Regulation of the intercellular adhesin (ica) locus under anaerobic conditions in Staphylococcus aureus

点击翻译按钮获取中文摘要

Products of the intercellular adhesion (ica) operon in Staphylococcus aureus and S. epidermidis synthesize a linear â-1,6 linked glucosaminglycan. This extracellular polysaccharide mediates bacterial adhesion and biofilm formation, which is thought to increase the virulence of both pathogens in association with prosthetic biomedical implants. We demonstrated that anaerobic growth in vitro leads to increased polysaccharide expression in both bacteria. Anaerobiosis also dramatically stimulates ica-specific mRNA expression in ica- and polysaccharide-positive strains. These data suggest a mechanism whereby ica gene expression and polysaccharide production may act as a virulence factor in an anaebobic environment in vivo. This project aims to identify and characterize the factor(s) that regulate ica expression in response to anaerobic conditions. A chromosomal ica-promotor-â-galactosidase reporter system will be used in a genetic screen for ica transcription under anaerobic and aerobic conditions. The influence of two previously identified factors (SigB and SsrA/B) on ica activity under anaerobic conditions will also be investigated. Finally, when a S. aureus micro-array chip becomes available during the course of this study, we will use RNA expression patterns under aerobic and anaerobic conditions to characterize regulator(s) and their target(s).