Isolation and Identification of Diesel oil-degrading Bacteria in used engine oil contaminated soil

This study was conducted to isolate and identify bacteria associated with spent diesel oil contaminated site by collecting three replicates contaminated soil from the works department of Admiralty University of Nigeria, while the pristine soil was obtained from the biological garden. pH and temperature of all the samples were checked and the bacteria isolates were identified by morphological and biochemical techniques using the taxonomy scheme of Bergey’s Manual of determinative bacteriology. The pH and temperature was highest (6.06 to 6.26) and (27 to 30◦C) in the contaminated soil than the pristine soil (5.83) and (23◦C). The mean microbial load count was highest (10.0x10^5cfu/ml)in the diesel oil contaminated soils than the pristine uncontaminated soils (9.0x0x10^5cfu/ml). However, there was no significant difference between the microbial loads in the soil samples. Eight bacteria species were obtained from the contaminated soil while six were obtained from the pristine soil. Klebsiella spp., Enterobacterae riginosa, Pseudomonas sp. and Escherichia coli showed highest growth in the contaminated soil and therefore may be considered as effective in the degradation of spent diesel oil hydrocarbons. It is likely that these bacteria when employed independently may be used to degrade hydrocarbons. Further research is necessary to assay for the degradative ability of the microorganisms.