Central Carbon Metabolism, Sodium-Motive Electron Transfer, and Ammonium Formation by the Vaginal Pathogen .

Replacement of the dominated vaginal microbiome by a mixed bacterial population including is associated with bacterial vaginosis (BV). To understand the impact of on this microbiome, its growth requirements and mode of energy production were studied. Anoxic growth with glucose depended on CO and resulted in succinate formation, indicating phosphoenolpyruvate carboxylation and fumarate reduction as critical steps. The reductive branch of fermentation relied on two highly active, membrane-bound enzymes, namely the quinol:fumarate reductase (QFR) and Na-translocating NADH:quinone oxidoreductase (NQR). Both enzymes were characterized by activity measurements, in-gel fluorography, and VIS difference spectroscopy, and the Na-dependent build-up of a transmembrane voltage was demonstrated. NQR is a potential drug target for BV treatment since it is neither found in humans nor in . In , the highly active enzymes L-asparaginase and aspartate ammonia lyase catalyze the conversion of asparagine to the electron acceptor fumarate. However, the by-product ammonium is highly toxic. It has been proposed that depends on ammonium-utilizing , another typical pathogen associated with BV, and provides key nutrients to it. The product pattern of growing on glucose in the presence of mixed amino acids substantiates this notion.