Transmission of Bacteriocinogenicity by Conjugation in Group D Streptococci

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Seventy-seven out of eighty-one group D streptococcal strains isolated from humans and animals were found to produce bacteriocins that were active on other streptococcal strains of gorup A and D, but inactive on their own cells. On the bases of the spectra of indicator strains, and the sensitivities to heat, chloroform, and trypsin, seven types of bacteriocins were classified. Streptococcus faecalis var. liquefaciens strain 4532 or strain A (liq-A) was UV-irradiated, and mutants which lost bacteriocinas well as the β-hemolysin-forming activities (Bact-. Hem-) were obtained. Cells of the type I bacteriocin producer (SMr. TCr. Bact-I+. Hem+) and nonproducer 2025 (PCr. Bact-I-. Hem-), both belonging to S. faecalis var. liquefaciens, were mixed and incubated in broth. Recombinants (PCr. SMs. TCs. Bact-I+. Hem+) were obtained at a high frequency (5.8% preinoculum size of PCr. Bact-I-. Hem-), and the character was stable for at least ten transfers. In the mixed culture, a marked decrease in the recipient 2025 cell number was observed. The occurrence of recombinants was not inhibited by deoxyribonuclease. A cell-free filtrate of Bact+. Hem+ cells mixed with Bact-. Hem-cells did not cause a mutation of the latter combined characters. The transfer of a genetic marker is discussed as an event of the cell-to-cell contact.

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