title: Epigallocatechin gallate induces upregulation of the two-component VraSR system by evoking a cell wall stress response in Staphylococcus aureus.
abstract: We previously found that a short exposure of Staphylococcus aureus to subinhibitory (SI) doses of epigallocatechin gallate (EGCG) results in increased cell wall thickness, adaptation, and enhanced tolerance to cell-wall-targeted antibiotics. In this study, the response to EGCG of sigB and vraSR transcription factor mutants was characterized. We show that in contrast to the results observed for wild-type (WT) strains, an S. aureus 315 vraSR null mutant exposed to SI doses of EGCG did not exhibit increased tolerance to EGCG and oxacillin. A diminished increase in tolerance to ampicillin (from 16-fold to 4-fold) and no change in the magnitude of resistance to vancomycin were observed. Preexposure to EGCG enhanced the tolerance of wild-type and sigB null mutant cells to lysostaphin, but this enhancement was much weaker in the vraSR null mutant. Marked upregulation (about 60-fold) of vraR and upregulation of the peptidoglycan biosynthesis-associated genes murA, murF, and pbp2 (2-, 5-, and 6-fold, respectively) in response to SI doses of EGCG were determined by quantitative reverse transcription-PCR (qRT-PCR). EGCG also induced the promoter of sas016 (encoding a cell wall stress protein of unknown function which is not induced in vraSR null mutants) in a concentration-dependent manner, showing kinetics comparable to those of cell-wall-targeting antibiotics. Taken together, our results suggest that the two-component VraSR system is involved in modulating the cell response to SI doses of EGCG.
authors.affiliation: Institute of Biochemistry, Food Science and Nutrition, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
authors.forename: Oren
authors.initials: O
authors.lastname: Levinger
authors.forename: Tamar
authors.initials: T
authors.lastname: Bikels-Goshen
authors.forename: Elad
authors.initials: E
authors.lastname: Landau
authors.forename: Merav
authors.initials: M
authors.lastname: Fichman
authors.forename: Roni
authors.initials: R
authors.lastname: Shapira
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D002392:Catechin / Q000031:analogs & derivatives* / Q000378:metabolism; D002473:Cell Wall / Q000187:drug effects* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D004361:Drug Tolerance; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D055786:Gene Knockout Techniques; D008248:Lysostaphin / Q000378:metabolism; D010068:Oxacillin / Q000378:metabolism / Q000494:pharmacology; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C478170:VraR protein, Staphylococcus aureus; C478169:VraS protein, Staphylococcus aureus; D002392:Catechin; C045651:epigallocatechin gallate; D008248:Lysostaphin; D010068:Oxacillin