Pentose transport by the ruminal bacterium Butyrivibrio fibrisolvens

Abstract

Butyrivibrio fibrisolvens is a fibrolytic ruminal bacterium that degrades hemicellulose and ferments the resulting pentose sugars. Washed cells of strain D1 accumulated radiolabelled xylose (Km = 1.5 microM) and arabinose (Km = 0.2 microM) when the organism was grown on xylose, arabinose, or glucose, but cultures grown on sucrose or cellobiose had little capacity to transport pentose. Glucose and xylose inhibited transport of each other non-competitively. Both sugars were utilized preferentially over arabinose, but since they did not inhibit transport of arabinose, it appeared that the preference was related to an internal metabolic step. Although the protonmotive force was completely abolished by ionophores, cells retained some ability to transport pentose. In contrast, the metabolic inhibitors iodoacetate, arsenate, and fluoride had little effect on protonmotive force but caused a large decrease in intracellular ATP and xylose and arabinose uptake. These results suggested that high-affinity, ATP-dependent mechanisms were responsible for pentose transport and hexose sugars affected the utilization of xylose and arabinose.

Genomic architecture of three newly isolated unclassified Butyrivibrio species elucidate their potential role in the rumen ecosystem

“…The strains XB500-5 and X503 had the genetic construction of the pentose phosphate pathway to utilize arabinose and xylose in contrast to CB08. Such concurrent hexose and pentose sugar utilization have been known in ruminal Butyrivibrio [62,63] [9,13,64]. Another fate of pyruvate to lactate was identified in our strains, where the ldh gene encoding lactate dehydrogenase (EC 1.1.1.28) was found responsible for catalyzing the reversible conversion of pyruvate to significant quantities of lactate [65].…”

“…The strains XB500-5 and X503 had the genetic construction of the pentose phosphate pathway to utilize arabinose and xylose in contrast to CB08. Such concurrent hexose and pentose sugar utilization have been known in ruminal Butyrivibrio [62,63]. [65].…”

Degradation and utilization of xylan by the ruminal bacteria Butyrivibrio fibrisolvens and Selenomonas ruminantium

“…When S. ruminantium was cocultured with B. fibrisolvens, accumulations of acid-alcoholsoluble products were still noted, but the composition of car- The utilization of a particular carbohydrate species in the mixture will likely be influenced by the carbohydrate concentrations and the substrate utilization pattern exhibited by each organism. Regulation of pentose utilization has been demonstrated for other strains of S. ruminantium and B. fibrisolvens (25,(28)(29)(30), but little is known about oligosaccharide utilization patterns by these or other species of ruminal bacteria. In the case of xylan, a wide variety of xylooligosaccharides could be produced during enzymatic hydrolysis with various degrees of substitution (i.e., with arabinose, uronic acids, etc.…”

The Rumen Microbial Ecosystem

“…Xylanase-, xylosidase-and xylose-transport activities in some strains of B. fibrisolvens were repressed by glucose and/or induced by xylan (Hespell et al, 1987;Sewell et al, 1988;Strobel, 1994); in others, activity appeared to be constitutive . Xylanase-, xylosidase-and xylose-transport activities in some strains of B. fibrisolvens were repressed by glucose and/or induced by xylan (Hespell et al, 1987;Sewell et al, 1988;Strobel, 1994); in others, activity appeared to be constitutive .…”