research Centre for Experimental Marine Biology and Biotechnology (PIE-UPV/EHU), 48620 Plentzia, Spain.
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43
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Ratib NR, Sabio EY, Mendoza C, Barnett MJ, Clover SB, Ortega JA, Dela Cruz FM, Balderas D, White H, Long SR, Chen EJ. Genome-wide identification of genes directly regulated by ChvI and a consensus sequence for ChvI binding in Sinorhizobium meliloti. Mol Microbiol 2018; 110:596-615. [PMID: 30192418 DOI: 10.1111/mmi.14119] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2018] [Revised: 08/16/2018] [Accepted: 09/04/2018] [Indexed: 12/11/2022]
Abstract
ExoS/ChvI two-component signaling in the nitrogen-fixing α-proteobacterium Sinorhizobium meliloti is required for symbiosis and regulates exopolysaccharide production, motility, cell envelope integrity and nutrient utilization in free-living bacteria. However, identification of many ExoS/ChvI direct transcriptional target genes has remained elusive. Here, we performed chromatin immunoprecipitation followed by microarray analysis (chIP-chip) to globally identify DNA regions bound by ChvI protein in S. meliloti. We then performed qRT-PCR with chvI mutant strains to test ChvI-dependent expression of genes downstream of the ChvI-bound DNA regions. We identified 64 direct target genes of ChvI, including exoY, rem and chvI itself. We also identified ChvI direct target candidates, like exoR, that are likely controlled by additional regulators. Analysis of upstream sequences from the 64 ChvI direct target genes identified a 15 bp-long consensus sequence. Using electrophoretic mobility shift assays and transcriptional fusions with exoY, SMb21440, SMc00084, SMc01580, chvI, and ropB1, we demonstrated this consensus sequence is important for ChvI binding to DNA and transcription of ChvI direct target genes. Thus, we have comprehensively identified ChvI regulon genes and a 'ChvI box' bound by ChvI. Many ChvI direct target genes may influence the cell envelope, consistent with the critical role of ExoS/ChvI in growth and microbe-host interactions.
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Affiliation(s)
- Nicole R Ratib
- Department of Biological Science, Center for Applied Biotechnology Studies, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - Erich Y Sabio
- Department of Biological Science, Center for Applied Biotechnology Studies, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - Carolina Mendoza
- Department of Biological Science, Center for Applied Biotechnology Studies, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | | | - Sarah B Clover
- Department of Biological Science, Center for Applied Biotechnology Studies, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - Jesus A Ortega
- Department of Biological Science, Center for Applied Biotechnology Studies, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - Francesca M Dela Cruz
- Department of Biological Science, Center for Applied Biotechnology Studies, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - David Balderas
- Department of Biological Science, Center for Applied Biotechnology Studies, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - Holly White
- Department of Biological Science, Center for Applied Biotechnology Studies, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - Sharon R Long
- Department of Biology, Stanford University, Stanford, CA, USA
| | - Esther J Chen
- Department of Biological Science, Center for Applied Biotechnology Studies, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
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44
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Abstract
Fixed (reduced) soil nitrogen plays a critical role in soil fertility and successful food growth. Much soil fertility relies on symbiotic nitrogen fixation: the bacterial partner infects the host plant roots and reduces atmospheric dinitrogen in exchange for host metabolic fuel, a process that involves complex interactions between the partners mediated by changes in gene expression in each partner. Here we test the roles of a family of 11 extracytoplasmic function (ECF) gene regulatory proteins (sigma factors [σs]) that interact with RNA polymerase to determine if they play a significant role in establishing a nitrogen-fixing symbiosis or in responding to various stresses, including cell envelope stress. We discovered that symbiotic nitrogen fixation occurs even when all 11 of these regulatory genes are deleted, that most ECF sigma factors control accessory functions, and that none of the ECF sigma factors are required to survive envelope stress. Bacteria must sense alterations in their environment and respond with changes in function and/or structure in order to cope. Extracytoplasmic function sigma factors (ECF σs) modulate transcription in response to cellular and environmental signals. The symbiotic nitrogen-fixing alphaproteobacterium Sinorhizobium meliloti carries genes for 11 ECF-like σs (RpoE1 to -E10 and FecI). We hypothesized that some of these play a role in mediating the interaction between the bacterium and its plant symbiotic partner. The bacterium senses changes in its immediate environment as it establishes contact with the plant root, initiates invasion of the plant as the root nodule is formed, traverses several root cell layers, and enters plant cortical cells via endocytosis. We used genetics, transcriptomics, and functionality to characterize the entire S. meliloti cohort of ECF σs. We discovered new targets for individual σs, confirmed others by overexpressing individual ECF σs, and identified or confirmed putative promoter motifs for nine of them. We constructed precise deletions of each ECF σ gene and its demonstrated or putative anti-σ gene and also a strain in which all 11 ECF σ and anti-σ genes were deleted. This all-ECF σ deletion strain showed no major defects in free-living growth, in Biolog Phenotype MicroArray assays, or in response to multiple stresses. None of the ECF σs were required for symbiosis on the host plants Medicago sativa and Medicago truncatula: the strain deleted for all ECF σ and anti-σ genes was symbiotically normal. IMPORTANCE Fixed (reduced) soil nitrogen plays a critical role in soil fertility and successful food growth. Much soil fertility relies on symbiotic nitrogen fixation: the bacterial partner infects the host plant roots and reduces atmospheric dinitrogen in exchange for host metabolic fuel, a process that involves complex interactions between the partners mediated by changes in gene expression in each partner. Here we test the roles of a family of 11 extracytoplasmic function (ECF) gene regulatory proteins (sigma factors [σs]) that interact with RNA polymerase to determine if they play a significant role in establishing a nitrogen-fixing symbiosis or in responding to various stresses, including cell envelope stress. We discovered that symbiotic nitrogen fixation occurs even when all 11 of these regulatory genes are deleted, that most ECF sigma factors control accessory functions, and that none of the ECF sigma factors are required to survive envelope stress.
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45
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Abstract
ABSTRACT
Although bacterial genomes are usually densely protein-coding, genome-wide mapping approaches of transcriptional start sites revealed that a significant fraction of the identified promoters drive the transcription of noncoding RNAs. These can be
trans
-acting RNAs, mainly originating from intergenic regions and, in many studied examples, possessing regulatory functions. However, a significant fraction of these noncoding RNAs consist of natural antisense transcripts (asRNAs), which overlap other transcriptional units. Naturally occurring asRNAs were first observed to play a role in bacterial plasmid replication and in bacteriophage λ more than 30 years ago. Today’s view is that asRNAs abound in all three domains of life. There are several examples of asRNAs in bacteria with clearly defined functions. Nevertheless, many asRNAs appear to result from pervasive initiation of transcription, and some data point toward global functions of such widespread transcriptional activity, explaining why the search for a specific regulatory role is sometimes futile. In this review, we give an overview about the occurrence of antisense transcription in bacteria, highlight particular examples of functionally characterized asRNAs, and discuss recent evidence pointing at global relevance in RNA processing and transcription-coupled DNA repair.
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46
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Abstract
ABSTRACT
Previously, leaderless mRNAs (lmRNAs) were perceived to make up only a minor fraction of the transcriptome in bacteria. However, advancements in RNA sequencing technology are uncovering vast numbers of lmRNAs, particularly in archaea,
Actinobacteria
, and extremophiles and thus underline their significance in cellular physiology and regulation. Due to the absence of conventional ribosome binding signals, lmRNA translation initiation is distinct from canonical mRNAs and can therefore be differentially regulated. The ribosome’s inherent ability to bind a 5′-terminal AUG can stabilize and protect the lmRNA from degradation or allow ribosomal loading for downstream initiation events. As a result, lmRNAs remain translationally competent during a variety of physiological conditions, allowing them to contribute to multiple regulatory mechanisms. Furthermore, the abundance of lmRNAs can increase during adverse conditions through the upregulation of lmRNA transcription from alternative promoters or by the generation of lmRNAs from canonical mRNAs cleaved by an endonucleolytic toxin. In these ways, lmRNA translation can continue during stress and contribute to regulation, illustrating their importance in the cell. Due to their presence in all domains of life and their ability to be translated by heterologous hosts, lmRNAs appear further to represent ancestral transcripts that might allow us to study the evolution of the ribosome and the translational process.
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47
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Functional Genomics Approaches to Studying Symbioses between Legumes and Nitrogen-Fixing Rhizobia. High Throughput 2018; 7:ht7020015. [PMID: 29783718 PMCID: PMC6023288 DOI: 10.3390/ht7020015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 05/13/2018] [Accepted: 05/16/2018] [Indexed: 01/24/2023] Open
Abstract
Biological nitrogen fixation gives legumes a pronounced growth advantage in nitrogen-deprived soils and is of considerable ecological and economic interest. In exchange for reduced atmospheric nitrogen, typically given to the plant in the form of amides or ureides, the legume provides nitrogen-fixing rhizobia with nutrients and highly specialised root structures called nodules. To elucidate the molecular basis underlying physiological adaptations on a genome-wide scale, functional genomics approaches, such as transcriptomics, proteomics, and metabolomics, have been used. This review presents an overview of the different functional genomics approaches that have been performed on rhizobial symbiosis, with a focus on studies investigating the molecular mechanisms used by the bacterial partner to interact with the legume. While rhizobia belonging to the alpha-proteobacterial group (alpha-rhizobia) have been well studied, few studies to date have investigated this process in beta-proteobacteria (beta-rhizobia).
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48
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Robledo M, Schlüter JP, Loehr LO, Linne U, Albaum SP, Jiménez-Zurdo JI, Becker A. An sRNA and Cold Shock Protein Homolog-Based Feedforward Loop Post-transcriptionally Controls Cell Cycle Master Regulator CtrA. Front Microbiol 2018; 9:763. [PMID: 29740411 PMCID: PMC5928217 DOI: 10.3389/fmicb.2018.00763] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2018] [Accepted: 04/04/2018] [Indexed: 11/13/2022] Open
Abstract
Adjustment of cell cycle progression is crucial for bacterial survival and adaptation under adverse conditions. However, the understanding of modulation of cell cycle control in response to environmental changes is rather incomplete. In α-proteobacteria, the broadly conserved cell cycle master regulator CtrA underlies multiple levels of control, including coupling of cell cycle and cell differentiation. CtrA levels are known to be tightly controlled through diverse transcriptional and post-translational mechanisms. Here, small RNA (sRNA)-mediated post-transcriptional regulation is uncovered as an additional level of CtrA fine-tuning. Computational predictions as well as transcriptome and proteome studies consistently suggested targeting of ctrA and the putative cold shock chaperone cspA5 mRNAs by the trans-encoded sRNA (trans-sRNA) GspR (formerly SmelC775) in several Sinorhizobium species. GspR strongly accumulated in the stationary growth phase, especially in minimal medium (MM) cultures. Lack of the gspR locus confers a fitness disadvantage in competition with the wild type, while its overproduction hampers cell growth, suggesting that this riboregulator interferes with cell cycle progression. An eGFP-based reporter in vivo assay, involving wild-type and mutant sRNA and mRNA pairs, experimentally confirmed GspR-dependent post-transcriptional down-regulation of ctrA and cspA5 expression, which most likely occurs through base-pairing to the respective mRNA. The energetically favored secondary structure of GspR is predicted to comprise three stem-loop domains, with stem-loop 1 and stem-loop 3 targeting ctrA and cspA5 mRNA, respectively. Moreover, this work reports evidence for post-transcriptional control of ctrA by CspA5. Thus, this regulation and GspR-mediated post-transcriptional repression of ctrA and cspA5 expression constitute a coherent feed-forward loop, which may enhance the negative effect of GspR on CtrA levels. This novel regulatory circuit involving the riboregulator GspR, CtrA, and a cold shock chaperone may contribute to fine-tuning of ctrA expression.
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Affiliation(s)
- Marta Robledo
- LOEWE Center for Synthetic Microbiology and Faculty of Biology, Philipps-Universität Marburg, Marburg, Germany.,Grupo de Ecología Genética de la Rizosfera, Estación Experimental del Zaidín (CSIC), Granada, Spain
| | - Jan-Philip Schlüter
- LOEWE Center for Synthetic Microbiology and Faculty of Biology, Philipps-Universität Marburg, Marburg, Germany
| | - Lars O Loehr
- LOEWE Center for Synthetic Microbiology and Faculty of Biology, Philipps-Universität Marburg, Marburg, Germany
| | - Uwe Linne
- LOEWE Center for Synthetic Microbiology and Faculty of Chemistry, Philipps-Universität Marburg, Marburg, Germany
| | - Stefan P Albaum
- Bioinformatics Resource Facility, Center for Biotechnology, Universität Bielefeld, Bielefeld, Germany
| | - José I Jiménez-Zurdo
- Grupo de Ecología Genética de la Rizosfera, Estación Experimental del Zaidín (CSIC), Granada, Spain
| | - Anke Becker
- LOEWE Center for Synthetic Microbiology and Faculty of Biology, Philipps-Universität Marburg, Marburg, Germany
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49
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OxyR-Dependent Transcription Response of Sinorhizobium meliloti to Oxidative Stress. J Bacteriol 2018; 200:JB.00622-17. [PMID: 29358497 DOI: 10.1128/jb.00622-17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 01/11/2018] [Indexed: 11/20/2022] Open
Abstract
Reactive oxygen species such as peroxides play an important role in plant development, cell wall maturation, and defense responses. During nodulation with the host plant Medicago sativa, Sinorhizobium meliloti cells are exposed to H2O2 in infection threads and developing nodules (R. Santos, D. Hérouart, S. Sigaud, D. Touati, and A. Puppo, Mol Plant Microbe Interact 14:86-89, 2001, https://doi.org/10.1094/MPMI.2001.14.1.86). S. meliloti cells likely also experience oxidative stress, from both internal and external sources, during life in the soil. Here, we present microarray transcription data for S. meliloti wild-type cells compared to a mutant deficient in the key oxidative regulatory protein OxyR, each in response to H2O2 treatment. Several alternative sigma factor genes are upregulated in the response to H2O2; the stress sigma gene rpoE2 shows OxyR-dependent induction by H2O2, while rpoH1 expression is induced by H2O2 irrespective of the oxyR genotype. The activity of the RpoE2 sigma factor in turn causes increased expression of two more sigma factor genes, rpoE5 and rpoH2 Strains with deletions of rpoH1 showed improved survival in H2O2 as well as increased levels of oxyR and total catalase expression. These results imply that ΔrpoH1 strains are primed to deal with oxidative stress. This work presents a global view of S. meliloti gene expression changes, and of regulation of those changes, in response to H2O2IMPORTANCE Like all aerobic organisms, the symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti experiences oxidative stress throughout its complex life cycle. This report describes the global transcriptional changes that S. meliloti makes in response to H2O2 and the roles of the OxyR transcriptional regulator and the RpoH1 sigma factor in regulating those changes. By understanding the complex regulatory response of S. meliloti to oxidative stress, we may further understand the role that reactive oxygen species play as both stressors and potential signals during symbiosis.
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50
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Lang C, Smith LS, Haney CH, Long SR. Characterization of Novel Plant Symbiosis Mutants Using a New Multiple Gene-Expression Reporter Sinorhizobium meliloti Strain. FRONTIERS IN PLANT SCIENCE 2018; 9:76. [PMID: 29467773 PMCID: PMC5808326 DOI: 10.3389/fpls.2018.00076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 01/15/2018] [Indexed: 06/08/2023]
Abstract
The formation of nitrogen fixing root nodules by Medicago truncatula and Sinorhizobium meliloti requires communication between both organisms and coordinated differentiation of plant and bacterial cells. After an initial signal exchange, the bacteria invade the tissue of the growing nodule via plant-derived tubular structures, called infection threads. The bacteria are released from the infection threads into invasion-competent plant cells, where they differentiate into nitrogen-fixing bacteroids. Both organisms undergo dramatic transcriptional, metabolic and morphological changes during nodule development. To identify plant processes that are essential for the formation of nitrogen fixing nodules after nodule development has been initiated, large scale mutageneses have been conducted to discover underlying plant symbiosis genes. Such screens yield numerous uncharacterized plant lines with nitrogen fixation deficient nodules. In this study, we report construction of a S. meliloti strain carrying four distinct reporter constructs to reveal stages of root nodule development. The strain contains a constitutively expressed lacZ reporter construct; a PexoY-mTFP fusion that is expressed in infection threads but not in differentiated bacteroids; a PbacA-mcherry construct that is expressed in infection threads and during bacteroid differentiation; and a PnifH-uidA construct that is expressed during nitrogen fixation. We used this strain together with fluorescence microscopy to study nodule development over time in wild type nodules and to characterize eight plant mutants from a fast neutron bombardment screen. Based on the signal intensity and the localization patterns of the reporter genes, we grouped mutants with similar phenotypes and placed them in a developmental context.
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Affiliation(s)
| | | | | | - Sharon R. Long
- Gilbert Lab, Department of Biology, Stanford University, Stanford, CA, United States
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