Effects of extracellular ph on the intracellular ph, membrane potential, and growth yield of megasphaera elsdenii in relation to the influence of monensin, ethanol, and acetate

Abstract

Megasphaera elsdenii was able to grow when the extracellular pH (pHe) was as low as 5.5, and maintained a near-neutral intracellular pH (pHj) in the wide range of pHe. The membrane potential (A 0) and Tglacose were decreased as the pHe was lowered from 6.7 to 5.5. When M. elsdenii was grown in the presence of 10 mg// monensin, 3% ethanol, or 25 mM acetate, both TgiUCose and pH; were decreased as the pHe declined. Acetate alleviated the growth inhibition by ethanol at low pHe. Unexpectedly, A 0 was increased remarkably by monensin or acetate only at pHe 6.0; this is inexplicable at present. Ethanol decreased the A(p as the pHe was decreased. © 1991, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.