title: Evidence for a chromosome-borne resistance transposon (Tn916) in Streptococcus faecalis that is capable of "conjugal" transfer in the absence of a conjugative plasmid.
abstract: Streptococcus faecalis strain DS16 harbors the conjugative hemolysin-bacteriocin plasmid pAD1 (35 megadaltons) and the nonconjugative R-plasmid pAD2 determining resistance to streptomycin, kanamycin, and erythromycin; a tetracycline resistance (Tetr) determinant is located on the chromosome. When strain DS16 was mated (on membrane filters) with the plasmid-free strain JH2-2, Tetr transconjugants could be obtained at a frequency of about 10(-6) per recipient. Analyses of transconjugants showed that some contained the Tetr determinant linked to pAD1. Subsequent studies showed that the Tetr determinant was located on a 10-megaldalton transposon, designated Tn916, which could insert into two hemolysin plasmids: pAM gamma 1 and pOB1. In addition, derivatives of DS16 devoid of pAD1 were capable of transferring Tetr to recipient strains. Transconjugants (plasmid-free) from such matings could subsequently act as donors in the transfer of Tetr. Both transposition and transfer were found to be rec independent.
mesh_terms: D001430:Bacteriocins / Q000096:biosynthesis; D002876:Chromosomes, Bacterial; D003227:Conjugation, Genetic; D004251:DNA Transposable Elements; D004352:Drug Resistance, Microbial; D013293:Enterococcus faecalis / Q000235:genetics* / Q000502:physiology; D006460:Hemolysin Proteins / Q000096:biosynthesis; D010957:Plasmids; D011995:Recombination, Genetic; D013752:Tetracycline / Q000494:pharmacology*
chemical_list: D001430:Bacteriocins; D004251:DNA Transposable Elements; D006460:Hemolysin Proteins; D013752:Tetracycline