Attractives in Rumen Protozoa

Onodera, Ryoji

doi:10.2508/chikusan.70.153

Cited by 1 publication

(1 citation statement)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Because one of the greatest merits of ruminants is the ability to utilize fiber, ionophores should be carefully used. Protozoa play important roles in the ruminal metabolism that are not replaceable by bacteria (Williams & Coleman 1997; Onodera 1999). In addition, rumen protozoa have the capacity to assimilate starch and soluble sugars and store these energy‐rich compounds inside the cell as amylopectin (Williams & Coleman 1997).…”

Section: Introductionmentioning

confidence: 99%

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

Asanuma

Hino

2002

Animal Science Journal

View full text Add to dashboard Cite

When high-starch diets are fed to ruminants, Streptococcus bovis often predominates in the rumen and produces lactate as the major fermentation product. Lactate production by S. bovis is regulated by the activity ratio of lactate dehydrogenase (LDH) to pyruvate formate-lyase (PFL) in response to an energy supply or the intracellular pH. The activities of LDH and PFL are affected not only by the amounts of enzyme proteins, but also by the concentrations of allosteric effectors, such as fructose-1, 6-bisphosphate (FBP) and triose phosphates. Synthesis of LDH and PFL is regulated at the transcriptional level in opposing directions. The inverse relationship between LDH and PFL synthesis amplifies a change in the proportion of lactate in the total fermentation products. A high capacity to regulate lactate production in response to low pH allows S. bovis to grow at low pH and as one of the most acid-tolerant bacteria among the prevailing ruminal bacteria, S. bovis also has a high capacity to extrude intracellular H + by an F 1 F 0 H + -ATPase, which is important for acid tolerance. In addition, S. bovis is able to augment H + -ATPase synthesis at the transcriptional level in response to low pH. The activities of H + -ATPase and pyruvate kinase are enhanced by FBP and strongly inhibited by inorganic phosphate (P i ). Intracellular FBP and P i concentrations affect sugar metabolism in S. bovis through regulation of the expression of catabolic genes and controlling the activity of sugar transport systems. Synthesis of the enzymes involved in sugar transport and fermentation appears to be regulated by the catabolite control protein A (CcpA) -phosphotransferase system (PTS) system.

show abstract

Section: Introductionmentioning

confidence: 99%