Anaerobic glucose and serine metabolism in Staphylococcus epidermidis

Anaerobically grown Staphylococcus epidermidis fermented glucose with the production of lactate and trace amounts of acetate, formate and CO2. Isotopic and inhibitor studies, assays for key enzymes of different metabolic pathways, and fermentation balances, all indicated that glucose was metabolized principally via glycolysis and to a very limited extent by the hexose monophosphate oxidative pathway. Serine fermentation proceeded via deamination and dismutation yielding NH3 and equimolar amounts of lactate, acetate and CO2; small amounts of formate arose by the operation of pyruvate-formate lyase. Incorporation of 0.5% (w/v) glucose in the growth medium depressed serine metabolism by repressing the activities of serine dehydratase and pyruvate dehydrogenase but, conversely, enhanced the activities of phosphofructokinase and lactate dehydrogenase. Glucose-grown organisms at various stages of anaerobic batch growth showed an inverse relationship between the rates of fermentation of serine and glucose. L-Lactate dehydrogenase activity in crude extracts depended on fructose 1,6-bisphosphate, and fructose 1,6-bisphosphate aldolase was found to be a class I aldolase. Despite the presence of ribokinase, D-ribose-5-phosphate isomerase, transaldolase and transketolase, the organisms utilized ribose only after growth aerobically in basal medium, and then at a slow rate after an initial lag period.