Heavy Metal Tolerance Bacillus spp Isolated From Crude Oil Polluted Soil

Abstract

Introduction: Indiscriminate dumping of spent oils enriched with heavy metals has led to increase in heavy metals load in the soil. Heavy metals exert toxic effects on biodegradation of organic pollutant in cocontaminated soil and there is need to find suitable strategies for their removal. Aim: The aim of this study was to assess the heavy metals resistance capability of indigenous Bacillus species in hydrocarbon polluted soil to nickel (Ni), Cadmium (Cd), Lead (Pb) and Chromium (Cr). Materials and Methods: Heavy metal tolerant bacteria were isolated from hydrocarbon polluted soil using Luria-Berthani agar supplemented with the respective metals and spread plate techniques. The isolates were putatively identified on the basis of 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 hydrocarbon polluted soil co-contaminated with heavy metals.