UV - Induced Mutagenesis in Lactic Acid Bacteria

摘要

Induced mutagenesis is widely used for selection of microorganisms producing biologically active substances and further improving of their activities. However, it is rarely used toward lactic acid bacteria (LAB) due to their genetic specificity. Determination of LABs sensitivity to UV light and evaluate the effectiveness of UV-induced mutagenesis by positive selection of antibiotic resistant mutants. Bacterial cells grown in LAPTg and NB broth up to late log phase were harvested by centrifugation and resuspended in phosphate buffer (pH 6.8) and irradiated by UV (15 w paired lamps) at distance of 30 cm and plated on LAPTg and NB agars with and without antibiotics for survivors count and positive selection of Rif and Str colonies. It was revealed that lactic acid bacteria were 1 to 2 log more resistant to UV in compression with E. coli. At dose 40 sec the difference in survival between L. lactis and E. coli was not so significant. The yield of rifampicin and streptomycin resistant mutants of LABs vary depending of UV exposure. The maximum yield about 2-3 log of both types of resistant mutants in lactobacilli and lactococcus were observed at dose 20 sec (0.1% survival). LAB possesses intrinsic resistance to UV irradiation 1-2 log higher than E. coli. The maximum yield of UV induced Rif and Str mutants in all LABs occurs at survival about 0.1%. Thus UV rays as an effective mutagen can be used in selection of dairy starters with improved technological and probiotics characteristic.