Genomic analysis of Bacteroides fragilis reveals extensive DNA inversions regulating cell surface adaptation.
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 (BT), 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.
Department of Molecular Bacteriology, Graduate School of Medicine, University of Tokushima, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan. tomomi@basic.med.tokushima-u.ac.jp
Tomomi
T
Kuwahara
Atsushi
A
Yamashita
Hideki
H
Hirakawa
Haruyuki
H
Nakayama
Hidehiro
H
Toh
Natsumi
N
Okada
Satoru
S
Kuhara
Masahira
M
Hattori
Tetsuya
T
Hayashi
Yoshinari
Y
Ohnishi
D001426:Bacterial Proteins / Q000235:genetics; D001441:Bacteroides fragilis / Q000235:genetics*; D001483:Base Sequence; D002462:Cell Membrane / Q000502:physiology; D007446:Chromosome Inversion; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial / Q000235:genetics; D018387:Codon, Initiator / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics*; D016680:Genome, Bacterial; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D011135:Polysaccharides, Bacterial / Q000235:genetics; D012329:RNA, Bacterial / Q000235:genetics
D001426:Bacterial Proteins; D018387:Codon, Initiator; D004269:DNA, Bacterial; D011135:Polysaccharides, Bacterial; D012329:RNA, Bacterial