PLASMID TRANSFERS BY CONJUGATION AND ELECTROPORATION IN PEDIOCOCCUS-ACIDILACTICI

Plasmid profiles of wild and mutant strains of Pediococcus acidilactici M showed that a 53.7 kb plasmid (pPR72) encodes the sucrose hydrolysis trait (Suc+) and an 11.1 kb plasmid encodes the bacteriocin production trait (Pap+). Neither of these plasmids encode traits involving fermentation of other carbohydrates, antibiotic resistance or resistance to bacteriocin. Broad host-range plasmids (pAM-beta-1 and pIP501) from Enterococcus faecalis and plasmid pPR72 from Ped. acidilactici were conjugally transferred by filter mating into two strains of Ped. acidilactici. Four plasmids, ranging in size from 4.4 to 53.7 kb, were also transferred into Ped. acidilactici strains by electroporation. Optimum transformation of the 4.4 kb plasmid, pGK12, was obtained at a DNA concentration of 1-mu-g/220-mu-l. The same amount of DNA gave lower transformation frequencies as the plasmid size increased. Results of these studies indicated that both conjugation and electroporation can be used to transfer plasmid-linked traits in Ped. acidilactici strains.