1
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Subhadra B, Cao D, Jensen R, Caswell C, Inzana TJ. Identification and initial characterization of Hfq-associated sRNAs in Histophilus somni strain 2336. PLoS One 2023; 18:e0286158. [PMID: 37220152 DOI: 10.1371/journal.pone.0286158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 05/09/2023] [Indexed: 05/25/2023] Open
Abstract
Small RNAs (sRNA), in association with the global chaperone regulator Hfq, positively or negatively regulate gene expression in bacteria. For this study, Histophilus somni sRNAs that bind to Hfq were identified and then partially characterized. The Hfq-associated sRNAs in H. somni were isolated and identified by co-immunoprecipitation using anti-Hfq antibody, followed by sRNA sequencing. Sequence analysis of the sRNA samples identified 100 putative sRNAs, out of which 16 were present in pathogenic strain 2336, but not in non-pathogenic strain 129Pt. Bioinformatic analyses suggested that the sRNAs HS9, HS79, and HS97 could bind to many genes putatively involved in virulence/biofilm formation. Furthermore, multi-sequence alignment of the sRNA regions in the genome revealed that HS9 and HS97 could interact with sigma 54, which is a transcription factor linked to important bacterial traits, including motility, virulence, and biofilm formation. Northern blotting was used to determine the approximate size, abundance and any processing events attributed to the sRNAs. Selected sRNA candidates were confirmed to bind Hfq, as determined by electrophoretic mobility shift assays using sRNAs synthesized by in vitro transcription and recombinant Hfq. The exact transcriptional start site of the sRNA candidates was determined by RNA ligase-mediated rapid amplification of cDNA ends, followed by cloning and sequencing. This is the first investigation of H. somni sRNAs that show they may have important regulatory roles in virulence and biofilm formation.
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Affiliation(s)
- Bindu Subhadra
- College of Veterinary Medicine, Long Island University, Brookville, New York, United States of America
| | - Dianjun Cao
- College of Veterinary Medicine, Long Island University, Brookville, New York, United States of America
| | - Roderick Jensen
- College of Science, Virginia Tech, Blacksburg, VA, United States of America
| | - Clayton Caswell
- Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States of America
| | - Thomas J Inzana
- College of Veterinary Medicine, Long Island University, Brookville, New York, United States of America
- Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States of America
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2
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Haskett TL, Geddes BA, Paramasivan P, Green P, Chitnavis S, Mendes MD, Jorrín B, Knights HE, Bastholm TR, Ramsay JP, Oldroyd GED, Poole PS. Rhizopine biosensors for plant-dependent control of bacterial gene expression. Environ Microbiol 2023; 25:383-396. [PMID: 36428208 PMCID: PMC10107442 DOI: 10.1111/1462-2920.16288] [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: 09/28/2022] [Accepted: 11/23/2022] [Indexed: 11/27/2022]
Abstract
Engineering signalling between plants and microbes could be exploited to establish host-specificity between plant-growth-promoting bacteria and target crops in the environment. We previously engineered rhizopine-signalling circuitry facilitating exclusive signalling between rhizopine-producing (RhiP) plants and model bacterial strains. Here, we conduct an in-depth analysis of rhizopine-inducible expression in bacteria. We characterize two rhizopine-inducible promoters and explore the bacterial host-range of rhizopine biosensor plasmids. By tuning the expression of rhizopine uptake genes, we also construct a new biosensor plasmid pSIR05 that has minimal impact on host cell growth in vitro and exhibits markedly improved stability of expression in situ on RhiP barley roots compared to the previously described biosensor plasmid pSIR02. We demonstrate that a sub-population of Azorhizobium caulinodans cells carrying pSIR05 can sense rhizopine and activate gene expression when colonizing RhiP barley roots. However, these bacteria were mildly defective for colonization of RhiP barley roots compared to the wild-type parent strain. This work provides advancement towards establishing more robust plant-dependent control of bacterial gene expression and highlights the key challenges remaining to achieve this goal.
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Affiliation(s)
| | - Barney A Geddes
- Department of Plant Sciences, University of Oxford, Oxford, UK
- Department of Microbiological Sciences, North Dakota State University, Fargo, North Dakota, USA
| | | | - Patrick Green
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Samir Chitnavis
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Marta D Mendes
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Beatriz Jorrín
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | | | - Tahlia R Bastholm
- Curtin Medical School and Curtin Health Innovation Research Institute, Curtin University, Perth, Western Australia, Australia
| | - Joshua P Ramsay
- Curtin Medical School and Curtin Health Innovation Research Institute, Curtin University, Perth, Western Australia, Australia
| | - Giles E D Oldroyd
- Sainsbury Laboratory, University of Cambridge, Cambridge, UK
- Crop Science Centre, University of Cambridge, Cambridge, UK
| | - Philip S Poole
- Department of Plant Sciences, University of Oxford, Oxford, UK
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3
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Li Y, Liu B, Chen J, Yue X. Carbon-Nitrogen-Sulfur-Related Microbial Taxa and Genes Maintained the Stability of Microbial Communities in Coals. ACS OMEGA 2022; 7:22671-22681. [PMID: 35811862 PMCID: PMC9260939 DOI: 10.1021/acsomega.2c02126] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/08/2022] [Indexed: 06/03/2023]
Abstract
Coal microbes are the predominant form of life in the subsurface ecosystem, which play a vital role in biogeochemical cycles. However, the systematic information about carbon-nitrogen-sulfur (C-N-S)-related microbial communities in coal seams is limited. In this study, 16S rRNA gene data from a total of 93 microbial communities in coals were collected for meta-analysis. The results showed that 718 functional genera were related to the C-N-S cycle, wherein N2 fixation, denitrification, and C degradation groups dominated in relative abundance, Chao1 richness, Shannon diversity, and niche width. Genus Pseudomonas having the most C-N-S-related functions showed the highest relative abundance, and genus Herbaspirillum with a higher abundance participated in C degradation, CH4 oxidation, N2 fixation, ammoxidation, and denitrification. Such Herbaspirillum was a core genus in the co-occurrence network of microbial prokaryotes and showed higher levels in weight degree, betweenness centrality, and eigenvector centrality. In addition, most of the methanogens could fix N2 and dominated in the N2 fixation groups. Among them, genera Methanoculleus and Methanosaeta showed higher levels in the betweenness centrality index. In addition, the genus Clostridium was linked to the methanogenesis co-occurrence network module. In parallel, the S reduction gene was present in the highest total relative abundance of genes, followed by the C degradation and the denitrification genes, and S genes (especially cys genes) were the main genes linked to the co-occurrence network of the C-N-S-related genes. In summary, this study strengthened our knowledge regarding the C-N-S-related coal microbial communities, which is of great significance in understanding the microbial ecology and geochemical cycle of coals.
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Affiliation(s)
- Yang Li
- State
Key Laboratory of Mining Response and Disaster Prevention and Control
in Deep Coal Mines, Anhui University of
Science & Technology, Huainan, Anhui 232001, China
- Institute
of Energy, Hefei Comprehensive National Science Center, Hefei, Anhui 230031, China
| | - Bingjun Liu
- State
Key Laboratory of Mining Response and Disaster Prevention and Control
in Deep Coal Mines, Anhui University of
Science & Technology, Huainan, Anhui 232001, China
- Institute
of Energy, Hefei Comprehensive National Science Center, Hefei, Anhui 230031, China
| | - Jian Chen
- Coal
Mining National Engineering and Technology Research Institute, Huainan, Anhui 232001, China
| | - Xuelian Yue
- Jinneng
Holding Shanxi Science and Technology Research Institute Co. LTD., Taiyuan, Shanxi 030600, China
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4
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Li Y, Liu B, Tu Q, Xue S, Liu X, Wu Z, An S, Chen J, Wang Z. The ecological roles of assembling genomes for Bacillales and Clostridiales in coal seams. FEMS Microbiol Lett 2022; 369:6605329. [PMID: 35687414 DOI: 10.1093/femsle/fnac053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 03/11/2022] [Accepted: 06/08/2022] [Indexed: 11/13/2022] Open
Abstract
Biogenic coalbed methane is produced by biological processes mediated by synergistic interactions of microbial complexes in coal seams. However, the ecological role of functional bacteria in biogenic coalbed methane remains poorly understood. Here, we studied the metagenome assembled genomes (MAGs) of Bacillales and Clostridiales from coal seams, revealing further expansion of hydrogen and acetogen producers involved in organic matter decomposition. In this study, Bacillales and Clostridiales were dominant orders (91.85 ± 0.94%) in cultured coal seams, and a total of 16 MAGs from 6 families, including Bacillus, Paenibacillus, Staphylococcus, Anaerosalibacter, Hungatella and Paeniclostridium, were reconstructed. These microbial groups possessed multiple metabolic pathways (glycolysis/gluconeogenesis, pentose phosphate, β-oxidation, TCA cycle, assimilatory sulfate reduction, nitrogen metabolism and encoding hydrogenase) that provided metabolic substrates (acetate and/or H2) for the methanogenic processes. Therein, the hydrogenase-encoding gene and hydrogenase maturation factors were merely found in all the Clostridiales MAGs. β-oxidation was the main metabolic pathway involved in short-chain fatty acid degradation and acetate production, and most of these pathways were detected and exhibited different operon structures in Bacillales MAGs. In addition, assimilatory sulfate reduction and nitrogen metabolism processes were also detected in some MAGs, and these processes were also closely related to acetate production and/or organic matter degradation according to their operon structures and metabolic pathways. In summary, this study enabled a better understanding of the ecological roles of Bacillales and Clostridiales in biogenic methane in coal seams based on a combination of bioinformatic techniques.
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Affiliation(s)
- Yang Li
- State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, Anhui University of Science & Technology, Huainan, Anhui province, China
| | - Bingjun Liu
- Institute of Energy, Hefei Comprehensive National Science Center, Anhui, Hefei, 230031, China
| | - Qingyi Tu
- State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, Anhui University of Science & Technology, Huainan, Anhui province, China
| | - Sheng Xue
- State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, Anhui University of Science & Technology, Huainan, Anhui province, China
| | - Xiaozhou Liu
- State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, Anhui University of Science & Technology, Huainan, Anhui province, China
| | - Zhijian Wu
- Coal Mining National Engineering and Technology Research Institute, Huainan, Anhui Province, China
| | - Shikai An
- Coal Mining National Engineering and Technology Research Institute, Huainan, Anhui Province, China
| | - Jian Chen
- Coal Mining National Engineering and Technology Research Institute, Huainan, Anhui Province, China
| | - Zhigen Wang
- China National Coal Xinji Group Corporation, Huainan, Anhui Province, China
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5
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Ferreira EGC, Gomes DF, Delai CV, Barreiros MAB, Grange L, Rodrigues EP, Henning LMM, Barcellos FG, Hungria M. Revealing potential functions of hypothetical proteins induced by genistein in the symbiosis island of Bradyrhizobium japonicum commercial strain SEMIA 5079 (= CPAC 15). BMC Microbiol 2022; 22:122. [PMID: 35513812 PMCID: PMC9069715 DOI: 10.1186/s12866-022-02527-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 04/11/2022] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Bradyrhizobium japonicum strain SEMIA 5079 (= CPAC 15) is a nitrogen-fixing symbiont of soybean broadly used in commercial inoculants in Brazil. Its genome has about 50% of hypothetical (HP) protein-coding genes, many in the symbiosis island, raising questions about their putative role on the biological nitrogen fixation (BNF) process. This study aimed to infer functional roles to 15 HP genes localized in the symbiosis island of SEMIA 5079, and to analyze their expression in the presence of a nod-gene inducer. RESULTS A workflow of bioinformatics tools/databases was established and allowed the functional annotation of the HP genes. Most were enzymes, including transferases in the biosynthetic pathways of cobalamin, amino acids and secondary metabolites that may help in saprophytic ability and stress tolerance, and hydrolases, that may be important for competitiveness, plant infection, and stress tolerance. Putative roles for other enzymes and transporters identified are discussed. Some HP proteins were specific to the genus Bradyrhizobium, others to specific host legumes, and the analysis of orthologues helped to predict roles in BNF. CONCLUSIONS All 15 HP genes were induced by genistein and high induction was confirmed in five of them, suggesting major roles in the BNF process.
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Affiliation(s)
- Everton Geraldo Capote Ferreira
- Londrina State University (UEL), Celso Garcia Cid Road (PR 445), km 380, CEP 86057-970 Londrina, PR Brazil
- Embrapa Soja, Rodovia Carlos João Strass, C.P. 231, CEP 86001-970 Londrina, PR Brazil
| | | | - Caroline Vanzzo Delai
- Federal University of Paraná (UFPR), Estrada dos Pioneiros 2153, CEP 85950-000 Palotina, PR Brazil
| | | | - Luciana Grange
- Federal University of Paraná (UFPR), Estrada dos Pioneiros 2153, CEP 85950-000 Palotina, PR Brazil
| | - Elisete Pains Rodrigues
- Londrina State University (UEL), Celso Garcia Cid Road (PR 445), km 380, CEP 86057-970 Londrina, PR Brazil
| | | | - Fernando Gomes Barcellos
- Londrina State University (UEL), Celso Garcia Cid Road (PR 445), km 380, CEP 86057-970 Londrina, PR Brazil
| | - Mariangela Hungria
- Londrina State University (UEL), Celso Garcia Cid Road (PR 445), km 380, CEP 86057-970 Londrina, PR Brazil
- Embrapa Soja, Rodovia Carlos João Strass, C.P. 231, CEP 86001-970 Londrina, PR Brazil
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6
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Wang J, Huang JJ, Lynch I. Seasonal and short-term variations of bacteria and pathogenic bacteria on road deposited sediments. ENVIRONMENTAL RESEARCH 2022; 204:111903. [PMID: 34454932 DOI: 10.1016/j.envres.2021.111903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/13/2021] [Accepted: 08/16/2021] [Indexed: 06/13/2023]
Abstract
The bacteria (including pathogenic bacteria) attached to road deposited sediments (RDS) may interrelate with the microbe in the atmosphere, soil and water through resuspension and wash-off, and is of great significance to human and ecological health. However, the characteristics of bacterial communities with different time scale on RDS were unknown to dates. Climate change prolonged the dry days between rain events in many areas, making the varied trend of bacterial communities might be more significant in short term. This study revealed the characteristics of bacterial communities on RDS in urban and suburban areas through seasonal and daily scale. The correlations between other factors (land use, particle size, and chemical components) and the bacterial communities were also analyzed. It was found that the season showed a higher association with the bacterial community diversity than land use and particle size in urban areas. The bacterial community diversity increased substantially throughout the short-term study period (41 days) and the variation of dominant bacteria could be fitted by quadratic function in suburbs. In addition, urbanization notably increased the bacterial community diversity, while the potential pathogenic bacteria were more abundant in the suburban areas, coarse RDS (>75 μm), and in spring. The chemical components on RDS showed special correlations with the relative abundance of dominant bacteria. The research findings would fill the knowledge gap on RDS bacterial communities and be helpful for the future research on the assembly process of bacterial communities.
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Affiliation(s)
- Jingshu Wang
- College of Environmental Science and Engineering/Sino-Canada Joint R&D Centre on Water and Environmental Safety, Nankai University, 300071, Tianjin, China
| | - Jinhui Jeanne Huang
- College of Environmental Science and Engineering/Sino-Canada Joint R&D Centre on Water and Environmental Safety, Nankai University, 300071, Tianjin, China.
| | - Iseult Lynch
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom
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7
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Allsopp LP, Collins ACZ, Hawkins E, Wood TE, Filloux A. RpoN/Sfa2-dependent activation of the Pseudomonas aeruginosa H2-T6SS and its cognate arsenal of antibacterial toxins. Nucleic Acids Res 2021; 50:227-243. [PMID: 34928327 PMCID: PMC8855297 DOI: 10.1093/nar/gkab1254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 11/26/2021] [Accepted: 12/16/2021] [Indexed: 12/13/2022] Open
Abstract
Pseudomonas aeruginosa uses three type six secretion systems
(H1-, H2- and H3-T6SS) to manipulate its environment, subvert host cells and for
microbial competition. These T6SS machines are loaded with a variety of
effectors/toxins, many being associated with a specific VgrG. How P.
aeruginosa transcriptionally coordinates the main T6SS clusters and
the multiple vgrG islands spread through the genome is unknown.
Here we show an unprecedented level of control with RsmA repressing most known
T6SS-related genes. Moreover, each of the H2- and H3-T6SS clusters encodes a
sigma factor activator (SFA) protein
called, Sfa2 and Sfa3, respectively. SFA proteins are enhancer binding proteins
necessary for the sigma factor RpoN. Using a combination of RNA-seq, ChIP-seq
and molecular biology approaches, we demonstrate that RpoN coordinates the T6SSs
of P. aeruginosa by activating the H2-T6SS but repressing the
H1- and H3-T6SS. Furthermore, RpoN and Sfa2 control the expression of the
H2-T6SS-linked VgrGs and their effector arsenal to enable very effective
interbacterial killing. Sfa2 is specific as Sfa3 from the H3-T6SS cannot
complement loss of Sfa2. Our study further delineates the regulatory mechanisms
that modulate the deployment of an arsenal of T6SS effectors likely enabling
P. aeruginosa to adapt to a range of environmental
conditions.
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Affiliation(s)
- Luke P Allsopp
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK.,National Heart and Lung Institute, Imperial College London, London, UK
| | - Alice C Z Collins
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Eleanor Hawkins
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - Thomas E Wood
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - Alain Filloux
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
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8
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Li K, Wu G, Liao Y, Zeng Q, Wang H, Liu F. RpoN1 and RpoN2 play different regulatory roles in virulence traits, flagellar biosynthesis, and basal metabolism in Xanthomonas campestris. MOLECULAR PLANT PATHOLOGY 2020; 21:907-922. [PMID: 32281725 PMCID: PMC7280030 DOI: 10.1111/mpp.12938] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 03/18/2020] [Accepted: 03/18/2020] [Indexed: 05/08/2023]
Abstract
Homologous regulatory factors are widely present in bacteria, but whether homologous regulators synergistically or differentially regulate different biological functions remains mostly unknown. Here, we report that the homologous regulators RpoN1 and RpoN2 of the plant pathogen Xanthomonas campestris pv. campestris (Xcc) play different regulatory roles with respect to virulence traits, flagellar biosynthesis, and basal metabolism. RpoN2 directly regulated Xcc fliC and fliQ to modulate flagellar synthesis in X. campestris, thus affecting the swimming motility of X. campestris. Mutation of rpoN2 resulted in reduced production of biofilms and extracellular polysaccharides in Xcc. These defects may together cause reduced virulence of the rpoN2 mutant against the host plant. Moreover, we demonstrated that RpoN1 could regulate branched-chain fatty acid production and modulate the synthesis of diffusible signal factor family quorum sensing signals. Although RpoN1 and RpoN2 are homologues, the regulatory roles and biological functions of these proteins were not interchangeable. Overall, our report provides new insights into the two different molecular roles that form the basis for the transcriptional specialization of RpoN homologues.
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Affiliation(s)
- Kaihuai Li
- College of Plant ProtectionNanjing Agricultural UniversityNanjingChina
| | - Guichun Wu
- Institute of Plant ProtectionJiangsu Academy of Agricultural SciencesNanjingChina
| | - Yuling Liao
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural OrganismsCollege of Life SciencesSouth China Agricultural UniversityGuangzhouChina
| | - Quan Zeng
- Department of Plant Pathology and EcologyThe Connecticut Agricultural Experiment StationNew HavenCTUSA
| | - Haihong Wang
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural OrganismsCollege of Life SciencesSouth China Agricultural UniversityGuangzhouChina
| | - Fengquan Liu
- College of Plant ProtectionNanjing Agricultural UniversityNanjingChina
- Institute of Plant ProtectionJiangsu Academy of Agricultural SciencesNanjingChina
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9
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Tikariha H, Purohit HJ. Assembling a genome for novel nitrogen-fixing bacteria with capabilities for utilization of aromatic hydrocarbons. Genomics 2018; 111:1824-1830. [PMID: 30552976 DOI: 10.1016/j.ygeno.2018.12.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 10/08/2018] [Accepted: 12/07/2018] [Indexed: 11/28/2022]
Abstract
Metagenome from refinery wastewater treatment plant running under nitrogen stress was analyzed for mining of novel aromatic hydrocarbon-degrading bacteria. The sequence data were assembled using metaspade followed by binning using the Metabat tool to assemble genome; where coverage and depth were calculated using bowtie and samtools. The analysis picked a novel genome belonging to family Bradyrhizobiaceae, identified based on 16S rDNA gene which was supported by CheckM and Kraken analysis. Using RAST, the assembled genome showed the capabilities for nitrogen fixation with the utilization of multiple hydrocarbon substrates with 14 different types of oxygenases as mapped by Minpath. An additional genetic feature like genes for stress and resistance towards heavy metals and antibiotic suggested that the genome has gone through the rigorous process of adaptation. If such bacteria could be cultivated then it will open the broad window of bioremediation strategies under nitrogen stress environment.
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Affiliation(s)
- Hitesh Tikariha
- Environmental Biotechnology and Genomics Division, CSIR-National Environmental Engineering Research Institute, Nehru Marg, Nagpur 440020, India
| | - Hemant J Purohit
- Environmental Biotechnology and Genomics Division, CSIR-National Environmental Engineering Research Institute, Nehru Marg, Nagpur 440020, India.
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10
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Fazli M, Rybtke M, Steiner E, Weidel E, Berthelsen J, Groizeleau J, Bin W, Zhi BZ, Yaming Z, Kaever V, Givskov M, Hartmann RW, Eberl L, Tolker-Nielsen T. Regulation of Burkholderia cenocepacia biofilm formation by RpoN and the c-di-GMP effector BerB. Microbiologyopen 2017; 6. [PMID: 28419759 PMCID: PMC5552954 DOI: 10.1002/mbo3.480] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 03/01/2017] [Accepted: 03/07/2017] [Indexed: 11/25/2022] Open
Abstract
Knowledge about the molecular mechanisms that are involved in the regulation of biofilm formation is essential for the development of biofilm‐control measures. It is well established that the nucleotide second messenger cyclic diguanosine monophosphate (c‐di‐GMP) is a positive regulator of biofilm formation in many bacteria, but more knowledge about c‐di‐GMP effectors is needed. We provide evidence that c‐di‐GMP, the alternative sigma factor RpoN (σ54), and the enhancer‐binding protein BerB play a role in biofilm formation of Burkholderia cenocepacia by regulating the production of a biofilm‐stabilizing exopolysaccharide. Our findings suggest that BerB binds c‐di‐GMP, and activates RpoN‐dependent transcription of the berA gene coding for a c‐di‐GMP‐responsive transcriptional regulator. An increased level of the BerA protein in turn induces the production of biofilm‐stabilizing exopolysaccharide in response to high c‐di‐GMP levels. Our findings imply that the production of biofilm exopolysaccharide in B. cenocepacia is regulated through a cascade involving two consecutive transcription events that are both activated by c‐di‐GMP. This type of regulation may allow tight control of the expenditure of cellular resources.
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Affiliation(s)
- Mustafa Fazli
- Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.,Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Morten Rybtke
- Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Elisabeth Steiner
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Elisabeth Weidel
- Department of Drug Design and Optimization, Helmholtz Institute for Pharmaceutical Research Saarland, Saarbrücken, Germany
| | - Jens Berthelsen
- Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Julie Groizeleau
- Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Wu Bin
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Boo Zhao Zhi
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Zhang Yaming
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Volkhard Kaever
- Research Core Unit Metabolomics, Institute of Pharmacology, Hannover Medical School, Hannover, Germany
| | - Michael Givskov
- Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
| | - Rolf W Hartmann
- Department of Drug Design and Optimization, Helmholtz Institute for Pharmaceutical Research Saarland, Saarbrücken, Germany
| | - Leo Eberl
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Tim Tolker-Nielsen
- Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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11
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Tian R, Heiden S, Osman WAM, Ardley JK, James EK, Gollagher MM, Tiwari R, Seshadri R, Kyrpides NC, Reeve WG. Evolution of a multi-step phosphorelay signal transduction system in Ensifer: recruitment of the sigma factor RpoN and a novel enhancer-binding protein triggers acid-activated gene expression. Mol Microbiol 2016; 103:829-844. [PMID: 27935141 DOI: 10.1111/mmi.13592] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/28/2016] [Indexed: 11/29/2022]
Abstract
Most Ensifer strains are comparatively acid sensitive, compromising their persistence in low pH soils. In the acid-tolerant strain Ensifer medicae WSM419, the acid-activated expression of lpiA is essential for enhancing survival in lethal acidic conditions. Here we characterise a multi-step phosphorelay signal transduction pathway consisting of TcsA, TcrA, FsrR, RpoN and its cognate enhancer-binding protein EbpA, which is required for the induction of lpiA and the downstream acvB gene. The fsrR, tcrA, tcsA and rpoN genes were constitutively expressed, whereas lpiA and acvB were strongly acid-induced. RACE mapping revealed that lpiA/acvB were co-transcribed as an operon from an RpoN promoter. In most Ensifer species, lpiA/acvB is located on the chromosome and the sequence upstream of lpiA lacks an RpoN-binding site. Nearly all Ensifer meliloti strains completely lack ebpA, tcrA, tcsA and fsrR regulatory loci. In contrast, E. medicae strains have lpiA/acvB and ebpA/tcrA/tcsA/fsrR co-located on the pSymA megaplasmid, with lpiA/acvB expression coupled to an RpoN promoter. Here we provide a model for the expression of lpiA/acvB in E. medicae. This unique acid-activated regulatory system provides insights into an evolutionary process which may assist the adaptation of E. medicae to acidic environmental niches.
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Affiliation(s)
- Rui Tian
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, 6150, Australia
| | - Stephan Heiden
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, 6150, Australia
| | - Wan A M Osman
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, 6150, Australia
| | - Julie K Ardley
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, 6150, Australia
| | - Euan K James
- The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK
| | - Margaret M Gollagher
- Curtin University Sustainability Policy Institute, Curtin University, Bentley, WA, Australia
| | - Ravi Tiwari
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, 6150, Australia
| | | | | | - Wayne G Reeve
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, 6150, Australia
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Ceizel Borella G, Lagares A, Valverde C. Expression of the Sinorhizobium meliloti small RNA gene mmgR is controlled by the nitrogen source. FEMS Microbiol Lett 2016; 363:fnw069. [PMID: 27010014 DOI: 10.1093/femsle/fnw069] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/2016] [Indexed: 01/30/2023] Open
Abstract
Small non-coding regulatory RNAs (sRNAs) are key players in post-transcriptional regulation of gene expression. Hundreds of sRNAs have been identified in Sinorhizobium meliloti, but their biological function remains unknown for most of them. In this study, we characterized the expression pattern of the gene encoding the 77-nt sRNA MmgR in S. meliloti strain 2011. A chromosomal transcriptional reporter fusion (PmmgR-gfp) showed that the mmgR promoter is active along different stages of the interaction with alfalfa roots. In pure cultures, PmmgR-gfp activity paralleled the sRNA abundance indicating that mmgR expression is primarily controlled at the level of transcriptional initiation. PmmgR-gfp activity was higher during growth in rhizobial defined medium (RDM) than in TY medium. Furthermore, PmmgR-gfp was induced at 60 min after shifting growing cells from TY to RDM medium, i.e. shorter than the cell doubling time. In defined RDM medium containing NO3 (-), both PmmgR-gfp and MmgR level were repressed by the addition of tryptone or single amino acids, suggesting that mmgR expression depends on the cellular nitrogen (N) status. In silico analysis failed to detect conserved motifs upstream the promoter RNA polymerase binding site, but revealed a strongly conserved motif centered at -28 that may be linked to the observed regulatory pattern by the N source.
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Affiliation(s)
- Germán Ceizel Borella
- Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal B1876BXD, Buenos Aires, Argentina
| | - Antonio Lagares
- Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal B1876BXD, Buenos Aires, Argentina
| | - Claudio Valverde
- Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal B1876BXD, Buenos Aires, Argentina
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Succinic Semialdehyde Promotes Prosurvival Capability of Agrobacterium tumefaciens. J Bacteriol 2016; 198:930-40. [PMID: 26755630 DOI: 10.1128/jb.00373-15] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 12/10/2015] [Indexed: 01/25/2023] Open
Abstract
UNLABELLED Succinic semialdehyde (SSA), an important metabolite of γ-aminobutyric acid (GABA), is a ligand of the repressor AttJ regulating the expression of the attJ-attKLM gene cluster in the plant pathogen Agrobacterium tumefaciens. While the response of A. tumefaciens to GABA and the function of attKLM have been extensively studied, genetic and physiological responses of A. tumefaciens to SSA remain unknown. In combination with microarray and genetic approaches, this study sets out to explore new roles of the SSA-AttJKLM regulatory mechanism during bacterial infection. The results showed that SSA plays a key role in regulation of several bacterial activities, including C4-dicarboxylate utilization, nitrate assimilation, and resistance to oxidative stress. Interestingly, while the SSA relies heavily on the functional AttKLM in mediating nitrate assimilation and oxidative stress resistance, the compound could regulate utilization of C4-dicarboxylates independent of AttJKLM. We further provide evidence that SSA controls C4-dicarboxylate utilization through induction of an SSA importer and that disruption of attKLM attenuates the tumorigenicity of A. tumefaciens. Taken together, these findings indicate that SSA could be a potent plant signal which, together with AttKLM, plays a vital role in promoting the bacterial prosurvival abilities during infection. IMPORTANCE Agrobacterium tumefaciens is a plant pathogen causing crown gall diseases and has been well known as a powerful tool for plant genetic engineering. During the long history of microbe-host interaction, A. tumefaciens has evolved the capabilities of recognition and response to plant-derived chemical metabolites. Succinic semialdehyde (SSA) is one such metabolite. Previous results have demonstrated that SSA functions to activate a quorum-quenching mechanism and thus to decrease the level of quorum-sensing signals, thereby avoiding the elicitation of a plant defense. Here, we studied the effect of SSA on gene expression at a genome-wide level and reported that SSA also promotes bacterial survival during infection. These findings provide a new insight on the biological significance of chemical signaling between agrobacteria and plant hosts.
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Unraveling the universe of small RNA regulators in the legume symbiont Sinorhizobium meliloti. Symbiosis 2015. [DOI: 10.1007/s13199-015-0345-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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15
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Peng Q, Wang G, Liu G, Zhang J, Song F. Identification of metabolism pathways directly regulated by sigma(54) factor in Bacillus thuringiensis. Front Microbiol 2015; 6:407. [PMID: 26029175 PMCID: PMC4428206 DOI: 10.3389/fmicb.2015.00407] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 04/19/2015] [Indexed: 11/13/2022] Open
Abstract
Sigma(54) (σ(54)) regulates nitrogen and carbon utilization in bacteria. Promoters that are σ(54)-dependent are highly conserved and contain short sequences located at the -24 and -12 positions upstream of the transcription initiation site. σ(54) requires regulatory proteins known as bacterial enhancer-binding proteins (bEBPs) to activate gene transcription. We show that σ(54) regulates the capacity to grow on various nitrogen sources using a Bacillus thuringiensis HD73 mutant lacking the sigL gene encoding σ(54) (ΔsigL). A 2-fold-change cutoff and a false discovery rate cutoff of P < 0.05 were used to analyze the DNA microarray data, which revealed 255 genes that were downregulated and 121 that were upregulated in the ΔsigL mutant relative to the wild-type HD73 strain. The σ(54) regulon (stationary phase) was characterized by DNA microarray, bioinformatics, and functional assay; 16 operons containing 47 genes were identified whose promoter regions contain the conserved -12/-24 element and whose transcriptional activities were abolished or reduced in the ΔsigL mutant. Eight σ(54)-dependent transcriptional bEBPs were found in the Bt HD73 genome, and they regulated nine σ(54)-dependent promoters. The metabolic pathways activated by σ(54) in this process have yet to be identified in Bacillus thuringiensis; nonetheless, the present analysis of the σ(54) regulon provides a better understanding of the physiological roles of σ factors in bacteria.
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Affiliation(s)
- Qi Peng
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences Beijing, China
| | - Guannan Wang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences Beijing, China
| | - Guiming Liu
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences Beijing, China
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences Beijing, China
| | - Fuping Song
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences Beijing, China
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σ54-Dependent Response to Nitrogen Limitation and Virulence in Burkholderia cenocepacia Strain H111. Appl Environ Microbiol 2015; 81:4077-89. [PMID: 25841012 DOI: 10.1128/aem.00694-15] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 03/31/2015] [Indexed: 11/20/2022] Open
Abstract
Members of the genus Burkholderia are versatile bacteria capable of colonizing highly diverse environmental niches. In this study, we investigated the global response of the opportunistic pathogen Burkholderia cenocepacia H111 to nitrogen limitation at the transcript and protein expression levels. In addition to a classical response to nitrogen starvation, including the activation of glutamine synthetase, PII proteins, and the two-component regulatory system NtrBC, B. cenocepacia H111 also upregulated polyhydroxybutyrate (PHB) accumulation and exopolysaccharide (EPS) production in response to nitrogen shortage. A search for consensus sequences in promoter regions of nitrogen-responsive genes identified a σ(54) consensus sequence. The mapping of the σ(54) regulon as well as the characterization of a σ(54) mutant suggests an important role of σ(54) not only in control of nitrogen metabolism but also in the virulence of this organism.
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Ronneau S, Moussa S, Barbier T, Conde-Álvarez R, Zuniga-Ripa A, Moriyon I, Letesson JJ. Brucella, nitrogen and virulence. Crit Rev Microbiol 2014; 42:507-25. [PMID: 25471320 DOI: 10.3109/1040841x.2014.962480] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The brucellae are α-Proteobacteria causing brucellosis, an important zoonosis. Although multiplying in endoplasmic reticulum-derived vacuoles, they cause no cell death, suggesting subtle but efficient use of host resources. Brucellae are amino-acid prototrophs able to grow with ammonium or use glutamate as the sole carbon-nitrogen source in vitro. They contain more than twice amino acid/peptide/polyamine uptake genes than the amino-acid auxotroph Legionella pneumophila, which multiplies in a similar vacuole, suggesting a different nutritional strategy. During these two last decades, many mutants of key actors in nitrogen metabolism (transporters, enzymes, regulators, etc.) have been described to be essential for full virulence of brucellae. Here, we review the genomic and experimental data on Brucella nitrogen metabolism and its connection with virulence. An analysis of various aspects of this metabolism (transport, assimilation, biosynthesis, catabolism, respiration and regulation) has highlighted differences and similarities in nitrogen metabolism with other α-Proteobacteria. Together, these data suggest that, during their intracellular life cycle, the brucellae use various nitrogen sources for biosynthesis, catabolism and respiration following a strategy that requires prototrophy and a tight regulation of nitrogen use.
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Affiliation(s)
| | - Simon Moussa
- a UNamur, URBM 61 rue de Bruxelles , Namur , Belgium and
| | | | - Raquel Conde-Álvarez
- b Departamento de Microbiología , Edificio de Investigación, Universidad de Navarra , Pamplona , Spain
| | - Amaia Zuniga-Ripa
- b Departamento de Microbiología , Edificio de Investigación, Universidad de Navarra , Pamplona , Spain
| | - Ignacio Moriyon
- b Departamento de Microbiología , Edificio de Investigación, Universidad de Navarra , Pamplona , Spain
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Shi M, Gao T, Ju L, Yao Y, Gao H. Effects of FlrBC on flagellar biosynthesis of Shewanella oneidensis. Mol Microbiol 2014; 93:1269-83. [PMID: 25074236 DOI: 10.1111/mmi.12731] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/24/2014] [Indexed: 11/27/2022]
Abstract
As a most conserved complex molecular machine made up of a large number of structural subunits, the flagellum is under tight regulation by hierarchical arrangements. Although variations in polar flagellar systems are found, most of them are restricted to multiple-copy components, such as flagellins and stators. Therefore, these features are regarded to be peripheral relative to the comprehensive conservation. In this study, however, we present evidence to show that the difference in highly conserved polar flagellar systems can be surprisingly profound, even at the heart of the classical regulatory hierarchy. In Gram-negative Shewanella oneidensis, two-component system FlrBC, whose counterpart is essential for flagellar biosynthesis and motility by directly controlling expression of class III genes in polarly flagellated bacteria such as Vibrio cholerae, is dispensable for the process. The system directly controls expression of the flaA gene, encoding a flagellin of weak motility. We further show that the ratio of two flagellins, FlaA and FlaB, determines motility of a flagellum. More strikingly, overproduction of FlrC results in a peritrichously multi-flagellated phenotype, and FlrC is likely to function as an activator in its unphosphorylated form for transcription of the flaA gene, contrasting the previously characterized counterpart.
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Affiliation(s)
- Miaomiao Shi
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, 310058, Zhejiang, China; Key Laboratory for Agro-Microbial Research and Utilization, Hangzhou, 310058, Zhejiang, China
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19
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Gomes DF, da Silva Batista JS, Rolla AAP, da Silva LP, Bloch C, Galli-Terasawa LV, Hungria M. Proteomic analysis of free-living Bradyrhizobium diazoefficiens: highlighting potential determinants of a successful symbiosis. BMC Genomics 2014; 15:643. [PMID: 25086822 PMCID: PMC4287336 DOI: 10.1186/1471-2164-15-643] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 07/25/2014] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Strain CPAC 7 (=SEMIA 5080) was recently reclassified into the new species Bradyrhizobium diazoefficiens; due to its outstanding efficiency in fixing nitrogen, it has been used in commercial inoculants for application to crops of soybean [Glycine max (L.) Merr.] in Brazil and other South American countries. Although the efficiency of B. diazoefficiens inoculant strains is well recognized, few data on their protein expression are available. RESULTS We provided a two-dimensional proteomic reference map of CPAC 7 obtained under free-living conditions, with the successful identification of 115 spots, representing 95 different proteins. The results highlighted the expression of molecular determinants potentially related to symbiosis establishment (e.g. inositol monophosphatase, IMPase), fixation of atmospheric nitrogen (N2) (e.g. NifH) and defenses against stresses (e.g. chaperones). By using bioinformatic tools, it was possible to attribute probable functions to ten hypothetical proteins. For another ten proteins classified as "NO related COG" group, we analyzed by RT-qPCR the relative expression of their coding-genes in response to the nodulation-gene inducer genistein. Six of these genes were up-regulated, including blr0227, which may be related to polyhydroxybutyrate (PHB) biosynthesis and competitiveness for nodulation. CONCLUSIONS The proteomic map contributed to the identification of several proteins of B. diazoefficiens under free-living conditions and our approach-combining bioinformatics and gene-expression assays-resulted in new information about unknown genes that might play important roles in the establishment of the symbiosis with soybean.
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Affiliation(s)
| | | | | | | | | | | | - Mariangela Hungria
- Embrapa Soja, Embrapa Soja, C,P, 231, 86001-970 Londrina, Paraná, Brazil.
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Sarkar A, Reinhold-Hurek B. Transcriptional profiling of nitrogen fixation and the role of NifA in the diazotrophic endophyte Azoarcus sp. strain BH72. PLoS One 2014; 9:e86527. [PMID: 24516534 PMCID: PMC3916325 DOI: 10.1371/journal.pone.0086527] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 12/09/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The model endophyte Azoarcus sp. strain BH72 is known to contribute fixed nitrogen to its host Kallar grass and also expresses nitrogenase genes endophytically in rice seedlings. Availability of nitrogen is a signal regulating the transcription of nitrogenase genes. Therefore, we analysed global transcription in response to differences in the nitrogen source. METHODOLOGY/PRINCIPAL FINDINGS A DNA microarray, comprising 70-mer oligonucleotides representing 3989 open reading frames of the genome of strain BH72, was used for transcriptome studies. Transcription profiles of cells grown microaerobically on N2 versus ammonium were compared. Expression of 7.2% of the genes was significantly up-regulated, and 5.8% down-regulated upon N2 fixation, respectively. A parallel genome-wide prediction of σ(54)-type promoter elements mapped to the upstream region of 38 sequences of which 36 were modulated under the N2 response. In addition to modulation of genes related to N2 fixation, the expressions of gene clusters that might be related to plant-microbe interaction and of several transcription factors were significantly enhanced. While comparing under N2-fixation conditions the transcriptome of wild type with a nifLA(-) insertion mutant, NifA being the essential transcriptional activator for nif genes, 24.5% of the genome was found to be affected in expression. A genome-wide prediction of 29 NifA binding sequences matched to 25 of the target genes whose expression was differential during microarray analysis, some of which were putatively negatively regulated by NifA. For selected genes, differential expression was corroborated by real time RT-PCR studies. CONCLUSION/SIGNIFICANCE Our data suggest that life under conditions of nitrogen fixation is an important part of the lifestyle of strain BH72 in roots, as a wide range of genes far beyond the nif regulon is modulated. Moreover, the NifA regulon in strain BH72 appears to encompass a wider range of cellular functions beyond the regulation of nif genes.
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Affiliation(s)
- Abhijit Sarkar
- University of Bremen, Faculty of Biology, Department of Microbe-Plant Interactions, Bremen, Germany
| | - Barbara Reinhold-Hurek
- University of Bremen, Faculty of Biology, Department of Microbe-Plant Interactions, Bremen, Germany
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21
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Provorov NA, Chuklina J, Vorobyov NI, Onishchuk OP, Simarov BV. Factor analysis of interactions between alfalfa nodule bacteria (Sinorhizobium meliloti) genes that regulate symbiotic nitrogen fixation. RUSS J GENET+ 2013. [DOI: 10.1134/s1022795413030150] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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22
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Sallet E, Roux B, Sauviac L, Jardinaud MF, Carrère S, Faraut T, de Carvalho-Niebel F, Gouzy J, Gamas P, Capela D, Bruand C, Schiex T. Next-generation annotation of prokaryotic genomes with EuGene-P: application to Sinorhizobium meliloti 2011. DNA Res 2013; 20:339-54. [PMID: 23599422 PMCID: PMC3738161 DOI: 10.1093/dnares/dst014] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The availability of next-generation sequences of transcripts from prokaryotic organisms offers the opportunity to design a new generation of automated genome annotation tools not yet available for prokaryotes. In this work, we designed EuGene-P, the first integrative prokaryotic gene finder tool which combines a variety of high-throughput data, including oriented RNA-Seq data, directly into the prediction process. This enables the automated prediction of coding sequences (CDSs), untranslated regions, transcription start sites (TSSs) and non-coding RNA (ncRNA, sense and antisense) genes. EuGene-P was used to comprehensively and accurately annotate the genome of the nitrogen-fixing bacterium Sinorhizobium meliloti strain 2011, leading to the prediction of 6308 CDSs as well as 1876 ncRNAs. Among them, 1280 appeared as antisense to a CDS, which supports recent findings that antisense transcription activity is widespread in bacteria. Moreover, 4077 TSSs upstream of protein-coding or non-coding genes were precisely mapped providing valuable data for the study of promoter regions. By looking for RpoE2-binding sites upstream of annotated TSSs, we were able to extend the S. meliloti RpoE2 regulon by ∼3-fold. Altogether, these observations demonstrate the power of EuGene-P to produce a reliable and high-resolution automatic annotation of prokaryotic genomes.
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Affiliation(s)
- Erika Sallet
- INRA, Laboratoire des Interactions Plantes-Microorganismes-LIPM, UMR 441, Castanet-Tolosan F-31326, France
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Schlüter JP, Reinkensmeier J, Barnett MJ, Lang C, Krol E, Giegerich R, Long SR, Becker A. Global mapping of transcription start sites and promoter motifs in the symbiotic α-proteobacterium Sinorhizobium meliloti 1021. BMC Genomics 2013; 14:156. [PMID: 23497287 PMCID: PMC3616915 DOI: 10.1186/1471-2164-14-156] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 02/12/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Sinorhizobium meliloti is a soil-dwelling α-proteobacterium that possesses a large, tripartite genome and engages in a nitrogen fixing symbiosis with its plant hosts. Although much is known about this important model organism, global characterization of genetic regulatory circuits has been hampered by a lack of information about transcription and promoters. RESULTS Using an RNAseq approach and RNA populations representing 16 different growth and stress conditions, we comprehensively mapped S. meliloti transcription start sites (TSS). Our work identified 17,001 TSS that we grouped into six categories based on the genomic context of their transcripts: mRNA (4,430 TSS assigned to 2,657 protein-coding genes), leaderless mRNAs (171), putative mRNAs (425), internal sense transcripts (7,650), antisense RNA (3,720), and trans-encoded sRNAs (605). We used this TSS information to identify transcription factor binding sites and putative promoter sequences recognized by seven of the 15 known S. meliloti σ factors σ70, σ54, σH1, σH2, σE1, σE2, and σE9). Altogether, we predicted 2,770 new promoter sequences, including 1,302 located upstream of protein coding genes and 722 located upstream of antisense RNA or trans-encoded sRNA genes. To validate promoter predictions for targets of the general stress response σ factor, RpoE2 (σE2), we identified rpoE2-dependent genes using microarrays and confirmed TSS for a subset of these by 5' RACE mapping. CONCLUSIONS By identifying TSS and promoters on a global scale, our work provides a firm foundation for the continued study of S. meliloti gene expression with relation to gene organization, σ factors and other transcription factors, and regulatory RNAs.
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Affiliation(s)
- Jan-Philip Schlüter
- Institute of Biology III, Faculty of Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
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Sullivan JT, Brown SD, Ronson CW. The NifA-RpoN regulon of Mesorhizobium loti strain R7A and its symbiotic activation by a novel LacI/GalR-family regulator. PLoS One 2013; 8:e53762. [PMID: 23308282 PMCID: PMC3538637 DOI: 10.1371/journal.pone.0053762] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 12/04/2012] [Indexed: 11/19/2022] Open
Abstract
Mesorhizobium loti is the microsymbiont of Lotus species, including the model legume L. japonicus. M. loti differs from other rhizobia in that it contains two copies of the key nitrogen fixation regulatory gene nifA, nifA1 and nifA2, both of which are located on the symbiosis island ICEMlSym(R7A). M. loti R7A also contains two rpoN genes, rpoN1 located on the chromosome outside of ICEMlSym(R7A) and rpoN2 that is located on ICEMlSym(R7A). The aims of the current work were to establish how nifA expression was activated in M. loti and to characterise the NifA-RpoN regulon. The nifA2 and rpoN2 genes were essential for nitrogen fixation whereas nifA1 and rpoN1 were dispensable. Expression of nifA2 was activated, possibly in response to an inositol derivative, by a novel regulator of the LacI/GalR family encoded by the fixV gene located upstream of nifA2. Other than the well-characterized nif/fix genes, most NifA2-regulated genes were not required for nitrogen fixation although they were strongly expressed in nodules. The NifA-regulated nifZ and fixU genes, along with nifQ which was not NifA-regulated, were required in M. loti for a fully effective symbiosis although they are not present in some other rhizobia. The NifA-regulated gene msi158 that encodes a porin was also required for a fully effective symbiosis. Several metabolic genes that lacked NifA-regulated promoters were strongly expressed in nodules in a NifA2-dependent manner but again mutants did not have an overt symbiotic phenotype. In summary, many genes encoded on ICEMlSym(R7A) were strongly expressed in nodules but not free-living rhizobia, but were not essential for symbiotic nitrogen fixation. It seems likely that some of these genes have functional homologues elsewhere in the genome and that bacteroid metabolism may be sufficiently plastic to adapt to loss of certain enzymatic functions.
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Affiliation(s)
- John T. Sullivan
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Steven D. Brown
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Clive W. Ronson
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- * E-mail:
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Bastiat B, Sauviac L, Picheraux C, Rossignol M, Bruand C. Sinorhizobium meliloti sigma factors RpoE1 and RpoE4 are activated in stationary phase in response to sulfite. PLoS One 2012; 7:e50768. [PMID: 23226379 PMCID: PMC3511301 DOI: 10.1371/journal.pone.0050768] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 10/24/2012] [Indexed: 12/02/2022] Open
Abstract
Rhizobia are soil bacteria able to establish a nitrogen-fixing symbiosis with legume plants. Both in soil and in planta, rhizobia spend non-growing periods resembling the stationary phase of in vitro-cultured bacteria. The primary objective of this work was to better characterize gene regulation in this biologically relevant growth stage in Sinorhizobium meliloti. By a tap-tag/mass spectrometry approach, we identified five sigma factors co-purifying with the RNA polymerase in stationary phase: the general stress response regulator RpoE2, the heat shock sigma factor RpoH2, and three extra-cytoplasmic function sigma factors (RpoE1, RpoE3 and RpoE4) belonging to the poorly characterized ECF26 subgroup. We then showed that RpoE1 and RpoE4 i) are activated upon metabolism of sulfite-generating compounds (thiosulfate and taurine), ii) display overlapping regulatory activities, iii) govern a dedicated sulfite response by controlling expression of the sulfite dehydrogenase SorT, iv) are activated in stationary phase, likely as a result of endogenous sulfite generation during bacterial growth. We showed that SorT is required for optimal growth of S. meliloti in the presence of sulfite, suggesting that the response governed by RpoE1 and RpoE4 may be advantageous for bacteria in stationary phase either by providing a sulfite detoxification function or by contributing to energy production through sulfite respiration. This paper therefore reports the first characterization of ECF26 sigma factors, the first description of sigma factors involved in control of sulphur metabolism, and the first indication that endogenous sulfite may act as a signal for regulation of gene expression upon entry of bacteria in stationary phase.
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Affiliation(s)
- Bénédicte Bastiat
- INRA, Laboratoire des Interactions Plantes-Microorganismes, UMR441, Castanet-Tolosan, France
- Centre National de la Recherche Scientifique, Laboratoire des Interactions Plantes-Microorganismes, UMR2594, Castanet-Tolosan, France
| | - Laurent Sauviac
- INRA, Laboratoire des Interactions Plantes-Microorganismes, UMR441, Castanet-Tolosan, France
- Centre National de la Recherche Scientifique, Laboratoire des Interactions Plantes-Microorganismes, UMR2594, Castanet-Tolosan, France
| | - Carole Picheraux
- Fédération de Recherche 3450, Agrobiosciences, Interactions et Biodiversités, Plateforme Protéomique Génopole Toulouse Midi-Pyrénées, Institut de Pharmacologie et de Biologie Structurale, Centre National de la Recherche Scientifique, Toulouse, France
- Université Paul Sabatier, Université de Toulouse, Toulouse, France
| | - Michel Rossignol
- Fédération de Recherche 3450, Agrobiosciences, Interactions et Biodiversités, Plateforme Protéomique Génopole Toulouse Midi-Pyrénées, Institut de Pharmacologie et de Biologie Structurale, Centre National de la Recherche Scientifique, Toulouse, France
- Université Paul Sabatier, Université de Toulouse, Toulouse, France
| | - Claude Bruand
- INRA, Laboratoire des Interactions Plantes-Microorganismes, UMR441, Castanet-Tolosan, France
- Centre National de la Recherche Scientifique, Laboratoire des Interactions Plantes-Microorganismes, UMR2594, Castanet-Tolosan, France
- * E-mail:
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Romeo A, Sonnleitner E, Sorger-Domenigg T, Nakano M, Eisenhaber B, Bläsi U. Transcriptional regulation of nitrate assimilation in Pseudomonas aeruginosa occurs via transcriptional antitermination within the nirBD–PA1779–cobA operon. Microbiology (Reading) 2012; 158:1543-1552. [DOI: 10.1099/mic.0.053850-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Alessandra Romeo
- Max F. Perutz Laboratories, Department of Microbiology, Immunobiology and Genetics, University of Vienna, Dr. Bohrgasse 9/4, 1030 Vienna, Austria
| | - Elisabeth Sonnleitner
- Max F. Perutz Laboratories, Department of Microbiology, Immunobiology and Genetics, University of Vienna, Dr. Bohrgasse 9/4, 1030 Vienna, Austria
| | - Theresa Sorger-Domenigg
- Max F. Perutz Laboratories, Department of Microbiology, Immunobiology and Genetics, University of Vienna, Dr. Bohrgasse 9/4, 1030 Vienna, Austria
| | - Masayuki Nakano
- Max F. Perutz Laboratories, Department of Microbiology, Immunobiology and Genetics, University of Vienna, Dr. Bohrgasse 9/4, 1030 Vienna, Austria
| | - Birgit Eisenhaber
- Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street, #07-01 Matrix, 138671 Singapore
| | - Udo Bläsi
- Max F. Perutz Laboratories, Department of Microbiology, Immunobiology and Genetics, University of Vienna, Dr. Bohrgasse 9/4, 1030 Vienna, Austria
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Fumeaux C, Bakkou N, Kopcińska J, Golinowski W, Westenberg DJ, Müller P, Perret X. Functional analysis of the nifQdctA1y4vGHIJ operon of Sinorhizobium fredii strain NGR234 using a transposon with a NifA-dependent read-out promoter. MICROBIOLOGY-SGM 2011; 157:2745-2758. [PMID: 21719545 DOI: 10.1099/mic.0.049999-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Rhizobia are a disparate collection of soil bacteria capable of reducing atmospheric nitrogen in symbiosis with legumes (Fix phenotype). Synthesis of the nitrogenase and its accessory components is under the transcriptional control of the key regulator NifA and is generally restricted to the endosymbiotic forms of rhizobia known as bacteroids. Amongst studied rhizobia, Sinorhizobium fredii strain NGR234 has the remarkable ability to fix nitrogen in association with more than 130 species in 73 legume genera that form either determinate, indeterminate or aeschynomenoid nodules. Hence, NGR234 is a model organism to study nitrogen fixation in association with a variety of legumes. The symbiotic plasmid pSfrNGR234a carries more than 50 genes that are under the transcriptional control of NifA. To facilitate the functional analysis of NifA-regulated genes a new transposable element, TnEKm-PwA, was constructed. This transposon combines the advantages of in vitro mutagenesis of cloned DNA fragments with a conditional read-out promoter from NGR234 (PwA) that reinitiates NifA-dependent transcription downstream of transposition sites. To test the characteristics of the new transposon, the nifQdctA1y4vGHIJ operon was mutated using either the Omega interposon or TnEKm-PwA. The symbiotic phenotypes on various hosts as well as the transcriptional characteristics of these mutants were analysed in detail and compared with the ineffective (Fix(-)) phenotype of strain NGRΔnifA, which lacks a functional copy of nifA. De novo transcription from inserted copies of TnEKm-PwA inside bacteroids was confirmed by qRT-PCR. Unexpectedly, polar mutants in dctA1 and nifQ were Fix(+) on all of the hosts tested, indicating that none of the six genes of the nifQ operon of NGR234 is essential for symbiotic nitrogen fixation on plants that form nodules of either determinate or indeterminate types.
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Affiliation(s)
- Coralie Fumeaux
- University of Geneva, Sciences III, Department of Botany and Plant Biology, Microbiology Unit, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - Nadia Bakkou
- University of Geneva, Sciences III, Department of Botany and Plant Biology, Microbiology Unit, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - Joanna Kopcińska
- Department of Botany, Faculty of Agriculture and Biology, Warsaw University of Life Sciences, ul. Nowoursynowska 159, 02-776 Warsaw, Poland
| | - Wladyslav Golinowski
- Department of Botany, Faculty of Agriculture and Biology, Warsaw University of Life Sciences, ul. Nowoursynowska 159, 02-776 Warsaw, Poland
| | - David J Westenberg
- Department of Biological Sciences, Missouri University of Science and Technology, 105A Schrenk Hall, 400 West 11th Street, Rolla, 65409-1120 MO, USA
| | - Peter Müller
- Fachbereich Biologie/Zellbiologie, Philipps Universität Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Xavier Perret
- University of Geneva, Sciences III, Department of Botany and Plant Biology, Microbiology Unit, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
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Yu LJ, Wu JR, Zheng ZY, Zhan XB, Lin CC. Changes of Curdlan Biosynthesis and Nitrogenous Compounds Utilization Characterized in ntrC Mutant of Agrobacterium sp. ATCC 31749. Curr Microbiol 2011; 63:60-7. [DOI: 10.1007/s00284-011-9942-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 04/18/2011] [Indexed: 10/18/2022]
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da Silva Neto JF, Koide T, Gomes SL, Marques MV. Global gene expression under nitrogen starvation in Xylella fastidiosa: contribution of the σ54 regulon. BMC Microbiol 2010; 10:231. [PMID: 20799976 PMCID: PMC3224663 DOI: 10.1186/1471-2180-10-231] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Accepted: 08/28/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Xylella fastidiosa, a Gram-negative fastidious bacterium, grows in the xylem of several plants causing diseases such as citrus variegated chlorosis. As the xylem sap contains low concentrations of amino acids and other compounds, X. fastidiosa needs to cope with nitrogen limitation in its natural habitat. RESULTS In this work, we performed a whole-genome microarray analysis of the X. fastidiosa nitrogen starvation response. A time course experiment (2, 8 and 12 hours) of cultures grown in defined medium under nitrogen starvation revealed many differentially expressed genes, such as those related to transport, nitrogen assimilation, amino acid biosynthesis, transcriptional regulation, and many genes encoding hypothetical proteins. In addition, a decrease in the expression levels of many genes involved in carbon metabolism and energy generation pathways was also observed. Comparison of gene expression profiles between the wild type strain and the rpoN null mutant allowed the identification of genes directly or indirectly induced by nitrogen starvation in a σ54-dependent manner. A more complete picture of the σ54 regulon was achieved by combining the transcriptome data with an in silico search for potential σ54-dependent promoters, using a position weight matrix approach. One of these σ54-predicted binding sites, located upstream of the glnA gene (encoding glutamine synthetase), was validated by primer extension assays, confirming that this gene has a σ54-dependent promoter. CONCLUSIONS Together, these results show that nitrogen starvation causes intense changes in the X. fastidiosa transcriptome and some of these differentially expressed genes belong to the σ54 regulon.
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Affiliation(s)
- José F da Silva Neto
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Prof. Lineu Prestes 1374, 05508-000 São Paulo, SP, Brazil
| | - Tie Koide
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, SP, Brazil
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Av. dos Bandeirantes 3900, 14049-900 Ribeirão Preto, SP, Brasil
| | - Suely L Gomes
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, SP, Brazil
| | - Marilis V Marques
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Prof. Lineu Prestes 1374, 05508-000 São Paulo, SP, Brazil
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Characterization of the NifA-RpoN regulon in Rhizobium etli in free life and in symbiosis with Phaseolus vulgaris. Appl Environ Microbiol 2010; 76:4510-20. [PMID: 20453139 DOI: 10.1128/aem.02007-09] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The NifA-RpoN complex is a master regulator of the nitrogen fixation genes in alphaproteobacteria. Based on the complete Rhizobium etli genome sequence, we constructed an R. etli CFN42 oligonucleotide (70-mer) microarray and utilized this tool, reverse transcription (RT)-PCR analysis (transcriptomics), proteomics, and bioinformatics to decipher the NifA-RpoN regulon under microaerobic conditions (free life) and in symbiosis with bean plants. The R. etli NifA-RpoN regulon was determined to contain 78 genes, including the genes involved in nitrogen fixation, and the analyses revealed 42 new NifA-RpoN-dependent genes. More importantly, this study demonstrated that the NifA-RpoN regulon is composed of genes and proteins that have very diverse functions, that play fundamental and previously less appreciated roles in regulating the normal physiology of the cell, and that have important functions in providing adequate conditions for efficient nitrogen fixation in symbiosis. The R. etli NifA-RpoN regulon defined here has some components in common with other NifA-RpoN regulons described previously, but the vast majority of the components have been found only in the R. etli regulon, suggesting that they have a specific role in this bacterium and particular requirements during nitrogen fixation compared with other symbiotic bacterial models.
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Koechler S, Cleiss-Arnold J, Proux C, Sismeiro O, Dillies MA, Goulhen-Chollet F, Hommais F, Lièvremont D, Arsène-Ploetze F, Coppée JY, Bertin PN. Multiple controls affect arsenite oxidase gene expression in Herminiimonas arsenicoxydans. BMC Microbiol 2010; 10:53. [PMID: 20167112 PMCID: PMC2848651 DOI: 10.1186/1471-2180-10-53] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2009] [Accepted: 02/18/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Both the speciation and toxicity of arsenic are affected by bacterial transformations, i.e. oxidation, reduction or methylation. These transformations have a major impact on environmental contamination and more particularly on arsenic contamination of drinking water. Herminiimonas arsenicoxydans has been isolated from an arsenic- contaminated environment and has developed various mechanisms for coping with arsenic, including the oxidation of As(III) to As(V) as a detoxification mechanism. RESULTS In the present study, a differential transcriptome analysis was used to identify genes, including arsenite oxidase encoding genes, involved in the response of H. arsenicoxydans to As(III). To get insight into the molecular mechanisms of this enzyme activity, a Tn5 transposon mutagenesis was performed. Transposon insertions resulting in a lack of arsenite oxidase activity disrupted aoxR and aoxS genes, showing that the aox operon transcription is regulated by the AoxRS two-component system. Remarkably, transposon insertions were also identified in rpoN coding for the alternative N sigma factor (sigma54) of RNA polymerase and in dnaJ coding for the Hsp70 co-chaperone. Western blotting with anti-AoxB antibodies and quantitative RT-PCR experiments allowed us to demonstrate that the rpoN and dnaJ gene products are involved in the control of arsenite oxidase gene expression. Finally, the transcriptional start site of the aoxAB operon was determined using rapid amplification of cDNA ends (RACE) and a putative -12/-24 sigma54-dependent promoter motif was identified upstream of aoxAB coding sequences. CONCLUSION These results reveal the existence of novel molecular regulatory processes governing arsenite oxidase expression in H. arsenicoxydans. These data are summarized in a model that functionally integrates arsenite oxidation in the adaptive response to As(III) in this microorganism.
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Affiliation(s)
- Sandrine Koechler
- UMR7156 Génétique Moléculaire, Génomique et Microbiologie, CNRS Université de Strasbourg, 28 rue Goethe, 67000 Strasbourg, France
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Zhao K, Liu M, Burgess RR. Promoter and regulon analysis of nitrogen assimilation factor, sigma54, reveal alternative strategy for E. coli MG1655 flagellar biosynthesis. Nucleic Acids Res 2009; 38:1273-83. [PMID: 19969540 PMCID: PMC2831329 DOI: 10.1093/nar/gkp1123] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Bacteria core RNA polymerase (RNAP) must associate with a σ factor to recognize promoter sequences. Promoters recognized by the σ54 (or σN) associated RNA polymerase are unique in having conserved positions around −24 and −12 nucleotides upstream from the transcriptional start site. Using DNA microarrays representing the entire Escherichia coli genome and promoter validation approaches, we identify 40 in vivo targets of σ54, the nitrogen assimilation σ factor, and estimate that there are 70 σ54 promoters in total. Immunoprecipitation assays have been performed to further evaluate the efficiency of our approaches. In addition, promoter consensus binding search and primer extension assay helped us to identify a new σ54 promoter carried by insB-5 in the upstream of flhDC operon. The involvement of σ54 in flagellar biosynthesis in sequenced E. coli strain MG1655 indicates a fluid gene regulation phenomenon carried by some mobile elements in bacteria genome.
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Affiliation(s)
- Kai Zhao
- McArdle Laboratory for Cancer Research, University of Wisconsin, Madison, WI 53706, USA
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Nitrogen recycling and nutritional provisioning by Blattabacterium, the cockroach endosymbiont. Proc Natl Acad Sci U S A 2009; 106:19521-6. [PMID: 19880743 DOI: 10.1073/pnas.0907504106] [Citation(s) in RCA: 190] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nitrogen acquisition and assimilation is a primary concern of insects feeding on diets largely composed of plant material. Reclaiming nitrogen from waste products provides a rich reserve for this limited resource, provided that recycling mechanisms are in place. Cockroaches, unlike most terrestrial insects, excrete waste nitrogen within their fat bodies as uric acids, postulated to be a supplement when dietary nitrogen is limited. The fat bodies of most cockroaches are inhabited by Blattabacterium, which are vertically transmitted, Gram-negative bacteria that have been hypothesized to participate in uric acid degradation, nitrogen assimilation, and nutrient provisioning. We have sequenced completely the Blattabacterium genome from Periplaneta americana. Genomic analysis confirms that Blattabacterium is a member of the Flavobacteriales (Bacteroidetes), with its closest known relative being the endosymbiont Sulcia muelleri, which is found in many sap-feeding insects. Metabolic reconstruction indicates that it lacks recognizable uricolytic enzymes, but it can recycle nitrogen from urea and ammonia, which are uric acid degradation products, into glutamate, using urease and glutamate dehydrogenase. Subsequently, Blattabacterium can produce all of the essential amino acids, various vitamins, and other required compounds from a limited palette of metabolic substrates. The ancient association with Blattabacterium has allowed cockroaches to subsist successfully on nitrogen-poor diets and to exploit nitrogenous wastes, capabilities that are critical to the ecological range and global distribution of cockroach species.
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Braeken K, Fauvart M, Vercruysse M, Beullens S, Lambrichts I, Michiels J. Pleiotropic effects of a rel mutation on stress survival of Rhizobium etli CNPAF512. BMC Microbiol 2008; 8:219. [PMID: 19077212 PMCID: PMC2631030 DOI: 10.1186/1471-2180-8-219] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Accepted: 12/10/2008] [Indexed: 12/04/2022] Open
Abstract
Background The rel gene of Rhizobium etli (relRet), the nodulating endosymbiont of the common bean plant, determines the cellular level of the alarmone (p)ppGpp and was previously shown to affect free-living growth and symbiosis. Here, we demonstrate its role in cellular adaptation and survival in response to various stresses. Results Growth of the R. etli relRet mutant was strongly reduced or abolished in the presence of elevated NaCl levels or at 37°C, compared to the wild type. In addition, depending on the cell density, decreased survival of exponentially growing or stationary phase relRet mutant cells was obtained after H2O2, heat or NaCl shock compared to the wild-type strain. Survival of unstressed stationary phase cultures was differentially affected depending on the growth medium used. Colony forming units (CFU) of relRet mutant cultures continuously decreased in minimal medium supplemented with succinate, whereas wild-type cultures stabilised at higher CFU levels. Microscopic examination of stationary phase cells indicated that the relRet mutant was unable to reach the typical coccoid morphology of the wild type in stationary phase cultures. Assessment of stress resistance of re-isolated bacteroids showed increased sensitivity of the relRet mutant to H2O2 and a slightly increased resistance to elevated temperature (45°C) or NaCl shock, compared to wild-type bacteroids. Conclusion The relRet gene is an important factor in regulating rhizobial physiology, during free-living growth as well as in symbiotic conditions. Additionally, differential responses to several stresses applied to bacteroids and free-living exponential or stationary phase cells point to essential physiological differences between the different states.
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Affiliation(s)
- Kristien Braeken
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Heverlee, Belgium.
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Iannino F, Ugalde RA, Iñón de Iannino N. Characterization of Brucella abortus sigma factor σ54 (rpoN): Genetic complementation of Sinorhizobium meliloti ntrA mutant. Microb Pathog 2008; 45:394-402. [DOI: 10.1016/j.micpath.2008.09.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Revised: 09/08/2008] [Accepted: 09/12/2008] [Indexed: 11/30/2022]
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Valverde C, Livny J, Schlüter JP, Reinkensmeier J, Becker A, Parisi G. Prediction of Sinorhizobium meliloti sRNA genes and experimental detection in strain 2011. BMC Genomics 2008; 9:416. [PMID: 18793445 PMCID: PMC2573895 DOI: 10.1186/1471-2164-9-416] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2008] [Accepted: 09/16/2008] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Small non-coding RNAs (sRNAs) have emerged as ubiquitous regulatory elements in bacteria and other life domains. However, few sRNAs have been identified outside several well-studied species of gamma-proteobacteria and thus relatively little is known about the role of RNA-mediated regulation in most other bacterial genera. Here we have conducted a computational prediction of putative sRNA genes in intergenic regions (IgRs) of the symbiotic alpha-proteobacterium S. meliloti 1021 and experimentally confirmed the expression of dozens of these candidate loci in the closely related strain S. meliloti 2011. RESULTS Our first sRNA candidate compilation was based mainly on the output of the sRNAPredictHT algorithm. A thorough manual sequence analysis of the curated list rendered an initial set of 18 IgRs of interest, from which 14 candidates were detected in strain 2011 by Northern blot and/or microarray analysis. Interestingly, the intracellular transcript levels varied in response to various stress conditions. We developed an alternative computational method to more sensitively predict sRNA-encoding genes and score these predicted genes based on several features to allow identification of the strongest candidates. With this novel strategy, we predicted 60 chromosomal independent transcriptional units that, according to our annotation, represent strong candidates for sRNA-encoding genes, including most of the sRNAs experimentally verified in this work and in two other contemporary studies. Additionally, we predicted numerous candidate sRNA genes encoded in megaplasmids pSymA and pSymB. A significant proportion of the chromosomal- and megaplasmid-borne putative sRNA genes were validated by microarray analysis in strain 2011. CONCLUSION Our data extend the number of experimentally detected S. meliloti sRNAs and significantly expand the list of putative sRNA-encoding IgRs in this and closely related alpha-proteobacteria. In addition, we have developed a computational method that proved useful to predict sRNA-encoding genes in S. meliloti. We anticipate that this predictive approach can be flexibly implemented in many other bacterial species.
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Affiliation(s)
- Claudio Valverde
- Programa Interacciones Biológicas, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal, Buenos Aires, B1876BXD, Argentina.
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Gautam US, Jajoo A, Singh A, Chakrabartty PK, Das SK. Characterization of an rpoN mutant of Mesorhizobium ciceri. J Appl Microbiol 2008; 103:1798-807. [PMID: 17953590 DOI: 10.1111/j.1365-2672.2007.03432.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIMS To study the genetic basis of C(4)-dicarboxylate transport (Dct) in relation to symbiotic nitrogen fixation in Mesorhizobium ciceri. METHODS AND RESULTS A Tn5-induced mutant strain (TL16) of M. ciceri, unable to grow on C(4)-dicarboxylates, was isolated from the wild-type strain TAL 620. The mutant lacked activities of the enzymes, which use C(4)-dicarboxylates as substrate. The sequencing of the 3.2kb EcoRI fragment, which was the site of Tn5 insertion, revealed three complete and two partial open reading frames. In the mutant, Tn5 interrupted the rpoN gene, of which only one copy was there. Complementation and biochemical studies suggest that the M. ciceri rpoN activity is required for C(4)-Dct, maturation of bacteroids and symbiotic nitrogen fixation. The fine structure of the ineffective nodules produced by TL16 on Cicer arietinum L changed in comparison with those produced by the wild type. CONCLUSIONS The mutant strain TL16 suffered a disruption in the rpoN gene. Only one copy of rpoN gene is present in M. ciceri. The mutation abolishes Dct activity. It additionally abolishes the symbiotic nitrogen fixation activity of the bacteroids in the nodules. SIGNIFICANCE AND IMPACT OF THE STUDY This first document in M. ciceri shows that a functional rpoN gene is essential for the transport of dicarboxylic acids and symbiotic nitrogen fixation.
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Affiliation(s)
- U S Gautam
- National Research Center on Plant Biotechnology, Indian Agricultural Research Institute, Pusa, New Delhi, India
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Ulvé VM, Sevin EW, Chéron A, Barloy-Hubler F. Identification of chromosomal alpha-proteobacterial small RNAs by comparative genome analysis and detection in Sinorhizobium meliloti strain 1021. BMC Genomics 2007; 8:467. [PMID: 18093320 PMCID: PMC2245857 DOI: 10.1186/1471-2164-8-467] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Accepted: 12/19/2007] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND Small untranslated RNAs (sRNAs) seem to be far more abundant than previously believed. The number of sRNAs confirmed in E. coli through various approaches is above 70, with several hundred more sRNA candidate genes under biological validation. Although the total number of sRNAs in any one species is still unclear, their importance in cellular processes has been established. However, unlike protein genes, no simple feature enables the prediction of the location of the corresponding sequences in genomes. Several approaches, of variable usefulness, to identify genomic sequences encoding sRNA have been described in recent years. RESULTS We used a combination of in silico comparative genomics and microarray-based transcriptional profiling. This approach to screening identified ~60 intergenic regions conserved between Sinorhizobium meliloti and related members of the alpha-proteobacteria sub-group 2. Of these, 14 appear to correspond to novel non-coding sRNAs and three are putative peptide-coding or 5' UTR RNAs (ORF smaller than 100 aa). The expression of each of these new small RNA genes was confirmed by Northern blot hybridization. CONCLUSION Small non coding RNA (sra) genes can be found in the intergenic regions of alpha-proteobacteria genomes. Some of these sra genes are only present in S. meliloti, sometimes in genomic islands; homologues of others are present in related genomes including those of the pathogens Brucella and Agrobacterium.
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Affiliation(s)
- Vincent M Ulvé
- CNRS UMR6061 Génétique et Développement, Groupe Modèles Génétiques, Université de Rennes 1, IFR140 GFAS, Faculté de médecine, 2 avenue du Professeur Léon Bernard, CS 34317, 35043 Rennes Cedex, France.
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Jones J, Studholme DJ, Knight CG, Preston GM. Integrated bioinformatic and phenotypic analysis of RpoN-dependent traits in the plant growth-promoting bacterium Pseudomonas fluorescens SBW25. Environ Microbiol 2007; 9:3046-64. [DOI: 10.1111/j.1462-2920.2007.01416.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Remans R, Snoeck C, Verreth C, Croonenborghs A, Luyten E, Ndayizeye M, Martínez-Romero E, Michiels J, Vanderleyden J. Inactivation of the nodH gene in Sinorhizobium sp. BR816 enhances symbiosis with Phaseolus vulgaris L. FEMS Microbiol Lett 2007; 266:210-7. [PMID: 17233732 DOI: 10.1111/j.1574-6968.2006.00521.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Sulfate modification on Rhizobium Nod factor signaling molecules is not a prerequisite for successful symbiosis with the common bean (Phaseolus vulgaris L.). However, many bean-nodulating rhizobia, including the broad host strain Sinorhizobium sp. BR816, produce sulfated Nod factors. Here, we show that the nodH gene, encoding a sulfotransferase, is responsible for the transfer of sulfate to the Nod factor backbone in Sinorhizobium sp. BR816, as was shown for other rhizobia. Interestingly, inactivation of nodH enables inoculated bean plants to fix significantly more nitrogen under different experimental setups. Our studies show that nodH in the wild-type strain is still expressed during the later stages of symbiosis. This is the first report on enhanced nitrogen fixation by blocking Nod factor sulfation.
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Affiliation(s)
- Roseline Remans
- Centre of Microbial and Plant Genetics, Kasteelpark Arenberg, Heverlee, Belgium
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Nukui N, Minamisawa K, Ayabe SI, Aoki T. Expression of the 1-aminocyclopropane-1-carboxylic acid deaminase gene requires symbiotic nitrogen-fixing regulator gene nifA2 in Mesorhizobium loti MAFF303099. Appl Environ Microbiol 2006; 72:4964-9. [PMID: 16820494 PMCID: PMC1489367 DOI: 10.1128/aem.02745-05] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many soil bacteria contain 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, which degrades ACC, a precursor of the phytohormone ethylene. In order to examine the regulation of the acdS gene encoding ACC deaminase in Mesorhizobium loti MAFF303099 during symbiosis with the host legume Lotus japonicus, we introduced the beta-glucuronidase (GUS) gene into acdS so that GUS was expressed under control of the acdS promoter, and we also generated disruption mutants with mutations in a nitrogen fixation regulator gene, nifA. The histochemical GUS assay showed that there was exclusive expression of acdS in mature root nodules. Two homologous nifA genes, mll5857 and mll5837, were found in the symbiosis island of M. loti and were designated nifA1 and nifA2, respectively. Quantitative reverse transcription-PCR demonstrated that nifA2 disruption resulted in considerably diminished expression of acdS, nifH, and nifA1 in bacteroid cells. In contrast, nifA1 disruption slightly enhanced expression of the acdS transcripts and suppressed nifH to some extent. These results indicate that the acdS gene and other symbiotic genes are positively regulated by the NifA2 protein, but not by the NifA1 protein, in M. loti. The mode of gene expression suggests that M. loti acdS participates in the establishment and/or maintenance of mature nodules by interfering with the production of ethylene, which induces negative regulation of nodulation.
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Affiliation(s)
- Noriyuki Nukui
- Department of Applied Biological Sciences, Nihon University, Fujisawa, Kanagawa 252-8510, Japan.
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Tian Z, Mao X, Su W, Li J, Becker A, Wang Y. Exogenous cAMP upregulates the expression of glnII and glnK-amtB genes in Sinorhizobium meliloti 1021. ACTA ACUST UNITED AC 2006. [DOI: 10.1007/s11434-006-2079-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Reiss DJ, Baliga NS, Bonneau R. Integrated biclustering of heterogeneous genome-wide datasets for the inference of global regulatory networks. BMC Bioinformatics 2006; 7:280. [PMID: 16749936 PMCID: PMC1502140 DOI: 10.1186/1471-2105-7-280] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Accepted: 06/02/2006] [Indexed: 12/23/2022] Open
Abstract
Background The learning of global genetic regulatory networks from expression data is a severely under-constrained problem that is aided by reducing the dimensionality of the search space by means of clustering genes into putatively co-regulated groups, as opposed to those that are simply co-expressed. Be cause genes may be co-regulated only across a subset of all observed experimental conditions, biclustering (clustering of genes and conditions) is more appropriate than standard clustering. Co-regulated genes are also often functionally (physically, spatially, genetically, and/or evolutionarily) associated, and such a priori known or pre-computed associations can provide support for appropriately grouping genes. One important association is the presence of one or more common cis-regulatory motifs. In organisms where these motifs are not known, their de novo detection, integrated into the clustering algorithm, can help to guide the process towards more biologically parsimonious solutions. Results We have developed an algorithm, cMonkey, that detects putative co-regulated gene groupings by integrating the biclustering of gene expression data and various functional associations with the de novo detection of sequence motifs. Conclusion We have applied this procedure to the archaeon Halobacterium NRC-1, as part of our efforts to decipher its regulatory network. In addition, we used cMonkey on public data for three organisms in the other two domains of life: Helicobacter pylori, Saccharomyces cerevisiae, and Escherichia coli. The biclusters detected by cMonkey both recapitulated known biology and enabled novel predictions (some for Halobacterium were subsequently confirmed in the laboratory). For example, it identified the bacteriorhodopsin regulon, assigned additional genes to this regulon with apparently unrelated function, and detected its known promoter motif. We have performed a thorough comparison of cMonkey results against other clustering methods, and find that cMonkey biclusters are more parsimonious with all available evidence for co-regulation.
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Affiliation(s)
- David J Reiss
- Institute for Systems Biology, 1441 N. 34th St. Seattle, WA 98103-8904, USA
| | - Nitin S Baliga
- Institute for Systems Biology, 1441 N. 34th St. Seattle, WA 98103-8904, USA
| | - Richard Bonneau
- New York University Dept. of Biology, Dept. of Computer Science, New York, USA
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Abstract
The ability to recognize and predict non-σ54promoters in the alphaproteobacteria is not well developed. In this study, 25 experimentally verifiedSinorhizobium melilotipromoter sequences were compiled and used to predict the location of other related promoters in theS. melilotigenome. Fourteen candidate predictions were targeted for verification and of these at least 12 proved to be genuine promoters. As a result, the experimental identification of 12 novel promoters linked to genesrpoD,topA,rpmJ,trpS,ropB1,metC,rpsT,secE,trkHand three tRNA genes is reported. In all, 99 predicted and verified promoters are reported, including those linked with 13 tRNA genes, eight ribosomal protein genes and a number of other physiologically important or essential genes. On the basis of sequence conservation and a mutational analysis of promoter activity, the −35 and −10 consensus for these promoters is 5-CTTGAC-N17-CTATAT. This promoter structure, which seems to be widely conserved amongst several other genera in the alphaproteobacteria, shares significant similarity with, but is skewed by a 1 nt step from, the canonicalEscherichia coliσ70promoter. Perhaps this difference is responsible for the observation thatS. melilotipromoters are often poorly expressed inE. coli. In this regard, expression data from plasmid-bornegfp-reporter fusions to eight of theS. melilotipromoters verified in this work revealed that while these promoters were very active inS. melilotiandAgrobacterium tumefaciensonly very low, near-background activity was detected inE. coli.
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Affiliation(s)
- Shawn R MacLellan
- Center for Environmental Genomics, Department of Biology, McMaster University, 1280 Main St West, Hamilton, Ontario L8S 4K1, Canada
| | - Allyson M MacLean
- Center for Environmental Genomics, Department of Biology, McMaster University, 1280 Main St West, Hamilton, Ontario L8S 4K1, Canada
| | - Turlough M Finan
- Center for Environmental Genomics, Department of Biology, McMaster University, 1280 Main St West, Hamilton, Ontario L8S 4K1, Canada
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Yuan ZC, Zaheer R, Morton R, Finan TM. Genome prediction of PhoB regulated promoters in Sinorhizobium meliloti and twelve proteobacteria. Nucleic Acids Res 2006; 34:2686-97. [PMID: 16717279 PMCID: PMC1464414 DOI: 10.1093/nar/gkl365] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In proteobacteria, genes whose expression is modulated in response to the external concentration of inorganic phosphate are often regulated by the PhoB protein which binds to a conserved motif (Pho box) within their promoter regions. Using a position weight matrix algorithm derived from known Pho box sequences, we identified 96 putative Pho regulon members whose promoter regions contained one or more Pho boxs in the Sinorhizobium meliloti genome. Expression of these genes was examined through assays of reporter gene fusions and through comparison with published microarray data. Of 96 genes, 31 were induced and 3 were repressed by Pi starvation in a PhoB dependent manner. Novel Pho regulon members included several genes of unknown function. Comparative analysis across 12 proteobacterial genomes revealed highly conserved Pho regulon members including genes involved in Pi metabolism (pstS, phnC and ppdK). Genes with no obvious association with Pi metabolism were predicted to be Pho regulon members in S.meliloti and multiple organisms. These included smc01605 and smc04317 which are annotated as substrate binding proteins of iron transporters and katA encoding catalase. This data suggests that the Pho regulon overlaps and interacts with several other control circuits, such as the oxidative stress response and iron homeostasis.
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Affiliation(s)
| | | | | | - Turlough M. Finan
- To whom correspondence should be addressed. Tel: +905 525 9140, ext. 22932; Fax: +905 522 6066;
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Rhodius VA, Suh WC, Nonaka G, West J, Gross CA. Conserved and variable functions of the sigmaE stress response in related genomes. PLoS Biol 2006; 4:e2. [PMID: 16336047 PMCID: PMC1312014 DOI: 10.1371/journal.pbio.0040002] [Citation(s) in RCA: 404] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2005] [Accepted: 10/13/2005] [Indexed: 11/19/2022] Open
Abstract
Bacteria often cope with environmental stress by inducing alternative sigma (σ) factors, which direct RNA polymerase to specific promoters, thereby inducing a set of genes called a regulon to combat the stress. To understand the conserved and organism-specific functions of each σ, it is necessary to be able to predict their promoters, so that their regulons can be followed across species. However, the variability of promoter sequences and motif spacing makes their prediction difficult. We developed and validated an accurate promoter prediction model for Escherichia coli σE, which enabled us to predict a total of 89 unique σE-controlled transcription units in E. coli K-12 and eight related genomes. σE controls the envelope stress response in E. coli K-12. The portion of the regulon conserved across genomes is functionally coherent, ensuring the synthesis, assembly, and homeostasis of lipopolysaccharide and outer membrane porins, the key constituents of the outer membrane of Gram-negative bacteria. The larger variable portion is predicted to perform pathogenesis-associated functions, suggesting that σE provides organism-specific functions necessary for optimal host interaction. The success of our promoter prediction model for σE suggests that it will be applicable for the prediction of promoter elements for many alternative σ factors. A model for predicting the variable promoter sequences associated with the bacterial stress response is developed and used to identify constituents of the transcriptional response to σE.
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Affiliation(s)
- Virgil A Rhodius
- 1 Department of Microbiology and Immunology, University of California, San Francisco, California, United States of America
| | - Won Chul Suh
- 1 Department of Microbiology and Immunology, University of California, San Francisco, California, United States of America
| | - Gen Nonaka
- 1 Department of Microbiology and Immunology, University of California, San Francisco, California, United States of America
| | - Joyce West
- 1 Department of Microbiology and Immunology, University of California, San Francisco, California, United States of America
| | - Carol A Gross
- 1 Department of Microbiology and Immunology, University of California, San Francisco, California, United States of America
- 2 Department of Cell and Tissue Biology, University of California, San Francisco, California, United States of America
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Moris M, Braeken K, Schoeters E, Verreth C, Beullens S, Vanderleyden J, Michiels J. Effective symbiosis between Rhizobium etli and Phaseolus vulgaris requires the alarmone ppGpp. J Bacteriol 2005; 187:5460-9. [PMID: 16030240 PMCID: PMC1196010 DOI: 10.1128/jb.187.15.5460-5469.2005] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The symbiotic interaction between Rhizobium etli and Phaseolus vulgaris, the common bean plant, ultimately results in the formation of nitrogen-fixing nodules. Many aspects of the intermediate and late stages of this interaction are still poorly understood. The R. etli relA gene was identified through a genome-wide screening for R. etli symbiotic mutants. RelA has a pivotal role in cellular physiology, as it catalyzes the synthesis of (p)ppGpp, which mediates the stringent response in bacteria. The synthesis of ppGpp was abolished in an R. etli relA mutant strain under conditions of amino acid starvation. Plants nodulated by an R. etli relA mutant had a strongly reduced nitrogen fixation activity (75% reduction). Also, at the microscopic level, bacteroid morphology was altered, with the size of relA mutant bacteroids being increased compared to that of wild-type bacteroids. The expression of the sigma(N)-dependent nitrogen fixation genes rpoN2 and iscN was considerably reduced in the relA mutant. In addition, the expression of the relA gene was negatively regulated by RpoN2, the symbiosis-specific sigma(N) copy of R. etli. Therefore, an autoregulatory loop controlling the expression of relA and rpoN2 seems operative in bacteroids. The production of long- and short-chain acyl-homoserine-lactones by the cinIR and raiIR systems was decreased in an R. etli relA mutant. Our results suggest that relA may play an important role in the regulation of gene expression in R. etli bacteroids and in the adaptation of bacteroid physiology.
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Affiliation(s)
- Martine Moris
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium
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Dombrecht B, Heusdens C, Beullens S, Verreth C, Mulkers E, Proost P, Vanderleyden J, Michiels J. Defence of Rhizobium etli bacteroids against oxidative stress involves a complexly regulated atypical 2-Cys peroxiredoxin. Mol Microbiol 2005; 55:1207-21. [PMID: 15686565 DOI: 10.1111/j.1365-2958.2005.04457.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In general, oxidative stress, the consequence of an aerobic lifestyle, induces bacterial antioxidant defence enzymes. Here we report on a peroxiredoxin of Rhizobium etli, prxS, strongly expressed under microaerobic conditions and during the symbiotic interaction with Phaseolus vulgaris. The microaerobic induction of the prxS-rpoN2 operon is mediated by the alternative sigma factor RpoN and the enhancer-binding protein NifA. The RpoN-dependent promoter is also active under low-nitrogen conditions through the enhancer-binding protein NtrC. An additional symbiosis-specific weak promoter is located between prxS and rpoN2. Constitutive expression of prxS confers enhanced survival and growth to R. etli in the presence of H2O2. Single prxS mutants are not affected in their symbiotic abilities or defence response against oxidative stress under free-living conditions. In contrast, a prxS katG double mutant has a significantly reduced (>40%) nitrogen fixation capacity, suggesting a functional redundancy between PrxS and KatG, a bifunctional catalase-peroxidase. In vitro assays demonstrate the reduction of PrxS protein by DTT and thioredoxin. PrxS displays substrate specificity towards H2O2 (Km = 62 microM) over alkyl hydroperoxides (Km > 1 mM). Peroxidase activity is abolished in both the peroxidatic (C56) and resolving (C156) cysteine PrxS mutants, while the conserved C81 residue is required for proper folding of the protein. Resolving of the R. etli PrxS peroxidatic cysteine is probably an intramolecular process and intra- and intersubunit associations were observed. Taken together, our data support, for the first time, a role for an atypical 2-Cys peroxiredoxin against oxidative stress in R. etli bacteroids.
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Affiliation(s)
- Bruno Dombrecht
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, 3001 Heverlee, Belgium
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McIntosh M, Stone BA, Stanisich VA. Curdlan and other bacterial (1→3)-β-d-glucans. Appl Microbiol Biotechnol 2005; 68:163-73. [PMID: 15818477 DOI: 10.1007/s00253-005-1959-5] [Citation(s) in RCA: 286] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2004] [Revised: 01/17/2005] [Accepted: 01/17/2005] [Indexed: 11/29/2022]
Abstract
Three structural classes of (1-->3)-beta-D-glucans are encountered in some important soil-dwelling, plant-associated or human pathogenic bacteria. Linear (1-->3)-beta-glucans and side-chain-branched (1-->3,1-->2)-beta-glucans are major constituents of capsular materials, with roles in bacterial aggregation, virulence and carbohydrate storage. Cyclic (1-->3,1-->6)-beta-glucans are predominantly periplasmic, serving in osmotic adaptation. Curdlan, the linear (1-->3)-beta-glucan from Agrobacterium, has unique rheological and thermal gelling properties, with applications in the food industry and other sectors. This review includes information on the structure, properties and molecular genetics of the bacterial (1-->3)-beta-glucans, together with an overview of the physiology and biotechnology of curdlan production and applications of this biopolymer and its derivatives.
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Affiliation(s)
- M McIntosh
- Department of Biochemistry, La Trobe University, Bundoora, 3086 Victoria, Australia
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Barnett MJ, Toman CJ, Fisher RF, Long SR. A dual-genome Symbiosis Chip for coordinate study of signal exchange and development in a prokaryote-host interaction. Proc Natl Acad Sci U S A 2004; 101:16636-41. [PMID: 15542588 PMCID: PMC527922 DOI: 10.1073/pnas.0407269101] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The soil-dwelling alpha-proteobacterium Sinorhizobium meliloti engages in a symbiosis with legumes: S. meliloti elicits the formation of plant root nodules where it converts dinitrogen to ammonia for use by the plant in exchange for plant photosynthate. To study the coordinate differentiation of S. meliloti and its legume partner during nodule development, we designed a custom Affymetrix GeneChip with the complete S. meliloti genome and approximately 10,000 probe sets for the plant host, Medicago truncatula. Expression profiling of free-living S. meliloti grown with the plant signal molecule luteolin in defined minimal and rich media or of strains altered in the expression of key regulatory proteins (NodD1, NodD3, and RpoN) confirms previous data and identifies previously undescribed regulatory targets. Analyses of root nodules show that this Symbiosis Chip allows the study of gene expression in both partners simultaneously. Our studies detail nearly 5,000 transcriptome changes in symbiosis and document complex transcriptional profiles of S. meliloti in different environments.
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Affiliation(s)
- Melanie J Barnett
- Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA
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