title: Transcriptomic and functional analysis of NaCl-induced stress in Enterococcus faecalis.
abstract: The robust physiology of Enterococcus faecalis facilitates tolerance to various stresses. We here report the transcriptional response of E. faecalis V583 to growth in the presence of 6.5% NaCl. Among the early responses observed was an immediate down-regulation of mscL, accompanied by an up-regulation of genes predicted to be involved in uptake of extracellular potassium and glycine betaine. The high NaCl concentration also induced expression of chaperons and cell envelope related traits, such as the enterococcal polysaccharide antigen (epa) locus. Functional genetic analysis revealed reduced salt stress resistance in both epaB and epaE mutants. The reduced salt resistance phenotype associated with the epaB mutant was restored by complementation, hence demonstrating a role of Epa in the physiological robustness of E. faecalis. Furthermore, we demonstrate that Epa confers increased resistance towards multiple cell envelope stress-inducing factors. Accordingly, these findings delineate a potential link between the robust nature of E. faecalis and its ability to perform as a human pathogen, and provide a new perspective on the mechanisms by which Epa contributes to virulence. Notably, the high NaCl concentration also resulted in strict repression of the gelE-sprE operon and impaired gelatinase activity. We demonstrate that NaCl antagonize the GBAP-pheromone dependent induction in a concentration dependent manner.
authors.affiliation: Laboratory of Microbial Gene Technology and Food Microbiology, The Norwegian University of Life Sciences, Ås, Norway.
authors.forename: Margrete
authors.initials: M
authors.lastname: Solheim
authors.affiliation: Laboratory of Microbial Gene Technology and Food Microbiology, The Norwegian University of Life Sciences, Ås, Norway.
authors.forename: Sabina Leanti
authors.initials: SL
authors.lastname: La Rosa
authors.affiliation: Laboratory of Microbial Gene Technology and Food Microbiology, The Norwegian University of Life Sciences, Ås, Norway.
authors.forename: Thomas
authors.initials: T
authors.lastname: Mathisen
authors.affiliation: Section for Biostatistics, Department of Chemistry, Biotechnology and Food Science, The Norwegian University of Life Sciences, Ås, Norway.
authors.forename: Lars G
authors.initials: LG
authors.lastname: Snipen
authors.affiliation: Laboratory of Microbial Gene Technology and Food Microbiology, The Norwegian University of Life Sciences, Ås, Norway.
authors.forename: Ingolf F
authors.initials: IF
authors.lastname: Nes
authors.affiliation: Laboratory of Microbial Gene Technology and Food Microbiology, The Norwegian University of Life Sciences, Ås, Norway.
authors.forename: Dag Anders
authors.initials: DA
authors.lastname: Brede
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism; D019610:Cytoprotection / Q000187:drug effects / Q000235:genetics; D013293:Enterococcus faecalis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005816:Genetic Complementation Test; D006801:Humans; D008826:Microbial Sensitivity Tests; D020411:Oligonucleotide Array Sequence Analysis; D009994:Osmolar Concentration; D011401:Promoter Regions, Genetic / Q000235:genetics; D015203:Reproducibility of Results; D012210:Rhamnose / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics*; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D059467:Transcriptome / Q000187:drug effects / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D012965:Sodium Chloride; D012210:Rhamnose
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