Analysis of a Capsular Polysaccharide Biosynthesis Locus ofBacteroides fragilis

Abstract

A major clinical manifestation of infection with Bacteroides fragilis is the formation of intra-abdominal abscesses, which are induced by the capsular polysaccharides of this organism. Transposon mutagenesis was used to locate 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 encoded by genes of other bacterial polysaccharide biosynthesis loci. Four genes encode products that are similar to enzymes involved in nucleotide sugar biosynthesis. Seven genes encode products that are similar to sugar transferases. Two gene products are similar toO-acetyltransferases, and two products are probably involved in polysaccharide transport and polymerization. The product of one ORF, WcfH, is similar to a set of deacetylases of the NodB family. Deletion mutants demonstrated that the wcf locus is necessary for the synthesis of polysaccharide B, one of the two capsular polysaccharides of B. fragilis 9343. The virulence of the polysaccharide B-deficient mutant was comparable to that of the wild type in terms of its ability to induce abscesses in a rat model of intra-abdominal infection.

Interstrain Variation of the Polysaccharide B Biosynthesis Locus of Bacteroides fragilis : Characterization of the Region from Strain 638R

“…The sequence of the PS B biosynthesis locus of strain NCTC 9343 has been reported (2). Here, we report the sequence of the PS B biosynthesis region of the most-studied B. fragilis strain, 638R, which produces a CPC that is immunologically distinct from the CPC of strain NCTC 9343.…”

“…The PS B biosynthesis locus of strain 638R was located by transposon mutagenesis as described previously (2). Bacterial strains and plasmids used in this study are listed in Table 1.…”

“…Bacterial strains and plasmids used in this study are listed in Table 1. Mutant 2-42 did not react with a MAb specific to the CPC of strain 638R, and the B. fragilis DNA at the junction of mutant 2-42 was cloned, creating plasmid pLEC6.1 (2). This plasmid was used as a probe to select pMJC10 from a 638R cosmid gene bank constructed by using a previously described protocol (2).…”

In vitroanalysis of 4-methylumbelliferone as a sole carbon source forLactobacillus helveticus2126

“…Another capsulated bacteria, Bacteroides fragilis has two distinct (A and B) high molecular weight polysaccharides. These capsular polysaccharides are vital virulence factors (Comstock et al 1999). Due to the effect of 4-MU on capsulated bacteria, 4-MU is used for identifying and isolating B. fragilis (Mangels et al 1993;Gupte 2012).…”

Genetic Diversity of the Capsular Polysaccharide C Biosynthesis Region of Bacteroides fragilis

“…These loci are flanked by genes common to both strains; however, the genes involved in polysaccharide biosynthesis are distinct. The structure of the repeating unit of the PS C of strain 9343 (PS C1) has not been determined; however, the biosynthesis locus contains a gene, wcfF, which encodes a product similar to sugar dehyrogenases of other bacterial polysaccharide biosynthesis loci, which would confer a negative charge to one of the monosaccharides of the PS C1 repeating unit (3).…”