Staphylococcus epidermidis: metabolic adaptation and biofilm formation in response to different oxygen concentrations.

Staphylococcus epidermidis has become a major health hazard. It is necessary to study its metabolism and hopefully uncover therapeutic targets. Cultivating S. epidermidis at increasing oxygen concentration [O2] enhanced growth, while inhibiting biofilm formation. Respiratory oxidoreductases were differentially expressed, probably to prevent reactive oxygen species formation. Under aerobiosis, S. epidermidis expressed high oxidoreductase activities, including glycerol-3-phosphate dehydrogenase, pyruvate dehydrogenase, ethanol dehydrogenase and succinate dehydrogenase, as well as cytochromes bo and aa3; while little tendency to form biofilms was observed. Under microaerobiosis, pyruvate dehydrogenase and ethanol dehydrogenase decreased while glycerol-3-phosphate dehydrogenase and succinate dehydrogenase nearly disappeared; cytochrome bo was present; anaerobic nitrate reductase activity was observed; biofilm formation increased slightly. Under anaerobiosis, biofilms grew; low ethanol dehydrogenase, pyruvate dehydrogenase and cytochrome bo were still present; nitrate dehydrogenase was the main terminal electron acceptor. KCN inhibited the aerobic respiratory chain and increased biofilm formation. In contrast, methylamine inhibited both nitrate reductase and biofilm formation. The correlation between the expression and/or activity or redox enzymes and biofilm-formation activities suggests that these are possible therapeutic targets to erradicate S. epidermidis.