TRANSPOSITION OF TN4351 IN PORPHYROMONAS-GINGIVALIS

Genetic analysis ofPorphyromonas gingivalis, an obligately anaerobic gram-negative bacterium, has been hindered by the apparent lack of naturally occurring bacteriophages, transposable elements, and plasmids. Plasmid R751::*Ω4 has previously been used as a suicide vector to demonstrate transposition of Tn4351 inB. uniformis. The erythromycin resistance gene on Tn4351 functions inBacteroides andPorphyromonas. Erythromycin-resistant transconjugants were obtained at a mean frequency of 1.6 × 10-7 from matings betweenEscherichia coli HB101 containing R751::*Ω4 andP. gingivalis 33277. Southern blot hybridization analysis indicated that about half of the erythromycin-resistantP. gingivalis transconjugants contained simple insertions of Tn4351 and half contained both Tn4351 and R751 sequences. The presence of R751 sequences in someP. gingivalis transconjugants most likely occurred from Tn4351-mediated cointegration of R751, since we were unable to detect autonomous plasmid in theseP. gingivalis transconjugants. TheP. gingivalis-Tn4351 DNA junction fragments from different transconjugants varied in size. These results are consistent with transposition of Tn4351 and with insertion at several different locations in theP. gingivalis chromosome. Tn4351 may be useful as a mutagen to isolate well-defined mutants ofP. gingivalis. © 1992 Academic Press, Inc. All rights of reproduction in any form reserved.