Genetic transfer of lactate-utilizing ability in the rumen bacterium Selenomonas ruminantium

Matings between the lactate-utilizing, tetracycline-sensitive Selenomonas ruminantium strains 5521C1 and 5934e and the lactate-non-utilizing, tetracycline-resistant strain FB322 resulted in putative recombinant strains capable of growth on lactate. Analysis of total protein by SDS-PAGE and chromosomal DNA by hybridization, indicated that the recombinants were derived from strain FB322. DNA hybridization produced no evidence that plasmid transfer occurred, leaving chromosomal DNA transfer as the most likely mechanism for the altered phenotype. Analysis of strains 5934e, FB322 and the resulting recombinant TC3 indicated that all three strains contained D-nLDH and L-nLDH activities. In addition strains 5934e and TC3 possessed D-iLDH activity when grown on DL-lactate. The ability of strain FB322 to grow on pyruvate but not lactate suggested that the lactate-utilizing recombinant had acquired the ability to synthesize D-iLDH.