Hydrocarbon Biodegrading Potentials of a Proteus vulgaris Strain Isolated from Fish Samples

A Proteus vulgaris bacterium SR-1 was isolated from a freshly killed fish sample collected close to the point of crude oil spill in the Niger Delta region, Nigeria. Problem statement: The application of native bacterial species in bioremediation processes has long been desired, because they would be cost effective and efficient in terms of acclimation time. The ability to isolate high numbers of certain oil-degrading microorganisms from oil-polluted environment is evidence that these microorganisms are the active degraders of that environment. In this study, we reported the potential of a candidate bacterium- Proteus vulgaris SR-1 in the biodegradation of Bonny light crude oil, diesel and kerosene. Approach: To screen for oil degrading capability, the bacterium was cultivated in Minimal Salts Medium (MSM) supplemented with 1% (v/v) sterile Bonny Light Crude Oil (BLCO). Oil degradation was monitored by measurement of turbidity using a spectrophotometer and the pH, total viable counts of the culture fluids were determined at time intervals as biodegradation indices. The ability of strain to degrade diesel and kerosene oils was also studied while the level of used hydrocarbon degradation was determined using the gravimetric analysis. The bacterium was screened for presence of Plasmid DNA and implication of plasmid in hydrocarbon degradation was investigated. Results: (1) The bacterium utilize hydrocarbons as sole source of carbon and it biodegraded Bonny light crude oil, kerosene and diesel media by as much as 78, 79 and 73.8% respectively, in the presence of 1.0% NaCl (w/v) after 96 h. The total viable count after 96, 120 and 168 h of biodegradation of the test hydrocarbons range between 6.2 and 9.1 log₁₀ c.f.u mL^-1, (2) The results showed that increasing NaCl concentration in water had decreasing effect on hydrocarbon degradation. (3) pH of media decreased from 7.0 to between 3.29 and 5.02 during the reaction period while growth increases. (4) Plasmid analysis revealed the presence of a plasmid of approximately 9.1 kb in the bacterial isolate. Conclusion/Recommendations: The results of this study showed that Proteus vulgaris SR-1 is a highly adapted bacterium with great potential to biodegrade hydrocarbons and the genes responsible for hydrocarbons biodegradation could be located on the (9.1 kb) plasmid it harbors.