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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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2
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Shepherd MJ, Pierce AP, Taylor TB. Evolutionary innovation through transcription factor rewiring in microbes is shaped by levels of transcription factor activity, expression, and existing connectivity. PLoS Biol 2023; 21:e3002348. [PMID: 37871011 PMCID: PMC10621929 DOI: 10.1371/journal.pbio.3002348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 11/02/2023] [Accepted: 09/25/2023] [Indexed: 10/25/2023] Open
Abstract
The survival of a population during environmental shifts depends on whether the rate of phenotypic adaptation keeps up with the rate of changing conditions. A common way to achieve this is via change to gene regulatory network (GRN) connections-known as rewiring-that facilitate novel interactions and innovation of transcription factors. To understand the success of rapidly adapting organisms, we therefore need to determine the rules that create and constrain opportunities for GRN rewiring. Here, using an experimental microbial model system with the soil bacterium Pseudomonas fluorescens, we reveal a hierarchy among transcription factors that are rewired to rescue lost function, with alternative rewiring pathways only unmasked after the preferred pathway is eliminated. We identify 3 key properties-high activation, high expression, and preexisting low-level affinity for novel target genes-that facilitate transcription factor innovation. Ease of acquiring these properties is constrained by preexisting GRN architecture, which was overcome in our experimental system by both targeted and global network alterations. This work reveals the key properties that determine transcription factor evolvability, and as such, the evolution of GRNs.
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Affiliation(s)
- Matthew J. Shepherd
- Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath, United Kingdom
- Division of Evolution and Genomic Sciences, School of Biological Sciences, University of Manchester, Manchester, United Kingdom
| | - Aidan P. Pierce
- Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath, United Kingdom
| | - Tiffany B. Taylor
- Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath, United Kingdom
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3
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Huang S, Zhang X, Song Z, Rahman MU, Fan B. Transcriptional Profiling and Transposon Mutagenesis Study of the Endophyte Pantoea eucalypti FBS135 Adapting to Nitrogen Starvation. Int J Mol Sci 2023; 24:14282. [PMID: 37762583 PMCID: PMC10532344 DOI: 10.3390/ijms241814282] [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: 08/17/2023] [Revised: 09/12/2023] [Accepted: 09/18/2023] [Indexed: 09/29/2023] Open
Abstract
The research on plant endophytes has been drawing a lot of attention in recent years. Pantoea belongs to a group of endophytes with plant growth-promoting activity and has been widely used in agricultural fields. In our earlier studies, Pantoea eucalypti FBS135 was isolated from healthy-growing Pinus massoniana and was able to promote pine growth. P. eucalypti FBS135 can grow under extremely low nitrogen conditions. To understand the mechanism of the low-nitrogen tolerance of this bacterium, the transcriptome of FBS135 in the absence of nitrogen was examined in this study. We found that FBS135 actively regulates its gene expression in response to nitrogen deficiency. Nearly half of the number (4475) of genes in FBS135 were differentially expressed under this condition, mostly downregulated, while it significantly upregulated many transportation-associated genes and some nitrogen metabolism-related genes. In the downregulated genes, the ribosome pathway-related ones were significantly enriched. Meanwhile, we constructed a Tn5 transposon library of FBS135, from which four genes involved in low-nitrogen tolerance were screened out, including the gene for the host-specific protein J, RNA polymerase σ factor RpoS, phosphoribosamine-glycine ligase, and serine acetyltransferase. Functional analysis of the genes revealed their potential roles in the adaptation to nitrogen limitation. The results obtained in this work shed light on the mechanism of endophytes represented by P. eucalypti FBS135, at the overall transcriptional level, to an environmentally limited nitrogen supply and provided a basis for further investigation on this topic.
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Affiliation(s)
- Shengquan Huang
- Department of Forestry, Nanjing Forestry University, Nanjing 210037, China (M.U.R.)
| | - Xiuyu Zhang
- Department of Biology and Environment, Nanjing Forestry University, Nanjing 210037, China
| | - Zongwen Song
- Department of Forestry, Nanjing Forestry University, Nanjing 210037, China (M.U.R.)
| | - Mati Ur Rahman
- Department of Forestry, Nanjing Forestry University, Nanjing 210037, China (M.U.R.)
| | - Ben Fan
- Department of Forestry, Nanjing Forestry University, Nanjing 210037, China (M.U.R.)
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4
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Mitra R, Xu T, Chen GQ, Xiang H, Han J. An updated overview on the regulatory circuits of polyhydroxyalkanoates synthesis. Microb Biotechnol 2021; 15:1446-1470. [PMID: 34473895 PMCID: PMC9049629 DOI: 10.1111/1751-7915.13915] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 08/20/2021] [Accepted: 08/23/2021] [Indexed: 11/30/2022] Open
Abstract
Polyhydroxyalkanoates (PHA) are a promising and sustainable alternative to the petroleum‐based synthetic plastics. Regulation of PHA synthesis is receiving considerable importance as engineering the regulatory factors might help developing strains with improved PHA‐producing abilities. PHA synthesis is dedicatedly regulated by a number of regulatory networks. They tightly control the PHA content, granule size and their distribution in cells. Most PHA‐accumulating microorganisms have multiple regulatory networks that impart a combined effect on PHA metabolism. Among them, several factors ranging from global to specific regulators, have been identified and characterized till now. This review is an attempt to categorically summarize the diverse regulatory circuits that operate in some important PHA‐producing microorganisms. However, in several organisms, the detailed mechanisms involved in the regulation of PHA synthesis is not well‐explored and hence further research is needed. The information presented in this review might help researcher to identify the prevailing research gaps in PHA regulation.
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Affiliation(s)
- Ruchira Mitra
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,International College, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Tong Xu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Guo-Qiang Chen
- Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Hua Xiang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jing Han
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing, 100049, China
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5
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Duan N, Ma X, Cui H, Wang Z, Chai Z, Yan J, Li X, Feng Y, Cao Y, Jin Y, Bai F, Wu W, Rikihisa Y, Cheng Z. Insights into the mechanism regulating the differential expression of the P28-OMP outer membrane proteins in obligatory intracellular pathogen Ehrlichia chaffeensis. Emerg Microbes Infect 2021; 10:461-471. [PMID: 33660592 PMCID: PMC7971322 DOI: 10.1080/22221751.2021.1899054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Ehrlichia chaffeensis causes human monocytic ehrlichiosis (HME), which is one of the most prevalent, life-threatening emerging infectious zoonoses. The life cycle of E. chaffeensis includes ticks and mammals, in which E. chaffeensis proteins are expressed differentially contributing to bacterial survival and infection. Among the E. chaffeensis P28-OMP outer membrane proteins, OMP-1B and P28 are predominantly expressed in tick cells and mammalian macrophages, respectively. The mechanisms regulating this differential expression have not been comprehensively studied. Here, we demonstrate that the transcriptional regulators EcxR and Tr1 regulate the differential expression of omp-1B and p28 in E. chaffeensis. Recombinant E. chaffeensis Tr1 bound to the promoters of omp-1B and p28, and transactivated omp-1B and p28 promoter-EGFP fusion constructs in Escherichia coli. The consensus sequence of Tr1 binding motifs was AC/TTATA as determined with DNase I footprint assay. Tr1 showed a higher affinity towards the p28 promoter than the omp-1B promoter as determined with surface plasmon resonance. EcxR activated the tr1 expression in response to a temperature decrease. At 37°C low level of Tr1 activated the p28 expression. At 25°C high level of Tr1 activated the omp-1B expression, while repressing the p28 expression by binding to an additional site upstream of the p28 gene. Our data provide insights into a novel mechanism mediated by Tr1 regulating E. chaffeensis differential gene expression, which may aid in the development of new therapeutics for HME.
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Affiliation(s)
- Nan Duan
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Xiaohui Ma
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Heting Cui
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Zhexuan Wang
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Zhouyi Chai
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Jiaqi Yan
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Xiaoxiao Li
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Yingxing Feng
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Yu Cao
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Yongxin Jin
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Fang Bai
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Weihui Wu
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - Yasuko Rikihisa
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA
| | - Zhihui Cheng
- Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People's Republic of China
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6
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Jacoby RP, Succurro A, Kopriva S. Nitrogen Substrate Utilization in Three Rhizosphere Bacterial Strains Investigated Using Proteomics. Front Microbiol 2020; 11:784. [PMID: 32411116 PMCID: PMC7198800 DOI: 10.3389/fmicb.2020.00784] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 04/01/2020] [Indexed: 12/25/2022] Open
Abstract
Nitrogen metabolism in the rhizosphere microbiome plays an important role in mediating plant nutrition, particularly under low inputs of mineral fertilizers. However, there is relatively little mechanistic information about which genes and metabolic pathways are induced by rhizosphere bacterial strains to utilize diverse nitrogen substrates. Here we investigate nitrogen substrate utilization in three taxonomically diverse bacterial strains previously isolated from Arabidopsis roots. The three strains represent taxa that are consistently detected as core members of the plant microbiome: Pseudomonas, Streptomyces, and Rhizobium. We use phenotype microarrays to determine the nitrogen substrate preferences of these strains, and compare the experimental results vs. computational simulations of genome-scale metabolic network models obtained with EnsembleFBA. Results show that all three strains exhibit generalistic nitrogen substrate preferences, with substrate utilization being well predicted by EnsembleFBA. Using label-free quantitative proteomics, we document hundreds of proteins in each strain that exhibit differential abundance values following cultivation on five different nitrogen sources: ammonium, glutamate, lysine, serine, and urea. The proteomic response to these nitrogen sources was strongly strain-dependent, with lysine nutrition eliciting widespread protein-level changes in Pseudomonas sp. Root9, whereas Rhizobium sp. Root491 showed relatively stable proteome composition across different nitrogen sources. Our results give new protein-level information about the specific transporters and enzymes induced by diverse rhizosphere bacterial strains to utilize organic nitrogen substrates.
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Affiliation(s)
- Richard P. Jacoby
- Institute for Plant Sciences and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
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7
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Możejko-Ciesielska J, Mostek A. A 2D-DIGE-based proteomic analysis brings new insights into cellular responses of Pseudomonas putida KT2440 during polyhydroxyalkanoates synthesis. Microb Cell Fact 2019; 18:93. [PMID: 31138236 PMCID: PMC6537436 DOI: 10.1186/s12934-019-1146-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 05/22/2019] [Indexed: 11/15/2022] Open
Abstract
Background Polyhydroxyalkanoates (PHAs) have attracted much attention in recent years as natural alternatives to petroleum-based synthetic polymers that can be broadly used in many applications. Pseudomonas putida KT2440 is a metabolically versatile microorganism that is able to synthesize medium-chain-length PHAs (mcl-PHAs). The phenomena that drive mcl-PHAs synthesis and accumulation seems to be complex and are still poorly understood. Therefore, here we determine new insights into cellular responses of Pseudomonas putida KT2440 during biopolymers production using two-dimensional difference gel-electrophoresis (2D-DIGE) followed by MALDI TOF/TOF mass spectrometry. Results The maximum mcl-PHAs content in Pseudomonas putida KT2440 cells was 24% of cell dry weight (CDW) and was triggered by nitrogen depletion. Proteomic analysis allowed the detection of 150 and 131 protein spots differentially regulated at 24 h and 48 h relative to the cell growth stage (8 h), respectively. From those, we successfully identified 84 proteins that had altered expression at 24 h and 74 proteins at 48 h of the mcl-PHAs synthesis process. The protein–protein interactions network indicated that the majority of identified proteins were functionally linkage. The abundance of proteins involved in carbon metabolism were significantly decreased at 24 h and 48 h of the cultivations. Moreover, proteins associated with ATP synthesis were up-regulated suggesting that the enhanced energy metabolism was necessary for the mcl-PHAs accumulation. Furthermore, the induction of proteins involved in nitrogen metabolism, ribosome synthesis and transport was observed. Our results indicate that mcl-PHAs accumulated in the bacterial cells changed the protein abundance involved in stress response and cellular homeostasis. Conclusions The presented data allow us to investigate time-course proteome rearrangement in response to nitrogen limitation and biopolyesters accumulation. Our results have pointed out novel proteins that might take part in cellular responses of mcl-PHA-accumulated bacteria. The study provides an additional knowledge that could be helpful to improve the efficiency of the bioprocess and make it more economically feasible. Electronic supplementary material The online version of this article (10.1186/s12934-019-1146-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Justyna Możejko-Ciesielska
- Department of Microbiology and Mycology, Faculty of Biology and Biotechnology, University of Warmia and Mazury in Olsztyn, Oczapowskiego 1A, 10-719, Olsztyn, Poland.
| | - Agnieszka Mostek
- Department of Gamete and Embryo Biology, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences in Olsztyn, Tuwima 10, Olsztyn, Poland
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8
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Barroso R, García-Mauriño SM, Tomás-Gallardo L, Andújar E, Pérez-Alegre M, Santero E, Canosa I. The CbrB Regulon: Promoter dissection reveals novel insights into the CbrAB expression network in Pseudomonas putida. PLoS One 2018; 13:e0209191. [PMID: 30557364 PMCID: PMC6296734 DOI: 10.1371/journal.pone.0209191] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 11/30/2018] [Indexed: 11/18/2022] Open
Abstract
CbrAB is a high ranked global regulatory system exclusive of the Pseudomonads that responds to carbon limiting conditions. It has become necessary to define the particular regulon of CbrB and discriminate it from the downstream cascades through other regulatory components. We have performed in vivo binding analysis of CbrB in P. putida and determined that it directly controls the expression of at least 61 genes; 20% involved in regulatory functions, including the previously identified CrcZ and CrcY small regulatory RNAs. The remaining are porines or transporters (20%), metabolic enzymes (16%), activities related to protein translation (5%) and orfs of uncharacterised function (38%). Amongst the later, we have selected the operon PP2810-13 to make an exhaustive analysis of the CbrB binding sequences, together with those of crcZ and crcY. We describe the implication of three independent non-palindromic subsites with a variable spacing in three different targets; CrcZ, CrcY and operon PP2810-13 in the CbrAB activation. CbrB is a quite peculiar σN-dependent activator since it is barely dependent on phosphorylation for transcriptional activation. With the depiction of the precise contacts of CbrB with the DNA, the analysis of the multimerisation status and its dependence on other factors such as RpoN o IHF, we propose a model of transcriptional activation.
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Affiliation(s)
- Rocío Barroso
- Universidad Pablo de Olavide, Centro Andaluz de Biología del Desarrollo/ Consejo Superior de Investigaciones Científicas/ Junta de Andalucía, Seville, Spain
| | - Sofía M. García-Mauriño
- Universidad Pablo de Olavide, Centro Andaluz de Biología del Desarrollo/ Consejo Superior de Investigaciones Científicas/ Junta de Andalucía, Seville, Spain
| | | | - Eloísa Andújar
- Genomics unit, CABIMER/ CSIC/ Universidad de Sevilla/ Universidad Pablo de Olavide/ Junta de Andalucía, Seville, Spain
| | - Mónica Pérez-Alegre
- Genomics unit, CABIMER/ CSIC/ Universidad de Sevilla/ Universidad Pablo de Olavide/ Junta de Andalucía, Seville, Spain
| | - Eduardo Santero
- Universidad Pablo de Olavide, Centro Andaluz de Biología del Desarrollo/ Consejo Superior de Investigaciones Científicas/ Junta de Andalucía, Seville, Spain
| | - Inés Canosa
- Universidad Pablo de Olavide, Centro Andaluz de Biología del Desarrollo/ Consejo Superior de Investigaciones Científicas/ Junta de Andalucía, Seville, Spain
- * E-mail:
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9
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Mindt M, Walter T, Risse JM, Wendisch VF. Fermentative Production of N-Methylglutamate From Glycerol by Recombinant Pseudomonas putida. Front Bioeng Biotechnol 2018; 6:159. [PMID: 30474025 PMCID: PMC6237917 DOI: 10.3389/fbioe.2018.00159] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 10/16/2018] [Indexed: 12/02/2022] Open
Abstract
N-methylated amino acids are present in diverse biological molecules in bacteria, archaea and eukaryotes. There is an increasing interest in this molecular class of alkylated amino acids by the pharmaceutical and chemical industries. N-alkylated amino acids have desired functions such as higher proteolytic stability, enhanced membrane permeability and longer peptide half-lives, which are important for the peptide-based drugs, the so-called peptidomimetics. Chemical synthesis of N-methylated amino acids often is limited by incomplete stereoselectivity, over-alkylation or the use of hazardous chemicals. Here, we describe metabolic engineering of Pseudomonas putida KT2440 for the fermentative production of N-methylglutamate from simple carbon sources and monomethylamine. P. putida KT2440, which is generally recognized as safe and grows with glucose and the alternative feedstock glycerol as sole carbon and energy source, was engineered for the production of N-methylglutamate using heterologous enzymes from Methylobacterium extorquens. About 3.9 g L−1N-methylglutamate accumulated within 48 h in shake flask cultures with minimal medium containing monomethylamine and glycerol. A fed-batch cultivation process yielded a N-methylglutamate titer of 17.9 g L−1.
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Affiliation(s)
- Melanie Mindt
- Genetics of Prokaryotes, Faculty of Biology and CeBiTec, Bielefeld University, Bielefeld, Germany
| | - Tatjana Walter
- Genetics of Prokaryotes, Faculty of Biology and CeBiTec, Bielefeld University, Bielefeld, Germany
| | - Joe Max Risse
- Fermentation Technology, Technical Faculty and CeBiTec, Bielefeld University, Bielefeld, Germany
| | - Volker F Wendisch
- Genetics of Prokaryotes, Faculty of Biology and CeBiTec, Bielefeld University, Bielefeld, Germany
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10
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Mozejko-Ciesielska J, Pokoj T, Ciesielski S. Transcriptome remodeling of Pseudomonas putida KT2440 during mcl-PHAs synthesis: effect of different carbon sources and response to nitrogen stress. J Ind Microbiol Biotechnol 2018; 45:433-446. [PMID: 29736608 PMCID: PMC6028892 DOI: 10.1007/s10295-018-2042-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 04/27/2018] [Indexed: 01/15/2023]
Abstract
Bacterial response to environmental stimuli is essential for survival. In response to fluctuating environmental conditions, the physiological status of bacteria can change due to the actions of transcriptional regulatory machinery. The synthesis and accumulation of polyhydroxyalkanoates (PHAs) are one of the survival strategies in harsh environments. In this study, we used transcriptome analysis of Pseudomonas putida KT2440 to gain a genome-wide view of the mechanisms of environmental-friendly biopolymers accumulation under nitrogen-limiting conditions during conversion of metabolically different carbon sources (sodium gluconate and oleic acid). Transcriptomic data revealed that phaG expression is associated with medium-chain-length-PHAs' synthesis not only on sodium gluconate but also on oleic acid, suggesting that PhaG may play a role in this process, as well. Moreover, genes involved in the β-oxidation pathway were induced in the PHAs production phase when sodium gluconate was supplied as the only carbon and energy source. The transition from exponential growth to stationary phase caused a significant expression of genes involved in nitrogen metabolism, energy supply, and transport system. In this study, several molecular mechanisms, which drive mcl-PHAs synthesis, have been investigated. The identified genes may provide valuable information to improve the efficiency of this bioprocess and make it more economically feasible.
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Affiliation(s)
- Justyna Mozejko-Ciesielska
- Department of Microbiology and Mycology, Faculty of Biology and Biotechnology, University of Warmia and Mazury in Olsztyn, Oczapowskiego 1A, 10-719, Olsztyn, Poland.
| | - Tomasz Pokoj
- Department of Environmental Biotechnology, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland
| | - Slawomir Ciesielski
- Department of Environmental Biotechnology, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland
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Sacomboio ENM, Kim EYS, Ruchaud Correa HL, Bonato P, de Oliveira Pedrosa F, de Souza EM, Chubatsu LS, Müller-Santos M. The transcriptional regulator NtrC controls glucose-6-phosphate dehydrogenase expression and polyhydroxybutyrate synthesis through NADPH availability in Herbaspirillum seropedicae. Sci Rep 2017; 7:13546. [PMID: 29051509 PMCID: PMC5648810 DOI: 10.1038/s41598-017-12649-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 09/12/2017] [Indexed: 11/09/2022] Open
Abstract
The NTR system is the major regulator of nitrogen metabolism in Bacteria. Despite its broad and well-known role in the assimilation, biosynthesis and recycling of nitrogenous molecules, little is known about its role in carbon metabolism. In this work, we present a new facet of the NTR system in the control of NADPH concentration and the biosynthesis of molecules dependent on reduced coenzyme in Herbaspirillum seropedicae SmR1. We demonstrated that a ntrC mutant strain accumulated high levels of polyhydroxybutyrate (PHB), reaching levels up to 2-fold higher than the parental strain. In the absence of NtrC, the activity of glucose-6-phosphate dehydrogenase (encoded by zwf) increased by 2.8-fold, consequently leading to a 2.1-fold increase in the NADPH/NADP+ ratio. A GFP fusion showed that expression of zwf is likewise controlled by NtrC. The increase in NADPH availability stimulated the production of polyhydroxybutyrate regardless the C/N ratio in the medium. The mutant ntrC was more resistant to H2O2 exposure and controlled the propagation of ROS when facing the oxidative condition, a phenotype associated with the increase in PHB content.
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Affiliation(s)
- Euclides Nenga Manuel Sacomboio
- Department of Biochemistry and Molecular Biology, Laboratory of Nitrogen Fixation, Federal University of Paraná (UFPR), Curitiba, Brazil
| | - Edson Yu Sin Kim
- Department of Biochemistry and Molecular Biology, Laboratory of Nitrogen Fixation, Federal University of Paraná (UFPR), Curitiba, Brazil
| | - Henrique Leonardo Ruchaud Correa
- Department of Biochemistry and Molecular Biology, Laboratory of Nitrogen Fixation, Federal University of Paraná (UFPR), Curitiba, Brazil
| | - Paloma Bonato
- Department of Biochemistry and Molecular Biology, Laboratory of Nitrogen Fixation, Federal University of Paraná (UFPR), Curitiba, Brazil
| | - Fabio de Oliveira Pedrosa
- Department of Biochemistry and Molecular Biology, Laboratory of Nitrogen Fixation, Federal University of Paraná (UFPR), Curitiba, Brazil
| | - Emanuel Maltempi de Souza
- Department of Biochemistry and Molecular Biology, Laboratory of Nitrogen Fixation, Federal University of Paraná (UFPR), Curitiba, Brazil
| | - Leda Satie Chubatsu
- Department of Biochemistry and Molecular Biology, Laboratory of Nitrogen Fixation, Federal University of Paraná (UFPR), Curitiba, Brazil
| | - Marcelo Müller-Santos
- Department of Biochemistry and Molecular Biology, Laboratory of Nitrogen Fixation, Federal University of Paraná (UFPR), Curitiba, Brazil.
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12
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Fernández I, Cornaciu I, Carrica MDC, Uchikawa E, Hoffmann G, Sieira R, Márquez JA, Goldbaum FA. Three-Dimensional Structure of Full-Length NtrX, an Unusual Member of the NtrC Family of Response Regulators. J Mol Biol 2017; 429:1192-1212. [PMID: 28088479 DOI: 10.1016/j.jmb.2016.12.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 12/21/2016] [Accepted: 12/29/2016] [Indexed: 12/15/2022]
Abstract
Bacteria sense and adapt to environmental changes using two-component systems. These signaling pathways are formed by a histidine kinase that phosphorylates a response regulator (RR), which finally modulates the transcription of target genes. The bacterium Brucella abortus codes for a two-component system formed by the histidine kinase NtrY and the RR NtrX that participates in sensing low oxygen tension and generating an adaptive response. NtrX is a modular protein with REC, AAA+, and DNA-binding domains, an architecture that classifies it among the NtrC subfamily of RRs. However, it lacks the signature GAFTGA motif that is essential for activating transcription by the mechanism proposed for canonical members of this subfamily. In this article, we present the first crystal structure of full-length NtrX, which is also the first structure of a full-length NtrC-like RR with all the domains solved, showing that the protein is structurally similar to other members of the subfamily. We also report that NtrX binds nucleotides and the structures of the protein bound to ATP and ADP. Despite binding ATP, NtrX does not have ATPase activity and does not form oligomers in response to phosphorylation or nucleotide binding. We also identify a nucleotide sequence recognized by NtrX that allows it to bind to a promoter region that regulates its own transcription and to establish a negative feedback mechanism to modulate its expression. Overall, this article provides a detailed description of the NtrX RR and supports that it functions by a mechanism different to classical NtrC-like RRs.
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Affiliation(s)
- Ignacio Fernández
- Fundación Instituto Leloir, IIBBA-CONICET, Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
| | - Irina Cornaciu
- European Molecular Biology Laboratory (EMBL), Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | | | - Emiko Uchikawa
- European Molecular Biology Laboratory (EMBL), Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Guillaume Hoffmann
- European Molecular Biology Laboratory (EMBL), Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Rodrigo Sieira
- Fundación Instituto Leloir, IIBBA-CONICET, Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
| | - José Antonio Márquez
- European Molecular Biology Laboratory (EMBL), Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Fernando A Goldbaum
- Fundación Instituto Leloir, IIBBA-CONICET, Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina.
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13
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Svenningsen NB, Nicolaisen MH, Hansen HCB, de Lorenzo V, Nybroe O. Nitrogen regulation of the xyl genes of Pseudomonas putida mt-2 propagates into a significant effect of nitrate on m-xylene mineralization in soil. Microb Biotechnol 2016; 9:814-823. [PMID: 27561962 PMCID: PMC5072197 DOI: 10.1111/1751-7915.12404] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 07/18/2016] [Accepted: 07/22/2016] [Indexed: 11/29/2022] Open
Abstract
The nitrogen species available in the growth medium are key factors determining expression of xyl genes for biodegradation of aromatic compounds by Pseudomonas putida. Nitrogen compounds are frequently amended to promote degradation at polluted sites, but it remains unknown how regulation observed in the test tube is propagated into actual catabolism of, e.g. m‐xylene in soil, the natural habitat of this bacterium. To address this issue, we have developed a test‐tube‐to‐soil model system that exposes the end‐effects of remediation practices influencing gene expression of P. putida mt‐2. We found that NO3− compared with NH4+ had a stimulating effect on xyl gene expression in pure culture as well as in soil, and that this stimulation was translated into increased m‐xylene mineralization in soil. Furthermore, expression analysis of the nitrogen‐regulated genes amtB and gdhA allowed us to monitor nitrogen sensing status in both experimental systems. Hence, for nitrogen sources, regulatory patterns that emerge in soil reflect those observed in liquid cultures. The current study shows how distinct regulatory traits can lead to discrete environmental consequences; and it underpins that attempts to improve bioremediation by nitrogen amendment should integrate knowledge on their effects on growth and on catabolic gene regulation under natural conditions.
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Affiliation(s)
- Nanna B Svenningsen
- Section for Microbial Ecology and Biotechnology, Department of Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg C, Denmark
| | - Mette H Nicolaisen
- Section for Microbial Ecology and Biotechnology, Department of Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg C, Denmark
| | - Hans Christian B Hansen
- Section for Environmental Chemistry and Physics, Department of Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg C, Denmark
| | - Victor de Lorenzo
- Systems and Synthetic Biology Program, Centro Nacional de Biotecnología (CNB-CSIC), Madrid, 28049, Spain
| | - Ole Nybroe
- Section for Microbial Ecology and Biotechnology, Department of Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg C, Denmark.
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14
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Mechanism of Antiactivation at the Pseudomonas sp. Strain ADP σN-Dependent PatzT Promoter. Appl Environ Microbiol 2016; 82:4350-4362. [PMID: 27208099 DOI: 10.1128/aem.00906-16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 05/04/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED PatzT is an internal promoter of the atzRSTUVW operon that directs the synthesis of AtzT, AtzU, AtzV, and AtzW, components of an ABC-type cyanuric acid transport system. PatzT is σ(N) dependent, activated by the general nitrogen control regulator NtrC with the assistance of protein integration host factor (IHF), and repressed by the LysR-type transcriptional regulator (LTTR) AtzR. We have used a variety of in vivo and in vitro gene expression and protein-DNA interaction assays to assess the mechanisms underlying AtzR-dependent repression of PatzT Here, we show that repression only occurs when AtzR and NtrC interact simultaneously with the PatzT promoter region, indicating that AtzR acts as an antiactivator to antagonize activation by NtrC. Furthermore, repression requires precise rotational orientation of the AtzR and NtrC binding sites, strongly suggesting protein-protein interaction between the two proteins on the promoter region. Further exploration of the antiactivation mechanism showed that although AtzR-dependent repression occurs prior to open complex formation, AtzR does not alter the oligomerization state of NtrC or inhibit NtrC ATPase activity when bound to the PatzT promoter region. Taken together, these results strongly suggest that PatzT-bound AtzR interacts with NtrC to prevent the coupling of NtrC-mediated ATP hydrolysis with the remodeling of the interactions between E-σ(N) and PatzT that lead to open complex formation. IMPORTANCE Here, we describe a unique mechanism by which the regulatory protein AtzR prevents the activation of the σ(N)-dependent promoter PatzT Promoters of this family are always positively regulated, but there are a few examples of overlapping negative regulation. The mechanism described here is highly unconventional and involves an interaction between the repressor and activator proteins to prevent the action of the repressor protein on the RNA polymerase-promoter complex.
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15
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Valentini M, García-Mauriño SM, Pérez-Martínez I, Santero E, Canosa I, Lapouge K. Hierarchical management of carbon sources is regulated similarly by the CbrA/B systems in Pseudomonas aeruginosa and Pseudomonas putida. MICROBIOLOGY-SGM 2014; 160:2243-2252. [PMID: 25031426 DOI: 10.1099/mic.0.078873-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The CbrA/B system in pseudomonads is involved in the utilization of carbon sources and carbon catabolite repression (CCR) through the activation of the small RNAs crcZ in Pseudomonas aeruginosa, and crcZ and crcY in Pseudomonas putida. Interestingly, previous works reported that the CbrA/B system activity in P. aeruginosa PAO1 and P. putida KT2442 responded differently to the presence of different carbon sources, thus raising the question of the exact nature of the signal(s) detected by CbrA. Here, we demonstrated that the CbrA/B/CrcZ(Y) signal transduction pathway is similarly activated in the two Pseudomonas species. We show that the CbrA sensor kinase is fully interchangeable between the two species and, moreover, responds similarly to the presence of different carbon sources. In addition, a metabolomics analysis supported the hypothesis that CCR responds to the internal energy status of the cell, as the internal carbon/nitrogen ratio seems to determine CCR and non-CCR conditions. The strong difference found in the 2-oxoglutarate/glutamine ratio between CCR and non-CCR conditions points to the close relationship between carbon and nitrogen availability, or the relationship between the CbrA/B and NtrB/C systems, suggesting that both regulatory systems sense the same sort or interrelated signal.
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Affiliation(s)
- Martina Valentini
- Department of Fundamental Microbiology, University of Lausanne, 1015 Lausanne, Switzerland
| | - Sofía M García-Mauriño
- Centro Andaluz de Biología del Desarollo/CSIC/Universidad Pablo de Olavide, 41013 Seville, Spain
| | - Isabel Pérez-Martínez
- Centro Andaluz de Biología del Desarollo/CSIC/Universidad Pablo de Olavide, 41013 Seville, Spain
| | - Eduardo Santero
- Centro Andaluz de Biología del Desarollo/CSIC/Universidad Pablo de Olavide, 41013 Seville, Spain
| | - Inés Canosa
- Centro Andaluz de Biología del Desarollo/CSIC/Universidad Pablo de Olavide, 41013 Seville, Spain
| | - Karine Lapouge
- Department of Fundamental Microbiology, University of Lausanne, 1015 Lausanne, Switzerland
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16
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García-Mauriño SM, Pérez-Martínez I, Amador CI, Canosa I, Santero E. Transcriptional activation of the CrcZ and CrcY regulatory RNAs by the CbrB response regulator in Pseudomonas putida. Mol Microbiol 2013; 89:189-205. [PMID: 23692431 DOI: 10.1111/mmi.12270] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/17/2013] [Indexed: 11/30/2022]
Abstract
The CbrAB two-component system has been described as a high-ranked element in the regulatory hierarchy of Pseudomonas putida that controls a variety of metabolic and behavioural traits required for adaptation to changing environmental conditions. We show that the response regulatory protein CbrB, an activator of σ(N) -dependent promoters, directly controls the expression of the small RNAs CrcZ and CrcY in P. putida. These two RNAs sequester the protein Crc, which is a translational repressor of multiple pathways linked to carbon catabolite repression. We characterized the in vivo and in vitro activation by CbrB at both crcZ and crcY promoters, and identified new DNA sequences where the protein binds. IHF, a co-activator at many σ(N) -dependent promoters, also binds to the promoter regions and contributes to the activation of the sRNAs. CbrB phosphorylation is necessary at physiological activation conditions, but a higher dose of the protein allows in vitro transcriptional activation in its non-phosphorylated form. We also show there is some production of CrcY coming from an upstream promoter independent of CbrB. Thus, CbrAB constitute a global signal transduction pathway integrated in a higher regulatory network that also controls catabolite repression through the expression of the two regulatory RNAs CrcZ and CrcY.
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Affiliation(s)
- Sofía Muñoz García-Mauriño
- Centro Andaluz de Biología del Desarrollo, CSIC, Universidad Pablo de Olavide, Carretera de Utrera, Km. 1, 41013, Seville, Spain
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17
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Bauer S, Endres M, Lange M, Schmidt T, Schumbrutzki C, Sickmann A, Beier D. Novel function assignment to a member of the essential HP1043 response regulator family of epsilon-proteobacteria. Microbiology (Reading) 2013; 159:880-889. [DOI: 10.1099/mic.0.066548-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Susanne Bauer
- Theodor-Boveri-Institut für Biowissenschaften, Lehrstuhl für Mikrobiologie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Michelle Endres
- Theodor-Boveri-Institut für Biowissenschaften, Lehrstuhl für Mikrobiologie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Manuel Lange
- Theodor-Boveri-Institut für Biowissenschaften, Lehrstuhl für Mikrobiologie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Theresa Schmidt
- Theodor-Boveri-Institut für Biowissenschaften, Lehrstuhl für Mikrobiologie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Cornelia Schumbrutzki
- Leibnitz-Institut für Analytische Wissenschaften – ISAS – e.V., Otto-Hahn-Str. 6B, D-44227 Dortmund, Germany
| | - Albert Sickmann
- Leibnitz-Institut für Analytische Wissenschaften – ISAS – e.V., Otto-Hahn-Str. 6B, D-44227 Dortmund, Germany
| | - Dagmar Beier
- Theodor-Boveri-Institut für Biowissenschaften, Lehrstuhl für Mikrobiologie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
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18
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Duque E, de la Torre J, Bernal P, Molina-Henares MA, Alaminos M, Espinosa-Urgel M, Roca A, Fernández M, de Bentzmann S, Ramos JL. Identification of reciprocal adhesion genes in pathogenic and non-pathogenicPseudomonas. Environ Microbiol 2012; 15:36-48. [DOI: 10.1111/j.1462-2920.2012.02732.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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19
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Escapa IF, García JL, Bühler B, Blank LM, Prieto MA. The polyhydroxyalkanoate metabolism controls carbon and energy spillage in Pseudomonas putida. Environ Microbiol 2012; 14:1049-63. [PMID: 22225632 DOI: 10.1111/j.1462-2920.2011.02684.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The synthesis and degradation of polyhydroxyalkanoates (PHAs), the storage polymer of many bacteria, is linked to the operation of central carbon metabolism. To rationalize the impact of PHA accumulation on central carbon metabolism of the prototype bacterium Pseudomonas putida, we have revisited PHA production in quantitative physiology experiments in the wild-type strain vs. a PHA negative mutant growing under low nitrogen conditions. When octanoic acid was used as PHA precursor and as carbon and energy source, we have detected higher intracellular flux via acetyl-CoA in the mutant strain than in the wild type, which correlates with the stimulation of the TCA cycle and glyoxylate shunt observed on the transcriptional level. The mutant defective in carbon and energy storage spills the additional resources, releasing CO(2) instead of generating biomass. Hence, P. putida operates the metabolic network to optimally exploit available resources and channels excess carbon and energy to storage via PHA, without compromising growth. These findings demonstrate that the PHA metabolism plays a critical role in synchronizing global metabolism to availability of resources in PHA-producing microorganisms.
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Affiliation(s)
- I F Escapa
- Environmental Biology Department, Centro de Investigaciones Biológicas, CSIC, 28040 Madrid, Spain
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