Phylogenetic and Functional Gene Analysis of Crude Oil and Produced Water-Derived Sulphate-Reducing Bacteria

Phylogenetic and functional gene analysis of sulphate-reducing bacteria (SRB) from crude oil and produced water was carried out using molecular methods. The concentration of hydrogen sulphide (H2S) produced by SRB, as an indication of SRB presence, was determined using spectrophotometric sulphide assay. More H2S was observed to be produced at 55 ˚C than at 30 ˚C, with sample B found to produce more H2S at these temperatures than sample A. This implies more SRB contamination in sample B, possibly from subterranean water. DNA was extracted from enrichment after incubation in Postgate's medium at 30 ˚C and 55 ˚C for 28 days and amplified by Polymerase Chain Reaction (PCR) using primers specific for SRB functional genes. PCR products were cloned and sequenced. Sequence analysis of the clones was found to display 99 % homology to SRB of the genera Desulfovibrio. Clones were found to be different species of SRB as shown by the distances between them. Phylogenetic analysis was successful and showed affiliation of the clones to related members of sulphate-reducing bacteria and sulphur-oxidizing bacteria.