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J. Bacteriol., Dec 1997, 7523-7529, Vol 179, No. 23
J Dworkin, OL Shedd and MJ Blaser
Wild-type strains of Campylobacter fetus are covered by a monomolecular
array of surface layer proteins (SLPs) critical for virulence. Each cell
possesses eight SLP gene cassettes, tightly clustered in the genome, that
encode SLPs of 97 to 149 kDa. Variation of SLP expression occurs by a
mechanism of nested DNA rearrangement that involves the inversion of a
6.2-kb sapA promoter-containing element alone or together with one or more
flanking SLP gene cassettes. The presence of extensive regions of identity
flanking the 5' and 3' ends of each SLP gene cassette and of a Chi-like
recognition sequence within the 5' region of identity suggests that
rearrangement of SLP gene cassettes may occur by a generalized
(RecA-dependent) homologous recombination pathway. To explore this
possibility, we cloned C. fetus recA and created mutant strains by marker
rescue, in which recA is disrupted in either S+ or S- strains. These
mutants then were assessed for their abilities to alter SLP expression
either in the presence or absence of a complementary shuttle plasmid
harboring native recA. In contrast to all previously reported programmed
DNA inversion systems, inversion in C. fetus is recA dependent.
Copyright © 1997, American Society for Microbiology
Nested DNA inversion of Campylobacter fetus S-layer genes is recA dependent
Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
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