Characterization of Plasmid pLD3 of Enterococcus hirae LD3 Isolated from a Popular Indian Fermented Food, Dosa

Enterococcus hirae LD3 was previously characterized for the production of bacteriocin with potential probiotic property. In this study, we have analysed the plasmid profile of E. hirae LD3 and its characterization using curing methods and gene sequencing. This bacterium was found to be resistant to gentamycin, kanamycin and streptomycin whereas sensitive to ampicillin, chloramphenicol, erythromycin and tetracycline. E. hirae LD3 showed the presence of a single plasmid, pLD3 with 33.3% GC content with molecular weight 28.69 kb. The plasmid sequence revealed the presence of stress response gene, rli28; multidrug efflux pump gene, emeA and kanamycin and gentamicin resistant gene, aph(2')-IIIa. The plasmid was cured using acriflavine, ethidium bromide and SDS. The plasmid-cured strain LD3 became sensitive to kanamycin and exhibited drastic reduction in the bacteriocin activity, 20–40 AU/mL compared to 160 AU/mL in wild-type strain LD3. Thus, E. hirae LD3 contains a plasmid with low GC content which is linked with antibiotic resistance.