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Infect. Immun., Jun 1995, 2185-2193, Vol 63, No. 6
SA Thompson and MJ Blaser
To understand the potential roles of the important DNA repair protein RecA
in Helicobacter pylori pathogenesis, we cloned the recA gene from H. pylori
84-183. Degenerate PCR primers based on conserved RecA protein regions were
used to amplify a portion of H. pylori recA, which was used as a probe to
isolate the full-length recA gene from H. pylori genomic libraries. The H.
pylori recA gene encoded a protein of 347 amino acids with a molecular mass
of 37.6 kDa. As expected, H. pylori RecA was highly similar to other RecA
proteins and most closely resembled that of Campylobacter jejuni (75%
identity). Immediately downstream of recA was an open reading frame whose
predicted product showed 58% identity to the Bacillus subtilis enolase
protein. recA and eno were disrupted in H. pylori 84-183 by insertion of
antibiotic resistance genes. Reverse transcription-PCR demonstrated that
recA and eno were cotranscribed and that insertion of the kanamycin
resistance gene into recA had polar effects on expression of the downstream
eno. The H. pylori recA mutants were severely impaired in their ability to
survive treatment with UV light and methyl methanesulfonate and with the
antimicrobial agents ciprofloxacin and metronidazole. The eno mutant had
sensitivities to UV light and metronidazole intermediate to those of
wild-type and recA strains, suggesting that truncation of the recA-eno
transcript resulted in lowered recA expression. For survival at low pH, a
recA mutant was approximately 10-fold more sensitive than strain 84-183,
while the eno mutant demonstrated intermediate susceptibility. This
difference occurred in the presence or absence of urea, implying the
involvement of a gene in the recA region in an acid resistance mechanism
distinct from that mediated by urease.
Copyright © 1995, American Society for Microbiology
Isolation of the Helicobacter pylori recA gene and involvement of the recA region in resistance to low pH
Division of Infectious Diseases, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
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