Characterization and antimicrobial activity of natural isolate Lactococcus lactis subsp. lactis BGSM1-19

Soj Lactococcus lactis subsp. lactis BGSM1-19, izolovan iz sira tradicionalno proizvedenog u domaćinstvu, sintetiše dva bakteriocina: bakteriocin BacSMa koji pripada grupi laktokokcina B i bakteriocin BacSMb koji pokazuje visoku homologiju sa lakticinom RM. Čišćenjem plazmida, sa relativno niskim prinosom (0,33%), dobijene su dve grupe derivata: BacSMa- BacSMas derivat i BacSMa- BacSMas, BacSMb-, BacSMbs.. Sinteza bakteriocina je ispitivana tokom logaritamske faze rasta pri čemu je utvrđen maksimum proizvodnje u kulturi staroj 8 sati gajenoj na temperaturi od 30oC, što odgovara ranoj stacionarnoj fazi rasta. Biohemijska karakterizacija je ukazala da soj BGSM1-19 zadržava antimikrobnu aktivnost u opsegu pH vrednosti od 1 do 12 kao i posle tretmana na 100 oC u trajanju od 15 minuta. Utvrđeno je da se antimikrobna aktivnost potpuno gubi nakon tretmana različitim proteolitičkim enzimima. Soj BGSM1-19 poseduje pet plazmida. U eksperimentima čišćenja od plazmida utvrđeno je da se geni za sintezu i imunost na bakteriocine nalaze na plazmidima. Pored toga, BGSM1-19 pokazuje antimikrobnu aktivnost na ispitivane patogene bakterije kao što su Salmonella paratyphi, Micrococcus flavus, Pseudomonas aeruginosa i Staphylococcus aureus.The strain Lactococcus lactis subsp. lactis BGSM1-19, isolated from traditionally homemade white cheese, produces two bacteriocins: lactococcin B-like bacteriocin named bacteriocin BacSMa and bacteriocin BacSMb which have shown similarity with lacticin RM. Plasmid curing resulted in a low yield (0.33%) of BacSMa- BacSMas and BacSMa- BacSMas, BacSMb-, BacSMbs derivatives. The bacteriocin biosynthesis was observed in the logarithmic phase of growth and the production plateau was reached after 8 h of incubation at 30oC, when the culture entered the early stationary phase. Biochemical characterization showed that strain BGSM1-19 retained antimicrobial activity within the pH range of 1 to 12 or after treatment at 100oC for 15 min. However, bacteriocin activity was completely lost after treatment with different proteolytic enzymes. The strain BGSM1-19 contains five plasmids. Plasmid curing indicated that genes coding for bacteriocins synthesis and immunity seem to be located on plasmids. BGSM1-19 exhibited antimicrobial activity against some pathogenic bacteria such as Salmonella paratyphi, Micrococcus flavus, Pseudomonas aeruginosa and Staphylococcus aureus