Staphylococcus epidermidis metabolic adaptation and biofilm formation in response to varying oxygen.

Abstract

Staphylococcus epidermidis is a Gram-positive saprophytic bacterium found in the microaerobic/anaerobic layers of the skin. It becomes a health hazard when introduced across the skin by punctures or wounds. S. epidermidis forms biofilms in low O2 environments. As oxygen concentrations ([O2]) decreased, the metabolism of S. epidermidis was modified ranging from fully aerobic to anaerobic. Respiratory activity increased at high [O2], while anaerobically grown cells exhibited the highest rate of fermentation. High aerobic metabolism coincided with high hydrogen peroxide-mediated damage. Remarkably, the rate of growth decreased at low [O2] even though the concentration of ATP was high. Under these conditions bacteria associated into biofilms. Then, in the presence of metabolic inhibitors, biofilm formation decreased. It is suggested that when [O2] is low S. epidermidis accumulates ATP in order to synthesize the proteins and polysaccharides needed to attach to surfaces and form biofilms.\n\nImportanceBacteria and humans coexist, establishing all kinds of relationships that may change from saprophytic to infectious as environmental conditions vary. S. epidermidis is saprophytic when living in the skin. Inside the organism it evokes a pathologic reaction and is thus rejected by the organism. Additionally it is forced to adapt to high oxygen concentrations, becoming vulnerable to reactive oxygen species, which may come from leukocyte attack. Avoiding both, high oxygen and leukocytes is a must for bacteria. Escaping from oxygen involves a clever response: whenever it finds a low oxygen environment it attaches to surfaces, associating into biofilms. Biofilms protect S. epidermidis against host cells. Understanding these responses is a must in order to develop treatments and prevent infection success.