DETECTION OF DNA REPAIR SYSTEMS OF THE BACTERIUM PSEUDOMONAS AERUGENOSA

Abstract

The bacterium Pseudomonas aeruginosa was irradiated with ultraviolete light with wave length ( 254 nm ) for different periods ( 50 , 100 , 150 , and 200 sec ) . part of irradiated bacterial culture was exposed to sun light and the other part was kept in the dark . The survivors of the cells exposed to the sun light was more than in the dark and this ensure possessing the bacterium photoreactivating repair system To investigate the excision repair system, the minimal inhibitory concentration ( MIC)of caffeine against bacteria was studied by exposing the bacterium to different concentrations of caffeine ( 10 , 15 , 20 and 25 mM ) and the MIC was 20 mM , then the bacterium was exposed to different doses of U.V. light in the presence of caffeine and the study ensured the survivors of the cells in the medium with caffeine was less than the medium with absence of caffeine and this refers to possess the bacterium excision repair system. To detect the recombination repair system , the bacterium was exposed to the concentrtions 0.1 ,0.2 , 0.3 , 0.4 µg / ml of acrivlavine and the MIC was 0.3 µg / ml , then the bacterium was exposed to different doses of U.V. light in the presence of acrivlavine . The survivors of the cells in the medium with acrivlavine was less compared with the absence of acrivlavine and this indicate possessing bacterium recombination repair system . To study SOS repair system the bacterium was mutated with direct mutagens represented with nitrous acid and indirect mutagens represented with U.V. light to isolate rifampicin and chloramphenicol mutants. The study ensured the sensitivity of bacterium for mutagenesis then possessing SOS repair system .