Regulation of fermentation in a ruminal bacterium, Streptococcus bovis, with special reference to rumen acidosis

摘要: When high-starch diets are fed to ruminants, Streptococcus bovis often predominates in the rumen and produces lactate as major fermentation product. Lactate production by S. is regulated activity ratio of dehydrogenase (LDH) pyruvate formate-lyase (PFL) response an energy supply or intracellular pH. The activities LDH PFL affected not only amounts enzyme proteins, but also concentrations allosteric effectors, such fructose-1, 6-bisphosphate (FBP) triose phosphates. Synthesis at transcriptional level opposing directions. inverse relationship between synthesis amplifies a change proportion total products. A high capacity regulate low pH allows grow one most acid-tolerant bacteria among prevailing ruminal bacteria, has extrude H+ F1F0 H+-ATPase, which important for acid tolerance. In addition, able augment H+-ATPase kinase enhanced FBP strongly inhibited inorganic phosphate (Pi). Intracellular Pi affect sugar metabolism through regulation expression catabolic genes controlling transport systems. enzymes involved appears be catabolite control protein (CcpA) –phosphotransferase system (PTS) system.