Abstract

Introduction: Indiscriminate dumping of spent oils enriched with heavy metals has led to increase in heavy metals load in the soil. Heavy metal exerts toxic effects on biodegradation of organic pollutant in co-contaminated soil and there is need to find suitable strategies for their removal. Aim: Our aim was to assess the tolerance ability of the indigenous Bacillus spp in crude oil polluted soil to the presence of nickel (Ni), cadmium (Cd), lead (Pb) and chromium (Cr). Materials and Methods: Heavy metal tolerance bacteria was isolated from the crude oil polluted soil using Luria-Berthani agar supplemented with the respective metals and spread plate techniques. The isolates obtained were putatively identified using their colonial morphology and biochemical characteristics and their antibiotics susceptibility pattern were evaluated using disc diffusion method. Results: The maximum tolerable concentration (MTC) of the four heavy metals to the selected isolates was 2 mM. Four bacteria isolates able to withstand the MTC were putatively identified as Bacillus subtilis, Bacillus megaterium, Bacillus laterosporus and Bacillus polymyxa. Out of the four Bacillus species, only B. laterosporus did not show multiple tolerance to the tested antibiotics which show that there is correlation between heavy metal tolerance and antibiotics resistance by the isolates. Conclusion: Multiple heavy metal tolerance Bacillus spp were isolated from crude oil polluted soil. These bacteria could be suitable agents for bioaugmentation of crude oil polluted soil co-contaminated with heavy metals. Key words: Antibiotics resistance, Bacillus spp, Crude oil, Multiple tolerances, Heavy metals. Introduction: Indiscriminate dumping of spent oils enriched with heavy metals has led to increase in heavy metals load in the soil. Heavy metal exerts toxic effects on biodegradation of organic pollutant in co-contaminated soil and there is need to find suitable strategies for their removal. Aim: Our aim was to assess the tolerance ability of the indigenous Bacillus spp in crude oil polluted soil to the presence of nickel (Ni), cadmium (Cd), lead (Pb) and chromium (Cr). Materials and Methods: Heavy metal tolerance bacteria was isolated from the crude oil polluted soil using Luria-Berthani agar supplemented with the respective metals and spread plate techniques. The isolates obtained were putatively identified using their colonial morphology and biochemical characteristics and their antibiotics susceptibility pattern were evaluated using disc diffusion method. Results: The maximum tolerable concentration (MTC) of the four heavy metals to the selected isolates was 2 mM. Four bacteria isolates able to withstand the MTC were putatively identified as Bacillus subtilis, Bacillus megaterium, Bacillus laterosporus and Bacillus polymyxa. Out of the four Bacillus species, only B. laterosporus did not show multiple tolerance to the tested antibiotics which show that there is correlation between heavy metal tolerance and antibiotics resistance by the isolates. Conclusion: Multiple heavy metal tolerance Bacillus spp were isolated from crude oil polluted soil. These bacteria could be suitable agents for bioaugmentation of crude oil polluted soil co-contaminated with heavy metals. Key words: Antibiotics resistance, Bacillus spp, Crude oil, Multiple tolerances, Heavy metals. Introduction: Indiscriminate dumping of spent oils enriched with heavy metals has led to increase in heavy metals load in the soil. Heavy metal exerts toxic effects on biodegradation of organic pollutant in co-contaminated soil and there is need to find suitable strategies for their removal. Aim: Our aim was to assess the tolerance ability of the indigenous Bacillus spp in crude oil polluted soil to the presence of nickel (Ni), cadmium (Cd), lead (Pb) and chromium (Cr). Materials and Methods: Heavy metal tolerance bacteria was isolated from the crude oil polluted soil using Luria-Berthani agar supplemented with the respective metals and spread plate techniques. The isolates obtained were putatively identified using their colonial morphology and biochemical characteristics and their antibiotics susceptibility pattern were evaluated using disc diffusion method. Results: The maximum tolerable concentration (MTC) of the four heavy metals to the selected isolates was 2 mM. Four bacteria isolates able to withstand the MTC were putatively identified as Bacillus subtilis, Bacillus megaterium, Bacillus laterosporus and Bacillus polymyxa. Out of the four Bacillus species, only B. laterosporus did not show multiple tolerance to the tested antibiotics which show that there is correlation between heavy metal tolerance and antibiotics resistance by the isolates. Conclusion: Multiple heavy metal tolerance Bacillus spp were isolated from crude oil polluted soil. These bacteria could be suitable agents for bioaugmentation of crude oil polluted soil co-contaminated with heavy metals.

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