The oxidative stress response in Enterococcus faecalis: relationship between H2O2 tolerance and H2O2 stress proteins.

The hydrogen peroxide (H2O2) stress response in Enterococcus faecalis ATCC19433 was investigated. A 2.4 mmol l-1 H2O2 pretreatment conferred protection against a lethal concentration (45 mmol l-1) of this agent. The relatively high concentrations of H2O2 used for adaptation and challenge treatments in Ent. faecalis emphasised the strong resistance towards oxidative stress in this species. Various stresses (NaCl, heat, ethanol, acidity and alkalinity) induced weak or strong H2O2 cross-protection. This paper describes the involvement of protein synthesis in the active response to lethal dose of H2O2, in addition to the impressive enhancement of synthesis of five H2O2 stress proteins. Combined results suggest that these proteins might play an important role in the H2O2 tolerance response.