STUDY THE HEAVY METALS TOLERANCE, BIOSORPTION AND ANTIBIOTIC RESISTANCE OF BACILLUS CEREUS ISOLATED FROM DIESEL FUEL POLLUTED SOIL
The heavy metals tolerance (chromium, cadmium, lead and zinc), biosortion of these ions and resistance of antibiotics were studied by using Bacillus cereus bacterium isolated from soil contaminated with diesel fuel. From 10 samples of soil polluted with diesel fuel, 7 isolates identified as rod of spore former (Bacillus spp.) and 3 of these isolates (DB.1, DB.2, and DB.5) were identified as species (B. cereus), the Bacillus isolate DB.5 (B. cereus) showed the highest MIC, where the range was 200 mg/L for Zn to 750 mg/L for the Cr, and this isolate selected for the other experiments. It was found that the isolate exhibited resistance to most of the tested antibiotics. Where the isolate was resist to amoxillin, cloxacillin, cephalexin, ceftriaxone, cefoxitin and trimethoprim, also it was sensitive to erythromycin, azithromycin and gentamycin and intermediate sensitive to vancomycin. The effect of chromium on the growth of B. cereus in Cr containing medium in contrast with control, indicated that B. cereus without chromium (Cr) revealed a lag phase of 2-3 hrs, after this the bacterium showed accelerated growth rate with maximum growth at 20 hrs. The bacterium with Cr stress (treated) however, showed lag phase of 4-8 hrs and maximum growth at 24hrs. but the number of bacteria was less than in control. It was found that B. cereus attained its maximum Cr biosorption of 73% after 48 hrs of incubation, while the removal efficiency of Cd, Pb and Zn ions from aqueous solution was 51, 45, and 16 % respectively after 48 hrs of incubation. Study showed that the metals tolerant B. cereus can be used for heavy metals bioremediation and this tolerance was correlated with antibiotic resistance.