%0 Journal Article %A Patrick, Sheila %A Houston, Simon %A Thacker, Zubin %A Blakely, Garry W. %T Mutational analysis of genes implicated in LPS and capsular polysaccharide biosynthesis in the opportunistic pathogen Bacteroides fragilis %D 2009 %J Microbiology, %V 155 %N 4 %P 1039-1049 %@ 1465-2080 %R https://doi.org/10.1099/mic.0.025361-0 %K EPS, extracellular polysaccharide(s) %K MC, micro-capsule %K PCP, polysaccharide copolymerase %K SC, small capsule %K R/M, restriction/modification %K HMMPS, high-molecular-mass polysaccharide %K IFM, immunofluorescence microscopy %K LC, large capsule %I Microbiology Society, %X The obligate anaerobe Bacteroides fragilis is a normal resident of the human gastrointestinal tract. The clinically derived B. fragilis strain NCTC 9343 produces an extensive array of extracellular polysaccharides (EPS), including antigenically distinct large, small and micro- capsules. The genome of NCTC 9343 encodes multiple gene clusters potentially involved in the biosynthesis of EPS, eight of which are implicated in production of the antigenically variable micro-capsule. We have developed a rapid and robust method for generating marked and markerless deletions, together with efficient electroporation using unmodified plasmid DNA to enable complementation of mutations. We show that deletion of a putative wzz homologue prevents production of high-molecular-mass polysaccharides (HMMPS), which form the micro-capsule. This observation suggests that micro-capsule HMMPS constitute the distal component of LPS in B. fragilis. The long chain length of this polysaccharide is strikingly different from classical enteric O-antigen, which consists of short-chain polysaccharides. We also demonstrate that deletion of a putative wbaP homologue prevents expression of the phase-variable large capsule and that expression can be restored by complementation. This suggests that synthesis of the large capsule is mechanistically equivalent to production of Escherichia coli group 1 and 4 capsules. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.025361-0