Intracellular pH of acid-tolerant ruminal bacteria

Abstract

Acid-tolerant ruminal bacteria (Bacteroides ruminicola B14, Selenomonas ruminantium HD4, Streptococcus bovis JB1, Megasphaera elsdenii B159, and strain F) allowed their intracellular pH to decline as a function of extracellular pH and did not generate a large pH gradient across the cell membrane until the extracellular pH was low (<5.2). This decline in intracellular pH prevented an accumulation of volatile fatty acid anions inside the cells.