Isolation and Identification of Chloroaromatic Degrading Bacterial Strain Isolated from Indigenous Microbial Communities of Petroleum Contaminated Soils

Soil and sludge samples polluted with petroleum waste from Cairo Oil Refining Company, Mostorod, Al-Qalyubia, Egypt for more than 41 years were used for isolation of indigenous microbial communities. These communities were grow on four chloroaromatic compounds [3-chlorobenzoic acid (3-CBA); 2,4-dichlorophenol (2,4-DCP); 2,6-dichlorophenol indole phenol (2,6-DCPP) and 1,2,4-trichlorobenzene (1,2,4-TCB)] as a sole carbon and energy source. The abilities of the eight different communities to grow and degrade these chlorinated compounds had been investigated by recording their growth (OD) and secretion of extracellular protein at zero time (initial), 7, 15 and 28 days of incubation period. Count of these communities was determined after 28 days incubation. The increase in bacterial count of the eight communities was ranging from 0.2 to 1.5 log cycles on 3-CBA, 1.0 to 2.3 log cycles on 2,4-DCP, 0.6 to 1.7 log cycles on 2,6-DCPP and 0.4 to 2.7 log cycles on 1,2,4-TCB. The highest total bacterial count (zero time) was 3.0×10 CFU/ml and 6 chloroaromatic degrading bacterial (CDB) count was 2.0×10 CFU/ml of community (3). The results cleared that 4 66% of bacterial count of community (3) was CDB. Only eighteen isolates were able to grow on one or more of the chloroaromatic compounds. Isolate MAM-24 have the ability to grow well on the three concentrations of 3-CBA, 2, 4-DCP, 1, 2, 4-TCB and the two concentrations of 2, 6-DCPP. The most promising bacterial isolate MAM-24 that have the ability to degrade the four compounds, was identified by comparative sequence analysis for its 16S-rRNA coding genes as member of the genus Bacillus. The 16S-rRNA of isolate MAM-24 showed similarity of 100% to Bacillus mucilaginosus (GQ866855) and it was identified as Bacillus mucilaginosus HQ013329. The dose response curve of this B. mucilaginosus indicated that as the dose of -radiation increased the viable count decreased exponentially. Dose of 10 KGy reduced the viable count by 3.5 log cycles.