1
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Li S, Liu Q, Duan C, Li J, Sun H, Xu L, Yang Q, Wang Y, Shen X, Zhang L. c-di-GMP inhibits the DNA binding activity of H-NS in Salmonella. Nat Commun 2023; 14:7502. [PMID: 37980414 PMCID: PMC10657408 DOI: 10.1038/s41467-023-43442-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 11/09/2023] [Indexed: 11/20/2023] Open
Abstract
Cyclic di-GMP (c-di-GMP) is a second messenger that transduces extracellular stimuli into cellular responses and regulates various biological processes in bacteria. H-NS is a global regulatory protein that represses expression of many genes, but how H-NS activity is modulated by environmental signals remains largely unclear. Here, we show that high intracellular c-di-GMP levels, induced by environmental cues, relieve H-NS-mediated transcriptional silencing in Salmonella enterica serovar Typhimurium. We find that c-di-GMP binds to the H-NS protein to inhibit its binding to DNA, thus derepressing genes silenced by H-NS. However, c-di-GMP is unable to displace H-NS from DNA. In addition, a K107A mutation in H-NS abolishes response to c-di-GMP but leaves its DNA binding activity unaffected in vivo. Our results thus suggest a mechanism by which H-NS acts as an environment-sensing regulator in Gram-negative bacteria.
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Affiliation(s)
- Shuyu Li
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, China
| | - Qinmeng Liu
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, China
| | - Chongyi Duan
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, China
| | - Jialin Li
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, China
| | - Hengxi Sun
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, China
| | - Lei Xu
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, China
| | - Qiao Yang
- ABI Group, College of Marine Science and Technology, Zhejiang Ocean University, Zhoushan, 316021, China
- Donghai Laboratory, Zhoushan, 316021, China
| | - Yao Wang
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, China
| | - Xihui Shen
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, China.
| | - Lei Zhang
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, China.
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2
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Rashid FZM, Dame RT. Three-dimensional chromosome re-modelling: The integral mechanism of transcription regulation in bacteria. Mol Microbiol 2023; 120:60-70. [PMID: 37433047 DOI: 10.1111/mmi.15062] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 03/28/2023] [Accepted: 03/29/2023] [Indexed: 07/13/2023]
Abstract
Nucleoid-associated proteins (NAPs) are architectural proteins of the bacterial chromosome and transcription factors that dynamically organise the chromosome and regulate gene expression in response to physicochemical environmental signals. While the architectural and regulatory functions of NAPs have been verified independently, the coupling between these functions in vivo has not been conclusively proven. Here we describe a model NAP - histone-like nucleoid structuring protein (H-NS) - as a coupled sensor-effector that directly regulates gene expression by chromatin re-modelling in response to physicochemical environmental signals. We outline how H-NS-binding partners and post-translational modifications modulate the role of H-NS as a transcription factor by influencing its DNA structuring properties. We consolidate our ideas in models of how H-NS may regulate the expression of the proVWX and hlyCABD operons by chromatin re-modelling. The interplay between chromosome structure and gene expression may be a common - but, at present, under-appreciated - concept of transcription regulation in bacteria.
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Affiliation(s)
- Fatema-Zahra M Rashid
- Macromolecular Biochemistry, Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands
- Centre for Interdisciplinary Genome Research, Leiden University, Leiden, The Netherlands
| | - Remus T Dame
- Macromolecular Biochemistry, Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands
- Centre for Interdisciplinary Genome Research, Leiden University, Leiden, The Netherlands
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3
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Cordeiro TFVB, Gontijo MTP, Jorge GP, Brocchi M. EbfC/YbaB: A Widely Distributed Nucleoid-Associated Protein in Prokaryotes. Microorganisms 2022; 10:microorganisms10101945. [PMID: 36296221 PMCID: PMC9610160 DOI: 10.3390/microorganisms10101945] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 09/13/2022] [Accepted: 09/20/2022] [Indexed: 11/06/2022] Open
Abstract
Genomic compaction is an essential characteristic of living organisms. Nucleoid-associated proteins (NAPs) are a group of small proteins that play crucial roles in chromosome architecture and affect DNA replication, transcription, and recombination by imposing topological alterations in genomic DNA, thereby modulating global gene expression. EbfC/YbaB was first described as a DNA-binding protein of Borrelia burgdorferi that regulates the expression of surface lipoproteins with roles in virulence. Further studies indicated that this protein binds specifically and non-specifically to DNA and colocalises with nucleoids in this bacterium. The data showed that this protein binds to DNA as a homodimer, although it can form other organised structures. Crystallography analysis indicated that the protein possesses domains responsible for protein–protein interactions and forms a “tweezer” structure probably involved in DNA binding. Moreover, sequence analysis revealed conserved motifs that may be associated with dimerisation. Structural analysis also showed that the tridimensional structure of EbfC/YbaB is highly conserved within the bacterial domain. The DNA-binding activity was observed in different bacterial species, suggesting that this protein can protect DNA during stress conditions. These findings indicate that EbfC/YbaB is a broadly distributed NAP. Here, we present a review of the existing data on this NAP.
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4
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Adler BA, Kazakov AE, Zhong C, Liu H, Kutter E, Lui LM, Nielsen TN, Carion H, Deutschbauer AM, Mutalik VK, Arkin AP. The genetic basis of phage susceptibility, cross-resistance and host-range in Salmonella. MICROBIOLOGY (READING, ENGLAND) 2021; 167. [PMID: 34910616 PMCID: PMC8744999 DOI: 10.1099/mic.0.001126] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Though bacteriophages (phages) are known to play a crucial role in bacterial fitness and virulence, our knowledge about the genetic basis of their interaction, cross-resistance and host-range is sparse. Here, we employed genome-wide screens in Salmonella enterica serovar Typhimurium to discover host determinants involved in resistance to eleven diverse lytic phages including four new phages isolated from a therapeutic phage cocktail. We uncovered 301 diverse host factors essential in phage infection, many of which are shared between multiple phages demonstrating potential cross-resistance mechanisms. We validate many of these novel findings and uncover the intricate interplay between RpoS, the virulence-associated general stress response sigma factor and RpoN, the nitrogen starvation sigma factor in phage cross-resistance. Finally, the infectivity pattern of eleven phages across a panel of 23 genome sequenced Salmonella strains indicates that additional constraints and interactions beyond the host factors uncovered here define the phage host range.
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Affiliation(s)
- Benjamin A Adler
- The UC Berkeley-UCSF Graduate Program in Bioengineering, Berkeley, California, USA.,Department of Bioengineering, University of California, Berkeley, Berkeley, California, USA.,Innovative Genomics Institute, University of California, Berkeley, California, USA
| | - Alexey E Kazakov
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Crystal Zhong
- Department of Bioengineering, University of California, Berkeley, Berkeley, California, USA
| | - Hualan Liu
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | | | - Lauren M Lui
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Torben N Nielsen
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Heloise Carion
- Department of Bioengineering, University of California, Berkeley, Berkeley, California, USA
| | - Adam M Deutschbauer
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.,Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Vivek K Mutalik
- Innovative Genomics Institute, University of California, Berkeley, California, USA.,Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Adam P Arkin
- Department of Bioengineering, University of California, Berkeley, Berkeley, California, USA.,Innovative Genomics Institute, University of California, Berkeley, California, USA.,Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
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5
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Prieto A, Bernabeu M, Falgenhauer L, Chakraborty T, Hüttener M, Juárez A. Overexpression of the third H-NS paralogue H-NS2 compensates fitness loss in hns mutants of the enteroaggregative Escherichia coli strain 042. Sci Rep 2020; 10:18131. [PMID: 33093592 PMCID: PMC7582179 DOI: 10.1038/s41598-020-75204-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 10/07/2020] [Indexed: 11/10/2022] Open
Abstract
Members of the H-NS protein family play a role both in the chromosome architecture and in the regulation of gene expression in bacteria. The genomes of the enterobacteria encode an H-NS paralogue, the StpA protein. StpA displays specific regulatory properties and provides a molecular backup for H-NS. Some enterobacteria also encode third H-NS paralogues. This is the case of the enteroaggregative E. coli (EAEC) strain 042, which encodes the hns, stpA and hns2 genes. We provide in this paper novel information about the role of the H-NS2 protein in strain 042. A C > T transition in the hns2 promoter leading to increased H-NS2 expression is readily selected in hns mutants. Increased H-NS2 expression partially compensates for H-NS loss. H-NS2 levels are critical for the strain 042 fitness. Under some circumstances, high H-NS2 expression levels dictated by the mutant hns2 promoter can be deleterious. The selection of T > C revertants or of clones harboring insertional inactivations of the hns2 gene can then occur. Temperature also plays a relevant role in the H-NS2 regulatory activity. At 37 °C, H-NS2 targets a subset of the H-NS repressed genes contributing to their silencing. When temperature drops to 25 °C, the repressory ability of H-NS2 is significantly reduced. At low temperature, H-NS plays the main repressory role.
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Affiliation(s)
- A Prieto
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - M Bernabeu
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - L Falgenhauer
- Institute of Hygiene and Environmental Medicine, Justus Liebig University Giessen, Schubertstrasse 81, 35392, Giessen, Germany.,German Center for Infection Research DZIF, Partner Site Giessen-Marburg-Langen, Campus, Giessen, Germany
| | - T Chakraborty
- German Center for Infection Research DZIF, Partner Site Giessen-Marburg-Langen, Campus, Giessen, Germany.,Institute of Medical Microbiology, Justus-Liebig University, Schubertstrasse 81, 35392, Giessen, Germany
| | - M Hüttener
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - A Juárez
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain. .,Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Barcelona, Spain.
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6
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Fitzgerald S, Kary SC, Alshabib EY, MacKenzie KD, Stoebel D, Chao TC, Cameron ADS. Redefining the H-NS protein family: a diversity of specialized core and accessory forms exhibit hierarchical transcriptional network integration. Nucleic Acids Res 2020; 48:10184-10198. [PMID: 32894292 PMCID: PMC7544231 DOI: 10.1093/nar/gkaa709] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 08/07/2020] [Accepted: 08/23/2020] [Indexed: 12/27/2022] Open
Abstract
H-NS is a nucleoid structuring protein and global repressor of virulence and horizontally-acquired genes in bacteria. H-NS can interact with itself or with homologous proteins, but protein family diversity and regulatory network overlap remain poorly defined. Here, we present a comprehensive phylogenetic analysis that revealed deep-branching clades, dispelling the presumption that H-NS is the progenitor of varied molecular backups. Each clade is composed exclusively of either chromosome-encoded or plasmid-encoded proteins. On chromosomes, stpA and newly discovered hlpP are core genes in specific genera, whereas hfp and newly discovered hlpC are sporadically distributed. Six clades of H-NS plasmid proteins (Hpp) exhibit ancient and dedicated associations with plasmids, including three clades with fidelity for plasmid incompatibility groups H, F or X. A proliferation of H-NS homologs in Erwiniaceae includes the first observation of potentially co-dependent H-NS forms. Conversely, the observed diversification of oligomerization domains may facilitate stable co-existence of divergent homologs in a genome. Transcriptomic and proteomic analysis in Salmonella revealed regulatory crosstalk and hierarchical control of H-NS homologs. We also discovered that H-NS is both a repressor and activator of Salmonella Pathogenicity Island 1 gene expression, and both regulatory modes are restored by Sfh (HppH) in the absence of H-NS.
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Affiliation(s)
- Stephen Fitzgerald
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
- Division of Immunity and Infection, The Roslin Institute and R(D)SVS, University of Edinburgh, Edinburgh EH25 9RG, UK
| | - Stefani C Kary
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Ebtihal Y Alshabib
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
- Institute for Microbial Systems and Society, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Keith D MacKenzie
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
- Institute for Microbial Systems and Society, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Daniel M Stoebel
- Department of Biology, Harvey Mudd College, Claremont, CA 91711, USA
| | - Tzu-Chiao Chao
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
- Institute of Environmental Change and Society, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Andrew D S Cameron
- Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
- Institute for Microbial Systems and Society, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
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7
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Hurtado-Escobar GA, Grépinet O, Raymond P, Abed N, Velge P, Virlogeux-Payant I. H-NS is the major repressor of Salmonella Typhimurium Pef fimbriae expression. Virulence 2020; 10:849-867. [PMID: 31661351 PMCID: PMC6844306 DOI: 10.1080/21505594.2019.1682752] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Fimbriae play an important role in adhesion and are therefore essential for the interaction of bacteria with the environments they encounter. Most of them are expressed in vivo but not in vitro, thus making difficult the full characterization of these fimbriae. Here, we characterized the silencing of plasmid-encoded fimbriae (Pef) expression, encoded by the pef operon, in the worldwide pathogen Salmonella Typhimurium. We demonstrated that the nucleoid-associated proteins H-NS and Hha, and their respective paralogs StpA and YdgT, negatively regulate at pH 5.1 and pH 7.1 the transcription of the pef operon. Two promoters, PpefB and PpefA, direct the transcription of this operon. All the nucleoid-associated proteins silence the PpefB promoter and H-NS also targets the PpefA promoter. While Hha and YdgT are mainly considered as acting primarily through H-NS to modulate gene transcription, our results strongly suggest that Hha and YdgT silence pef transcription at acidic pH either by interacting with StpA or independently of H-NS and StpA. We also confirmed the previously described post-transcriptional repression of Pef fimbriae by CsrA titration via the fim mRNA and CsrB and CsrC sRNA. Finally, among all these regulators, H-NS clearly appeared as the major repressor of Pef expression. These results open new avenues of research to better characterize the regulation of these bacterial adhesive proteins and to clarify their role in the virulence of pathogens.
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Affiliation(s)
| | | | | | - Nadia Abed
- ISP, INRA, Université de Tours, Nouzilly, France
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8
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Shen BA, Landick R. Transcription of Bacterial Chromatin. J Mol Biol 2019; 431:4040-4066. [PMID: 31153903 PMCID: PMC7248592 DOI: 10.1016/j.jmb.2019.05.041] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 05/22/2019] [Accepted: 05/23/2019] [Indexed: 12/12/2022]
Abstract
Decades of research have probed the interplay between chromatin (genomic DNA associated with proteins and RNAs) and transcription by RNA polymerase (RNAP) in all domains of life. In bacteria, chromatin is compacted into a membrane-free region known as the nucleoid that changes shape and composition depending on the bacterial state. Transcription plays a key role in both shaping the nucleoid and organizing it into domains. At the same time, chromatin impacts transcription by at least five distinct mechanisms: (i) occlusion of RNAP binding; (ii) roadblocking RNAP progression; (iii) constraining DNA topology; (iv) RNA-mediated interactions; and (v) macromolecular demixing and heterogeneity, which may generate phase-separated condensates. These mechanisms are not mutually exclusive and, in combination, mediate gene regulation. Here, we review the current understanding of these mechanisms with a focus on gene silencing by H-NS, transcription coordination by HU, and potential phase separation by Dps. The myriad questions about transcription of bacterial chromatin are increasingly answerable due to methodological advances, enabling a needed paradigm shift in the field of bacterial transcription to focus on regulation of genes in their native state. We can anticipate answers that will define how bacterial chromatin helps coordinate and dynamically regulate gene expression in changing environments.
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Affiliation(s)
- Beth A Shen
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, United States
| | - Robert Landick
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, United States; Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, United States.
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9
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Rudenko I, Ni B, Glatter T, Sourjik V. Inefficient Secretion of Anti-sigma Factor FlgM Inhibits Bacterial Motility at High Temperature. iScience 2019; 16:145-154. [PMID: 31170626 PMCID: PMC6551532 DOI: 10.1016/j.isci.2019.05.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 04/01/2019] [Accepted: 05/15/2019] [Indexed: 12/03/2022] Open
Abstract
Temperature is one of the key cues that enable microorganisms to adjust their physiology in response to environmental changes. Here we show that motility is the major cellular function of Escherichia coli that is differentially regulated between growth at normal host temperature of 37°C and the febrile temperature of 42°C. Expression of both class II and class III flagellar genes is reduced at 42°C because of lowered level of the upstream activator FlhD. Class III genes are additionally repressed because of the destabilization and malfunction of secretion apparatus at high temperature, which prevents secretion of the anti-sigma factor FlgM. This mechanism of repression apparently accelerates loss of motility at 42°C. We hypothesize that E. coli perceives high temperature as a sign of inflammation, downregulating flagella to escape detection by the immune system of the host. Secretion-dependent coupling of gene expression to the environmental temperature is likely common among many bacteria. E. coli motility is tightly turned off at febrile temperature (42°C) Repression of motility is achieved at two levels of hierarchical gene regulation Lowered FlhD level reduces expression of all flagellar genes Impaired FlgM secretion tightens repression of class III genes
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Affiliation(s)
- Iaroslav Rudenko
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg 35043, Germany
| | - Bin Ni
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg 35043, Germany
| | - Timo Glatter
- Core Facility for Mass Spectrometry & Proteomics, Max Planck Institute for Terrestrial Microbiology, Marburg 35043, Germany
| | - Victor Sourjik
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg 35043, Germany.
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10
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Park M, Nam D, Kweon DH, Shin D. ATP reduction by MgtC and Mg 2+ homeostasis by MgtA and MgtB enables Salmonella to accumulate RpoS upon low cytoplasmic Mg 2+ stress. Mol Microbiol 2018; 110:283-295. [PMID: 30112818 DOI: 10.1111/mmi.14105] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/10/2018] [Indexed: 12/22/2022]
Abstract
RpoS is one of several alternative sigma factors known to alter gene expression profiles by RpoS-associated RNA polymerase in response to a variety of stresses. The enteric bacteria Salmonella enterica and Escherichia coli accumulate RpoS under low Mg2+ concentrations via a common mechanism in which the PhoP regulator activates expression of antiadaptor proteins that, by sequestering the adaptor RssB, prevent RpoS degradation by the protease ClpXP. Here, we demonstrate that this genetic program alone does not fully support RpoS accumulation when cytoplasmic Mg2+ concentration drops to levels that impair protein synthesis. Under these circumstances, only S. enterica continues RpoS accumulation in a manner dependent on other PhoP-activated programs (i.e. ATP reduction by the MgtC protein and Mg2+ import by the MgtA and MgtB transporters) that maintain translation homeostasis. Moreover, we provide evidence that the mgtC gene, which is present in S. enterica but not in E. coli, is responsible for the differences in RpoS accumulation between these two bacterial species. Our results suggest that bacteria possess a mechanism to control RpoS accumulation responding to cytoplasmic Mg2+ levels, the difference of which causes distinct RpoS accumulation in closely related bacterial species.
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Affiliation(s)
- Myungseo Park
- Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon, Korea
| | - Daesil Nam
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Dae-Hyuk Kweon
- Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon, Korea
| | - Dongwoo Shin
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Korea.,Samsung Medical Center, Sungkyunkwan University School of Medicine, Suwon, Korea
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11
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Krogh TJ, Møller-Jensen J, Kaleta C. Impact of Chromosomal Architecture on the Function and Evolution of Bacterial Genomes. Front Microbiol 2018; 9:2019. [PMID: 30210483 PMCID: PMC6119826 DOI: 10.3389/fmicb.2018.02019] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 08/09/2018] [Indexed: 12/14/2022] Open
Abstract
The bacterial nucleoid is highly condensed and forms compartment-like structures within the cell. Much attention has been devoted to investigating the dynamic topology and organization of the nucleoid. In contrast, the specific nucleoid organization, and the relationship between nucleoid structure and function is often neglected with regard to importance for adaption to changing environments and horizontal gene acquisition. In this review, we focus on the structure-function relationship in the bacterial nucleoid. We provide an overview of the fundamental properties that shape the chromosome as a structured yet dynamic macromolecule. These fundamental properties are then considered in the context of the living cell, with focus on how the informational flow affects the nucleoid structure, which in turn impacts on the genetic output. Subsequently, the dynamic living nucleoid will be discussed in the context of evolution. We will address how the acquisition of foreign DNA impacts nucleoid structure, and conversely, how nucleoid structure constrains the successful and sustainable chromosomal integration of novel DNA. Finally, we will discuss current challenges and directions of research in understanding the role of chromosomal architecture in bacterial survival and adaptation.
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Affiliation(s)
- Thøger J Krogh
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Jakob Møller-Jensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Christoph Kaleta
- Institute of Experimental Medicine, Christian-Albrechts-University Kiel, Kiel, Germany
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12
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Boudreau BA, Hron DR, Qin L, van der Valk RA, Kotlajich MV, Dame RT, Landick R. StpA and Hha stimulate pausing by RNA polymerase by promoting DNA-DNA bridging of H-NS filaments. Nucleic Acids Res 2018; 46:5525-5546. [PMID: 29718386 PMCID: PMC6009659 DOI: 10.1093/nar/gky265] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 03/12/2018] [Accepted: 04/03/2018] [Indexed: 11/22/2022] Open
Abstract
In enterobacteria, AT-rich horizontally acquired genes, including virulence genes, are silenced through the actions of at least three nucleoid-associated proteins (NAPs): H-NS, StpA and Hha. These proteins form gene-silencing nucleoprotein filaments through direct DNA binding by H-NS and StpA homodimers or heterodimers. Both linear and bridged filaments, in which NAPs bind one or two DNA segments, respectively, have been observed. Hha can interact with H-NS or StpA filaments, but itself lacks a DNA-binding domain. Filaments composed of H-NS alone can inhibit transcription initiation and, in the bridged conformation, slow elongating RNA polymerase (RNAP) by promoting backtracking at pause sites. How the other NAPs modulate these effects of H-NS is unknown, despite evidence that they help regulate subsets of silenced genes in vivo (e.g. in pathogenicity islands). Here we report that Hha and StpA greatly enhance H-NS-stimulated pausing by RNAP at 20°C. StpA:H-NS or StpA-only filaments also stimulate pausing at 37°C, a temperature at which Hha:H-NS or H-NS-only filaments have much less effect. In addition, we report that both Hha and StpA greatly stimulate DNA-DNA bridging by H-NS filaments. Together, these observations indicate that Hha and StpA can affect H-NS-mediated gene regulation by stimulating bridging of H-NS/DNA filaments.
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Affiliation(s)
- Beth A Boudreau
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Daniel R Hron
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Liang Qin
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC, Leiden, Netherlands
| | - Ramon A van der Valk
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC, Leiden, Netherlands
| | - Matthew V Kotlajich
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Remus T Dame
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC, Leiden, Netherlands
| | - Robert Landick
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
- Department of Bacteriology, University of Wisconsin–Madison, Madison, WI 53706, USA
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13
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Prieto A, Bernabeu M, Aznar S, Ruiz-Cruz S, Bravo A, Queiroz MH, Juárez A. Evolution of Bacterial Global Modulators: Role of a Novel H-NS Paralogue in the Enteroaggregative Escherichia coli Strain 042. mSystems 2018; 3:e00220-17. [PMID: 29577085 PMCID: PMC5861252 DOI: 10.1128/msystems.00220-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 02/14/2018] [Indexed: 11/20/2022] Open
Abstract
Bacterial genomes sometimes contain genes that code for homologues of global regulators, the function of which is unclear. In members of the family Enterobacteriaceae, cells express the global regulator H-NS and its paralogue StpA. In Escherichia coli, out of providing a molecular backup for H-NS, the role of StpA is poorly characterized. The enteroaggregative E. coli strain 042 carries, in addition to the hns and stpA genes, a third gene encoding an hns paralogue (hns2). We present in this paper information about its biological function. Transcriptomic analysis has shown that the H-NS2 protein targets a subset of the genes targeted by H-NS. Genes targeted by H-NS2 correspond mainly with horizontally transferred (HGT) genes and are also targeted by the Hha protein, a fine-tuner of H-NS activity. Compared with H-NS, H-NS2 expression levels are lower. In addition, H-NS2 expression exhibits specific features: it is sensitive to the growth temperature and to the nature of the culture medium. This novel H-NS paralogue is widespread within the Enterobacteriaceae. IMPORTANCE Global regulators such as H-NS play key relevant roles enabling bacterial cells to adapt to a changing environment. H-NS modulates both core and horizontally transferred (HGT) genes, but the mechanism by which H-NS can differentially regulate these genes remains to be elucidated. There are several instances of bacterial cells carrying genes that encode homologues of the global regulators. The question is what the roles of these proteins are. We noticed that the enteroaggregative E. coli strain 042 carries a new hitherto uncharacterized copy of the hns gene. We decided to investigate why this pathogenic E. coli strain requires an extra H-NS paralogue, termed H-NS2. In our work, we show that H-NS2 displays specific expression and regulatory properties. H-NS2 targets a subset of H-NS-specific genes and may help to differentially modulate core and HGT genes by the H-NS cellular pool.
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Affiliation(s)
- A. Prieto
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - M. Bernabeu
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - S. Aznar
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - S. Ruiz-Cruz
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - A. Bravo
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - M. H. Queiroz
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - A. Juárez
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Barcelona, Spain
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14
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Bouillet S, Genest O, Jourlin-Castelli C, Fons M, Méjean V, Iobbi-Nivol C. The General Stress Response σS Is Regulated by a Partner Switch in the Gram-negative Bacterium Shewanella oneidensis. J Biol Chem 2016; 291:26151-26163. [PMID: 27810894 DOI: 10.1074/jbc.m116.751933] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 11/02/2016] [Indexed: 11/06/2022] Open
Abstract
Here, we show that a partner-switching system of the aquatic Proteobacterium Shewanella oneidensis regulates post-translationally σS (also called RpoS), the general stress response sigma factor. Genes SO2118 and SO2119 encode CrsA and CrsR, respectively. CrsR is a three-domain protein comprising a receiver, a phosphatase, and a kinase/anti-sigma domains, and CrsA is an anti-sigma antagonist. In vitro, CrsR sequesters σS and possesses kinase and phosphatase activities toward CrsA. In turn, dephosphorylated CrsA binds the anti-sigma domain of CrsR to allow the release of σS This study reveals a novel pathway that post-translationally regulates the general stress response sigma factor differently than what was described for other proteobacteria like Escherichia coli We argue that this pathway allows probably a rapid bacterial adaptation.
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Affiliation(s)
- Sophie Bouillet
- From the Aix-Marseille Université, CNRS, BIP UMR7281, 13402 Marseille, France
| | - Olivier Genest
- From the Aix-Marseille Université, CNRS, BIP UMR7281, 13402 Marseille, France
| | | | - Michel Fons
- From the Aix-Marseille Université, CNRS, BIP UMR7281, 13402 Marseille, France
| | - Vincent Méjean
- From the Aix-Marseille Université, CNRS, BIP UMR7281, 13402 Marseille, France
| | - Chantal Iobbi-Nivol
- From the Aix-Marseille Université, CNRS, BIP UMR7281, 13402 Marseille, France
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15
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Fröhlich KS, Haneke K, Papenfort K, Vogel J. The target spectrum of SdsR small RNA in Salmonella. Nucleic Acids Res 2016; 44:10406-10422. [PMID: 27407104 PMCID: PMC5137417 DOI: 10.1093/nar/gkw632] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 06/11/2016] [Accepted: 06/29/2016] [Indexed: 12/28/2022] Open
Abstract
Model enteric bacteria such as Escherichia coli and Salmonella enterica express hundreds of small non-coding RNAs (sRNAs), targets for most of which are yet unknown. Some sRNAs are remarkably well conserved, indicating that they serve cellular functions that go beyond the necessities of a single species. One of these ‘core sRNAs’ of largely unknown function is the abundant ∼100-nucleotide SdsR sRNA which is transcribed by the general stress σ-factor, σS and accumulates in stationary phase. In Salmonella, SdsR was known to inhibit the synthesis of the species-specific porin, OmpD. However, sdsR genes are present in almost all enterobacterial genomes, suggesting that additional, conserved targets of this sRNA must exist. Here, we have combined SdsR pulse-expression with whole genome transcriptomics to discover 20 previously unknown candidate targets of SdsR which include mRNAs coding for physiologically important regulators such as the carbon utilization regulator, CRP, the nucleoid-associated chaperone, StpA and the antibiotic resistance transporter, TolC. Processing of SdsR by RNase E results in two cellular SdsR variants with distinct target spectra. While the overall physiological role of this orphan core sRNA remains to be fully understood, the new SdsR targets present valuable leads to determine sRNA functions in resting bacteria.
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Affiliation(s)
- Kathrin S Fröhlich
- RNA Biology Group, Institute for Molecular Infection Biology, University of Würzburg, Josef-Schneider-Straße 2, D-97080 Würzburg, Germany.,Department of Biology I, Microbiology, Ludwig-Maximilians-University Munich, D-82152 Martinsried, Germany
| | - Katharina Haneke
- RNA Biology Group, Institute for Molecular Infection Biology, University of Würzburg, Josef-Schneider-Straße 2, D-97080 Würzburg, Germany
| | - Kai Papenfort
- Department of Biology I, Microbiology, Ludwig-Maximilians-University Munich, D-82152 Martinsried, Germany
| | - Jörg Vogel
- RNA Biology Group, Institute for Molecular Infection Biology, University of Würzburg, Josef-Schneider-Straße 2, D-97080 Würzburg, Germany
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16
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Runkel S, Wells HC, Rowley G. Living with Stress: A Lesson from the Enteric Pathogen Salmonella enterica. ADVANCES IN APPLIED MICROBIOLOGY 2016; 83:87-144. [PMID: 23651595 DOI: 10.1016/b978-0-12-407678-5.00003-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The ability to sense and respond to the environment is essential for the survival of all living organisms. Bacterial pathogens such as Salmonella enterica are of particular interest due to their ability to sense and adapt to the diverse range of conditions they encounter, both in vivo and in environmental reservoirs. During this cycling from host to non-host environments, Salmonella encounter a variety of environmental insults ranging from temperature fluctuations, nutrient availability and changes in osmolarity, to the presence of antimicrobial peptides and reactive oxygen/nitrogen species. Such fluctuating conditions impact on various areas of bacterial physiology including virulence, growth and antimicrobial resistance. A key component of the success of any bacterial pathogen is the ability to recognize and mount a suitable response to the discrete chemical and physical stresses elicited by the host. Such responses occur through a coordinated and complex programme of gene expression and protein activity, involving a range of transcriptional regulators, sigma factors and two component regulatory systems. This review briefly outlines the various stresses encountered throughout the Salmonella life cycle and the repertoire of regulatory responses with which Salmonella counters. In particular, how these Gram-negative bacteria are able to alleviate disruption in periplasmic envelope homeostasis through a group of stress responses, known collectively as the Envelope Stress Responses, alongside the mechanisms used to overcome nitrosative stress, will be examined in more detail.
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Affiliation(s)
- Sebastian Runkel
- School of Biological Sciences, University of East Anglia, Norwich, UK
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17
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Fitzgerald S, Dillon SC, Chao TC, Wiencko HL, Hokamp K, Cameron ADS, Dorman CJ. Re-engineering cellular physiology by rewiring high-level global regulatory genes. Sci Rep 2015; 5:17653. [PMID: 26631971 PMCID: PMC4668568 DOI: 10.1038/srep17653] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 10/30/2015] [Indexed: 01/10/2023] Open
Abstract
Knowledge of global regulatory networks has been exploited to rewire the gene control programmes of the model bacterium Salmonella enterica serovar Typhimurium. The product is an organism with competitive fitness that is superior to that of the wild type but tuneable under specific growth conditions. The paralogous hns and stpA global regulatory genes are located in distinct regions of the chromosome and control hundreds of target genes, many of which contribute to stress resistance. The locations of the hns and stpA open reading frames were exchanged reciprocally, each acquiring the transcription control signals of the other. The new strain had none of the compensatory mutations normally associated with alterations to hns expression in Salmonella; instead it displayed rescheduled expression of the stress and stationary phase sigma factor RpoS and its regulon. Thus the expression patterns of global regulators can be adjusted artificially to manipulate microbial physiology, creating a new and resilient organism.
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Affiliation(s)
- Stephen Fitzgerald
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin 2, Ireland.,Department of Biology, University of Regina, Saskatchewan, Canada
| | - Shane C Dillon
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin 2, Ireland
| | - Tzu-Chiao Chao
- Department of Biology, University of Regina, Saskatchewan, Canada
| | - Heather L Wiencko
- Department of Genetics, Smurfit Institute, Trinity College Dublin, Dublin 2, Ireland
| | - Karsten Hokamp
- Department of Genetics, Smurfit Institute, Trinity College Dublin, Dublin 2, Ireland
| | | | - Charles J Dorman
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin 2, Ireland
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18
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Moore JM, Magnan D, Mojica AK, Núñez MAB, Bates D, Rosenberg SM, Hastings PJ. Roles of Nucleoid-Associated Proteins in Stress-Induced Mutagenic Break Repair in Starving Escherichia coli. Genetics 2015; 201:1349-62. [PMID: 26500258 PMCID: PMC4676537 DOI: 10.1534/genetics.115.178970] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 10/18/2015] [Indexed: 01/02/2023] Open
Abstract
The mutagenicity of DNA double-strand break repair in Escherichia coli is controlled by DNA-damage (SOS) and general (RpoS) stress responses, which let error-prone DNA polymerases participate, potentially accelerating evolution during stress. Either base substitutions and indels or genome rearrangements result. Here we discovered that most small basic proteins that compact the genome, nucleoid-associated proteins (NAPs), promote or inhibit mutagenic break repair (MBR) via different routes. Of 15 NAPs, H-NS, Fis, CspE, and CbpA were required for MBR; Dps inhibited MBR; StpA and Hha did neither; and five others were characterized previously. Three essential genes were not tested. Using multiple tests, we found the following: First, Dps, which reduces reactive oxygen species (ROS), inhibited MBR, implicating ROS in MBR. Second, CbpA promoted F' plasmid maintenance, allowing MBR to be measured in an F'-based assay. Third, Fis was required for activation of the SOS DNA-damage response and could be substituted in MBR by SOS-induced levels of DinB error-prone DNA polymerase. Thus, Fis promoted MBR by allowing SOS activation. Fourth, H-NS represses ROS detoxifier sodB and was substituted in MBR by deletion of sodB, which was not otherwise mutagenic. We conclude that normal ROS levels promote MBR and that H-NS promotes MBR by maintaining ROS. CspE positively regulates RpoS, which is required for MBR. Four of five previously characterized NAPs promoted stress responses that enhance MBR. Hence, most NAPs affect MBR, the majority via regulatory functions. The data show that a total of six NAPs promote MBR by regulating stress responses, indicating the importance of nucleoid structure and function to the regulation of MBR and of coupling mutagenesis to stress, creating genetic diversity responsively.
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Affiliation(s)
- Jessica M Moore
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, 77030 Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, 77030
| | - David Magnan
- Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, 77030 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030
| | - Ana K Mojica
- Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, 77030 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030 Undergraduate Program on Genomic Sciences, National Autonomous University of Mexico, Cuernavaca, 62210, Morelos, Mexico
| | - María Angélica Bravo Núñez
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, 77030 Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, 77030 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030
| | - David Bates
- Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, 77030 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030 Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, 77030
| | - Susan M Rosenberg
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, 77030 Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, 77030 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030 Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, 77030
| | - P J Hastings
- Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas, 77030 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030
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19
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Marshall JM, Gunn JS. The O-Antigen Capsule of Salmonella enterica Serovar Typhimurium Facilitates Serum Resistance and Surface Expression of FliC. Infect Immun 2015; 83:3946-59. [PMID: 26195553 PMCID: PMC4567616 DOI: 10.1128/iai.00634-15] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 07/16/2015] [Indexed: 11/20/2022] Open
Abstract
Group IV polysaccharide capsules are common in enteric bacteria and have more recently been described in nontyphoidal Salmonella species. Such capsules are known as O-antigen (O-Ag) capsules, due to their high degree of similarity to the O-Ag of the lipopolysaccharide (LPSO-Ag). Capsular polysaccharides are known virulence factors of many bacterial pathogens, facilitating evasion of immune recognition and systemic dissemination within the host. Previous studies on the O-Ag capsule of salmonellae have focused primarily on its role in bacterial surface attachment and chronic infection; however, the potential effects of the O-Ag capsule on acute pathogenesis have yet to be investigated. While much of the in vivo innate immune resistance of Salmonella enterica serovar Typhimurium is attributed to the high-molecular-weight LPS, we hypothesized that the O-Ag capsule may enhance this resistance by diminishing surface expression of pathogen-associated molecular patterns, such as flagella, and increasing resistance to host immune molecules. To test this hypothesis, O-Ag capsule-deficient mutants were constructed, and the loss of O-Ag capsular surface expression was confirmed through microscopy and immunoblotting. Loss of O-Ag capsule production did not alter bacterial growth or production of LPS. Western blot analysis and confocal microscopy revealed that O-Ag capsule-deficient mutants demonstrate reduced resistance to killing by human serum. Furthermore, O-Ag capsule-deficient mutants produced exclusively phase I flagellin (FliC). Although O-Ag capsule-deficient mutants did not exhibit reduced virulence in a murine model of acute infection, in vitro results indicate that the O-Ag capsule may function to modify the antigenic nature of the bacterial surface, warranting additional investigation of a potential role of the structure in pathogenesis.
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Affiliation(s)
- Joanna M Marshall
- Department of Microbial Infection and Immunity, Center for Microbial Interface Biology, The Ohio State University, Columbus, Ohio, USA
| | - John S Gunn
- Department of Microbial Infection and Immunity, Center for Microbial Interface Biology, The Ohio State University, Columbus, Ohio, USA
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20
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Solórzano C, Srikumar S, Canals R, Juárez A, Paytubi S, Madrid C. Hha has a defined regulatory role that is not dependent upon H-NS or StpA. Front Microbiol 2015; 6:773. [PMID: 26284052 PMCID: PMC4519777 DOI: 10.3389/fmicb.2015.00773] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 07/14/2015] [Indexed: 11/13/2022] Open
Abstract
The Hha family of proteins is involved in the regulation of gene expression in enterobacteria by forming complexes with H-NS-like proteins. Whereas several amino acid residues of both proteins participate in the interaction, some of them play a key role. Residue D48 of Hha protein is essential for the interaction with H-NS, thus the D48N substitution in Hha protein abrogates H-NS/Hha interaction. Despite being a paralog of H-NS protein, StpA interacts with HhaD48N with higher affinity than with the wild type Hha protein. To analyze whether Hha is capable of acting independently of H-NS and StpA, we conducted transcriptomic analysis on the hha and stpA deletion strains and the hhaD48N substitution strain of Salmonella Typhimurium using a custom microarray. The results obtained allowed the identification of 120 genes regulated by Hha in an H-NS/StpA-independent manner, 38% of which are horizontally acquired genes. A significant number of the identified genes are involved in functions related to cell motility, iron uptake, and pathogenicity. Thus, motility assays, siderophore detection and intra-macrophage replication assays were performed to confirm the transcriptomic data. Our findings point out the importance of Hha protein as an independent regulator in S. Typhimurium, highlighting a regulatory role on virulence.
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Affiliation(s)
- Carla Solórzano
- Departament de Microbiologia, Universitat de Barcelona Barcelona, Spain
| | | | - Rocío Canals
- Institute of Integrative Biology, University of Liverpool Liverpool, UK
| | - Antonio Juárez
- Departament de Microbiologia, Universitat de Barcelona Barcelona, Spain ; Institut de Bioenginyeria de Catalunya, Parc Científic de Barcelona Barcelona, Spain
| | - Sonia Paytubi
- Departament de Microbiologia, Universitat de Barcelona Barcelona, Spain
| | - Cristina Madrid
- Departament de Microbiologia, Universitat de Barcelona Barcelona, Spain
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21
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Perez-Rueda E, Ibarra JA. Distribution of putative xenogeneic silencers in prokaryote genomes. Comput Biol Chem 2015; 58:167-72. [PMID: 26247404 DOI: 10.1016/j.compbiolchem.2015.06.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 06/05/2015] [Accepted: 06/27/2015] [Indexed: 12/30/2022]
Abstract
Gene silencing is an important function as it keeps newly acquired foreign DNA repressed, thereby avoiding possible deleterious effects in the host organism. Known transcriptional regulators associated with this process are called xenogeneic silencers (XS) and belong to either the H-NS, Lsr2, MvaT or Rok families. In the work described here we looked for XS-like regulators and their distribution in prokaryotic organisms was evaluated. Our analysis showed that putative XS regulators similar to H-NS, Lsr2, MvaT or Rok are present only in bacteria (31.7%). This does not exclude the existence of alternative XS in the rest of the organisms analyzed. Additionally, of the four XS groups evaluated in this work, those from the H-NS family have diversified more than the other groups. In order to compare the distribution of these putative XS regulators we also searched for other nucleoid-associated proteins (NAPs) not included in this group such as Fis, EbfC/YbaB, HU/IHF and Alba. Results showed that NAPs from the Fis, EbfC/YbaB, HU/IHF and Alba families are widely (94%) distributed among prokaryotes. These NAPs were found in multiple combinations with or without XS-like proteins. In regard with XS regulators, results showed that only XS proteins from one family were found in those organisms containing them. This suggests specificity for this type of regulators and their corresponding genomes.
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Affiliation(s)
- Ernesto Perez-Rueda
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología UNAM, Av. Universidad 2001, Cuernavaca, Morelos CP 62210, Mexico; Unidad Multidisciplinaria de Docencia e Investigación, Sisal Facultad de Ciencias, Sisal, Yucatán, UNAM, Mexico
| | - J Antonio Ibarra
- Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Prol. de Carpio y Plan de Ayala. Col. Sto. Tomás, Distrito Federal, CP 11340, Mexico.
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22
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Shintani M, Suzuki-Minakuchi C, Nojiri H. Nucleoid-associated proteins encoded on plasmids: Occurrence and mode of function. Plasmid 2015; 80:32-44. [PMID: 25952329 DOI: 10.1016/j.plasmid.2015.04.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Revised: 04/14/2015] [Accepted: 04/22/2015] [Indexed: 01/31/2023]
Abstract
Nucleoid-associated proteins (NAPs) play a role in changing the shape of microbial DNA, making it more compact and affecting the regulation of transcriptional networks in host cells. Genes that encode NAPs include H-NS family proteins (H-NS, Ler, MvaT, BpH3, Bv3F, HvrA, and Lsr2), FIS, HU, IHF, Lrp, and NdpA, and are found in both microbial chromosomes and plasmid DNA. In the present study, NAP genes were distributed among 442 plasmids out of 4602 plasmid sequences, and many H-NS family proteins, and HU, IHF, Lrp, and NdpA were found in plasmids of Alpha-, Beta-, and Gammaproteobacteria, while HvrA, Lsr2, HU, and Lrp were found in other classes including Actinobacteria and Bacilli. Larger plasmids frequently carried multiple NAP genes. In addition, NAP genes were more frequently found in conjugative plasmids than non-transmissible plasmids. Several host cells carried the same types of H-NS family proteins on both their plasmids and chromosome(s), while this was not observed for other NAPs. Recent studies have shown that NAP genes on plasmids and chromosomes play important roles in the physical and regulatory integration of plasmids into the host cell.
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Affiliation(s)
- Masaki Shintani
- Applied Chemistry and Biochemical Engineering Course, Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan; Department of Bioscience, Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan
| | - Chiho Suzuki-Minakuchi
- Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Hideaki Nojiri
- Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
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23
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Ali SS, Soo J, Rao C, Leung AS, Ngai DHM, Ensminger AW, Navarre WW. Silencing by H-NS potentiated the evolution of Salmonella. PLoS Pathog 2014; 10:e1004500. [PMID: 25375226 PMCID: PMC4223078 DOI: 10.1371/journal.ppat.1004500] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 10/02/2014] [Indexed: 11/17/2022] Open
Abstract
The bacterial H-NS protein silences expression from sequences with higher AT-content than the host genome and is believed to buffer the fitness consequences associated with foreign gene acquisition. Loss of H-NS results in severe growth defects in Salmonella, but the underlying reasons were unclear. An experimental evolution approach was employed to determine which secondary mutations could compensate for the loss of H-NS in Salmonella. Six independently derived S. Typhimurium hns mutant strains were serially passaged for 300 generations prior to whole genome sequencing. Growth rates of all lineages dramatically improved during the course of the experiment. Each of the hns mutant lineages acquired missense mutations in the gene encoding the H-NS paralog StpA encoding a poorly understood H-NS paralog, while 5 of the mutant lineages acquired deletions in the genes encoding the Salmonella Pathogenicity Island-1 (SPI-1) Type 3 secretion system critical to invoke inflammation. We further demonstrate that SPI-1 misregulation is a primary contributor to the decreased fitness in Salmonella hns mutants. Three of the lineages acquired additional loss of function mutations in the PhoPQ virulence regulatory system. Similarly passaged wild type Salmonella lineages did not acquire these mutations. The stpA missense mutations arose in the oligomerization domain and generated proteins that could compensate for the loss of H-NS to varying degrees. StpA variants most able to functionally substitute for H-NS displayed altered DNA binding and oligomerization properties that resembled those of H-NS. These findings indicate that H-NS was central to the evolution of the Salmonellae by buffering the negative fitness consequences caused by the secretion system that is the defining characteristic of the species.
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Affiliation(s)
- Sabrina S. Ali
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Jeremy Soo
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Chitong Rao
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Andrea S. Leung
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - David Hon-Man Ngai
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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24
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Dorman CJ. H-NS-like nucleoid-associated proteins, mobile genetic elements and horizontal gene transfer in bacteria. Plasmid 2014; 75:1-11. [DOI: 10.1016/j.plasmid.2014.06.004] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 06/23/2014] [Accepted: 06/25/2014] [Indexed: 11/29/2022]
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25
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Suzuki C, Kawazuma K, Horita S, Terada T, Tanokura M, Okada K, Yamane H, Nojiri H. Oligomerization mechanisms of an H-NS family protein, Pmr, encoded on the plasmid pCAR1 provide a molecular basis for functions of H-NS family members. PLoS One 2014; 9:e105656. [PMID: 25137042 PMCID: PMC4138198 DOI: 10.1371/journal.pone.0105656] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 07/26/2014] [Indexed: 11/19/2022] Open
Abstract
Enterobacterial H-NS-like proteins and Pseudomonas MvaT-like proteins share low homology at the amino acid sequence level, but both can function as xenogeneic silencers and are included in the H-NS family of proteins. H-NS family members have dimerization/oligomerization and DNA-binding domains connected by a flexible linker and form large nucleoprotein complexes using both domains. Pmr, an MvaT-like protein encoded on the IncP-7 carbazole-degradative plasmid pCAR1, is a key regulator of an interaction between pCAR1 and its host Pseudomonas putida KT2440. KT2440 has two transcribed genes that encode the MvaT-like proteins TurA and TurB. Our previous transcriptome analyses suggested that the functions of Pmr, TurA and TurB are non-equivalent, although the detailed underlying mechanisms remain unclear. In this study, we focused on the protein–protein interactions of Pmr, and assessed the homo-oligomerization capacity of various substituted and truncated Pmr derivatives by protein–protein cross-linking analysis. Six of the seven residues identified as important for homo-oligomerization in Pmr were located near the N-terminus, and the putative flexible linker or the region near that was not involved in homo-oligomerization, suggesting that Pmr homo-oligomerization is different from that of enterobacterial H-NS and that the functional mechanism differs between H-NS-like and MvaT-like proteins. In addition, we assessed homo- and hetero-oligomerization of Pmr by surface plasmon resonance analysis and found that the coupling ratio of TurB-Pmr oligomers is smaller than that of Pmr-Pmr or TurA-Pmr oligomers. These results raised the possibility that composition of the hetero-oligomers of Pmr, TurA, and TurB could explain why the different gene sets were affected by either pmr, turA, or turB disruption in our previous studies.
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Affiliation(s)
- Chiho Suzuki
- Biotechnology Research Center, The University of Tokyo, Tokyo, Japan
| | - Kohei Kawazuma
- Biotechnology Research Center, The University of Tokyo, Tokyo, Japan
| | - Shoichiro Horita
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Tohru Terada
- Agricultural Bioinformatics Research Unit, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Masaru Tanokura
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Kazunori Okada
- Biotechnology Research Center, The University of Tokyo, Tokyo, Japan
| | - Hisakazu Yamane
- Biotechnology Research Center, The University of Tokyo, Tokyo, Japan
| | - Hideaki Nojiri
- Biotechnology Research Center, The University of Tokyo, Tokyo, Japan
- Agricultural Bioinformatics Research Unit, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
- * E-mail:
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26
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Wang KC, Hsu YH, Huang YN, Chen TH, Lin JH, Hsuan SL, Chien MS, Lee WC, Yeh KS. A low-pH medium in vitro or the environment within a macrophage decreases the transcriptional levels of fimA, fimZ and lrp in Salmonella enterica serovar Typhimurium. J Biosci 2014; 38:499-507. [PMID: 23938383 DOI: 10.1007/s12038-013-9347-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Many Salmonella Typhimurium isolates produce type 1 fimbriae and exhibit fimbrial phase variation in vitro. Static broth culture favours the production of fimbriae, while solid agar medium inhibits the generation of these appendages. Little information is available regarding whether S. Typhimurium continues to produce type 1 fimbriae during in vivo growth. We used a type 1 fimbrial phase-variable strain S. Typhimurium LB5010 and its derivatives to infect RAW 264.7 macrophages. Following entry into macrophages, S. Typhimurium LB5010 gradually decreased the transcript levels of fimbrial subunit gene fimA, positive regulatory gene fimZ, and global regulatory gene lrp. A similar decrease in transcript levels was detected by RT-PCRwhen the pH of static brothmediumwas shifted frompH 7 to amore acidic pH 4. A fimA-deleted strain continued to multiply within macrophages as did the parental strain. An lrp deletion strain was unimpaired for in vitro growth at pH 7 or pH 4, while a strain harboring an lrp-containing plasmid exhibited impaired in vitro growth at pH 4. We propose that acidic medium, which resembles one aspect of the intracellular environment in a macrophage, inhibits type 1 fimbrial production by down-regulation of the expression of lrp, fimZ and fimA.
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Affiliation(s)
- Ke-Chuan Wang
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan
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27
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Identification of HilD-regulated genes in Salmonella enterica serovar Typhimurium. J Bacteriol 2013; 196:1094-101. [PMID: 24375101 DOI: 10.1128/jb.01449-13] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Salmonella enterica serovar Typhimurium (S. Typhimurium) pathogenicity island 1 (SPI-1) encodes a type III secretion system required for invasion of host gut epithelial cells. Expression of SPI-1 virulence genes is controlled by a complex hierarchy of transcription factors encoded within and outside SPI-1. The master regulator of SPI-1, HilA, is itself regulated by three homologous transcription factors, HilD, HilC, and RtsA. HilD activates transcription of hilA and other target genes in response to environmental conditions associated with the intestinal microenvironment of the host. We have mapped the binding of HilD across the S. Typhimurium genome using chromatin immunoprecipitation-sequencing (ChIP-seq). Thus, we have identified 17 regions bound by HilD, including 11 novel targets. The majority of HilD targets are located outside SPI-1. We demonstrate transcription activation of 8 genes by HilD; four of these genes have not been previously described as being regulated by HilD, including lpxR, which encodes a lipid A deacylase important for immune evasion. We also show that HilD-activated genes are frequently activated by HilC and RtsA, indicating extensive overlap of the HilD, HilC, and RtsA regulons.
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28
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Pathoadaptive mutations in Salmonella enterica isolated after serial passage in mice. PLoS One 2013; 8:e70147. [PMID: 23936152 PMCID: PMC3723669 DOI: 10.1371/journal.pone.0070147] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 06/20/2013] [Indexed: 12/18/2022] Open
Abstract
How pathogenic bacteria adapt and evolve in the complex and variable environment of the host remains a largely unresolved question. Here we have used whole genome sequencing of Salmonella enterica serovar Typhimurium LT2 populations serially passaged in mice to identify mutations that adapt bacteria to systemic growth in mice. We found unique pathoadaptive mutations in two global regulators, phoQ and stpA, which increase the competitive indexes of the bacteria 3- to 5-fold. Also, all mouse-adapted lineages had changed the orientation of the hin invertable element, resulting in production of a FliC type of flagellum. Competition experiments in mice with locked flagellum mutants showed that strains expressing the FliC type of flagellum had a 5-fold increase in competitive index as compared to those expressing FljB type flagellum. Combination of the flagellum cassette inversion with the stpA mutation increased competitive indexes up to 20-fold. These experiments show that Salmonella can rapidly adapt to a mouse environment by acquiring a few mutations of moderate individual effect that when combined confer substantial increases in growth.
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29
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Srinivasan R, Chandraprakash D, Krishnamurthi R, Singh P, Scolari VF, Krishna S, Seshasayee ASN. Genomic analysis reveals epistatic silencing of "expensive" genes in Escherichia coli K-12. MOLECULAR BIOSYSTEMS 2013; 9:2021-33. [PMID: 23661089 DOI: 10.1039/c3mb70035f] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A barrier for horizontal gene transfer is high gene expression, which is metabolically expensive. Silencing of horizontally-acquired genes in the bacterium Escherichia coli is caused by the global transcriptional repressor H-NS. The activity of H-NS is enhanced or diminished by other proteins including its homologue StpA, and Hha and YdgT. The interconnections of H-NS with these regulators and their role in silencing gene expression in E. coli are not well understood on a genomic scale. In this study, we use transcriptome sequencing to show that there is a bi-layered gene silencing system - involving the homologous H-NS and StpA - operating on horizontally-acquired genes among others. We show that H-NS-repressed genes belong to two types, termed "epistatic" and "unilateral". In the absence of H-NS, the expression of "epistatically controlled genes" is repressed by StpA, whereas that of "unilaterally controlled genes" is not. Epistatic genes show a higher tendency to be non-essential and recently acquired, when compared to unilateral genes. Epistatic genes reach much higher expression levels than unilateral genes in the absence of the silencing system. Finally, epistatic genes contain more high affinity H-NS binding motifs than unilateral genes. Therefore, both the DNA binding sites of H-NS as well as the function of StpA as a backup system might be selected for silencing highly transcribable genes.
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Affiliation(s)
- Rajalakshmi Srinivasan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK, Bellary Road, Bangalore 560065, India
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30
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Qu Y, Lim CJ, Whang YR, Liu J, Yan J. Mechanism of DNA organization by Mycobacterium tuberculosis protein Lsr2. Nucleic Acids Res 2013; 41:5263-72. [PMID: 23580555 PMCID: PMC3664827 DOI: 10.1093/nar/gkt249] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Bacterial nucleoid-associated proteins, such as H-NS-like proteins in Enterobacteriaceae, are abundant DNA-binding proteins that function in chromosomal DNA organization and gene transcription regulation. The Mycobacterium tuberculosis Lsr2 protein has been proposed to be the first identified H-NS analogue in Gram-positive bacteria based on its capability to complement numerous in vivo functions of H-NS. Here, we report that Lsr2 cooperatively binds to DNA forming a rigid Lsr2 nucleoprotein complex that restricts DNA accessibility, similar to H-NS. On large DNA, the rigid Lsr2 nucleoprotein complexes can mediate DNA condensation into highly compact DNA conformations. In addition, the responses of Lsr2 nucleoprotein complex to environmental factors (salt concentration, temperature and pH) were studied over physiological ranges. These results provide mechanistic insights into how Lsr2 may mediate its gene silencing, genomic DNA protection and organization functions in vivo. Finally, our results strongly support that Lsr2 is an H-NS-like protein in Gram-positive bacteria from a structural perspective.
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Affiliation(s)
- Yuanyuan Qu
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
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31
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Le MT, Porcelli I, Weight CM, Gaskin DJH, Carding SR, van Vliet AHM. Acid-shock of Campylobacter jejuni induces flagellar gene expression and host cell invasion. Eur J Microbiol Immunol (Bp) 2012; 2:12-9. [PMID: 24611116 DOI: 10.1556/eujmi.2.2012.1.3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 01/14/2012] [Indexed: 11/19/2022] Open
Abstract
The bacterial pathogen Campylobacter jejuni is the leading cause of foodborne gastroenteritis in the developed world, with the organism being transmitted by ingestion of contaminated and undercooked poultry. Exposure to acid is an inevitable stressor for C. jejuni during gastric passage, yet the effect of low pH on C. jejuni virulence is still poorly understood. Here, we investigate the effect of acid-shock on C. jejuni viability, gene expression and host-cell invasion. C. jejuni strain NCTC 11168 survived acid exposure at pH 3.5 and above for up to 30 min without a drop in viability, and this exposure induced the expression of flagellar genes transcribed from σ(54)-dependent promoters. Furthermore, acid-shock resulted in increased C. jejuni invasion of m-ICcl2 mouse small intestine crypt cells grown on transwells, but not when the cells were grown on flat-bottomed wells. This suggests that C. jejuni might be invading intestinal epithelial cells at the basolateral side, possibly after paracellular passage. We hypothesize that acid-shock prior to intestinal entry may serve as a signal that primes C. jejuni to express its virulence gene repertoire including flagellar motility genes, but this requires further study in the context of an appropriate colonization or disease model.
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32
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H-NS regulation of IraD and IraM antiadaptors for control of RpoS degradation. J Bacteriol 2012; 194:2470-8. [PMID: 22408168 DOI: 10.1128/jb.00132-12] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
RpoS, the master sigma factor during stationary phase and under a variety of stress conditions, is regulated at multiple levels, including regulated degradation. Degradation is dependent upon ClpXP and the RssB adaptor protein. H-NS, a nucleoid-associated protein, affects the regulated degradation of RpoS; in the absence of H-NS, RpoS is stable. The mechanisms involved in this regulation were not known. We have found that H-NS inhibits the expression of iraD and iraM, the genes coding for two antiadaptor proteins that stabilize RpoS when overexpressed. The regulation by H-NS of iraM is independent from the previously demonstrated regulation by the PhoP/PhoQ two-component system. Moreover, differences in the behavior of several hns alleles are explained by a role for StpA, an H-NS-like protein, in the regulation of RpoS stability. This finding parallels recent observations for a role of StpA in regulation of RpoS stability in Salmonella.
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33
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34
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Knudsen GM, Nielsen MB, Grassby T, Danino-Appleton V, Thomsen LE, Colquhoun IJ, Brocklehurst TF, Olsen JE, Hinton JCD. A third mode of surface-associated growth: immobilization of Salmonella enterica serovar Typhimurium modulates the RpoS-directed transcriptional programme. Environ Microbiol 2012; 14:1855-75. [PMID: 22356617 DOI: 10.1111/j.1462-2920.2012.02703.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Although the growth of bacteria has been studied for more than a century, it is only in recent decades that surface-associated growth has received attention. In addition to the well-characterized biofilm and swarming lifestyles, bacteria can also develop as micro-colonies supported by structured environments in both food products and the GI tract. This immobilized mode of growth has not been widely studied. To develop our understanding of the effects of immobilization upon a food-borne bacterial pathogen, we used the IFR Gel Cassette model. The transcriptional programme and metabolomic profile of Salmonella enterica serovar Typhimurium ST4/74 were compared during planktonic and immobilized growth, and a number of immobilization-specific characteristics were identified. Immobilized S.Typhimurium did not express motility and chemotaxis genes, and electron microscopy revealed the absence of flagella. The expression of RpoS-dependent genes and the level of RpoS protein were increased in immobilized bacteria, compared with planktonic growth. Immobilized growth prevented the induction of SPI1, SPI4 and SPI5 gene expression, likely mediated by the FliZ transcriptional regulator. Using an epithelial cell-based assay, we showed that immobilized S.Typhimurium was significantly less invasive than planktonic bacteria, and we suggest that S.Typhimurium grown in immobilized environments are less virulent than planktonic bacteria. Our findings identify immobilization as a third type of surface-associated growth that is distinct from the biofilm and swarming lifestyles of Salmonella.
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Affiliation(s)
- Gitte M Knudsen
- Institute of Food Research, Norwich Research Park, Norwich, NR4 7UA, UK
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35
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Battesti A, Majdalani N, Gottesman S. The RpoS-mediated general stress response in Escherichia coli. Annu Rev Microbiol 2012; 65:189-213. [PMID: 21639793 DOI: 10.1146/annurev-micro-090110-102946] [Citation(s) in RCA: 636] [Impact Index Per Article: 53.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Under conditions of nutrient deprivation or stress, or as cells enter stationary phase, Escherichia coli and related bacteria increase the accumulation of RpoS, a specialized sigma factor. RpoS-dependent gene expression leads to general stress resistance of cells. During rapid growth, RpoS translation is inhibited and any RpoS protein that is synthesized is rapidly degraded. The complex transition from exponential growth to stationary phase has been partially dissected by analyzing the induction of RpoS after specific stress treatments. Different stress conditions lead to induction of specific sRNAs that stimulate RpoS translation or to induction of small-protein antiadaptors that stabilize the protein. Recent progress has led to a better, but still far from complete, understanding of how stresses lead to RpoS induction and what RpoS-dependent genes help the cell deal with the stress.
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Affiliation(s)
- Aurelia Battesti
- Laboratory of Molecular Biology, National Cancer Institute, Bethesda, Maryland 20892, USA.
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36
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Lim CJ, Whang YR, Kenney LJ, Yan J. Gene silencing H-NS paralogue StpA forms a rigid protein filament along DNA that blocks DNA accessibility. Nucleic Acids Res 2011; 40:3316-28. [PMID: 22187157 PMCID: PMC3333869 DOI: 10.1093/nar/gkr1247] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Nucleoid-associated proteins are bacterial proteins that are responsible for chromosomal DNA compaction and global gene regulation. One such protein is Escherichia coli Histone-like nucleoid structuring protein (H-NS) which functions as a global gene silencer. Whereas the DNA-binding mechanism of H-NS is well-characterized, its paralogue, StpA which is also able to silence genes is less understood. Here we show that StpA is similar to H-NS in that it is able to form a rigid filament along DNA. In contrast to H-NS, the StpA filament interacts with a naked DNA segment to cause DNA bridging which results in simultaneous stiffening and bridging of DNA. DNA accessibility is effectively blocked after the formation of StpA filament on DNA, suggesting rigid filament formation is the important step in promoting gene silencing. We also show that >1 mM magnesium promotes higher order DNA condensation, suggesting StpA may also play a role in chromosomal DNA packaging.
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Affiliation(s)
- Ci Ji Lim
- NUS Graduate school for Integrative Sciences and Engineering, National University of Singapore, 28 Medical Drive, Singapore, 119077, Singapore
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37
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Lag phase is a distinct growth phase that prepares bacteria for exponential growth and involves transient metal accumulation. J Bacteriol 2011; 194:686-701. [PMID: 22139505 DOI: 10.1128/jb.06112-11] [Citation(s) in RCA: 327] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lag phase represents the earliest and most poorly understood stage of the bacterial growth cycle. We developed a reproducible experimental system and conducted functional genomic and physiological analyses of a 2-h lag phase in Salmonella enterica serovar Typhimurium. Adaptation began within 4 min of inoculation into fresh LB medium with the transient expression of genes involved in phosphate uptake. The main lag-phase transcriptional program initiated at 20 min with the upregulation of 945 genes encoding processes such as transcription, translation, iron-sulfur protein assembly, nucleotide metabolism, LPS biosynthesis, and aerobic respiration. ChIP-chip revealed that RNA polymerase was not "poised" upstream of the bacterial genes that are rapidly induced at the beginning of lag phase, suggesting a mechanism that involves de novo partitioning of RNA polymerase to transcribe 522 bacterial genes within 4 min of leaving stationary phase. We used inductively coupled plasma mass spectrometry (ICP-MS) to discover that iron, calcium, and manganese are accumulated by S. Typhimurium during lag phase, while levels of cobalt, nickel, and sodium showed distinct growth-phase-specific patterns. The high concentration of iron during lag phase was associated with transient sensitivity to oxidative stress. The study of lag phase promises to identify the physiological and regulatory processes responsible for adaptation to new environments.
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38
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Ohniwa RL, Ushijima Y, Saito S, Morikawa K. Proteomic analyses of nucleoid-associated proteins in Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus. PLoS One 2011; 6:e19172. [PMID: 21541338 PMCID: PMC3082553 DOI: 10.1371/journal.pone.0019172] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 03/29/2011] [Indexed: 11/18/2022] Open
Abstract
Background The bacterial nucleoid contains several hundred kinds of nucleoid-associated proteins (NAPs), which play critical roles in genome functions such as transcription and replication. Several NAPs, such as Hu and H-NS in Escherichia coli, have so far been identified. Methodology/Principal Findings Log- and stationary-phase cells of E. coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus were lysed in spermidine solutions. Nucleoids were collected by sucrose gradient centrifugation, and their protein constituents analyzed by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). Over 200 proteins were identified in each species. Envelope and soluble protein fractions were also identified. By using these data sets, we obtained lists of contaminant-subtracted proteins enriched in the nucleoid fractions (csNAP lists). The lists do not cover all of the NAPs, but included Hu regardless of the growth phases and species. In addition, the csNAP lists of each species suggested that the bacterial nucleoid is equipped with the species-specific set of global regulators, oxidation-reduction enzymes, and fatty acid synthases. This implies bacteria individually developed nucleoid associated proteins toward obtaining similar characteristics. Conclusions/Significance Ours is the first study to reveal hundreds of NAPs in the bacterial nucleoid, and the obtained data set enabled us to overview some important features of the nucleoid. Several implications obtained from the present proteomic study may make it a landmark for the future functional and evolutionary study of the bacterial nucleoid.
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Affiliation(s)
- Ryosuke L Ohniwa
- Institute of Basic Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tennodai, Tsukuba, Ibaraki, Japan.
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39
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Rimsky S, Travers A. Pervasive regulation of nucleoid structure and function by nucleoid-associated proteins. Curr Opin Microbiol 2011; 14:136-41. [PMID: 21288763 DOI: 10.1016/j.mib.2011.01.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 01/07/2011] [Accepted: 01/07/2011] [Indexed: 01/10/2023]
Abstract
Bacterial DNA is organised in a compact nucleoid body that is tightly associated with the coupled transcription and translation of mRNAs. This structure contains abundant DNA-binding proteins which perform both structural and regulatory roles, and, in Escherichia coli, serve to buffer and organise pervasive DNA superhelicity. We argue that NAPs coordinate regulation of gene expression and superhelicity at the global (or chromosomal) and at local (corresponding to promoter activity and genetic recombination) levels.
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Affiliation(s)
- Sylvie Rimsky
- LBPA, Ecole Normale Supérieure de Cachan, CNRS, 94235 Cachan, France.
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40
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Mangan MW, Lucchini S, Ó Cróinín T, Fitzgerald S, Hinton JCD, Dorman CJ. Nucleoid-associated protein HU controls three regulons that coordinate virulence, response to stress and general physiology in Salmonella enterica serovar Typhimurium. MICROBIOLOGY-SGM 2011; 157:1075-1087. [PMID: 21212121 DOI: 10.1099/mic.0.046359-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The role of the HU nucleoid-associated proteins in gene regulation was examined in Salmonella enterica serovar Typhimurium. The dimeric HU protein consists of different combinations of its α and β subunits. Transcriptomic analysis was performed with cultures growing at 37 °C at 1, 4 and 6 h after inoculation with mutants that lack combinations of HU α and HU β. Distinct but overlapping patterns of gene expression were detected at each time point for each of the three mutants, revealing not one but three regulons of genes controlled by the HU proteins. Mutations in the hup genes altered the expression of regulatory and structural genes in both the SPI1 and SPI2 pathogenicity islands. The hupA hupB double mutant was defective in invasion of epithelial cell lines and in its ability to survive in macrophages. The double mutant also had defective swarming activity and a competitive fitness disadvantage compared with the wild-type. In contrast, inactivation of just the hupB gene resulted in increased fitness and correlated with the upregulation of members of the RpoS regulon in exponential-phase cultures. Our data show that HU coordinates the expression of genes involved in central metabolism and virulence and contributes to the success of S. enterica as a pathogen.
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Affiliation(s)
- Michael W Mangan
- Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland
| | - Sacha Lucchini
- Department of Molecular Microbiology, Institute for Food Research, Colney, Norwich NR4 7UA, UK
| | - Tadhg Ó Cróinín
- Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland
| | - Stephen Fitzgerald
- Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland
| | - Jay C D Hinton
- Department of Molecular Microbiology, Institute for Food Research, Colney, Norwich NR4 7UA, UK
- Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland
| | - Charles J Dorman
- Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland
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41
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Browning DF, Grainger DC, Busby SJW. Effects of nucleoid-associated proteins on bacterial chromosome structure and gene expression. Curr Opin Microbiol 2010; 13:773-80. [DOI: 10.1016/j.mib.2010.09.013] [Citation(s) in RCA: 230] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Accepted: 09/16/2010] [Indexed: 11/25/2022]
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42
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Castang S, Dove SL. High-order oligomerization is required for the function of the H-NS family member MvaT in Pseudomonas aeruginosa. Mol Microbiol 2010; 78:916-31. [PMID: 20815825 DOI: 10.1111/j.1365-2958.2010.07378.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
H-NS is an abundant DNA-binding protein that has been implicated in the silencing of foreign DNA in several different bacteria. The ability of H-NS dimers to form higher-order oligomers is thought to aid the polymerization of the protein across AT-rich stretches of DNA and facilitate gene silencing. Although the oligomerization of H-NS from enteric bacteria has been the subject of intense investigation, little is known regarding the oligomerization of H-NS family members from bacteria outside of the enterobacteriaceae, many of which share little sequence similarity with their enteric counterparts. Here we show that MvaT, a member of the H-NS family of proteins from Pseudomonas aeruginosa, can form both dimers and higher-order oligomers, and we identify a region within MvaT that mediates higher-order oligomer formation. Using genetic assays we identify mutants of MvaT that are defective for higher-order oligomer formation. We present evidence that these mutants are functionally impaired and exhibit DNA-binding defects because of their inability to form higher-order oligomers. Our findings support a model in which the ability of MvaT to bind efficiently to the DNA depends upon protein-protein interactions between MvaT dimers and suggest that the ability to form higher-order oligomers is a conserved and essential feature of H-NS family members.
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Affiliation(s)
- Sandra Castang
- Division of Infectious Diseases, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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Dillon SC, Cameron ADS, Hokamp K, Lucchini S, Hinton JCD, Dorman CJ. Genome-wide analysis of the H-NS and Sfh regulatory networks in Salmonella Typhimurium identifies a plasmid-encoded transcription silencing mechanism. Mol Microbiol 2010; 76:1250-65. [PMID: 20444106 DOI: 10.1111/j.1365-2958.2010.07173.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The conjugative IncHI1 plasmid pSfR27 from Shigella flexneri 2a strain 2457T encodes the Sfh protein, a paralogue of the global transcriptional repressor H-NS. Sfh allows pSfR27 to be transmitted to new bacterial hosts with minimal impact on host fitness, providing a 'stealth' function whose molecular mechanism has yet to be determined. The impact of the Sfh protein on the Salmonella enterica serovar Typhimurium transcriptome was assessed and binding sites for Sfh in the Salmonella Typhimurium genome were identified by chromatin immunoprecipitation. Sfh did not bind uniquely to any sites. Instead, it bound to a subset of the larger H-NS regulatory network. Analysis of Sfh binding in the absence of H-NS revealed a greatly expanded population of Sfh binding sites that included the majority of H-NS target genes. Furthermore, the presence of plasmid pSfR27 caused a decrease in H-NS interactions with the S. Typhimurium chromosome, suggesting that the A + T-rich DNA of this large plasmid acts to titrate H-NS, removing it from chromosomal locations. It is proposed that Sfh acts as a molecular backup for H-NS and that it provides its 'stealth' function by replacing H-NS on the chromosome, thus minimizing disturbances to the H-NS-DNA binding pattern in cells that acquire pSfR27.
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Affiliation(s)
- Shane C Dillon
- Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin 2, Ireland
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Dorman CJ. Horizontally acquired homologues of the nucleoid-associated protein H-NS: implications for gene regulation. Mol Microbiol 2009; 75:264-7. [PMID: 20015146 DOI: 10.1111/j.1365-2958.2009.06996.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
H-NS is one of the most intensively studied members of the family of bacterial nucleoid-associated proteins. It is a DNA-binding protein with a preference for A+T-rich DNA sequences, and it represses the transcription of hundreds of genes in Gram-negative bacteria, including pathogens. In most cases where the issue has been investigated, the repressive activity of H-NS is opposed by the intervention of an antagonistically acting DNA-binding protein, a remodelling of local DNA structure, or a combination of these two. H-NS activity can also be modulated by protein-protein interaction with members of the Hha/YdgT protein family, molecules that share partial amino acid sequence similarity to the oligomerization domain of H-NS. Of particular interest is the ability of H-NS to interact with the full-length paralogue StpA or full-length orthologues that have been acquired by horizontal DNA transfer. In this issue of Molecular Microbiology, Müller et al. describe the H-NS orthologue Hfp and present evidence that in bacteria that acquire Hfp the range of activities of H-NS is modified with important implications for the physiology of the bacterium.
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Affiliation(s)
- Charles J Dorman
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland.
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Abstract
Understanding mechanisms of bacterial pathogenesis is critical for infectious disease control and treatment. Infection is a sophisticated process that requires the participation of global regulators to coordinate expression of not only genes coding for virulence factors but also those involved in other physiological processes, such as stress response and metabolic flux, to adapt to host environments. RpoS is a key response regulator to stress conditions in Escherichia coli and many other proteobacteria. In contrast to its conserved well-understood role in stress response, effects of RpoS on pathogenesis are highly variable and dependent on species. RpoS contributes to virulence through either enhancing survival against host defense systems or directly regulating expression of virulence factors in some pathogens, while RpoS is dispensable, or even inhibitory, to virulence in others. In this review, we focus on the distinct and niche-dependent role of RpoS in virulence by surveying recent findings in many pathogens.
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