Competitiveness of different polysaccharide utilization mutants of Bacteroides thetaiotaomicron in the intestinal tracts of germfree mice

Bacteroides thetaiotaomicron, an obligate anaerobe found in high numbers in human colons, can utilize a variety of polysaccharides. To determine which type of polysaccharide contributes most to the nutrition of B. thetaiotaomicron in vivo, we isolated and characterized transposon-generated mutants deficient in the ability to use different polysaccharides. Some mutants were deficient in polysaccharide utilization because of the inability to utilize a component monosaccharide. These mutants included a mutant that was unable to utilize L-fucose (a component of goblet cell mucin), a mutant that was unable to utilize D-galactose (a component of raffinose, stachyose, arabinogalactan, and goblet cell mucin), and a mutant that was unable to utilize either glucuronic acid (a component of mucopolysaccharides) or galacturonic acid (a component of polygalacturonic acid or pectin). Other mutants were unable to use the polysaccharide but could use the component sugars. These included four mutants that were unable to utilize starch and one mutant that was unable to utilize polygalacturonic acid. The mutants were tested for the ability to compete with the wild type for colonization of the intestinal tracts of germfree mice. The only mutants against which the wild type competed successfully in the intestinal tracts of germfree mice were a galactose-negative mutant and a uronic acid-negative mutant. These mutations differed from the others tested in that they affected utilization of more than one type of polysaccharide.(ABSTRACT TRUNCATED AT 250 WORDS)