LACTOBACILLUS GASSERI G7 – A BACTERIOCINOGENIC STRAIN ISOLATED FROM VAGINAL SAMPLE
GALINA STOYANCHEVA1*, ELENA CHORUKOVA2
1 – Department of Microbial Genetics, The Stephan Angeloff Institute of Microbiology, Bulgarian Academy of Sciences, Acad. G. Bonchev str. bl. 26, Sofia, Bulgaria
2 – Department of Applied Microbiology, The Stephan Angeloff Institute of Microbiology
*Corresponding author: galinadinkova@abv.bg
Keywords: Lactobacillus gasseri, gassericin genes
Abstract: Lactobacilli exert antagonistic activity against many microorganisms as a result of the production of organic acids, hydrogen peroxide, diacetyl, inhibitory enzymes and bacteriocins. In our study, we performed species identification of strain G7 isolated from human vaginal sample; determined its antimicrobial activities against human pathogen microorganisms; analyzed the genes encoding bacteriocins and determined the primary physicochemical nature of the active substance. According to 16S rRNA gene sequence analysis our strain G7 belongs to Lactobacillus gasseri species. By well diffusion test using neutralized, treated with catalase, cell-free supernatant, G7 strain inhibits the growth of Escherichia coli. The isolate G7 was tested for the presence of genes encoding the bacteriocins with primers targeting gassericin A and gassericin T gene. The positive results were confirmed by sequencing of the PCR products. New primer pairs were designed, targeting gassericin T and gassericin A bacteriocin operons. Partial characterization of the antimicrobial substance was made. The filter-sterilized supernatant was inactivated by the proteolytic enzymes proteinase K, pepsin and trypsin, indicating the proteinaceous nature of the inhibitory substances. The use of lactobacilli as therapeutic agents for the treatment and prevention of urogenital infections is an alternative to conventional antibiotic therapy and our study could contribute to the development of this strategy.