The recA gene in Porphyromonas gingivalis is expressed during infection of the murine host.

The recA gene in Porphyromonas gingivalis is involved in DNA repair. To further elucidate the importance of the recA locus in the pathogenesis of P. gingivalis, we assessed its ability for expression in an animal host. The promoterless xa-tetA(Q)2 cassette was used in heterodiploid mutants to study recA promoter activity during infection. P. gingivalis FLL118.1 had the xa-tetA(Q)2 cassette under the control of recA promoter whereas P. gingivalis FLL119 had the cassette in the opposite orientation. xa encodes a bifunctional xylosidase/arabinosidase enzyme (XA) and the tetA(Q)2 gene product confers tetracycline resistance. Intramuscular infection in a mouse model allowed the recovery of the bacteria from inguinal lymph nodes. Infusion of tetracycline in the animals permitted the enrichment P. gingivalis FLL118.1 over the wild-type strain, during a mixed infection. The xylosidase activity of FLL118.1 could be detected on agar plates in the presence of 5-methylumbellifiry-beta-D-xyloside. No such enrichment for xylosidase activity was detected when the mixture of P. gingivalis W83 and P. gingivalis FLL119 was used to infect the mouse or cultured in vitro. These results indicated that recA promoter was transcriptionally active during the infection of the murine host and further support the importance of this locus during the P. gingivalis infection process.