Eep confers lysozyme resistance to enterococcus faecalis via the activation of the extracytoplasmic function sigma factor SigV
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Issue Date
2013-05-03Author
Varahan, Sriram
Iyer, Vljayalakshmi S.
Moore, William T.
Hancock, Lynn E.
Publisher
American Society of Microbiology
Type
Article
Article Version
Scholarly/refereed, publisher version
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Show full item recordAbstract
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.
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Citation
Sriram Varahan et al. (2013). Eep confers lysozyme resistance to
enterococcus faecalis via the activation of the extracytoplasmic function
sigma factor SigV. Journal of bacteriology 195(14):3125-34. http://www.dx.doi.org/10.1128/JB.00291-13
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