Submitted to: Annual Wind River Conference on Procaryotic Biology
Publication Type: Abstract Only
Publication Acceptance Date: June 8, 1997
Publication Date: N/A
Technical Abstract: Xylan is an abundant polysaccharide in plant cell walls and comprises a significant portion of the diets of ruminant livestock. The digestion of the xylan component of plant cell walls is incomplete and contributes to the inefficient conversion of feed into animal products. Enzymatic digestion of xylan is accompanied by the formation of oligosaccharides. These oligosaccharides can be utilized by several species of xylanolytic ruminal bacteria and Selenomonas ruminantium, a non-xylanolytic species. The objective of the current study was to study the fermentation of xylooligosaccharides by strains of S. ruminantium and examine the enzymes and genes that may be important in the utilization of xylooligosaccharides. Strains of S. ruminantium varied considerably in their capacity to ferment xylooligosaccharides derived from oatspelt xylan. Lactic acid was the major fermentation product formed by all strains. The ability of S. ruminantium strains to utilize xylooligosaccharides was correlated with the presence of xylosidase and arabinosidase activities. The production of these activities appears to be regulated. Both activities were induced by growth on xylose or xylooligosaccharides. A gene from S. ruminantium GA192 was isolated in Escherichia coli that produced both xylosidase and arabinosidase activities. Analyses of proteins from the E. coli clone and S. ruminantium GA192 indicated that a single protein was responsible for both activities. The enzyme expressed in E. coli was capable of degrading xylooligosaccharides derived from oatspelt xylan. Attempts are underway to introduce the xylosidase/arabinosidase gene into S. ruminantium strains lacking these enzyme activities.