Effects of the Enterococcus faecalis hypR Gene Encoding a New Transcriptional Regulator on Oxidative Stress Response and Intracellular Survival within Macrophages

Abstract

In order to identify regulators of the oxidative stress response in Enterococcus faecalis, an important human pathogen, several genes annotated as coding for transcriptional regulators were inactivated by insertional mutagenesis. One mutant, affected in the ef2958 locus (designated hypR [hydrogen peroxide regulator]), appeared to be highly sensitive to oxidative challenge caused by hydrogen peroxide. Moreover, testing of the hypR mutant by using an in vivo-in vitro macrophage infection model resulted in a highly significant reduction in survival compared to the survival of parent strain JH2-2. Northern blot analyses were carried out with probes specific for genes encoding known antioxidant enzymes, and they showed that the ahpCF (alkyl hydroperoxide reductase) transcript was expressed less in mutant cells. Mobility shift protein-DNA binding assays revealed that HypR regulated directly the expression of hypR itself and the ahpCF operon. Our combined results showed that HypR appeared to be directly involved in the expression of ahpCF genes under oxidative stress conditions and suggested that this regulator could contribute to the virulence of E. faecalis.

Stress Physiology of Lactic Acid Bacteria

“…These findings indicate that although PerR plays a role in the virulence of E. faecalis, its involvement in the oxidative stress response of this bacterium may be different from that in B. subtilis (94). E. faecalis HypR was identified as a regulator of the oxidative stress response and as a virulence factor (533). It is a transcriptional activator of several genes during oxidative stress, including ahpCF, tpx, ef3270 (encoding a glutathione reductase), sodA, and katA (248,534).…”

“…It is a transcriptional activator of several genes during oxidative stress, including ahpCF, tpx, ef3270 (encoding a glutathione reductase), sodA, and katA (248,534). An E. faecalis hypR mutant was highly sensitive to H 2 O 2 and showed a reduced ability to survive in macrophages and a decreased lethality in a mouse peritonitis model (533,534). Recent studies have shown that streptococcal genomes encode two copies of the redox-sensing Spx regulator, designated SpxA1 and SpxA2.…”

Implication of (Mn)superoxide dismutase of Enterococcus faecalis in oxidative stress responses and survival inside macrophages

“…Several studies have shown that Ent. faecalis can survive relatively well in mouse peritoneal macrophages, whereas E. coli is rapidly killed under these conditions (Gentry-Weeks et al, 1999;Verneuil et al, 2004). This ability may play a pivotal role in infection and disease.…”

“…Recently, hypR has been identified as the main transcriptional regulator of the oxidative stress response of Ent. faecalis, and survival of a hypR mutant is severely affected within macrophages (Verneuil et al, 2004).…”

“…Survival of Ent. faecalis in mouse peritoneal macrophages was tested using an in vivo-in vitro infection model, as described previously (Verneuil et al, 2004). Briefly, the Ent.…”