Qualitative Assessment of Growth Utilization of Crude Oil by Genetically Modified Non-Crude Oil-Degrading Refinery Effluent Indigenous Bacteria

Abstract

Genetically modified non-hydrocarbon utilizing bacteria indigenous to refinery effluent were investigated for potential utilization of crude for growth. Bacteria were isolated from refinery effluent and screened for hydrocarbon growth utilization potentials using Bushnell-Haas media incorporated with crude oil. The isolates were identified by molecular methods and the hydrocarbon utilizers were Bacillus cereus, Enterobacter mori and Pseudomonas aeruginosa while those incapable of growth in the crude oil medium were Escherichia coli and Proteus columbae. The non-hydrocarbon utilizers were modified by conjugation with hydrocarbon utilizers and the success was indicated by growth in Bushnell Haas medium supplemented with crude oil, Nutrient and MacConkey media. The modified organisms (recombinants) had similarities in phenotypic characteristics with the wild (donor) organisms.  Growth of the recombinants in crude oil medium varied, but the three recombinants involving E. coli (P. aeruginosa/E. coli, B. cereus/E. coli, E. mori/E. coli) had the best growth (+++). Agarose gel electrophoresis of selected functional genes revealed that the organisms tested positive for PAH-RHD gene. The presence of PAH-RHD gene indicated the capacity of the modified organisms to utilize the polyaromatic components of crude oil. Genetic modification of bacteria by conjugation with other bacteria from the same ecological niche in order to enhance degradation of hydrocarbon via bio-augmentation can be of advantage because of prior adaptation to the environment.