100A-1 |
Photoreactivation and dark repair of cross linked genomic DNA in UV treated pathogens |
T. KIM1, T. C. Chen2, and J. L. Silva1. (1) Food Science and Technology, Mississippi State University, Box 9805, Mississippi State, MS 39762, (2) Poultry Science, Mississippi State University Ultraviolet (UV) treated microorganisms can be reactivated with and without light exposure. Little information has been reported on the effects of UV treatment and reactivation on genomic DNA of microorganisms. Objective of this study was to investigate the effects of photoreactivation and dark repair on crossed genomic DNA of selected pathogenic microorganisms. Suspensions of Salmonella typhimurium, Escherichia coli O:157:H7, and Listeria monocytogenes serotype 1 in peptone solution were prepared and exposed to two levels of UV (300 and 1500 J/m2). The UV radiated suspensions were activated either in dark or under fluorescent light for one hour. Microbial enumeration was done before and after the reactivations. Genomic DNA of the cells before and after activation along with their controls were isolated and electrophoresed in neutral agarose gel. The UV irradiation has greater effect on E.coli O157:H7 and Listeria monocytogenes than Salmonella typhimurium. Recovery of injured cells varied when exposed to 1500 J/m2 but did not vary exposed to 300J/m2. No recovery was found for E.coli O:157:H7 and Listeria monocytogenes cells treated with 1500 J/m2; while a strong dark repair was observed for salmonella typhimurium. Regardless of pathogens, cross linked genomic DNA was increased from the UV irradiated cells, especially for those treated at the higher dose. This increased cross linked genomic DNA disappeared as the treated cells reactivated or repaired. This study demonstrated that the effect of UV on pathogens varied with species. An increase in cross linked genomic DNAs was observed at treated pathogens and this increased cross linked genomic DNA decreased with photoreactivation and dark repair.
Session 100A, Food Microbiology: General II
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