Abstract
Megasphaera elsdenii was able to grow when the entracellular pH (Phe) was as low as, 5.5, and maintained a near-neutral intracellular pH (pHi) in the wide range of pHe. The membrane potential (Δφ) and Yglucose were decreased as the pHe was lowered from 6.7 to 5.5. When M. elsdenii was grown in the presence of 10mg/l monensin, 3% ethanol, or 25mM acetate, both Yglucose and pHi were decreased as the pHe declined. Acetate alleviated the growth inhibition by ethanol at low pHe. Unexpectedly, Δφ was increased remarkably by monensin or acetate only at pHe 6.0; this is inexplicable at present. Ethanol decreased the Δφ as the pHe was decreased.
