Characterization and effect of gamma irradiation on indigenous chloroaromatic degrading bacteria

Ten bacterial strains isolated from indigenous microbial communities of different soil and water samples were characterized and examined by light and scanning electron microscope (SEM). The bacterial strains included gram positive short rods Bacilli, gram positive spore forming Bacilli and gram positive Cocci. The sensitivity of each strain to gamma irradiation revealed that the gram positive strains were more sensitive than the gram positive strains. The dose of 3 KGy completely reduced the viable count of the isolates MAM-104,106,107, 108 and 109 (gram positive short rods), while the most resistant bacterial strains were the isolates MAM-96 (10 KGy reduced its viability by 2.5 log cycles). The most promising gram positive spore forming Bacillus (isolate MAM-96) was capable of growing on 8 mM of chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, 2-chloroaniline, 4-chloroaniline and its mutant on 4-chloro phenol singly as a sole carbon and energy source and when grown on 3m M of the chloro aromatic compounds for 15 days, such compounds can be degraded with values of 100%, 100%, 98.5%, 98.3%, 95.3% and 15%, respectively. Also, this strain when grown on 1 mM 2,6-dichlorophenol iodophenol sodium salt can degrade this compound by 77% after 15 days incubation period