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Ramón A, Esteves A, Villadóniga C, Chalar C, Castro-Sowinski S. A general overview of the multifactorial adaptation to cold: biochemical mechanisms and strategies. Braz J Microbiol 2023; 54:2259-2287. [PMID: 37477802 PMCID: PMC10484896 DOI: 10.1007/s42770-023-01057-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 06/29/2023] [Indexed: 07/22/2023] Open
Abstract
Cold environments are more frequent than people think. They include deep oceans, cold lakes, snow, permafrost, sea ice, glaciers, cold soils, cold deserts, caves, areas at elevations greater than 3000 m, and also artificial refrigeration systems. These environments are inhabited by a diversity of eukaryotic and prokaryotic organisms that must adapt to the hard conditions imposed by cold. This adaptation is multifactorial and includes (i) sensing the cold, mainly through the modification of the liquid-crystalline membrane state, leading to the activation of a two-component system that transduce the signal; (ii) adapting the composition of membranes for proper functions mainly due to the production of double bonds in lipids, changes in hopanoid composition, and the inclusion of pigments; (iii) producing cold-adapted proteins, some of which show modifications in the composition of amino acids involved in stabilizing interactions and structural adaptations, e.g., enzymes with high catalytic efficiency; and (iv) producing ice-binding proteins and anti-freeze proteins, extracellular polysaccharides and compatible solutes that protect cells from intracellular and extracellular ice. However, organisms also respond by reprogramming their metabolism and specifically inducing cold-shock and cold-adaptation genes through strategies such as DNA supercoiling, distinctive signatures in promoter regions and/or the action of CSPs on mRNAs, among others. In this review, we describe the main findings about how organisms adapt to cold, with a focus in prokaryotes and linking the information with findings in eukaryotes.
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Affiliation(s)
- Ana Ramón
- Sección Bioquímica, Instituto de Biología, Facultad de Ciencias, Universidad de La República, Igua 4225, 11400, Montevideo, Uruguay
| | - Adriana Esteves
- Sección Bioquímica, Instituto de Biología, Facultad de Ciencias, Universidad de La República, Igua 4225, 11400, Montevideo, Uruguay
| | - Carolina Villadóniga
- Laboratorio de Biocatalizadores Y Sus Aplicaciones, Facultad de Ciencias, Instituto de Química Biológica, Universidad de La República, Igua 4225, 11400, Montevideo, Uruguay
| | - Cora Chalar
- Sección Bioquímica, Instituto de Biología, Facultad de Ciencias, Universidad de La República, Igua 4225, 11400, Montevideo, Uruguay
| | - Susana Castro-Sowinski
- Sección Bioquímica, Instituto de Biología, Facultad de Ciencias, Universidad de La República, Igua 4225, 11400, Montevideo, Uruguay.
- Laboratorio de Biocatalizadores Y Sus Aplicaciones, Facultad de Ciencias, Instituto de Química Biológica, Universidad de La República, Igua 4225, 11400, Montevideo, Uruguay.
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Gahlot DK, Wai SN, Erickson DL, Francis MS. Cpx-signalling facilitates Hms-dependent biofilm formation by Yersinia pseudotuberculosis. NPJ Biofilms Microbiomes 2022; 8:13. [PMID: 35351893 PMCID: PMC8964730 DOI: 10.1038/s41522-022-00281-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 02/18/2022] [Indexed: 11/30/2022] Open
Abstract
Bacteria often reside in sessile communities called biofilms, where they adhere to a variety of surfaces and exist as aggregates in a viscous polymeric matrix. Biofilms are resistant to antimicrobial treatments, and are a major contributor to the persistence and chronicity of many bacterial infections. Herein, we determined that the CpxA-CpxR two-component system influenced the ability of enteropathogenic Yersinia pseudotuberculosis to develop biofilms. Mutant bacteria that accumulated the active CpxR~P isoform failed to form biofilms on plastic or on the surface of the Caenorhabditis elegans nematode. A failure to form biofilms on the worm surface prompted their survival when grown on the lawns of Y. pseudotuberculosis. Exopolysaccharide production by the hms loci is the major driver of biofilms formed by Yersinia. We used a number of molecular genetic approaches to demonstrate that active CpxR~P binds directly to the promoter regulatory elements of the hms loci to activate the repressors of hms expression and to repress the activators of hms expression. Consequently, active Cpx-signalling culminated in a loss of exopolysaccharide production. Hence, the development of Y. pseudotuberculosis biofilms on multiple surfaces is controlled by the Cpx-signalling, and at least in part this occurs through repressive effects on the Hms-dependent exopolysaccharide production.
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Mattila M, Somervuo P, Korkeala H, Stephan R, Tasara T. Transcriptomic and Phenotypic Analyses of the Sigma B-Dependent Characteristics and the Synergism between Sigma B and Sigma L in Listeria monocytogenes EGD-e. Microorganisms 2020; 8:microorganisms8111644. [PMID: 33114171 PMCID: PMC7690807 DOI: 10.3390/microorganisms8111644] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 10/20/2020] [Accepted: 10/21/2020] [Indexed: 12/19/2022] Open
Abstract
Numerous gene expression and stress adaptation responses in L. monocytogenes are regulated through alternative sigma factors σB and σL. Stress response phenotypes and transcriptomes were compared between L. monocytogenes EGD-e and its ΔsigB and ΔsigBL mutants. Targeted growth phenotypic analysis revealed that the ΔsigB and ΔsigBL mutants are impaired during growth under cold and organic-acid stress conditions. Phenotypic microarrays revealed increased sensitivity in both mutants to various antimicrobial compounds. Genes de-regulated in these two mutants were identified by genome-wide transcriptome analysis during exponential growth in BHI. The ΔsigB and ΔsigBL strains repressed 198 and 254 genes, respectively, compared to the parent EGD-e strain at 3 °C, whereas 86 and 139 genes, respectively, were repressed in these mutants during growth at 37 °C. Genes repressed in these mutants are involved in various cellular functions including transcription regulation, energy metabolism and nutrient transport functions, and viral-associated processes. Exposure to cold stress induced a significant increase in σB and σL co-dependent genes of L. monocytogenes EGD-e since most (62%) of the down-regulated genes uncovered at 3 °C were detected in the ΔsigBL double-deletion mutant but not in ΔsigB or ΔsigL single-deletion mutants. Overall, the current study provides an expanded insight into σB and σL phenotypic roles and functional interactions in L. monocytogenes. Besides previously known σB- and σL-dependent genes, the transcriptomes defined in ΔsigB and ΔsigBL mutants reveal several new genes that are positively regulated by σB alone, as well as those co-regulated through σB- and σL-dependent mechanisms during L. monocytogenes growth under optimal and cold-stress temperature conditions.
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Affiliation(s)
- Mirjami Mattila
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014 Helsinki, Finland; (M.M.); (P.S.); (H.K.)
| | - Panu Somervuo
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014 Helsinki, Finland; (M.M.); (P.S.); (H.K.)
| | - Hannu Korkeala
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014 Helsinki, Finland; (M.M.); (P.S.); (H.K.)
| | - Roger Stephan
- Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Winterthurerstr. 272, CH-8057 Zurich, Switzerland;
| | - Taurai Tasara
- Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Winterthurerstr. 272, CH-8057 Zurich, Switzerland;
- Correspondence: ; Tel.: +41-44-635-8669
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Role of DEAD-box RNA helicase genes in the growth of Yersinia pseudotuberculosis IP32953 under cold, pH, osmotic, ethanol and oxidative stresses. PLoS One 2019; 14:e0219422. [PMID: 31287844 PMCID: PMC6615604 DOI: 10.1371/journal.pone.0219422] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 06/24/2019] [Indexed: 01/03/2023] Open
Abstract
Yersinia pseudotuberculosis is an important foodborne pathogen threatening modern food safety due to its ability to survive and grow at low temperatures. DEAD-box RNA helicase CsdA has been shown to play an important role in the low-temperature growth of psychrotrophic Y. pseudotuberculosis. A total of five DEAD-box RNA helicase genes (rhlB, csdA, rhlE, dbpA, srmB) have been identified in Y. pseudotuberculosis IP32953. However, their role in various stress conditions used in food production is unclear. We studied the involvement of the DEAD-box RNA helicase-encoding genes in the cold tolerance of Y. pseudotuberculosis IP32953 using quantitative real-time reverse transcription (RT-qPCR) and mutational analysis. Quantitative RT-PCR revealed that mRNA transcriptional levels of csdA, rhlE, dbpA and srmB were significantly higher after cold shock at 3°C compared to non-shocked culture at 28°C, suggesting the involvement of these four genes in cold shock response at the transcriptional level. The deletion of csdA ceased growth, while the deletion of dbpA or srmB significantly impaired growth at 3°C, suggesting the requirement of these three genes in Y. pseudotuberculosis at low temperatures. Growth of each DEAD-box RNA helicase mutant was also investigated under pH, osmotic, ethanol and oxidative stress conditions. The five helicase-encoding genes did not play major roles in the growth of Y. pseudotuberculosis IP32953 under pH, osmotic, ethanol or oxidative stress.
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Ethanol Stimulates Trehalose Production through a SpoT-DksA-AlgU-Dependent Pathway in Pseudomonas aeruginosa. J Bacteriol 2019; 201:JB.00794-18. [PMID: 30936375 DOI: 10.1128/jb.00794-18] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 03/26/2019] [Indexed: 01/06/2023] Open
Abstract
Pseudomonas aeruginosa frequently resides among ethanol-producing microbes, making its response to the microbially produced concentrations of ethanol relevant to understanding its biology. Our transcriptome analysis found that genes involved in trehalose metabolism were induced by low concentrations of ethanol, and biochemical assays showed that levels of intracellular trehalose increased significantly upon growth with ethanol. The increase in trehalose was dependent on the TreYZ pathway but not other trehalose-metabolic enzymes (TreS or TreA). The sigma factor AlgU (AlgT), a homolog of RpoE in other species, was required for increased expression of the treZ gene and trehalose levels, but induction was not controlled by the well-characterized proteolysis of its anti-sigma factor, MucA. Growth with ethanol led to increased SpoT-dependent (p)ppGpp accumulation, which stimulates AlgU-dependent transcription of treZ and other AlgU-regulated genes through DksA, a (p)ppGpp and RNA polymerase binding protein. Ethanol stimulation of trehalose also required acylhomoserine lactone (AHL)-mediated quorum sensing (QS), as induction was not observed in a ΔlasR ΔrhlR strain. A network analysis using a model, eADAGE, built from publicly available P. aeruginosa transcriptome data sets (J. Tan, G. Doing, K. A. Lewis, C. E. Price, et al., Cell Syst 5:63-71, 2017, https://doi.org/10.1016/j.cels.2017.06.003) provided strong support for our model in which treZ and coregulated genes are controlled by both AlgU- and AHL-mediated QS. Consistent with (p)ppGpp- and AHL-mediated quorum-sensing regulation, ethanol, even when added at the time of culture inoculation, stimulated treZ transcript levels and trehalose production in cells from post-exponential-phase cultures but not in cells from exponential-phase cultures. These data highlight the integration of growth and cell density cues in the P. aeruginosa transcriptional response to ethanol.IMPORTANCE Pseudomonas aeruginosa is often found with bacteria and fungi that produce fermentation products, including ethanol. At concentrations similar to those produced by environmental microbes, we found that ethanol stimulated expression of trehalose-biosynthetic genes and cellular levels of trehalose, a disaccharide that protects against environmental stresses. The induction of trehalose by ethanol required the alternative sigma factor AlgU through DksA- and SpoT-dependent (p)ppGpp. Trehalose accumulation also required AHL quorum sensing and occurred only in post-exponential-phase cultures. This work highlights how cells integrate cell density and growth cues in their responses to products made by other microbes and reveals a new role for (p)ppGpp in the regulation of AlgU activity.
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Chai B, Tsoi TV, Iwai S, Liu C, Fish JA, Gu C, Johnson TA, Zylstra G, Teppen BJ, Li H, Hashsham SA, Boyd SA, Cole JR, Tiedje JM. Sphingomonas wittichii Strain RW1 Genome-Wide Gene Expression Shifts in Response to Dioxins and Clay. PLoS One 2016; 11:e0157008. [PMID: 27309357 PMCID: PMC4911050 DOI: 10.1371/journal.pone.0157008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 05/23/2016] [Indexed: 12/23/2022] Open
Abstract
Sphingomonas wittichii strain RW1 (RW1) is one of the few strains that can grow on dibenzo-p-dioxin (DD). We conducted a transcriptomic study of RW1 using RNA-Seq to outline transcriptional responses to DD, dibenzofuran (DF), and the smectite clay mineral saponite with succinate as carbon source. The ability to grow on DD is rare compared to growth on the chemically similar DF even though the same initial dioxygenase may be involved in oxidation of both substrates. Therefore, we hypothesized the reason for this lies beyond catabolic pathways and may concern genes involved in processes for cell-substrate interactions such as substrate recognition, transport, and detoxification. Compared to succinate (SUC) as control carbon source, DF caused over 240 protein-coding genes to be differentially expressed, whereas more than 300 were differentially expressed with DD. Stress response genes were up-regulated in response to both DD and DF. This effect was stronger with DD than DF, suggesting a higher toxicity of DD compared to DF. Both DD and DF caused changes in expression of genes involved in active cross-membrane transport such as TonB-dependent receptor proteins, but the patterns of change differed between the two substrates. Multiple transcription factor genes also displayed expression patterns distinct to DD and DF growth. DD and DF induced the catechol ortho- and the salicylate/gentisate pathways, respectively. Both DD and DF induced the shared down-stream aliphatic intermediate compound pathway. Clay caused category-wide down-regulation of genes for cell motility and chemotaxis, particularly those involved in the synthesis, assembly and functioning of flagella. This is an environmentally important finding because clay is a major component of soil microbes’ microenvironment influencing local chemistry and may serve as a geosorbent for toxic pollutants. Similar to clay, DD and DF also affected expression of genes involved in motility and chemotaxis.
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Affiliation(s)
- Benli Chai
- Center for Microbial Ecology, Michigan State University, East Lansing, MI, United States of America
| | - Tamara V. Tsoi
- Center for Microbial Ecology, Michigan State University, East Lansing, MI, United States of America
| | - Shoko Iwai
- Center for Microbial Ecology, Michigan State University, East Lansing, MI, United States of America
| | - Cun Liu
- Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, United States of America
| | - Jordan A. Fish
- Center for Microbial Ecology, Michigan State University, East Lansing, MI, United States of America
| | - Cheng Gu
- School of the Environment, Nanjing University, Nanjing, China
| | - Timothy A. Johnson
- Center for Microbial Ecology, Michigan State University, East Lansing, MI, United States of America
- Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, United States of America
| | - Gerben Zylstra
- Department of Biochemistry & Microbiology, Rutgers University, New Brunswick, NJ, United States of America
| | - Brian J. Teppen
- Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, United States of America
| | - Hui Li
- Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, United States of America
| | - Syed A. Hashsham
- Civil and Environmental Engineering, Michigan State University, East Lansing, MI, United States of America
| | - Stephen A. Boyd
- Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, United States of America
| | - James R. Cole
- Center for Microbial Ecology, Michigan State University, East Lansing, MI, United States of America
| | - James M. Tiedje
- Center for Microbial Ecology, Michigan State University, East Lansing, MI, United States of America
- * E-mail:
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Chen S, Thompson KM, Francis MS. Environmental Regulation of Yersinia Pathophysiology. Front Cell Infect Microbiol 2016; 6:25. [PMID: 26973818 PMCID: PMC4773443 DOI: 10.3389/fcimb.2016.00025] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 02/15/2016] [Indexed: 12/26/2022] Open
Abstract
Hallmarks of Yersinia pathogenesis include the ability to form biofilms on surfaces, the ability to establish close contact with eukaryotic target cells and the ability to hijack eukaryotic cell signaling and take over control of strategic cellular processes. Many of these virulence traits are already well-described. However, of equal importance is knowledge of both confined and global regulatory networks that collaborate together to dictate spatial and temporal control of virulence gene expression. This review has the purpose to incorporate historical observations with new discoveries to provide molecular insight into how some of these regulatory mechanisms respond rapidly to environmental flux to govern tight control of virulence gene expression by pathogenic Yersinia.
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Affiliation(s)
- Shiyun Chen
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Chinese Academy of Sciences Wuhan, China
| | - Karl M Thompson
- Department of Microbiology, College of Medicine, Howard University Washington, DC, USA
| | - Matthew S Francis
- Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden; Department of Molecular Biology, Umeå UniversityUmeå, Sweden
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Tarusawa T, Ito S, Goto S, Ushida C, Muto A, Himeno H. (p)ppGpp-dependent and -independent pathways for salt tolerance inEscherichia coli. J Biochem 2016; 160:19-26. [DOI: 10.1093/jb/mvw008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 12/27/2015] [Indexed: 11/13/2022] Open
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Tan F, Wu B, Dai L, Qin H, Shui Z, Wang J, Zhu Q, Hu G, He M. Using global transcription machinery engineering (gTME) to improve ethanol tolerance of Zymomonas mobilis. Microb Cell Fact 2016; 15:4. [PMID: 26758018 PMCID: PMC4711062 DOI: 10.1186/s12934-015-0398-y] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 12/15/2015] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND With the increasing global crude oil crisis and resulting environmental concerns, the production of biofuels from renewable resources has become increasingly important. One of the major challenges faced during the process of biofuel production is the low tolerance of the microbial host towards increasing biofuel concentrations. RESULTS Here, we demonstrate that the ethanol tolerance of Zymomonas mobilis can be greatly enhanced through the random mutagenesis of global transcription factor RpoD protein, (σ(70)). Using an enrichment screening, four mutants with elevated ethanol tolerance were isolated from error-prone PCR libraries. All mutants showed significant growth improvement in the presence of ethanol stress when compared to the control strain. After an ethanol (9 %) stress exposure lasting 22 h, the rate of glucose consumption was approximately 1.77, 1.78 and 1.39 g L(-1) h(-1) in the best ethanol-tolerant strain ZM4-mrpoD4, its rebuilt mutant strain ZM4-imrpoD and the control strain, respectively. Our results indicated that both ZM4-mrpoD4 and ZM4-imrpoD consumed glucose at a faster rate after the initial 9 % (v/v) ethanol stress, as nearly 0.64 % of the initial glucose remained after 54 h incubation versus approximately 5.43 % for the control strain. At 9 % ethanol stress, the net ethanol productions by ZM4-mrpoD4 and ZM4-imrpoD during the 30-54 h were 13.0-14.1 g/l versus only 6.6-7.7 g/l for the control strain. The pyruvate decarboxylase activity of ZM4-mrpoD4 was 62.23 and 68.42 U/g at 24 and 48 h, respectively, which were 2.6 and 1.6 times higher than the control strain. After 24 and 48 h of 9 % ethanol stress, the alcohol dehydrogenase activities of ZM4-mrpoD4 were also augmented, showing an approximate 1.4 and 1.3 times increase, respectively, when compared to the control strain. Subsequent quantitative real-time PCR analysis under these stress conditions revealed that the relative expression of pdc in cultured (6 and 24 h) ZM4-mrpoD4 increased by 9.0- and 12.7-fold when compared to control strain. CONCLUSIONS Collectively, these results demonstrate that the RpoD mutation can enhance ethanol tolerance in Z. mobilis. Our results also suggested that RpoD may play an important role in resisting high ethanol concentration in Z. mobilis and manipulating RpoD via global transcription machinery engineering (gTME) can provide an alternative and useful approach for strain improvement for complex phenotypes.
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Affiliation(s)
- Furong Tan
- Biogas Institute of Ministry of Agriculture, Biomass Energy Technology Research Centre, Section 4-13, Renmin Nanlu, Chengdu, 610041, China.
| | - Bo Wu
- Biogas Institute of Ministry of Agriculture, Biomass Energy Technology Research Centre, Section 4-13, Renmin Nanlu, Chengdu, 610041, China.
| | - Lichun Dai
- Biogas Institute of Ministry of Agriculture, Biomass Energy Technology Research Centre, Section 4-13, Renmin Nanlu, Chengdu, 610041, China.
| | - Han Qin
- Biogas Institute of Ministry of Agriculture, Biomass Energy Technology Research Centre, Section 4-13, Renmin Nanlu, Chengdu, 610041, China.
| | - Zongxia Shui
- Biogas Institute of Ministry of Agriculture, Biomass Energy Technology Research Centre, Section 4-13, Renmin Nanlu, Chengdu, 610041, China.
| | - Jingli Wang
- Biogas Institute of Ministry of Agriculture, Biomass Energy Technology Research Centre, Section 4-13, Renmin Nanlu, Chengdu, 610041, China.
| | - Qili Zhu
- Biogas Institute of Ministry of Agriculture, Biomass Energy Technology Research Centre, Section 4-13, Renmin Nanlu, Chengdu, 610041, China.
| | - Guoquan Hu
- Biogas Institute of Ministry of Agriculture, Biomass Energy Technology Research Centre, Section 4-13, Renmin Nanlu, Chengdu, 610041, China.
- Key Laboratory of Development and Application of Rural Renewable Energy, Ministry of Agriculture, Chengdu, 610041, China.
| | - Mingxiong He
- Biogas Institute of Ministry of Agriculture, Biomass Energy Technology Research Centre, Section 4-13, Renmin Nanlu, Chengdu, 610041, China.
- Key Laboratory of Development and Application of Rural Renewable Energy, Ministry of Agriculture, Chengdu, 610041, China.
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Almagro-Moreno S, Kim TK, Skorupski K, Taylor RK. Proteolysis of virulence regulator ToxR is associated with entry of Vibrio cholerae into a dormant state. PLoS Genet 2015; 11:e1005145. [PMID: 25849031 PMCID: PMC4388833 DOI: 10.1371/journal.pgen.1005145] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 03/16/2015] [Indexed: 12/20/2022] Open
Abstract
Vibrio cholerae O1 is a natural inhabitant of aquatic environments and causes the diarrheal disease, cholera. Two of its primary virulence regulators, TcpP and ToxR, are localized in the inner membrane. TcpP is encoded on the Vibrio Pathogenicity Island (VPI), a horizontally acquired mobile genetic element, and functions primarily in virulence gene regulation. TcpP has been shown to undergo regulated intramembrane proteolysis (RIP) in response to environmental conditions that are unfavorable for virulence gene expression. ToxR is encoded in the ancestral genome and is present in non-pathogenic strains of V. cholerae, indicating it has roles outside of the human host. In this study, we show that ToxR undergoes RIP in V. cholerae in response to nutrient limitation at alkaline pH, a condition that occurs during the stationary phase of growth. This process involves the site-2 protease RseP (YaeL), and is dependent upon the RpoE-mediated periplasmic stress response, as deletion mutants for the genes encoding these two proteins cannot proteolyze ToxR under nutrient limitation at alkaline pH. We determined that the loss of ToxR, genetically or by proteolysis, is associated with entry of V. cholerae into a dormant state in which the bacterium is normally found in the aquatic environment called viable but nonculturable (VBNC). Strains that can proteolyze ToxR, or do not encode it, lose culturability, experience a change in morphology associated with cells in VBNC, yet remain viable under nutrient limitation at alkaline pH. On the other hand, mutant strains that cannot proteolyze ToxR remain culturable and maintain the morphology of cells in an active state of growth. Overall, our findings provide a link between the proteolysis of a virulence regulator and the entry of a pathogen into an environmentally persistent state.
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Affiliation(s)
- Salvador Almagro-Moreno
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
- * E-mail:
| | - Tae K. Kim
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
| | - Karen Skorupski
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
| | - Ronald K. Taylor
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
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The RpoE Stress Response Pathway Mediates Reduction of the Virulence of Enteropathogenic Escherichia coli by Zinc. Appl Environ Microbiol 2015; 81:3766-74. [PMID: 25819956 DOI: 10.1128/aem.00507-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 03/19/2015] [Indexed: 11/20/2022] Open
Abstract
Zinc supplements are an effective clinical treatment for infantile diarrheal disease caused by enteric pathogens. Previous studies demonstrated that zinc acts on enteropathogenic Escherichia coli (EPEC) bacteria directly to suppress several virulence-related genes at a concentration that can be achieved by oral delivery of dietary zinc supplements. Our in vitro studies showed that a micromolar concentration of zinc induced the envelope stress response and suppressed virulence in EPEC, providing a possible mechanistic explanation for zinc's therapeutic action. In this report, we investigated the molecular and physiological changes in EPEC induced by zinc. We found that micromolar concentrations of zinc reduced the bacterial growth rate without affecting viability. We observed increased membrane permeability caused by zinc. Zinc upregulated the RpoE-dependent envelope stress response pathway and suppressed EPEC virulence gene expression. RpoE alone was sufficient to inhibit virulence factor expression and to attenuate attaching and effacing lesion formation on human host cells. By mutational analysis we demonstrate that the DNA-binding motif of RpoE is necessary for suppression of the LEE1, but not the LEE4, operon. Predictably, inhibition of the RpoE-mediated envelope stress response in combination with micromolar concentrations of zinc reduced EPEC viability. In conclusion, zinc induces the RpoE and stress response pathways in EPEC, and the alternate sigma factor RpoE downregulates EPEC LEE and non-LEE virulence genes by multiple mechanisms.
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