Article Abstract:
Two chondroitin utilization mutants of Bacteroides thetaioitaomicron were analyzed. Mutant 46-1is outcompeted by the wild type for the colonization of the intestinal tract ofwild type mice, while mutant 46-4 is not. Analysis showed that both mutants mayaffect regulatory loci which are required for the expression of chondroitin sulfate utilization genes. Mutant 46-1 was shown to be unable to grow on heparin, while 46-4 was. This may explain the inability of 46-1 to compete withwild type in the germfree mouse intestine.
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Article Abstract:
A 3.8-kbp segment of the Bacteroides ovatus chromosome which contains the genes for xylanase (xylI) and xylosidase-arabinosidase (xsa) was analyzed. Site-directed insertion mutagenesis showed that xylI and xsa belong to a single operon, with xylI in the upstream orientation. In addition, preliminary indications suggest the presence of another arabinosidase gene upstream of xylI. Physiological analyses of the insertion mutants showed that the product of xsa is the rate-limiting enzyme in xylan utilization.
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Article Abstract:
The major sources of carbohydrate for Bacteroides ovatus in the intestinal tract of germfree mice were determined by analysis of the bacterial disaccharidase expression patterns. The enzymes with the highest activities were beta- and alpha-glucosidase and alpha-galactosidase. The patterns observed were most consistent with low-level utilization of many different substrates rather than a single major carbohydrate source. Hence, the absence of even a minor substrate could have deleterious effects in vivo.
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