Enterococcal Rgg-Like Regulator ElrR Activates Expression of the elrA Operon

Abstract

ABSTRACT The Enterococcus faecalis leucine-rich protein ElrA promotes virulence by stimulating bacterial persistence in macrophages and production of the interleukin-6 (IL-6) cytokine. The ElrA protein is encoded within an operon that is poorly expressed under laboratory conditions but induced in vivo . In this study, we identify ef2687 (renamed elrR ), which encodes a member of the Rgg ( r egulator g ene for g lucosyltransferase) family of putative regulatory proteins. Using quantitative reverse transcription-PCR, translational lacZ fusions, and electrophoretic mobility shift assays, we demonstrate that ElrR positively regulates expression of elrA . These results correlate with the attenuated virulence of the Δ elrR strain in a mouse peritonitis model. Virulence of simple and double elrR and elrA deletion mutants also suggests a remaining ElrR-independent expression of elrA in vivo and additional virulence-related genes controlled by ElrR.