Molecular characterization of crude oil degrading bacterial isolates from polluted soils and cow dung

Crude oil contamination of agricultural soil is frequent in the Niger- Delta Region of Nigeria and can devastate the soil thereby, negatively affecting the socio-economic lives of the people. This study aimed to characterize twelve bacterial isolates with potential for crude oil degradation using conventional and molecular tools. Isolates with potential for crude oil degradation were selected from among the crude oil degrading bacteria obtained from petroleum contaminated agricultural soils and Cow dung all in Ondo State, Nigeria. The identities of the isolates were confirmed via morphological and biochemical characterization and thereafter the CTAB method was used to prepare the DNA. PCR amplification of 16S rRNA gene of isolates was carried out using universal primers for bacteria. The PCR products were then purified using ethanol precipitation and thereafter sequenced with automated DNA sequencing machine. The sequence data were compared with gene sequences in GenBank database (NCBI) using a BLAST search to find closely related sequences. Phylogenetic analyses of 16S rRNA gene sequences were examined in order to determine the evolutionary relatedness of the isolates. Results revealed eight (8) gram positive bacteria consisting of Staphylococcus hominis, Geobacillus sp., Lactobacillus plantarum and four (4) different species of Bacillus, while the gram negative bacterial isolates were Brevundimonas diminuta, Klebsiella oxytoca, Esherichia coli and Enterobacter tabaci with 83% to 100% ribosomal RNA homology. Crude oil degrading bacteria characterized in this study can be developed as inoculums with high survival and activity to bioaugment the degradation of crude oil polluted agricultural soil.