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Yang QE, Ma X, Li M, Zhao M, Zeng L, He M, Deng H, Liao H, Rensing C, Friman VP, Zhou S, Walsh TR. Evolution of triclosan resistance modulates bacterial permissiveness to multidrug resistance plasmids and phages. Nat Commun 2024; 15:3654. [PMID: 38688912 PMCID: PMC11061290 DOI: 10.1038/s41467-024-48006-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 04/17/2024] [Indexed: 05/02/2024] Open
Abstract
The horizontal transfer of plasmids has been recognized as one of the key drivers for the worldwide spread of antimicrobial resistance (AMR) across bacterial pathogens. However, knowledge remain limited about the contribution made by environmental stress on the evolution of bacterial AMR by modulating horizontal acquisition of AMR plasmids and other mobile genetic elements. Here we combined experimental evolution, whole genome sequencing, reverse genetic engineering, and transcriptomics to examine if the evolution of chromosomal AMR to triclosan (TCS) disinfectant has correlated effects on modulating bacterial pathogen (Klebsiella pneumoniae) permissiveness to AMR plasmids and phage susceptibility. Herein, we show that TCS exposure increases the evolvability of K. pneumoniae to evolve TCS-resistant mutants (TRMs) by acquiring mutations and altered expression of several genes previously associated with TCS and antibiotic resistance. Notably, nsrR deletion increases conjugation permissiveness of K. pneumoniae to four AMR plasmids, and enhances susceptibility to various Klebsiella-specific phages through the downregulation of several bacterial defense systems and changes in membrane potential with altered reactive oxygen species response. Our findings suggest that unrestricted use of TCS disinfectant imposes a dual impact on bacterial antibiotic resistance by augmenting both chromosomally and horizontally acquired AMR mechanisms.
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Affiliation(s)
- Qiu E Yang
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Xiaodan Ma
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Minchun Li
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Mengshi Zhao
- Fujian Key Laboratory of Traditional Chinese Veterinary Medicine and Animal Health, College of Animal Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Lingshuang Zeng
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Minzhen He
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Hui Deng
- Fujian Key Laboratory of Traditional Chinese Veterinary Medicine and Animal Health, College of Animal Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Hanpeng Liao
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Christopher Rensing
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Ville-Petri Friman
- Department of Microbiology, University of Helsinki, 00014, Helsinki, Finland
| | - Shungui Zhou
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
| | - Timothy R Walsh
- Ineos Oxford Institute for Antimicrobial Research, Department of Biology, University of Oxford, Oxford, OX1 3RE, UK.
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Heme A Synthase Deficiency Affects the Ability of Bacillus cereus to Adapt to a Nutrient-Limited Environment. Int J Mol Sci 2022; 23:ijms23031033. [PMID: 35162964 PMCID: PMC8835132 DOI: 10.3390/ijms23031033] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 01/12/2022] [Accepted: 01/14/2022] [Indexed: 11/30/2022] Open
Abstract
The branched aerobic respiratory chain in Bacillus cereus comprises three terminal oxidases: cytochromes aa3, caa3, and bd. Cytochrome caa3 requires heme A for activity, which is produced from heme O by heme A synthase (CtaA). In this study, we deleted the ctaA gene in B. cereus AH187 strain, this deletion resulted in loss of cytochrome caa3 activity. Proteomics data indicated that B. cereus grown in glucose-containing medium compensates for the loss of cytochrome caa3 activity by remodeling its respiratory metabolism. This remodeling involves up-regulation of cytochrome aa3 and several proteins involved in redox stress response—to circumvent sub-optimal respiratory metabolism. CtaA deletion changed the surface-composition of B. cereus, affecting its motility, autoaggregation phenotype, and the kinetics of biofilm formation. Strikingly, proteome remodeling made the ctaA mutant more resistant to cold and exogenous oxidative stresses compared to its parent strain. Consequently, we hypothesized that ctaA inactivation could improve B. cereus fitness in a nutrient-limited environment.
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3
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Distinct Interaction Mechanism of RNAP and ResD and Distal Subsites for Transcription Activation of Nitrite Reductase in Bacillus subtilisψ. J Bacteriol 2021; 204:e0043221. [PMID: 34898263 DOI: 10.1128/jb.00432-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ResD-ResE signal transduction system plays a pivotal role in anaerobic nitrate respiration in Bacillus subtilis. The nasD operon encoding nitrite reductase is essential for nitrate respiration and is tightly controlled by the ResD response regulator. To understand the mechanism of ResD-dependent transcription activation of the nasD operon, we explored ResD-RNA polymerase (RNAP), ResD-DNA, and RNAP-DNA interactions required for nasD transcription. Full transcriptional activation requires the upstream promoter region where five molecules of ResD bind. The distal ResD-binding subsite at -87 to -84 partially overlaps a sequence similar to the consensus distal subsite of the upstream (UP) element with which the Escherichia coli C-terminal domain of the α subunit (αCTD) of RNAP interacts to stimulate transcription. We propose that interaction between αCTD and ResD at the promoter-distal site is essential for stimulating nasD transcription. Although nasD has an extended -10 promoter, it lacks a reasonable -35 element. Genetic analysis and structural simulations predicted that the absence of the -35 element might be compensated by interactions between σA and αCTD, and between αCTD and ResD at the promoter-proximal ResD-binding subsite. Thus, our work suggested that ResD likely participates in nasD transcription activation by binding to two αCTD subunits at the proximal and distal promoter sites, representing a unique configuration for transcription activation. IMPORTANCE A significant number of ResD-controlled genes have been identified and transcription regulatory pathways in which ResD participates have emerged. Nevertheless, the mechanism of how ResD activates transcription of different genes in a nucleotide sequence-specific manner has been less explored. This study suggested that among the five ResD-binding subsites in the promoter of the nasD operon, the promoter-proximal and -distal ResD-binding subsites play important roles in nasD activation by adapting different modes of protein-protein and protein-DNA interactions. The finding of a new-type of protein-promoter architecture provides insight into the understanding of transcription activation mechanisms controlled by transcription factors including the ubiquitous response regulators of two-component regulatory systems particularly in Gram-positive bacteria.
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Zhang H, Liu Y, Wu G, Dong X, Xiong Q, Chen L, Xu Z, Feng H, Zhang R. Bacillus velezensis tolerance to the induced oxidative stress in root colonization contributed by the two-component regulatory system sensor ResE. PLANT, CELL & ENVIRONMENT 2021; 44:3094-3102. [PMID: 33864643 DOI: 10.1111/pce.14068] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 04/08/2021] [Accepted: 04/08/2021] [Indexed: 06/12/2023]
Abstract
Efficient root colonization of plant growth-promoting rhizobacteria is critical for their plant-beneficial functions. However, the strategy to overcome plant immunity during root colonization is not well understood. In particular, how Bacillus strains cope with plant-derived reactive oxygen species (ROS), which function as the first barrier of plant defence, is not clear. In the present study, we found that the homolog of flg22 in Bacillus velezensis SQR9 (flg22SQR9 ) has 78.95% identity to the typical flg22 (flg22P.s. ) and induces a significant oxidative burst in cucumber and Arabidopsis. In contrast to pathogenic or beneficial Pseudomonas, live B. velezensis SQR9 also induced an oxidative burst in cucumber. We further found that B. velezensis SQR9 tolerated higher H2 O2 levels than Pst DC3000, the pathogen that harbours the typical flg22, and that it possesses the ability to suppress the flg22-induced oxidative burst, indicating that B. velezensis SQR9 may exploit a more efficient ROS tolerance system than DC3000. Further experimentation with mutagenesis of bacteria and Arabidopsis showed that the two-component regulatory system, ResDE, in B. velezensis SQR9 is involved in tolerance to plant-derived oxidative stress, thus contributing to root colonization. This study supports a further investigation of the interaction between beneficial rhizobacteria and plant immunity.
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Affiliation(s)
- Huihui Zhang
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, China
| | - Yunpeng Liu
- Key Laboratory of Agricultural Microbial Resources Collection and Preservation, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Gengwei Wu
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, China
| | - Xiaoyan Dong
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, China
| | - Qin Xiong
- Key Laboratory of Agricultural Microbial Resources Collection and Preservation, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Lin Chen
- Experimental Center of Forestry in North China, Chinese Academy of Forestry, Beijing, China
| | - Zhihui Xu
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, China
| | - Haichao Feng
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, China
| | - Ruifu Zhang
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, China
- Key Laboratory of Agricultural Microbial Resources Collection and Preservation, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China
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5
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Porrini C, Ramarao N, Tran SL. Dr. NO and Mr. Toxic - the versatile role of nitric oxide. Biol Chem 2021; 401:547-572. [PMID: 31811798 DOI: 10.1515/hsz-2019-0368] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 12/04/2019] [Indexed: 12/25/2022]
Abstract
Nitric oxide (NO) is present in various organisms from humans, to plants, fungus and bacteria. NO is a fundamental signaling molecule implicated in major cellular functions. The role of NO ranges from an essential molecule to a potent mediator of cellular damages. The ability of NO to react with a broad range of biomolecules allows on one hand its regulation and a gradient concentration and on the other hand to exert physiological as well as pathological functions. In humans, NO is implicated in cardiovascular homeostasis, neurotransmission and immunity. However, NO can also contribute to cardiovascular diseases (CVDs) or septic shock. For certain denitrifying bacteria, NO is part of their metabolism as a required intermediate of the nitrogen cycle. However, for other bacteria, NO is toxic and harmful. To survive, those bacteria have developed processes to resist this toxic effect and persist inside their host. NO also contributes to maintain the host/microbiota homeostasis. But little is known about the impact of NO produced during prolonged inflammation on microbiota integrity, and some pathogenic bacteria take advantage of the NO response to colonize the gut over the microbiota. Taken together, depending on the environmental context (prolonged production, gradient concentration, presence of partners for interaction, presence of oxygen, etc.), NO will exert its beneficial or detrimental function. In this review, we highlight the dual role of NO for humans, pathogenic bacteria and microbiota, and the mechanisms used by each organism to produce, use or resist NO.
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Affiliation(s)
- Constance Porrini
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, 78350, Jouy-en-Josas, France
| | - Nalini Ramarao
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, 78350, Jouy-en-Josas, France
| | - Seav-Ly Tran
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, 78350, Jouy-en-Josas, France
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6
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Porrini C, Guérin C, Tran SL, Dervyn R, Nicolas P, Ramarao N. Implication of a Key Region of Six Bacillus cereus Genes Involved in Siroheme Synthesis, Nitrite Reductase Production and Iron Cluster Repair in the Bacterial Response to Nitric Oxide Stress. Int J Mol Sci 2021; 22:ijms22105079. [PMID: 34064887 PMCID: PMC8151001 DOI: 10.3390/ijms22105079] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/01/2021] [Accepted: 05/04/2021] [Indexed: 12/30/2022] Open
Abstract
Bacterial response to nitric oxide (NO) is of major importance for bacterial survival. NO stress is a main actor of the eukaryotic immune response and several pathogenic bacteria have developed means for detoxification and repair of the damages caused by NO. However, bacterial mechanisms of NO resistance by Gram-positive bacteria are poorly described. In the opportunistic foodborne pathogen Bacillus cereus, genome sequence analyses did not identify homologs to known NO reductases and transcriptional regulators, such as NsrR, which orchestrate the response to NO of other pathogenic or non-pathogenic bacteria. Using a transcriptomic approach, we investigated the adaptation of B. cereus to NO stress. A cluster of 6 genes was identified to be strongly up-regulated in the early phase of the response. This cluster contains an iron-sulfur cluster repair enzyme, a nitrite reductase and three enzymes involved in siroheme biosynthesis. The expression pattern and close genetic localization suggest a functional link between these genes, which may play a pivotal role in the resistance of B. cereus to NO stress during infection.
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Affiliation(s)
- Constance Porrini
- Micalis Institute, AgroParisTech, INRAE, Université Paris-Saclay, 78350 Jouy-en-Josas, France; (C.P.); (S.-L.T.); (R.D.)
| | - Cyprien Guérin
- MaIAGE, INRAE, Université Paris-Saclay, 78350 Jouy-en-Josas, France; (C.G.); (P.N.)
| | - Seav-Ly Tran
- Micalis Institute, AgroParisTech, INRAE, Université Paris-Saclay, 78350 Jouy-en-Josas, France; (C.P.); (S.-L.T.); (R.D.)
| | - Rozenn Dervyn
- Micalis Institute, AgroParisTech, INRAE, Université Paris-Saclay, 78350 Jouy-en-Josas, France; (C.P.); (S.-L.T.); (R.D.)
| | - Pierre Nicolas
- MaIAGE, INRAE, Université Paris-Saclay, 78350 Jouy-en-Josas, France; (C.G.); (P.N.)
| | - Nalini Ramarao
- Micalis Institute, AgroParisTech, INRAE, Université Paris-Saclay, 78350 Jouy-en-Josas, France; (C.P.); (S.-L.T.); (R.D.)
- Correspondence:
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7
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Durand S, Guillier M. Transcriptional and Post-transcriptional Control of the Nitrate Respiration in Bacteria. Front Mol Biosci 2021; 8:667758. [PMID: 34026838 PMCID: PMC8139620 DOI: 10.3389/fmolb.2021.667758] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Accepted: 03/29/2021] [Indexed: 12/02/2022] Open
Abstract
In oxygen (O2) limiting environments, numerous aerobic bacteria have the ability to shift from aerobic to anaerobic respiration to release energy. This process requires alternative electron acceptor to replace O2 such as nitrate (NO3 -), which has the next best reduction potential after O2. Depending on the organism, nitrate respiration involves different enzymes to convert NO3 - to ammonium (NH4 +) or dinitrogen (N2). The expression of these enzymes is tightly controlled by transcription factors (TFs). More recently, bacterial small regulatory RNAs (sRNAs), which are important regulators of the rapid adaptation of microorganisms to extremely diverse environments, have also been shown to control the expression of genes encoding enzymes or TFs related to nitrate respiration. In turn, these TFs control the synthesis of multiple sRNAs. These results suggest that sRNAs play a central role in the control of these metabolic pathways. Here we review the complex interplay between the transcriptional and the post-transcriptional regulators to efficiently control the respiration on nitrate.
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Affiliation(s)
- Sylvain Durand
- CNRS, UMR 8261, Université de Paris, Institut de Biologie Physico-Chimique, Paris, France
| | - Maude Guillier
- CNRS, UMR 8261, Université de Paris, Institut de Biologie Physico-Chimique, Paris, France
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8
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Cole JA. Anaerobic bacterial response to nitric oxide stress: Widespread misconceptions and physiologically relevant responses. Mol Microbiol 2021; 116:29-40. [PMID: 33706420 DOI: 10.1111/mmi.14713] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 03/04/2021] [Accepted: 03/09/2021] [Indexed: 11/27/2022]
Abstract
How anaerobic bacteria protect themselves against nitric oxide-induced stress is controversial, not least because far higher levels of stress were used in the experiments on which most of the literature is based than bacteria experience in their natural environments. This results in chemical damage to enzymes that inactivates their physiological function. This review illustrates how transcription control mechanisms reveal physiological roles of the encoded gene products. Evidence that the hybrid cluster protein, Hcp, is a major high affinity NO reductase in anaerobic bacteria is reviewed: if so, its trans-nitrosation activity is a nonspecific secondary consequence of chemical inactivation. Whether the flavorubredoxin, NorV, is equally effective at such low [NO] is unknown. YtfE is proposed to be an enzyme rather than a source of iron for the repair of iron-sulfur proteins damaged by nitrosative stress. Any reaction catalyzed by YtfE needs to be revealed. The concentration of NO that accumulates in the cytoplasm of anaerobic bacteria is unknown, but indirect evidence indicates that it is in the pM to low nM range. Also unknown are the functions of the NO-inducible cytoplasmic proteins YgbA, YeaR, or YoaG. Experiments to resolve some of these questions are proposed.
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Affiliation(s)
- J A Cole
- School of Biosciences and Institute of Microbiology and Infection, University of Birmingham, Birmingham, UK
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9
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Chou WK, Vaikunthan M, Schröder HV, Link AJ, Kim H, Brynildsen MP. Synergy Screening Identifies a Compound That Selectively Enhances the Antibacterial Activity of Nitric Oxide. Front Bioeng Biotechnol 2020; 8:1001. [PMID: 32984281 PMCID: PMC7477088 DOI: 10.3389/fbioe.2020.01001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 07/31/2020] [Indexed: 01/04/2023] Open
Abstract
Antibiotic resistance poses a serious threat to global health. To reinforce the anti-infective arsenal, many novel therapeutic strategies to fight bacterial infections are being explored. Among them, anti-virulence therapies, which target pathways important for virulence, have attracted much attention. Nitric oxide (NO) defense systems have been identified as critical for the pathogenesis of various bacteria, making them an appealing therapeutic target. In this study, we performed chemical screens to identify inhibitors of NO detoxification in Escherichia coli. We found that 2-mercaptobenzothiazole (2-MBT) can potently inhibit cellular detoxification of NO, achieving a level of inhibition that resembled the effect of genetically removing Hmp, the dominant detoxification enzyme under oxygenated conditions. Further analysis revealed that in the presence of NO, 2-MBT impaired the catalysis of Hmp and synthesis of Hmp and other proteins, whereas in its absence there were minimal perturbations to growth and protein synthesis. In addition, by studying the structure-activity relationship of 2-MBT, we found that both sulfur atoms in 2-MBT were vital for its inhibition of NO detoxification. Interestingly, when 2-mercaptothiazole (2-MT), which lacked the benzene ring, was used, differing biological activities were observed, although they too were NO dependent. Specifically, 2-MT could still prohibit NO detoxification, though it did not interfere with Hmp catalysis; rather, it was a stronger inhibitor of protein synthesis and it reduced the transcript levels of hmp, which was not observed with 2-MBT. Overall, these results provide a strong foundation for further exploration of 2-MBT and 2-MT for therapeutic applications.
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Affiliation(s)
- Wen Kang Chou
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, United States
| | - Mathini Vaikunthan
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, United States
| | - Hendrik V. Schröder
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, United States
| | - A. James Link
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, United States
- Frick Chemistry Laboratory, Department of Chemistry, Princeton University, Princeton, NJ, United States
- Department of Molecular Biology, Princeton University, Princeton, NJ, United States
| | - Hahn Kim
- Frick Chemistry Laboratory, Department of Chemistry, Princeton University, Princeton, NJ, United States
- Small Molecule Screening Center, Princeton University, Princeton, NJ, United States
| | - Mark P. Brynildsen
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, United States
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10
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Abstract
Flavohaemoglobins were first described in yeast as early as the 1970s but their functions were unclear. The surge in interest in nitric oxide biology and both serendipitous and hypothesis-driven discoveries in bacterial systems have transformed our understanding of this unusual two-domain globin into a comprehensive, yet undoubtedly incomplete, appreciation of its pre-eminent role in nitric oxide detoxification. Here, I focus on research on the flavohaemoglobins of microorganisms, especially of bacteria, and update several earlier and more comprehensive reviews, emphasising advances over the past 5 to 10 years and some controversies that have arisen. Inevitably, in light of space restrictions, details of nitric oxide metabolism and globins in higher organisms are brief.
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Affiliation(s)
- Robert K. Poole
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Sheffield, S10 2TN, UK
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11
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Abstract
This chapter provides an overview of current knowledge of how anaerobic bacteria protect themselves against nitrosative stress. Nitric oxide (NO) is the primary source of this stress. Aerobically its removal is an oxidative process, whereas reduction is required anaerobically. Mechanisms required to protect aerobic and anaerobic bacteria are therefore different. Several themes recur in the review. First, how gene expression is regulated often provides clues to the physiological function of the gene products. Second, the physiological significance of reports based upon experiments under extreme conditions that bacteria do not encounter in their natural environment requires reassessment. Third, responses to the primary source of stress need to be distinguished from secondary consequences of chemical damage due to failure of repair mechanisms to cope with extreme conditions. NO is generated by many mechanisms, some of which remain undefined. An example is the recent demonstration that the hybrid cluster protein combines with YtfE (or RIC protein, for repair of iron centres damaged by nitrosative stress) in a new pathway to repair key iron-sulphur proteins damaged by nitrosative stress. The functions of many genes expressed in response to nitrosative stress remain either controversial or are completely unknown. The concentration of NO that accumulates in the bacterial cytoplasm is essentially unknown, so dogmatic statements cannot be made that damage to transcription factors (Fur, FNR, SoxRS, MelR, OxyR) occurs naturally as part of a physiologically relevant signalling mechanism. Such doubts can be resolved by simple experiments to meet six proposed criteria.
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12
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Alvarez L, Quintáns NG, Blesa A, Baquedano I, Mencía M, Bricio C, Berenguer J. Hierarchical Control of Nitrite Respiration by Transcription Factors Encoded within Mobile Gene Clusters of Thermus thermophilus. Genes (Basel) 2017; 8:genes8120361. [PMID: 29194386 PMCID: PMC5748679 DOI: 10.3390/genes8120361] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 11/23/2017] [Accepted: 11/29/2017] [Indexed: 11/16/2022] Open
Abstract
Denitrification in Thermus thermophilus is encoded by the nitrate respiration conjugative element (NCE) and nitrite and nitric oxide respiration (nic) gene clusters. A tight coordination of each cluster’s expression is required to maximize anaerobic growth, and to avoid toxicity by intermediates, especially nitric oxides (NO). Here, we study the control of the nitrite reductases (Nir) and NO reductases (Nor) upon horizontal acquisition of the NCE and nic clusters by a formerly aerobic host. Expression of the nic promoters PnirS, PnirJ, and PnorC, depends on the oxygen sensor DnrS and on the DnrT protein, both NCE-encoded. NsrR, a nic-encoded transcription factor with an iron–sulfur cluster, is also involved in Nir and Nor control. Deletion of nsrR decreased PnorC and PnirJ transcription, and activated PnirS under denitrification conditions, exhibiting a dual regulatory role never described before for members of the NsrR family. On the basis of these results, a regulatory hierarchy is proposed, in which under anoxia, there is a pre-activation of the nic promoters by DnrS and DnrT, and then NsrR leads to Nor induction and Nir repression, likely as a second stage of regulation that would require NO detection, thus avoiding accumulation of toxic levels of NO. The whole system appears to work in remarkable coordination to function only when the relevant nitrogen species are present inside the cell.
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Affiliation(s)
- Laura Alvarez
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain.
- Current Address: Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå University, 90187 Umeå, Sweden.
| | - Nieves G Quintáns
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain.
| | - Alba Blesa
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain.
| | - Ignacio Baquedano
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain.
| | - Mario Mencía
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain.
| | - Carlos Bricio
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain.
| | - José Berenguer
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain.
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13
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Ebert M, Schweyen P, Bröring M, Laass S, Härtig E, Jahn D. Heme and nitric oxide binding by the transcriptional regulator DnrF from the marine bacterium Dinoroseobacter shibae increases napD promoter affinity. J Biol Chem 2017; 292:15468-15480. [PMID: 28765283 DOI: 10.1074/jbc.m117.798728] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/24/2017] [Indexed: 12/27/2022] Open
Abstract
Under oxygen-limiting conditions, the marine bacterium Dinoroseobacter shibae DFL12T generates energy via denitrification, a respiratory process in which nitric oxide (NO) is an intermediate. Accumulation of NO may cause cytotoxic effects. The response to this nitrosative (NO-triggered) stress is controlled by the Crp/Fnr-type transcriptional regulator DnrF. We analyzed the response to NO and the mechanism of NO sensing by the DnrF regulator. Using reporter gene fusions and transcriptomics, here we report that DnrF selectively repressed nitrate reductase (nap) genes, preventing further NO formation. In addition, DnrF induced the expression of the NO reductase genes (norCB), which promote NO consumption. We used UV-visible and EPR spectroscopy to characterize heme binding to DnrF and subsequent NO coordination. DnrF detects NO via its bound heme cofactor. We found that the dimeric DnrF bound one molecule of heme per subunit. Purified recombinant apo-DnrF bound its target promoter sequences (napD, nosR2, norC, hemA, and dnrE) in electromobility shift assays, and we identified a specific palindromic DNA-binding site 5'-TTGATN4ATCAA-3' in these target sequences via mutagenesis studies. Most importantly, successive addition of heme as well as heme and NO to purified recombinant apo-DnrF protein increased affinity of the holo-DnrF for its specific binding motif in the napD promoter. On the basis of these results, we propose a model for the DnrF-mediated NO stress response of this marine bacterium.
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Affiliation(s)
- Matthias Ebert
- From the Institute of Microbiology, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig
| | - Peter Schweyen
- the Institute for Inorganic and Analytical Chemistry, Technische Universität Braunschweig, Hagenring 30, D-38106 Braunschweig
| | - Martin Bröring
- the Institute for Inorganic and Analytical Chemistry, Technische Universität Braunschweig, Hagenring 30, D-38106 Braunschweig
| | - Sebastian Laass
- the Institute for Molecular Biosciences, Goethe-University Frankfurt, Max-von-Laue-Str. 9, D-60438 Frankfurt, and
| | - Elisabeth Härtig
- From the Institute of Microbiology, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig,
| | - Dieter Jahn
- the Braunschweig Integrated Centre of Systems Biology (BRICS), Technische Universität Braunschweig, Rebenring 56, D-38106 Braunschweig, Germany
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Exploring the Amino Acid Residue Requirements of the RNA Polymerase (RNAP) α Subunit C-Terminal Domain for Productive Interaction between Spx and RNAP of Bacillus subtilis. J Bacteriol 2017; 199:JB.00124-17. [PMID: 28484046 DOI: 10.1128/jb.00124-17] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 05/01/2017] [Indexed: 01/21/2023] Open
Abstract
Bacillus subtilis Spx is a global transcriptional regulator that is conserved among Gram-positive bacteria, in which Spx is required for preventing oxidatively induced proteotoxicity. Upon stress induction, Spx engages RNA polymerase (RNAP) through interaction with the C-terminal domain of the rpoA-encoded RNAP α subunit (αCTD). Previous mutational analysis of rpoA revealed that substitutions of Y263 in αCTD severely impaired Spx-activated transcription. Attempts to substitute alanine for αCTD R261, R268, R289, E255, E298, and K294 were unsuccessful, suggesting that these residues are essential. To determine whether these RpoA residues were required for productive Spx-RNAP interaction, we ectopically expressed the putatively lethal rpoA mutant alleles in the rpoAY263C mutant, where "Y263C" indicates the amino acid change that results from mutation of the allele. By complementation analysis, we show that Spx-bound αCTD amino acid residues are not essential for Spx-activated transcription in vivo but that R261A, E298A, and E255A mutants confer a partial defect in NaCl-stress induction of Spx-controlled genes. In addition, strains expressing rpoAE255A are defective in disulfide stress resistance and produce RNAP having a reduced affinity for Spx. The E255 residue corresponds to Escherichia coli αD259, which has been implicated in αCTD-σ70 interaction (σ70 R603, corresponding to R362 of B. subtilis σA). However, the combined rpoAE255A and sigAR362A mutations have an additive negative effect on Spx-dependent expression, suggesting the residues' differing roles in Spx-activated transcription. Our findings suggest that, while αCTD is essential for Spx-activated transcription, Spx is the primary DNA-binding determinant of the Spx-αCTD complex.IMPORTANCE Though extensively studied in Escherichia coli, the role of αCTD in activator-stimulated transcription is largely uncharacterized in Bacillus subtilis Here, we conduct phenotypic analyses of putatively lethal αCTD alanine codon substitution mutants to determine whether these residues function in specific DNA binding at the Spx-αCTD-DNA interface. Our findings suggest that multisubunit RNAP contact to Spx is optimal for activation while Spx fulfills the most stringent requirement of upstream promoter binding. Furthermore, several αCTD residues targeted for mutagenesis in this study are conserved among many bacterial species and thus insights on their function in other regulatory systems may be suggested herein.
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15
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Genome-Wide Analysis of ResD, NsrR, and Fur Binding in Bacillus subtilis during Anaerobic Fermentative Growth by In Vivo Footprinting. J Bacteriol 2017; 199:JB.00086-17. [PMID: 28439033 DOI: 10.1128/jb.00086-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 04/13/2017] [Indexed: 12/20/2022] Open
Abstract
Upon oxygen limitation, the Bacillus subtilis ResE sensor kinase and its cognate ResD response regulator play primary roles in the transcriptional activation of genes functioning in anaerobic respiration. The nitric oxide (NO)-sensitive NsrR repressor controls transcription to support nitrate respiration. In addition, the ferric uptake repressor (Fur) can modulate transcription under anaerobic conditions. However, whether these controls are direct or indirect has been investigated only in a gene-specific manner. To gain a genomic view of anaerobic gene regulation, we determined the genome-wide in vivo DNA binding of ResD, NsrR, and Fur transcription factors (TFs) using in situ DNase I footprinting combined with chromatin affinity precipitation sequencing (ChAP-seq; genome footprinting by high-throughput sequencing [GeF-seq]). A significant number of sites were targets of ResD and NsrR, and a majority of them were also bound by Fur. The binding of multiple TFs to overlapping targets affected each individual TF's binding, which led to combinatorial transcriptional control. ResD bound to both the promoters and the coding regions of genes under its positive control. Other genes showing enrichment of ResD at only the promoter regions are targets of direct ResD-dependent repression or antirepression. The results support previous findings of ResD as an RNA polymerase (RNAP)-binding protein and indicated that ResD can associate with the transcription elongation complex. The data set allowed us to reexamine consensus sequence motifs of Fur, ResD, and NsrR and uncovered evidence that multiple TGW (where W is A or T) sequences surrounded by an A- and T-rich sequence are often found at sites where all three TFs competitively bind.IMPORTANCE Bacteria encounter oxygen fluctuation in their natural environment as well as in host organisms. Hence, understanding how bacteria respond to oxygen limitation will impact environmental and human health. ResD, NsrR, and Fur control transcription under anaerobic conditions. This work using in situ DNase I footprinting uncovered the genome-wide binding profile of the three transcription factors (TFs). Binding of the TFs is often competitive or cooperative depending on the promoters and the presence of other TFs, indicating that transcriptional regulation by multiple TFs is much more complex than we originally thought. The results from this study provide a more complete picture of anaerobic gene regulation governed by ResD, NsrR, and Fur and contribute to our further understanding of anaerobic physiology.
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16
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Oogai Y, Kawada-Matsuo M, Komatsuzawa H. Staphylococcus aureus SrrAB Affects Susceptibility to Hydrogen Peroxide and Co-Existence with Streptococcus sanguinis. PLoS One 2016; 11:e0159768. [PMID: 27441894 PMCID: PMC4956065 DOI: 10.1371/journal.pone.0159768] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 07/06/2016] [Indexed: 11/30/2022] Open
Abstract
Staphylococcus aureus is a pathogen and a commensal bacterial species that is found in humans. Bacterial two-component systems (TCSs) sense and respond to environmental stresses, which include antimicrobial agents produced by other bacteria. In this study, we analyzed the relation between the TCS SrrAB and susceptibility to the hydrogen peroxide (H2O2) that is produced by Streptococcus sanguinis, which is a commensal oral streptococcus. An srrA-inactivated S. aureus mutant demonstrated low susceptibility to the H2O2 produced by S. sanguinis. We investigated the expression of anti-oxidant factors in the mutant. The expression of katA in the mutant was significantly higher than in the wild-type (WT) in the presence or absence of 0.4 mM H2O2. The expression of dps in the mutant was significantly increased compared with the WT in the presence of H2O2 but not in the absence of H2O2. A katA or a dps-inactivated mutant had high susceptibility to H2O2 compared with WT. In addition, we found that the nitric oxide detoxification protein (flavohemoglobin: Hmp), which is regulated by SrrAB, was related to H2O2 susceptibility. The hmp-inactivated mutant had slightly lower susceptibility to the H2O2 produced by S. sanguinis than did WT. When a srrA-inactivated mutant or the WT were co-cultured with S. sanguinis, the population percentage of the mutant was significantly higher than the WT. In conclusion, SrrAB regulates katA, dps and hmp expression and affects H2O2 susceptibility. Our findings suggest that SrrAB is related in vivo to the co-existence of S. aureus with S. sanguinis.
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Affiliation(s)
- Yuichi Oogai
- Department of Oral Microbiology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Miki Kawada-Matsuo
- Department of Oral Microbiology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Hitoshi Komatsuzawa
- Department of Oral Microbiology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
- * E-mail:
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17
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Crack JC, Munnoch J, Dodd EL, Knowles F, Al Bassam MM, Kamali S, Holland AA, Cramer SP, Hamilton CJ, Johnson MK, Thomson AJ, Hutchings MI, Le Brun NE. NsrR from Streptomyces coelicolor is a nitric oxide-sensing [4Fe-4S] cluster protein with a specialized regulatory function. J Biol Chem 2015; 290:12689-704. [PMID: 25771538 PMCID: PMC4432287 DOI: 10.1074/jbc.m115.643072] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Indexed: 12/31/2022] Open
Abstract
The Rrf2 family transcription factor NsrR controls expression of genes in a wide range of bacteria in response to nitric oxide (NO). The precise form of the NO-sensing module of NsrR is the subject of controversy because NsrR proteins containing either [2Fe-2S] or [4Fe-4S] clusters have been observed previously. Optical, Mössbauer, resonance Raman spectroscopies and native mass spectrometry demonstrate that Streptomyces coelicolor NsrR (ScNsrR), previously reported to contain a [2Fe-2S] cluster, can be isolated containing a [4Fe-4S] cluster. ChIP-seq experiments indicated that the ScNsrR regulon is small, consisting of only hmpA1, hmpA2, and nsrR itself. The hmpA genes encode NO-detoxifying flavohemoglobins, indicating that ScNsrR has a specialized regulatory function focused on NO detoxification and is not a global regulator like some NsrR orthologues. EMSAs and DNase I footprinting showed that the [4Fe-4S] form of ScNsrR binds specifically and tightly to an 11-bp inverted repeat sequence in the promoter regions of the identified target genes and that DNA binding is abolished following reaction with NO. Resonance Raman data were consistent with cluster coordination by three Cys residues and one oxygen-containing residue, and analysis of ScNsrR variants suggested that highly conserved Glu-85 may be the fourth ligand. Finally, we demonstrate that some low molecular weight thiols, but importantly not physiologically relevant thiols, such as cysteine and an analogue of mycothiol, bind weakly to the [4Fe-4S] cluster, and exposure of this bound form to O2 results in cluster conversion to the [2Fe-2S] form, which does not bind to DNA. These data help to account for the observation of [2Fe-2S] forms of NsrR.
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Affiliation(s)
- Jason C Crack
- From the Centre for Molecular and Structural Biochemistry, School of Chemistry
| | | | - Erin L Dodd
- From the Centre for Molecular and Structural Biochemistry, School of Chemistry
| | | | | | - Saeed Kamali
- the Department of Chemistry, University of California, Davis, California 95616, and
| | - Ashley A Holland
- the Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602
| | - Stephen P Cramer
- the Department of Chemistry, University of California, Davis, California 95616, and
| | - Chris J Hamilton
- the School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, United Kingdom
| | - Michael K Johnson
- the Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602
| | - Andrew J Thomson
- From the Centre for Molecular and Structural Biochemistry, School of Chemistry
| | | | - Nick E Le Brun
- From the Centre for Molecular and Structural Biochemistry, School of Chemistry,
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18
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Fujikawa M, Kobayashi K, Kozawa T. Mechanistic studies on formation of the dinitrosyl iron complex of the [2Fe-2S] cluster of SoxR protein. J Biochem 2014; 156:163-72. [DOI: 10.1093/jb/mvu029] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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19
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Stern AM, Zhu J. An introduction to nitric oxide sensing and response in bacteria. ADVANCES IN APPLIED MICROBIOLOGY 2014; 87:187-220. [PMID: 24581392 DOI: 10.1016/b978-0-12-800261-2.00005-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Nitric oxide (NO) is a radical gas that has been intensively studied for its role as a bacteriostatic agent. NO reacts in complex ways with biological molecules, especially metal centers and other radicals, to generate other bioactive compounds that inhibit enzymes, oxidize macromolecules, and arrest bacterial growth. Bacteria encounter not only NO derived from the host during infection but also NO derived from other bacteria and inorganic sources. The transcriptional responses used by bacteria to respond to NO are diverse but usually involve an iron-containing transcription factor that binds NO and alters its affinity for either DNA or factors involved in transcription, leading to the production of enzymatic tolerance systems. Some of these systems, such as flavohemoglobin and flavorubredoxin, directly remove NO. Some do not but are still important for NO tolerance through other mechanisms. The targets of NO that are protected by these systems include many metabolic pathways such as the tricarboxylic acid cycle and branched chain amino acid synthesis. This chapter discusses these topics and others and serves as a general introduction to microbial NO biology.
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20
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The Staphylococcus aureus SrrAB two-component system promotes resistance to nitrosative stress and hypoxia. mBio 2013; 4:e00696-13. [PMID: 24222487 PMCID: PMC3892780 DOI: 10.1128/mbio.00696-13] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Staphylococcus aureus is both a commensal and a pathogen of the human host. Survival in the host environment requires resistance to host-derived nitric oxide (NO·). However, S. aureus lacks the NO·-sensing transcriptional regulator NsrR that is used by many bacteria to sense and respond to NO·. In this study, we show that S. aureus is able to sense and respond to both NO· and hypoxia by means of the SrrAB two-component system (TCS). Analysis of the S. aureus transcriptome during nitrosative stress demonstrates the expression of SrrAB-dependent genes required for cytochrome biosynthesis and assembly (qoxABCD, cydAB, hemABCX), anaerobic metabolism (pflAB, adhE, nrdDG), iron-sulfur cluster repair (scdA), and NO· detoxification (hmp). Targeted mutations in SrrAB-regulated loci show that hmp and qoxABCD are required for NO· resistance, whereas nrdDG is specifically required for anaerobic growth. We also show that SrrAB is required for survival in static biofilms, most likely due to oxygen limitation. Activation by hypoxia, NO·, or a qoxABCD quinol oxidase mutation suggests that the SrrAB TCS senses impaired electron flow in the electron transport chain rather than directly interacting with NO· in the manner of NsrR. Nevertheless, like NsrR, SrrAB achieves the physiological goals of selectively expressing hmp in the presence of NO· and minimizing the potential for Fenton chemistry. Activation of the SrrAB regulon allows S. aureus to maintain energy production and essential biosynthetic processes, repair damage, and detoxify NO· in diverse host environments. The Hmp flavohemoglobin is required for nitric oxide resistance and is widely distributed in bacteria. Hmp expression must be tightly regulated, because expression under aerobic conditions in the absence of nitric oxide can exacerbate oxidative stress. In most organisms, hmp expression is controlled by the Fe-S cluster-containing repressor NsrR, but this transcriptional regulator is absent in the human pathogen Staphylococcus aureus. We show here that S. aureus achieves hmp regulation in response to nitric oxide and oxygen limitation by placing it under the control of the SrrAB two-component system, which senses reduced electron flow through the respiratory chain. This provides a striking example of convergent evolution, in which the common physiological goals of responding to nitrosative stress while minimizing Fenton chemistry are achieved by distinct regulatory mechanisms.
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21
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The ResD response regulator, through functional interaction with NsrR and fur, plays three distinct roles in Bacillus subtilis transcriptional control. J Bacteriol 2013; 196:493-503. [PMID: 24214949 DOI: 10.1128/jb.01166-13] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The ResD response regulator activates transcription of diverse genes in Bacillus subtilis in response to oxygen limitation. ResD regulon genes that are the most highly induced during nitrate respiration include the nitrite reductase operon (nasDEF) and the flavohemoglobin gene (hmp), whose products function in nitric oxide (NO) metabolism. Transcription of these genes is also under the negative control of the NO-sensitive NsrR repressor. Recent studies showed that the NsrR regulon contains genes with no apparent relevance to NO metabolism and that the ResD response regulator and NsrR coordinately regulate transcription. To determine whether these genes are direct targets of NsrR and ResD, we used chromatin affinity precipitation coupled with tiling chip (ChAP-chip) and ChAP followed by quantitative PCR (ChAP-qPCR) analyses. The study showed that ResD and NsrR directly control transcription of the ykuNOP operon in the Fur regulon. ResD functions as an activator at the nasD and hmp promoters, whereas it functions at the ykuN promoter as an antirepressor of Fur and a corepressor for NsrR. This mechanism likely participates in fine-tuning of transcript levels in response to different sources of stress, such as oxygen limitation, iron limitation, and exposure to NO.
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22
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Abstract
The Gram-positive soil bacterium Bacillus subtilis encounters changing environmental conditions in its habitat. The access to oxygen determines the mode of energy generation. A complex regulatory network is employed to switch from oxygen respiration to nitrate respiration and various fermentative processes. During adaptation, oxygen depletion is sensed by the [4Fe-4S](2+) cluster containing Fnr and the two-component regulatory system ResDE consisting of the membrane-bound histidine kinase ResE and the cytoplasmic ResD regulator. Nitric oxide is the signal recognized by NsrR. Acetate formation and decreasing pH are measured via AlsR. Finally, Rex is responding to changes in the cellular NAD(+)/NADH ration. The fine-tuned interplay of these regulators at approximately 400 target gene promoters ensures efficient adaptation of the B. subtilis physiology.
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Affiliation(s)
- Elisabeth Härtig
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Germany.
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23
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Yukl ET, Elbaz MA, Nakano MM, Moënne-Loccoz P. Transcription Factor NsrR from Bacillus subtilis Senses Nitric Oxide with a 4Fe-4S Cluster (†). Biochemistry 2012; 47:13084-92. [PMID: 19006327 DOI: 10.1021/bi801342x] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
In Bacillus subtilis, NsrR is required for the upregulation of ResDE-dependent genes in the presence of nitric oxide (NO). NsrR was shown to bind to the promoters of these genes and inhibit their transcription in vitro. NO relieves this inhibition by an unknown mechanism. Here, we use spectroscopic techniques (UV-vis, resonance Raman, and EPR) to show that anaerobically isolated NsrR from B. subtilis contains a [4Fe-4S](2+) cluster, which reacts with NO to form dinitrosyl iron complexes. This method of NO sensing is analogous to that of the FNR protein of Escherichia coli. The Fe-S cluster of NsrR is also reactive toward other exogenous ligands such as cyanide, dithiothreitol, and O(2). These results, together with the fact that there are only three cysteine residues in NsrR, suggest that the 4Fe-4S cluster contains a noncysteinyl labile ligand to one of the iron atoms, leading to high reactivity. Size exclusion chromatography and cross-linking experiments show that NsrR adopts a dimeric structure in its [4Fe-4S](2+) holo form as well as in the apo form. These findings provide a first stepping stone to investigate the mechanism of NO sensing in NsrR.
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Affiliation(s)
- Erik T Yukl
- Department of Science and Engineering, School of Medicine, Oregon Health & Science University, 20,000 NW Walker Road, Beaverton, Oregon 97006-8921
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24
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Forrester MT, Foster MW. Protection from nitrosative stress: a central role for microbial flavohemoglobin. Free Radic Biol Med 2012; 52:1620-33. [PMID: 22343413 DOI: 10.1016/j.freeradbiomed.2012.01.028] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 01/22/2012] [Accepted: 01/27/2012] [Indexed: 12/31/2022]
Abstract
Nitric oxide (NO) is an inevitable product of life in an oxygen- and nitrogen-rich environment. This reactive diatomic molecule exhibits microbial cytotoxicity, in large part by facilitating nitrosative stress and inhibiting heme-containing proteins within the aerobic respiratory chain. Metabolism of NO is therefore essential for microbial life. In many bacteria, fungi, and protozoa, the evolutionarily ancient flavohemoglobin (flavoHb) converts NO and O(2) to inert nitrate (NO(3)(-)) and undergoes catalytic regeneration via flavin-dependent reduction. Since its identification, widespread efforts have characterized roles for flavoHb in microbial nitrosative stress protection. Subsequent genomic studies focused on flavoHb have elucidated the transcriptional machinery necessary for inducible NO protection, such as NsrR in Escherichia coli, as well as additional proteins that constitute a nitrosative stress protection program. As an alternative strategy, flavoHb has been heterologously employed in higher eukaryotic organisms such as plants and human tumors to probe the function(s) of endogenous NO signaling. Such an approach may also provide a therapeutic route to in vivo NO depletion. Here we focus on the molecular features of flavoHb, the hitherto characterized NO-sensitive transcriptional machinery responsible for its induction, the roles of flavoHb in resisting mammalian host defense systems, and heterologous applications of flavoHb in plant/mammalian systems (including human tumors), as well as unresolved questions surrounding this paradigmatic NO-consuming enzyme.
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Affiliation(s)
- Michael T Forrester
- Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
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25
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Bueno E, Mesa S, Bedmar EJ, Richardson DJ, Delgado MJ. Bacterial adaptation of respiration from oxic to microoxic and anoxic conditions: redox control. Antioxid Redox Signal 2012; 16:819-52. [PMID: 22098259 PMCID: PMC3283443 DOI: 10.1089/ars.2011.4051] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 11/16/2011] [Accepted: 11/18/2011] [Indexed: 12/22/2022]
Abstract
Under a shortage of oxygen, bacterial growth can be faced mainly by two ATP-generating mechanisms: (i) by synthesis of specific high-affinity terminal oxidases that allow bacteria to use traces of oxygen or (ii) by utilizing other substrates as final electron acceptors such as nitrate, which can be reduced to dinitrogen gas through denitrification or to ammonium. This bacterial respiratory shift from oxic to microoxic and anoxic conditions requires a regulatory strategy which ensures that cells can sense and respond to changes in oxygen tension and to the availability of other electron acceptors. Bacteria can sense oxygen by direct interaction of this molecule with a membrane protein receptor (e.g., FixL) or by interaction with a cytoplasmic transcriptional factor (e.g., Fnr). A third type of oxygen perception is based on sensing changes in redox state of molecules within the cell. Redox-responsive regulatory systems (e.g., ArcBA, RegBA/PrrBA, RoxSR, RegSR, ActSR, ResDE, and Rex) integrate the response to multiple signals (e.g., ubiquinone, menaquinone, redox active cysteine, electron transport to terminal oxidases, and NAD/NADH) and activate or repress target genes to coordinate the adaptation of bacterial respiration from oxic to anoxic conditions. Here, we provide a compilation of the current knowledge about proteins and regulatory networks involved in the redox control of the respiratory adaptation of different bacterial species to microxic and anoxic environments.
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Affiliation(s)
- Emilio Bueno
- Estación Experimental del Zaidín, CSIC, Granada, Spain
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Aono S. Novel bacterial gas sensor proteins with transition metal-containing prosthetic groups as active sites. Antioxid Redox Signal 2012; 16:678-86. [PMID: 21902455 DOI: 10.1089/ars.2011.4248] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
SIGNIFICANCE Gas molecules function as signaling molecules in many biological regulatory systems responsible for transcription, chemotaxis, and other complex physiological processes. Gas sensor proteins play a crucial role in regulating such biological systems in response to gas molecules. RECENT ADVANCES New sensor proteins that sense oxygen or nitric oxide have recently been found, and they have been characterized by X-ray crystallographic and/or spectroscopic analysis. It has become clear that the interaction between a prosthetic group and gas molecules triggers dynamic structural changes in the protein backbone when a gas sensor protein senses gas molecules. Gas sensor proteins employ novel mechanisms to trigger conformational changes in the presence of a gas. CRITICAL ISSUES In gas sensor proteins that have iron-sulfur clusters as active sites, the iron-sulfur clusters undergo structural changes, which trigger a conformational change. Heme-based gas sensor proteins reconstruct hydrogen-bonding networks around the heme and heme-bound ligand. FUTURE DIRECTION Gas sensor proteins have two functional states, on and off, which are active and inactive, respectively, for subsequent signal transduction in response to their physiological effector molecules. To fully understand the structure-function relationships of gas sensor proteins, it is vital to perform X-ray crystal structure analyses of full-length proteins in both the on and off states.
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Affiliation(s)
- Shigetoshi Aono
- Okazaki Institute of Natural Sciences, National Institutes of Natural Sciences, Myodaiji, Okazaki, Japan.
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Evidence that a single monomer of Spx can productively interact with RNA polymerase in Bacillus subtilis. J Bacteriol 2012; 194:1697-707. [PMID: 22307755 DOI: 10.1128/jb.06660-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Spx activates transcription initiation in Bacillus subtilis by directly interacting with the C-terminal domain of the RNA polymerase (RNAP) holoenzyme α subunit, which generates a complex that recognizes the promoter regions of genes within the Spx regulon. Many Gram-positive species possess multiple paralogs of Spx, suggesting that two paralogous forms of Spx could simultaneously contact RNAP. The composition of Spx/RNAP was examined in vitro using an Spx variant (SpxΔCHA) bearing a 12-amino-acid deletion of the C terminus (SpxΔC) and a hemagglutinin (HA) epitope tag and Spxc-Myc, a full-length Spx with a C-terminal myelocytomatosis oncoprotein (c-Myc) epitope tag. All Spx/RNAP complexes bearing deletion or C-terminal-tagged variants were transcriptionally active in vivo and in vitro. Reaction mixtures containing SpxΔCHA and Spxc-Myc combined with RNAP were applied to either anti-HA or anti-c-Myc affinity columns. Eluted fractions contained RNAP with only one of the epitope-tagged Spx derivatives. The resin-bound RNAP complex bearing a single epitope-tagged Spx derivative was transcriptionally active. In vivo production of SpxΔC and SpxΔCHA followed by anti-HA affinity column chromatography of a cleared lysate resulted in retrieval of Spx/RNAP with only the SpxΔCHA derivative. Binding reactions that combined active Spxc-Myc, inactive Spx(R60E)ΔCHA, and RNAP, when applied to the anti-HA affinity column, yielded only inactive Spx(R60E)ΔCHA/RNAP complexes. The results strongly argue for a model in which a single Spx monomer engages RNAP to generate an active transcriptional complex.
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Abstract
The NO-sensitive NsrR repressor of Bacillus subtilis, which carries a [4Fe-4S] cluster, controls transcription of nasD and hmp (class I regulation) under anaerobic conditions. Here, we describe another class of NsrR regulation (class II regulation) that controls a more diverse collection of genes. Base substitution analysis showed that [4Fe-4S]-NsrR recognizes a partial dyad symmetry within the class I cis-acting sites, whereas NO-insensitive interaction of NsrR with an A+T-rich class II regulatory site showed relaxed sequence specificity. Genome-wide transcriptome studies identified genes that are under the control of the class II NsrR regulation. The class II NsrR regulon includes genes controlled by both AbrB and Rok repressors, which also recognize A+T-rich sequences, and by the Fur repressor. Transcription of class II genes was elevated in an nsrR mutant during anaerobic fermentative growth with pyruvate. Although NsrR binding to the class II regulatory sites was NO insensitive in vitro, transcription of class II genes was moderately induced by NO, which involved reversal of NsrR-dependent repression, suggesting that class II repression is also NO sensitive. In all NsrR-repressed genes tested, the loss of NsrR repressor activity was not sufficient to induce transcription as induction required the ResD response regulator. The ResD-ResE signal transduction system is essential for activation of genes involved in aerobic and anaerobic respiration. This study indicated coordinated regulation between ResD and NsrR and uncovered a new role of ResD and NsrR in transcriptional regulation during anaerobiosis of B. subtilis.
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Huis in 't Veld RAG, Willemsen AM, van Kampen AHC, Bradley EJ, Baas F, Pannekoek Y, van der Ende A. Deep sequencing whole transcriptome exploration of the σE regulon in Neisseria meningitidis. PLoS One 2011; 6:e29002. [PMID: 22194974 PMCID: PMC3240639 DOI: 10.1371/journal.pone.0029002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Accepted: 11/18/2011] [Indexed: 01/24/2023] Open
Abstract
Bacteria live in an ever-changing environment and must alter protein expression promptly to adapt to these changes and survive. Specific response genes that are regulated by a subset of alternative σ70-like transcription factors have evolved in order to respond to this changing environment. Recently, we have described the existence of a σE regulon including the anti-σ-factor MseR in the obligate human bacterial pathogen Neisseria meningitidis. To unravel the complete σE regulon in N. meningitidis, we sequenced total RNA transcriptional content of wild type meningococci and compared it with that of mseR mutant cells (ΔmseR) in which σE is highly expressed. Eleven coding genes and one non-coding gene were found to be differentially expressed between H44/76 wildtype and H44/76ΔmseR cells. Five of the 6 genes of the σE operon, msrA/msrB, and the gene encoding a pepSY-associated TM helix family protein showed enhanced transcription, whilst aniA encoding a nitrite reductase and nspA encoding the vaccine candidate Neisserial surface protein A showed decreased transcription. Analysis of differential expression in IGRs showed enhanced transcription of a non-coding RNA molecule, identifying a σE dependent small non-coding RNA. Together this constitutes the first complete exploration of an alternative σ-factor regulon in N. meningitidis. The results direct to a relatively small regulon indicative for a strictly defined response consistent with a relatively stable niche, the human throat, where N. meningitidis resides.
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Treece E, Pinkham A, Kim T. Aminoguanidine down-regulates the expression of mreB-like protein in Bacillus subtilis. Curr Microbiol 2011; 64:112-7. [PMID: 22048160 DOI: 10.1007/s00284-011-0039-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Accepted: 10/08/2011] [Indexed: 10/16/2022]
Abstract
Nitric oxide synthase (NOS), the enzyme responsible for the production of endogenous nitric oxide from arginine, has been recently discovered in a number of Gram-positive bacteria. While bacterial NOS has been implicated in mediating nitrosative stress, much remains unknown about the functional role of endogenous nitric oxide in bacteria. Using the known NOS inhibitor aminoguanidine, we examined changes in the protein expression profile using two-dimensional gel electrophoresis. Treatment with aminoguanidine induced several changes in protein expression in Bacillus subtilis. In particular, mreB-like protein (Mbl) was fully down-regulated in the aminoguanidine-treated samples. The expression of Mbl was also examined by reverse transcriptase-polymerase chain reaction and Mbl was found to be fully down-regulated at the transcriptional level as well. Given the role that Mbl plays in the maintenance of cytoskeletal structure, it appears that bacterial NOS may participate in specific biosynthetic pathways with ramifications toward the regulation of antibiotic resistance.
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Affiliation(s)
- Erin Treece
- Department of Chemistry, Rochester Institute of Technology, Rochester, NY, USA
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Isabella VM, Clark VL. Deep sequencing-based analysis of the anaerobic stimulon in Neisseria gonorrhoeae. BMC Genomics 2011; 12:51. [PMID: 21251255 PMCID: PMC3032703 DOI: 10.1186/1471-2164-12-51] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Accepted: 01/20/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Maintenance of an anaerobic denitrification system in the obligate human pathogen, Neisseria gonorrhoeae, suggests that an anaerobic lifestyle may be important during the course of infection. Furthermore, mounting evidence suggests that reduction of host-produced nitric oxide has several immunomodulary effects on the host. However, at this point there have been no studies analyzing the complete gonococcal transcriptome response to anaerobiosis. Here we performed deep sequencing to compare the gonococcal transcriptomes of aerobically and anaerobically grown cells. Using the information derived from this sequencing, we discuss the implications of the robust transcriptional response to anaerobic growth. RESULTS We determined that 198 chromosomal genes were differentially expressed (~10% of the genome) in response to anaerobic conditions. We also observed a large induction of genes encoded within the cryptic plasmid, pJD1. Validation of RNA-seq data using translational-lacZ fusions or RT-PCR demonstrated the RNA-seq results to be very reproducible. Surprisingly, many genes of prophage origin were induced anaerobically, as well as several transcriptional regulators previously unknown to be involved in anaerobic growth. We also confirmed expression and regulation of a small RNA, likely a functional equivalent of fnrS in the Enterobacteriaceae family. We also determined that many genes found to be responsive to anaerobiosis have also been shown to be responsive to iron and/or oxidative stress. CONCLUSIONS Gonococci will be subject to many forms of environmental stress, including oxygen-limitation, during the course of infection. Here we determined that the anaerobic stimulon in gonococci was larger than previous studies would suggest. Many new targets for future research have been uncovered, and the results derived from this study may have helped to elucidate factors or mechanisms of virulence that may have otherwise been overlooked.
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Affiliation(s)
- Vincent M Isabella
- Department of Microbiology and Immunology, School of Medicine and Dentistry, University of Rochester, Box 672, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Virginia L Clark
- Department of Microbiology and Immunology, School of Medicine and Dentistry, University of Rochester, Box 672, 601 Elmwood Avenue, Rochester, NY 14642, USA
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Kommineni S, Yukl E, Hayashi T, Delepine J, Geng H, Moënne-Loccoz P, Nakano MM. Nitric oxide-sensitive and -insensitive interaction of Bacillus subtilis NsrR with a ResDE-controlled promoter. Mol Microbiol 2010; 78:1280-93. [PMID: 21091510 DOI: 10.1111/j.1365-2958.2010.07407.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
NsrR is a nitric oxide (NO)-sensitive transcription repressor that controls NO metabolism in a wide range of bacteria. In Bacillus subtilis, NsrR represses transcription of the nitrite reductase (nasDEF) genes that are under positive control of the ResD-ResE two-component signal transduction system. Derepression is achieved by reaction of NO with NsrR. Unlike some NsrR orthologues that were shown to contain a NO-sensitive [2Fe-2S] cluster, B. subtilis NsrR, when purified anaerobically either from aerobic or from anaerobic Escherichia coli and B. subtilis cultures, contains a [4Fe-4S] cluster. [4Fe-4S]-NsrR binds around the -35 element of the nasD promoter with much higher affinity than apo-NsrR and binding of [4Fe-4S]-NsrR, but not apo-protein, is sensitive to NO. RNA polymerase and phosphorylated ResD make a ternary complex at the nasD promoter and NsrR dissociates the preformed ternary complex. In addition to the -35 region, NsrR binds to two distinct sites of the upstream regulatory region where ResD also binds. These interactions, unlike the high-affinity site binding, do not depend on the NsrR [4Fe-4S] cluster and binding is not sensitive to NO, suggesting a role for apo-NsrR in transcriptional regulation.
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Affiliation(s)
- Sushma Kommineni
- Department of Science & Engineering, School of Medicine, Oregon Health & Science University, 20000 NW Walker Road, Beaverton, OR 97006, USA
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Role of flavohemoglobin in combating nitrosative stress in uropathogenic Escherichia coli – Implications for urinary tract infection. Microb Pathog 2010; 49:59-66. [DOI: 10.1016/j.micpath.2010.04.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Revised: 04/01/2010] [Accepted: 04/09/2010] [Indexed: 11/22/2022]
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Lu TT, Yang LB, Liaw WF. Trigonal Bipyramidal {Fe(NO)} 7Complex [(NO)Fe(SC 9H 6N) 2] Containing an Equatorial Nitrosyl Ligand: The Critical Role of Chelating Ligands in Regulating the Geometry and Transformation of Mononitrosyl Iron Complex (MNIC). J CHIN CHEM SOC-TAIP 2010. [DOI: 10.1002/jccs.201000126] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Nakano MM, Lin A, Zuber CS, Newberry KJ, Brennan RG, Zuber P. Promoter recognition by a complex of Spx and the C-terminal domain of the RNA polymerase alpha subunit. PLoS One 2010; 5:e8664. [PMID: 20084284 PMCID: PMC2801614 DOI: 10.1371/journal.pone.0008664] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Accepted: 12/19/2009] [Indexed: 12/20/2022] Open
Abstract
Background Spx, an ArsC (arsenate reductase) family member, is a global transcriptional regulator of the microbial stress response and is highly conserved amongst Gram-positive bacteria. Bacillus subtilis Spx protein exerts positive and negative control of transcription through its interaction with the C-terminal domain of the RNA polymerase (RNAP) α subunit (αCTD). Spx activates trxA (thioredoxin) and trxB (thioredoxin reductase) in response to thiol stress, and bears an N-terminal C10XXC13 redox disulfide center that is oxidized in active Spx. Methodology/Principal Findings The structure of mutant SpxC10S showed a change in the conformation of helix α4. Amino acid substitutions R60E and K62E within and adjacent to helix α4 conferred defects in Spx-activated transcription but not Spx-dependent repression. Electrophoretic mobility-shift assays showed αCTD interaction with trxB promoter DNA, but addition of Spx generated a supershifted complex that was disrupted in the presence of reductant (DTT). Interaction of αCTD/Spx complex with promoter DNA required the cis-acting elements -45AGCA-42 and -34AGCG-31 of the trxB promoter. The SpxG52R mutant, defective in αCTD binding, did not interact with the αCTD-trxB complex. SpxR60E not only failed to complex with αCTD-trxB, but also disrupted αCTD-trxB DNA interaction. Conclusions/Significance The results show that Spx and αCTD form a complex that recognizes the promoter DNA of an Spx-controlled gene. A conformational change during oxidation of Spx to the disulfide form likely alters the structure of Spx α helix α4, which contains residues that function in transcriptional activation and αCTD/Spx-promoter interaction. The results suggest that one of these residues, R60 of the α4 region of oxidized Spx, functions in αCTD/Spx-promoter contact but not in αCTD interaction.
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Affiliation(s)
- Michiko M. Nakano
- Department of Science & Engineering, School of Medicine, Oregon Health & Science University, Beaverton, Oregon, United States of America
| | - Ann Lin
- Department of Science & Engineering, School of Medicine, Oregon Health & Science University, Beaverton, Oregon, United States of America
| | - Cole S. Zuber
- Department of Science & Engineering, School of Medicine, Oregon Health & Science University, Beaverton, Oregon, United States of America
| | - Kate J. Newberry
- Department of Biochemistry and Molecular Biology, University of Texas, M. D. Anderson Cancer Center, Texas, United States of America
| | - Richard G. Brennan
- Department of Biochemistry and Molecular Biology, University of Texas, M. D. Anderson Cancer Center, Texas, United States of America
| | - Peter Zuber
- Department of Science & Engineering, School of Medicine, Oregon Health & Science University, Beaverton, Oregon, United States of America
- * E-mail:
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Abstract
The spore-forming bacterium and model prokaryotic genetic system, Bacillus subtilis, is extremely useful in the study of oxidative stress management through proteomic and genome-wide transcriptomic analyses, as well as through detailed structural studies of the regulatory factors that govern the oxidative stress response. The factors that sense oxidants and induce expression of protective activities include the PerR and OhrR proteins, which show acute discrimination for their peroxide stimuli, whereas the general stress control factor, the RNA polymerase sigma(B) subunit and the thiol-based sensor Spx, govern the protective response to oxidants under multiple stress conditions. Some specific and some redundant protective mechanisms are mobilized at different stages of the Bacillus developmental cycle to deal with vulnerable cells in stationary-phase conditions and during spore germination and outgrowth. An important unknown is the nature and influence of the low-molecular-weight thiols that mediate the buffering of the redox environment.
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Affiliation(s)
- Peter Zuber
- Department of Science & Engineering, School of Medicine, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
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Barth KR, Isabella VM, Clark VL. Biochemical and genomic analysis of the denitrification pathway within the genus Neisseria. MICROBIOLOGY-SGM 2009; 155:4093-4103. [PMID: 19762442 DOI: 10.1099/mic.0.032961-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Since Neisseria gonorrhoeae and Neisseria meningitidis are obligate human pathogens, a comparison with commensal species of the same genus could reveal differences important in pathogenesis. The recent completion of commensal Neisseria genome draft assemblies allowed us to perform a comparison of the genes involved in the catalysis, assembly and regulation of the denitrification pathway, which has been implicated in the virulence of several bacteria. All species contained a highly conserved nitric oxide reductase (NorB) and a nitrite reductase (AniA or NirK) that was highly conserved in the catalytic but divergent in the N-terminal lipid modification and C-terminal glycosylation domains. Only Neisseria mucosa contained a nitrate reductase (Nar), and only Neisseria lactamica, Neisseria cinerea, Neisseria subflava, Neisseria flavescens and Neisseria sicca contained a nitrous oxide reductase (Nos) complex. The regulators of the denitrification genes, FNR, NarQP and NsrR, were highly conserved, except for the GAF domain of NarQ. Biochemical examination of laboratory strains revealed that all of the neisserial species tested except N. mucosa had a two- to fourfold lower nitrite reductase activity than N. gonorrhoeae, while N. meningitidis and most of the commensal Neisseria species had a two- to fourfold higher nitric oxide (NO) reductase activity. For N. meningitidis and most of the commensal Neisseria, there was a greater than fourfold reduction in the NO steady-state level in the presence of nitrite as compared with N. gonorrhoeae. All of the species tested generated an NO steady-state level in the presence of an NO donor that was similar to that of N. gonorrhoeae. The greatest difference between the Neisseria species was the lack of a functional Nos system in the pathogenic species N. gonorrhoeae and N. meningitidis.
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Affiliation(s)
- Kenneth R Barth
- Department of Microbiology and Immunology, School of Medicine and Dentistry, University of Rochester, Box 672, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Vincent M Isabella
- Department of Microbiology and Immunology, School of Medicine and Dentistry, University of Rochester, Box 672, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Virginia L Clark
- Department of Microbiology and Immunology, School of Medicine and Dentistry, University of Rochester, Box 672, 601 Elmwood Avenue, Rochester, NY 14642, USA
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Lu TT, Huang HW, Liaw WF. Anionic Mixed Thiolate−Sulfide-Bridged Roussin’s Red Esters [(NO)2Fe(μ-SR)(μ-S)Fe(NO)2]− (R = Et, Me, Ph): A Key Intermediate for Transformation of Dinitrosyl Iron Complexes (DNICs) to [2Fe-2S] Clusters. Inorg Chem 2009; 48:9027-35. [DOI: 10.1021/ic9012679] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tsai-Te Lu
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Hsiao-Wen Huang
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Wen-Feng Liaw
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
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Barbe V, Cruveiller S, Kunst F, Lenoble P, Meurice G, Sekowska A, Vallenet D, Wang T, Moszer I, Médigue C, Danchin A. From a consortium sequence to a unified sequence: the Bacillus subtilis 168 reference genome a decade later. MICROBIOLOGY (READING, ENGLAND) 2009; 155:1758-1775. [PMID: 19383706 PMCID: PMC2885750 DOI: 10.1099/mic.0.027839-0] [Citation(s) in RCA: 257] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Revised: 02/25/2009] [Accepted: 02/25/2009] [Indexed: 11/18/2022]
Abstract
Comparative genomics is the cornerstone of identification of gene functions. The immense number of living organisms precludes experimental identification of functions except in a handful of model organisms. The bacterial domain is split into large branches, among which the Firmicutes occupy a considerable space. Bacillus subtilis has been the model of Firmicutes for decades and its genome has been a reference for more than 10 years. Sequencing the genome involved more than 30 laboratories, with different expertises, in a attempt to make the most of the experimental information that could be associated with the sequence. This had the expected drawback that the sequencing expertise was quite varied among the groups involved, especially at a time when sequencing genomes was extremely hard work. The recent development of very efficient, fast and accurate sequencing techniques, in parallel with the development of high-level annotation platforms, motivated the present resequencing work. The updated sequence has been reannotated in agreement with the UniProt protein knowledge base, keeping in perspective the split between the paleome (genes necessary for sustaining and perpetuating life) and the cenome (genes required for occupation of a niche, suggesting here that B. subtilis is an epiphyte). This should permit investigators to make reliable inferences to prepare validation experiments in a variety of domains of bacterial growth and development as well as build up accurate phylogenies.
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Affiliation(s)
- Valérie Barbe
- CEA, Institut de Génomique, Génoscope, 2 rue Gaston Crémieux, 91057 Évry, France
| | - Stéphane Cruveiller
- CEA, Institut de Génomique, Laboratoire de Génomique Comparative/CNRS UMR8030, Génoscope, 2 rue Gaston Crémieux, 91057 Évry, France
| | - Frank Kunst
- CEA, Institut de Génomique, Génoscope, 2 rue Gaston Crémieux, 91057 Évry, France
| | - Patricia Lenoble
- CEA, Institut de Génomique, Génoscope, 2 rue Gaston Crémieux, 91057 Évry, France
| | - Guillaume Meurice
- Institut Pasteur, Intégration et Analyse Génomiques, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France
| | - Agnieszka Sekowska
- Institut Pasteur, Génétique des Génomes Bactériens/CNRS URA2171, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France
| | - David Vallenet
- CEA, Institut de Génomique, Laboratoire de Génomique Comparative/CNRS UMR8030, Génoscope, 2 rue Gaston Crémieux, 91057 Évry, France
| | - Tingzhang Wang
- Institut Pasteur, Génétique des Génomes Bactériens/CNRS URA2171, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France
| | - Ivan Moszer
- Institut Pasteur, Intégration et Analyse Génomiques, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France
| | - Claudine Médigue
- CEA, Institut de Génomique, Laboratoire de Génomique Comparative/CNRS UMR8030, Génoscope, 2 rue Gaston Crémieux, 91057 Évry, France
| | - Antoine Danchin
- Institut Pasteur, Génétique des Génomes Bactériens/CNRS URA2171, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France
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Hecker M, Reder A, Fuchs S, Pagels M, Engelmann S. Physiological proteomics and stress/starvation responses in Bacillus subtilis and Staphylococcus aureus. Res Microbiol 2009; 160:245-58. [PMID: 19403106 DOI: 10.1016/j.resmic.2009.03.008] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Revised: 03/20/2009] [Accepted: 03/23/2009] [Indexed: 10/20/2022]
Abstract
Gel-based proteomics is a useful approach for visualizing the responses of bacteria to stress and starvation stimuli. In order to face stress/starvation, bacteria have developed very complicated gene expression networks. A proteomic view of stress/starvation responses, however, is only a starting point which should promote follow-up studies aimed at the comprehensive description of single regulons, their signal transduction pathways on the one hand, and their adaptive functions on the other, and finally their integration into complex gene expression networks. This "road map of physiological proteomics" will be demonstrated for the general stress regulon controlled by sigma(B) in Bacillus subtilis and the oxygen starvation response with Rex as a master regulator in Staphylococcus aureus.
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Affiliation(s)
- Michael Hecker
- Institute for Microbiology, Ernst-Moritz-Arndt-University Greifswald, Jahnstrasse 15A, 17487 Greifswald, Germany.
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Isabella VM, Lapek JD, Kennedy EM, Clark VL. Functional analysis of NsrR, a nitric oxide-sensing Rrf2 repressor in Neisseria gonorrhoeae. Mol Microbiol 2009; 71:227-39. [PMID: 19007408 DOI: 10.1111/j.1365-2958.2008.06522.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Nitric oxide (NO) has been shown to be an important component of the human immune response, and as such, it is important to understand how pathogenic organisms respond to its presence. In Neisseria gonorrhoeae, recent work has revealed that NsrR, an Rrf2-type transcriptional repressor, can sense NO and control the expression of genes responsible for NO metabolism. A highly pure extract of epitope-tagged NsrR was isolated and mass spectroscopic analysis suggested that the protein contained a [2Fe-2S] cluster. NsrR/DNA interactions were thoroughly analysed in vitro. Using EMSA analysis, NsrR::FLAG was shown to interact with predicted operators in the norB, aniA and nsrR upstream regions with a K(d) of 7, 19 and 35 nM respectively. DNase I footprint analysis was performed on the upstream regions of norB and nsrR, where NsrR was shown to protect the predicted 29 bp binding sites. The presence of exogenously added NO inhibited DNA binding by NsrR. Alanine substitution of C90, C97 or C103 in NsrR abrogated repression of norB::lacZ and inhibited DNA binding, consistent with their presumed role in co-ordination of a NO-sensitive Fe-S centre required for DNA binding.
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Affiliation(s)
- Vincent M Isabella
- Department of Microbiology and Immunology, University of Rochester, 601 Elmwood Avenue, Rochester, NY, USA
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Justino MC, Baptista JM, Saraiva LM. Di-iron proteins of the Ric family are involved in iron–sulfur cluster repair. Biometals 2009; 22:99-108. [DOI: 10.1007/s10534-008-9191-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Accepted: 12/07/2008] [Indexed: 10/21/2022]
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Abstract
Bacterial gene regulators containing transition metal cofactors that function as binding sites for small ligands were first described in the 1990s. Since then, numerous metal-containing regulators have been discovered, and our knowledge of the diversity of proteins, their cofactors and the signals that they sense has greatly increased. The present article reviews recent developments, with a particular focus on bacterial sensors of nitric oxide.
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Tucker NP, Hicks MG, Clarke TA, Crack JC, Chandra G, Le Brun NE, Dixon R, Hutchings MI. The transcriptional repressor protein NsrR senses nitric oxide directly via a [2Fe-2S] cluster. PLoS One 2008; 3:e3623. [PMID: 18989365 PMCID: PMC2577008 DOI: 10.1371/journal.pone.0003623] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2008] [Accepted: 10/16/2008] [Indexed: 01/08/2023] Open
Abstract
The regulatory protein NsrR, a member of the Rrf2 family of transcription repressors, is specifically dedicated to sensing nitric oxide (NO) in a variety of pathogenic and non-pathogenic bacteria. It has been proposed that NO directly modulates NsrR activity by interacting with a predicted [Fe-S] cluster in the NsrR protein, but no experimental evidence has been published to support this hypothesis. Here we report the purification of NsrR from the obligate aerobe Streptomyces coelicolor. We demonstrate using UV-visible, near UV CD and EPR spectroscopy that the protein contains an NO-sensitive [2Fe-2S] cluster when purified from E. coli. Upon exposure of NsrR to NO, the cluster is nitrosylated, which results in the loss of DNA binding activity as detected by bandshift assays. Removal of the [2Fe-2S] cluster to generate apo-NsrR also resulted in loss of DNA binding activity. This is the first demonstration that NsrR contains an NO-sensitive [2Fe-2S] cluster that is required for DNA binding activity.
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Affiliation(s)
- Nicholas P. Tucker
- Department of Molecular Microbiology, John Innes Centre, Norwich Research Park, Norwich, United Kingdom
- * E-mail: (NPT); (MIH)
| | - Matthew G. Hicks
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Thomas A. Clarke
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Jason C. Crack
- School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Govind Chandra
- Department of Molecular Microbiology, John Innes Centre, Norwich Research Park, Norwich, United Kingdom
| | - Nick E. Le Brun
- School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Ray Dixon
- Department of Molecular Microbiology, John Innes Centre, Norwich Research Park, Norwich, United Kingdom
| | - Matthew I. Hutchings
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
- School of Medicine, Health Policy and Practice, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
- * E-mail: (NPT); (MIH)
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Reder A, Höper D, Weinberg C, Gerth U, Fraunholz M, Hecker M. The Spx paralogue MgsR (YqgZ) controls a subregulon within the general stress response ofBacillus subtilis. Mol Microbiol 2008; 69:1104-20. [DOI: 10.1111/j.1365-2958.2008.06332.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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46
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Monk CE, Pearson BM, Mulholland F, Smith HK, Poole RK. Oxygen- and NssR-dependent globin expression and enhanced iron acquisition in the response of campylobacter to nitrosative stress. J Biol Chem 2008; 283:28413-25. [PMID: 18682395 DOI: 10.1074/jbc.m801016200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Pathogenic bacteria experience nitrosative stress from NO generated in the host and from nitrosating species such as S-nitrosoglutathione. The food-borne pathogen Campylobacter jejuni responds by activating gene expression from a small regulon under the control of the NO-sensitive regulator, NssR. Here, we describe the full extent of the S-nitrosoglutathione response using transcriptomic and proteomic analysis of batch- and chemostat-cultured C. jejuni. In addition to the NssR regulon, which includes two hemoglobins (Cgb and Ctb), we identify more than 90 other up-regulated genes, notably those encoding heat shock proteins and proteins involved in oxidative stress tolerance and iron metabolism/transport. Up-regulation of a subset of these genes, including cgb, is also elicited by NO-releasing compounds. Mutation of the iron-responsive regulator Fur results in insensitivity of growth to NO, suggesting that derepression of iron-regulated genes and augmentation of iron acquisition is a physiological response to nitrosative damage. We describe the effect of oxygen availability on nitrosative stress tolerance; cells cultured at higher rates of oxygen diffusion have elevated levels of hemoglobins, are more resistant to inhibition by NO of both growth and respiration, and consume NO more rapidly. The oxygen response is mediated by NssR. Thus, in addition to NO detoxification catalyzed by the hemoglobins Cgb and possibly Ctb, C. jejuni mounts an extensive stress response. We suggest that inhibition of respiration by NO may increase availability of oxygen for Cgb synthesis and function.
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Affiliation(s)
- Claire E Monk
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, United Kingdom
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Escherichia coli NsrR regulates a pathway for the oxidation of 3-nitrotyramine to 4-hydroxy-3-nitrophenylacetate. J Bacteriol 2008; 190:6170-7. [PMID: 18658270 DOI: 10.1128/jb.00508-08] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Chromatin immunoprecipitation and microarray (ChIP-chip) analysis showed that the nitric oxide (NO)-sensitive repressor NsrR from Escherichia coli binds in vivo to the promoters of the tynA and feaB genes. These genes encode the first two enzymes of a pathway that is required for the catabolism of phenylethylamine (PEA) and its hydroxylated derivatives tyramine and dopamine. Deletion of nsrR caused small increases in the activities of the tynA and feaB promoters in cultures grown on PEA. Overexpression of nsrR severely retarded growth on PEA and caused a marked repression of the tynA and feaB promoters. Both the growth defect and the promoter repression were reversed in the presence of a source of NO. These results are consistent with NsrR mediating repression of the tynA and feaB genes by binding (in an NO-sensitive fashion) to the sites identified by ChIP-chip. E. coli was shown to use 3-nitrotyramine as a nitrogen source for growth, conditions which partially induce the tynA and feaB promoters. Mutation of tynA (but not feaB) prevented growth on 3-nitrotyramine. Growth yields, mutant phenotypes, and analyses of culture supernatants suggested that 3-nitrotyramine is oxidized to 4-hydroxy-3-nitrophenylacetate, with growth occurring at the expense of the amino group of 3-nitrotyramine. Accordingly, enzyme assays showed that 3-nitrotyramine and its oxidation product (4-hydroxy-3-nitrophenylacetaldehyde) could be oxidized by the enzymes encoded by tynA and feaB, respectively. The results suggest that an additional physiological role of the PEA catabolic pathway is to metabolize nitroaromatic compounds that may accumulate in cells exposed to NO.
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Geng H, Zuber P, Nakano MM. Regulation of respiratory genes by ResD-ResE signal transduction system in Bacillus subtilis. Methods Enzymol 2008; 422:448-64. [PMID: 17628154 DOI: 10.1016/s0076-6879(06)22023-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
Abstract
Successful respiration in Bacillus subtilis using oxygen or nitrate as the terminal electron acceptor requires the ResD-ResE signal transduction system. Although transcription of ResDE-controlled genes is induced at the stationary phase of aerobic growth, it is induced to a higher extent upon oxygen limitation. Furthermore, maximal transcriptional activation requires not only oxygen limitation, but also nitric oxide (NO). Oxygen limitation likely results in conversion of the ResE sensor kinase activity from a phosphatase-dominant to a kinase-dominant mode. In addition, low oxygen levels promote the production and maintenance of NO during nitrate respiration, which leads to elimination of the repression exerted by the NO-sensitive transcriptional regulator NsrR. ResD, after undergoing ResE-mediated phosphorylation, interacts with the C-terminal domain of the alpha subunit of RNA polymerase to activate transcription initiation at ResDE-controlled promoters.
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Affiliation(s)
- Hao Geng
- Department of Environmental System, Oregon Health and Science University, Beaverton, Oregon, USA
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49
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Nitric oxide stress induces different responses but mediates comparable protein thiol protection in Bacillus subtilis and Staphylococcus aureus. J Bacteriol 2008; 190:4997-5008. [PMID: 18487332 DOI: 10.1128/jb.01846-07] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The nonpathogenic Bacillus subtilis and the pathogen Staphylococcus aureus are gram-positive model organisms that have to cope with the radical nitric oxide (NO) generated by nitrite reductases of denitrifying bacteria and by the inducible NO synthases of immune cells of the host, respectively. The response of both microorganisms to NO was analyzed by using a two-dimensional gel approach. Metabolic labeling of the proteins revealed major changes in the synthesis pattern of cytosolic proteins after the addition of the NO donor MAHMA NONOate. Whereas B. subtilis induced several oxidative stress-responsive regulons controlled by Fur, PerR, OhrR, and Spx, as well as the general stress response controlled by the alternative sigma factor SigB, the more resistant S. aureus showed an increased synthesis rate of proteins involved in anaerobic metabolism. These data were confirmed by nuclear magnetic resonance analyses indicating that NO causes a drastically higher increase in the formation of lactate and butanediol in S. aureus than in B. subtilis. Monitoring the intracellular protein thiol state, we observed no increase in reversible or irreversible protein thiol modifications after NO stress in either organism. Obviously, NO itself does not cause general protein thiol oxidations. In contrast, exposure of cells to NO prior to peroxide stress diminished the irreversible thiol oxidation caused by hydrogen peroxide.
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Nishimura T, Teramoto H, Vertès AA, Inui M, Yukawa H. ArnR, a novel transcriptional regulator, represses expression of the narKGHJI operon in Corynebacterium glutamicum. J Bacteriol 2008; 190:3264-73. [PMID: 18296524 PMCID: PMC2347399 DOI: 10.1128/jb.01801-07] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Accepted: 02/12/2008] [Indexed: 11/20/2022] Open
Abstract
The narKGHJI operon that comprises putative nitrate/nitrite transporter (narK) and nitrate reductase (narGHJI) genes is required for the anaerobic growth of Corynebacterium glutamicum with nitrate as a terminal electron acceptor. In this study, we identified a gene, arnR, which encodes a transcriptional regulator that represses the expression of the narKGHJI operon in C. glutamicum cells under aerobic conditions. Disruption of arnR induced nitrate reductase activities of C. glutamicum cells and increased narKGHJI mRNA levels under aerobic growth conditions. DNA microarray analyses revealed that besides the narKGHJI operon, the hmp gene, which encodes flavohemoglobin, is negatively regulated by ArnR under aerobic conditions. Promoter-reporter assays indicated that arnR gene expression was positively autoregulated by its gene product, ArnR, under both aerobic and anaerobic conditions. Electrophoretic mobility shift assay experiments showed that purified hexahistidyl-tagged ArnR protein specifically binds to promoter regions of the narKGHJI operon and the hmp and arnR genes. A consensus sequence, TA(A/T)TTAA(A/T)TA, found in the promoter regions of these genes was demonstrated to be involved in the binding of ArnR. Effects on LacZ activity by deletion of the ArnR binding sites within the promoter regions fused to the reporter gene were consistent with the view that the expression of the narKGHJI operon is repressed by the ArnR protein under aerobic conditions, whereas the expression of the arnR gene is autoinduced by ArnR.
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Affiliation(s)
- Taku Nishimura
- Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai, Kizugawa, Kyoto 619-0292, Japan
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