Phylogenetic Relationship of Bacterial Species Involved in Bioremediation of Hydrocarbon Polluted Soils

The bio-stimulation of hydrocarbon degrading microbial population in soil using agricultural wastes was carried out. Top soil (0-25 cm depth) from three points were bulked to form composite soil samples, 6 kg each of the composite soil sample was weighed and transferred into 150 plastic buckets with drainage holes at the base. The soil in each plastic bucket was spiked with 300 ml crude oil and amended with different concentrations of agro-wastes and allowed for duration of 30, 60 and 90 days. The soil samples were then collected and analysed for both total heterotrophic bacterial counts and crude-oil utilizing bacterial counts. Data collected were subjected to a three-way analysis of variance and significant means were separated using Least Significant Difference Test at 5% probability level. The result showed that the application of the amendments increased the bacterial counts in the soil at different treatment levels. However, a higher proliferation rate was observed with bacteria counts exposed to higher waste concentrations compared to their counterparts exposed to lower waste concentrations. The phylogenetic relationship of the hydrocarbon degrading bacterial species shows that the identified bacteria were in two clusters: cluster 1 consist of Bacillus cereus, Bacillus thuringiensis, Bacillus altitudinis, Pseudomonas aeruginosa, Proteus mirabilis and Proteus penneri, while cluster 2 consist of Serratia marcescens, Providencia rettgeri and Enterobacter asburiae. The bacterial species obtained shows a greater relationship, this imply that the similarity of the bacterial species could be the reason for their high proficiency in degrading the hydrocarbons in the soil.