The
            <i>Enterococcus faecalis</i>
            SigV Protein Is an Extracytoplasmic Function Sigma Factor Contributing to Survival following Heat, Acid, and Ethanol Treatments

Benachour, Abdellah; Muller, Cécile; Coton, Monika; Breton, Yoann Le; Giard, Jean‐Christophe; Rincé, Alain; Auffray, Yanick; Hartke, Axel

doi:10.1128/jb.187.3.1022-1035.2005

Cited by 61 publications

(76 citation statements)

References 58 publications

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“…has not been fully described. Benachour et al (24) identified two genes (sigV and rsiV) in E. faecalis that are under the control of the same operon and are predicted to encode sigma and anti-sigma factors. Further analysis indicated the differential expression of the operon in response to exposure to various stresses; notably, it was overexpressed under conditions of glucose starvation and complete starvation, suggesting that it plays an important role in the response of enterococci to nutrient depletion (24).…”

Section: Responses To Environmental Stressorsmentioning

confidence: 99%

“…Benachour et al (24) identified two genes (sigV and rsiV) in E. faecalis that are under the control of the same operon and are predicted to encode sigma and anti-sigma factors. Further analysis indicated the differential expression of the operon in response to exposure to various stresses; notably, it was overexpressed under conditions of glucose starvation and complete starvation, suggesting that it plays an important role in the response of enterococci to nutrient depletion (24). Another E. faecium regulatory protein ( 54 ) was suggested to be a potential virulence factor capable of influencing the rate of autolysis (and, by extension, the nature and composition of the biofilm matrix [173]) and governing sensitivity to certain bacteriocins (51,74).…”

Section: Responses To Environmental Stressorsmentioning

confidence: 99%

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Enterococci in the Environment

Byappanahalli

Nevers

Korajkic

et al. 2012

Microbiol Mol Biol Rev

565

383

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SUMMARYEnterococci are common, commensal members of gut communities in mammals and birds, yet they are also opportunistic pathogens that cause millions of human and animal infections annually. Because they are shed in human and animal feces, are readily culturable, and predict human health risks from exposure to polluted recreational waters, they are used as surrogates for waterborne pathogens and as fecal indicator bacteria (FIB) in research and in water quality testing throughout the world. Evidence from several decades of research demonstrates, however, that enterococci may be present in high densities in the absence of obvious fecal sources and that environmental reservoirs of these FIB are important sources and sinks, with the potential to impact water quality. This review focuses on the distribution and microbial ecology of enterococci in environmental (secondary) habitats, including the effect of environmental stressors; an outline of their known and apparent sources, sinks, and fluxes; and an overview of the use of enterococci as FIB. Finally, the significance of emerging methodologies, such as microbial source tracking (MST) and empirical predictive models, as tools in water quality monitoring is addressed. The mounting evidence for widespread extraenteric sources and reservoirs of enterococci demonstrates the versatility of the genusEnterococcusand argues for the necessity of a better understanding of their ecology in natural environments, as well as their roles as opportunistic pathogens and indicators of human pathogens.

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Section: Responses To Environmental Stressorsmentioning

confidence: 99%

Section: Responses To Environmental Stressorsmentioning

confidence: 99%

Enterococci in the Environment

Byappanahalli

Nevers

Korajkic

et al. 2012

Microbiol Mol Biol Rev

565

383

View full text Add to dashboard Cite

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“…Eep confers resistance to other biological stressors. Benachour et al (4) showed that a sigV deletion mutant is attenuated compared to a wild type when subjected to high-temperature, low-pH, and ethanol stress conditions. Having established a link between Eep and SigV phenotypes for lysozyme resistance, we reasoned that other biological stresses known to impact a sigV mutant might also negatively affect an eep mutant compared to their effects on its isogenic parent.…”

Section: Deletion Of Eep Renders E Faecalis More Susceptible To Lysomentioning

confidence: 99%

“…pSV14 (P sigV -lacZ) and pVI16 (P pgdA -lacZ) were created by amplifying the promoter regions of sigV with primers SigVP1 and SigV2 and the pgdA promoter with primers PgdAP1 and PgdAP2. The promoter regions for both these plasmids were defined based on the known transcriptional start sites for both sigV and pgdA (4). These promoters contain the consensus SigV promoter recognition sequence (5= TGAAAC-N 17 -CGTC 3=), and we included an additional ϳ1-kb region (1,188 bp for sigV and 914 bp for pgdA) upstream from the transcriptional start site to provide additional genetic context for the promoter fusion studies.…”

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confidence: 99%

Eep Confers Lysozyme Resistance to Enterococcus faecalis via the Activation of the Extracytoplasmic Function Sigma Factor SigV

Varahan

Iyer

Moore

et al. 2013

Journal of Bacteriology

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Enterococcus faecalis is a commensal bacterium found in the gastrointestinal tract of most mammals, including humans, and is one of the leading causes of nosocomial infections. One of the hallmarks of E. faecalis pathogenesis is its unusual ability to tolerate high concentrations of lysozyme, which is an important innate immune component of the host. Previous studies have shown that the presence of lysozyme leads to the activation of SigV, an extracytoplasmic function (ECF) sigma factor in E. faecalis, and that the deletion of sigV increases the susceptibility of the bacterium toward lysozyme. Here, we describe the contribution of Eep, a membrane-bound zinc metalloprotease, to the activation of SigV under lysozyme stress by its effects on the stability of the anti-sigma factor RsiV. We demonstrate that the ⌬eep mutant phenocopies the ⌬sigV mutant in lysozyme, heat, ethanol, and acid stress susceptibility. We also show, using an immunoblot analysis, that in an eep deletion mutant, the anti-sigma factor RsiV is only partially degraded after lysozyme exposure, suggesting that RsiV is processed by unknown protease(s) prior to the action of Eep. An additional observation is that the deletion of rsiV, which results in constitutive SigV expression, leads to chaining of cells, suggesting that SigV might be involved in regulating cell wall-modifying enzymes important in cell wall turnover. We also demonstrate that, in the absence of eep or sigV, enterococci bind significantly more lysozyme, providing a plausible explanation for the increased sensitivity of these mutants toward lysozyme. Enterococcus faecalis is a commensal organism present in the mammalian gastrointestinal system (1). Over the past few decades, E. faecalis has arisen as one of the leading causes of nosocomial infection (2). Its role as an opportunistic pathogen is strengthened by the mobile genetic elements it harbors, which are often responsible for conferring resistance to a broad range of antibiotics, including vancomycin (3). In addition, E. faecalis is known to demonstrate a heightened ability to survive in the presence of environmental stress factors, such as increased temperature, acidic pH, and oxidative stress (4). In addition to persistence in the presence of the aforementioned stress factors, previous studies have shown that E. faecalis is also highly resistant to lysozyme (5). This high-level resistance to lysozyme (Ͼ62 mg/ml) is predominantly attributed to the extracytoplasmic function (ECF) sigma factor SigV (5). ECF sigma factors are sequestered by membrane-bound anti-sigma factors and rendered inactive in the absence of a given external stress. Under stress-inducing conditions, the anti-sigma factors are degraded by membrane and cytosolic proteases, leading to the activation of ECF sigma factors in a process referred to as regulated intramembrane proteolysis (RIP) (6).RIP has been shown to play an important role in multiple transmembrane signaling processes associated with increased virulence and environmental fitness (7). In Escherichia ...

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“…The recent availability of the E. faecalis V583 genome sequence (28) provides a tool for the identification of potential E. faecalis regulatory components, such as alternative sigma factors (2), transcriptional regulators (41,42), and two-component systems (6,17,25,37), that could be involved in the infection process.…”

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confidence: 99%

The Response Regulator CroR Modulates Expression of the Secreted Stress-Induced SalB Protein in Enterococcus faecalis

et al. 2006

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. In this report, we provide genetic and biochemical evidence that salB encodes a secreted protein that is expressed from a monocistronic stress-inducible operon. Consistent with CroR being a direct transcriptional activator of the salB expression, CroR was found to bind to the salB promoter region in electrophoretic mobility shift assays. Interestingly, we provide evidence that SalB does not play a role in the intrinsic ␤-lactam resistance associated with CroRS. We also show that the CroRS system is able to regulate its own expression. The sequence of the CroRS binding site in the salB and croR promoter regions was determined using DNase I footprinting assays.Enterococci have been traditionally considered commensal inhabitants of the gastrointestinal tract of human and animals and able to colonize a large range of ecological niches. Their presence in food products has been regarded as an indicator of insufficient sanitary quality (14), even though they contribute in some cases to flavor development of European dairy products (9). Enterococci were also regarded as low-grade pathogens, involved in few cases of food poisoning, mainly due to production of biogenic amines (7,14). Over the last two decades, however, they have emerged as significant opportunistic pathogens in intensive care units, particularly affecting immunosuppressed patients (13,15). Enterococcus faecalis is the most common species involved in these enterococcal nosocomial infections. The mechanisms by which this bacterium is able to cross the barrier from inoffensive commensal to major hospital-acquired pathogen are still not well understood. Virulence traits carried principally by mobile genetic elements have been described previously (13, 34), but intrinsic physiological properties of E. faecalis, such as its exceptional stress response capacities (29) and inherent antibiotic resistance (21), may also provide an advantage during the infection process as they do for other opportunistic pathogens (39).The recent availability of the E. faecalis V583 genome sequence (28) provides a tool for the identification of potential E. faecalis regulatory components, such as alternative sigma factors (2), transcriptional regulators (41, 42), and two-component systems (6,17,25,37), that could be involved in the infection process.Many aspects of bacterial physiology are under the control of two-component systems (for reviews, see references 18, 19, and 36). These regulatory pathways involve an archetypical mode of signal transduction based on a phosphotransfer from a stress-activated sensor histidine-kinase to its cognate response regulator (35). The response regulator then adjusts gene expression in order for the cell to respond to the signal that initiates the process. Inactivation of twocomponent system genes in different E. faecalis strains (6,17,25,37) failed to uncover a general role for these systems, largely due to heterogeneity within the pool of two-component pathways present in the different E. faecalis strains studied. Nevertheless, some E. faecalis...

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The Enterococcus faecalis SigV Protein Is an Extracytoplasmic Function Sigma Factor Contributing to Survival following Heat, Acid, and Ethanol Treatments

Cited by 61 publications

References 58 publications

Enterococci in the Environment

Enterococci in the Environment

Eep Confers Lysozyme Resistance to Enterococcus faecalis via the Activation of the Extracytoplasmic Function Sigma Factor SigV

The Response Regulator CroR Modulates Expression of the Secreted Stress-Induced SalB Protein in Enterococcus faecalis

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