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Infect. Immun., Nov 1997, 4592-4597, Vol 65, No. 11
HM Fletcher, RM Morgan and FL Macrina
Degenerate oligonucleotide primers were used in PCR to amplify a region of
the recA homolog from Porphyromonas gingivalis W83. The resulting PCR
fragment was used as a probe to identify a recombinant lambda DASH phage
(L10) carrying the P. gingivalis recA homolog. The recA homolog was
localized to a 2.1-kb BamHI fragment. The nucleotide sequence of this
2.1-kb fragment was determined, and a 1.02-kb open reading frame (341 amino
acids) was detected. The predicted amino acid sequence was strikingly
similar (90% identical residues) to the RecA protein from Bacteroides
fragilis. No SOS box, characteristic of LexA-regulated promoters, was found
in the 5' upstream region of the P. gingivalis recA homolog. In both methyl
methanesulfonate and UV survival experiments the recA homolog from P.
gingivalis complemented the recA mutation of Escherichia coli HB101. The
cloned P. gingivalis recA gene was insertionally inactivated with the
ermF-ermAM antibiotic resistance cassette to create a recA-deficient mutant
(FLL33) by allelic exchange. The recA-deficient mutant was significantly
more sensitive to UV irradiation than the wild-type strain, W83. W83 and
FLL33 showed the same level of virulence in in vivo experiments using a
mouse model. These results suggest that the recA gene in P. gingivalis W83
plays the expected role of repairing DNA damage caused by UV irradiation.
However, inactivation of this gene did not alter the virulence of P.
gingivalis in the mouse model.
Copyright © 1997, American Society for Microbiology
Nucleotide sequence of the Porphyromonas gingivalis W83 recA homolog and construction of a recA-deficient mutant
Department of Microbiology and Molecular Genetics, Loma Linda University, California 92350, USA. HFLETCHER@CCMAIL.LLU.EDU
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