Genomic analysis of Bacteroides fragilis reveals extensive DNA inversions regulating cell surface adaptation

Tomomi Kuwahara, Atsushi Yamashita, Hideki Hirakawa, Haruyuki Nakayama, Hidehiro Toh, Natsumi Okada, Satoru Kuhara, Masahira Hattori, Tetsuya Hayashi, Yoshinari Ohnishi

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Abstract

Bacteroides are predominant human colonic commensals, but the principal pathogenic species, Bacteroides fragilis (BF), lives closely associated with the mucosal surface, whereas a second major species, Bacteroides thetaiotaomicron (ST), concentrates within the colon. We find corresponding differences in their genomes, based on determination of the genome sequence of BF and comparative analysis with BT. Both species have acquired two mechanisms that contribute to their dominance among the colonic microbiota: an exceptional capability to use a wide range of dietary polysaccharides by gene amplification and the capacity to create variable surface antigenicities by multiple DNA inversion systems. However, the gene amplification for polysaccharide assimilation is more developed in BT, in keeping with its internal localization. In contrast, external antigenic structures can be changed more systematically in BF. Thereby, at the mucosal surface, where microbes encounter continuous attack by host defenses, BF evasion of the immune system is favored, and its colonization and infectious potential are increased.

Original languageEnglish
Pages (from-to)14919-14924
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume101
Issue number41
DOIs
Publication statusPublished - Oct 12 2004

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