Affiliation:
1. Department of Microbiology, The University of Sydney, Sydney, N.S.W. 2006, Australia
Abstract
ABSTRACT
O antigen is part of the lipopolysaccharide present in the outer membrane of gram-negative bacteria.
Escherichia coli
and
Salmonella enterica
each have many forms of O antigen, but only three are common to the two species. It has been found that, in general, O-antigen genes are of low GC content. This deviation in GC content from that of typical
S. enterica
or
E. coli
genes (51%) is thought to indicate that the O-antigen DNA originated in species other than
S. enterica
or
E. coli
and was captured by lateral transfer. The O-antigen structure of
Salmonella enterica
O35 is identical to that of
E. coli
O111, commonly found in enteropathogenic
E. coli
strains. This O antigen, which has been shown to be a virulence factor in
E. coli
, contains colitose, a 3,6-dideoxyhexose found only rarely in the
Enterobacteriaceae
. Sequencing of the O35-antigen gene cluster of
S. enterica
serovar Adelaide revealed the same gene order and flanking genes as in
E. coli
O111. The divergence between corresponding genes of these two gene clusters at the nucleotide level ranges from 21.8 to 11.7%, within the normal range of divergence between
S. enterica
and
E. coli
. We conclude that the ancestor of
E. coli
and
S. enterica
had an O antigen identical to the O111 and O35 antigens, respectively, of these species and that the gene cluster encoding it has survived in both species.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
49 articles.
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