Organization of heat shock dnaK and groE operons of the nosocomial pathogen Enterococcus faecium

Enterococcus faecium is a frequently antibiotic-resistant opportunistic pathogen that is commonly recovered from hospitalized patients. The genetic organization of the dnaK operon was analyzed and was shown to consist of at least four heat shock genes, hrcA–grpE–dnaK–dnaJ. The dnaK/J intergenic region was 140 bp shorter than in E. faecalis. The dnaK operon was expressed from a putative σA-type promoter (PhrcA) upstream of the hrcA start codon and was preceded by two conserved CIRCE sequences. Northern hybridization revealed the presence of multiple mRNAs in the dnaK operon. Conversely, the groE operon was transcribed as a single mRNA. Induction of dnaK and groEL genes occurred in response to either heat shock or exposure to other stress agents.