Analysis of a capsular polysaccharide biosynthesis locus of Bacteroides fragilis

A major clinical manifestation of infection with Bacteroides fragilis is th e formation of intra-abdominal abscesses, which are induced by the capsular polysaccharides of this organism, Transposon mutagenesis was used to locat e genes involved in the synthesis of capsular polysaccharides, A 24,454-bp region was sequenced and found to contain a 15,379-bp locus (designated wcf ) with 16 open reading frames (ORFs) encoding products similar to those enc oded by genes of other bacterial polysaccharide biosynthesis loci. Four gen es encode products that are similar to enzymes involved in nucleotide sugar biosynthesis, Seven genes encode products that are similar to sugar transf erases. Two gene products are similar to O-acetyltransferases, and two prod ucts are probably involved in polysaccharide transport and polymerization, The product of one ORF, WcfH, is similar to a set of deacetylases of the No dB family. Deletion mutants demonstrated that the wcf locus is necessary fo r the synthesis of polysaccharide B, one of the two capsular polysaccharide s of B. fragilis 9343, The virulence of the polysaccharide B-deficient muta nt was comparable to that of the wild type in terms of its ability to induc e abscesses in a rat model of intra-abdominal infection.