Kentucky Community & Technical College System
UV-C Resistance of Probiotic Lactobacilli and Deinococcus Radiodurans
Faculty Advisor/ Mentor
Norman Strobel; Larry Porter
Abstract
The bacterium Deinococcus radiodurans is unusually resistant to damage and death caused by diverse promoters of oxidative damage, including gamma radiation, UV-C radiation, hydrogen peroxide (H2O2), and dessication. This resistance is apparently due primarily to the presence of a manganese-based antioxident system that protects cell proteins from oxidative damage and inactivation. Several bacterial species in the genus Lactobacillus are also relatively resistant to gamma radiation and accumulate manganese. Thus, it was hypothesized that a mixed Lactobacillus culture from a commercial probiotic product would exhibit manganese-dependent UV-C resistance similar to that of D. radiodurans. This was tested experimentally by spreading dilute bacteria suspensions on the surface of agar media, followed by exposure to UV-C for 40, 60, 80, or 120 seconds. Control plates received bacteria but were not exposed to UV-C. Colonies formed by surviving bacteria were counted after 1-2 days of incubation. Results of preliminary experiments indicated that the two mixed Lactobacillus cultures employed were more resistant to UV-C than was a known susceptible bacterium, Serratia marcescens. A laboratory strain of Escherichia coli was intermediate in its UV-C resistance. The UV-C resistance of one Lactobacillus culture was greatly enhanced by growth on a manganese-rich medium prior to UVC exposure. Results of experiments designed to compare the manganese-dependence of UV-C resistance in Lactobacilli and D. radiodurans are presented. The possible contribution of oxidative stress resistance of Lactobacilli to their probiotic effects are discussed.
UV-C Resistance of Probiotic Lactobacilli and Deinococcus Radiodurans
The bacterium Deinococcus radiodurans is unusually resistant to damage and death caused by diverse promoters of oxidative damage, including gamma radiation, UV-C radiation, hydrogen peroxide (H2O2), and dessication. This resistance is apparently due primarily to the presence of a manganese-based antioxident system that protects cell proteins from oxidative damage and inactivation. Several bacterial species in the genus Lactobacillus are also relatively resistant to gamma radiation and accumulate manganese. Thus, it was hypothesized that a mixed Lactobacillus culture from a commercial probiotic product would exhibit manganese-dependent UV-C resistance similar to that of D. radiodurans. This was tested experimentally by spreading dilute bacteria suspensions on the surface of agar media, followed by exposure to UV-C for 40, 60, 80, or 120 seconds. Control plates received bacteria but were not exposed to UV-C. Colonies formed by surviving bacteria were counted after 1-2 days of incubation. Results of preliminary experiments indicated that the two mixed Lactobacillus cultures employed were more resistant to UV-C than was a known susceptible bacterium, Serratia marcescens. A laboratory strain of Escherichia coli was intermediate in its UV-C resistance. The UV-C resistance of one Lactobacillus culture was greatly enhanced by growth on a manganese-rich medium prior to UVC exposure. Results of experiments designed to compare the manganese-dependence of UV-C resistance in Lactobacilli and D. radiodurans are presented. The possible contribution of oxidative stress resistance of Lactobacilli to their probiotic effects are discussed.