Symbiotic Degradation Of Crude Oil

A review of: Hii, Y.S., Law, A.T., Shazili, N.A.M., Abdul-Rashid, M.K., Lee, C.W., (2009), Biodegradation of Tapis blended crude oil in marine sediment by a consortium of symbiotic bacteria, International Biodeterioration & Biodegradation, 63, 142-150

As the human population increases, so does its demand for fossil fuels, this raised demand has lead to larger, and more frequent transportation modes for distribution, one of the most widely used is in large ocean tankers. The increased traffic of these leads to an increased risk of oil spills in the marine environment. The spillages of oil in the world oceans is a huge threat to the marine habitat and the organisms in it. The most affected part of the habitat due to oil spills is in the sediment, and considering the importance of the habitat provided by marine sediments, this is very problematic. Oil also has a longer residential time in sediments when compared to water, and can pose long-term hazards to marine life.

The aim of this study is to provide information on the consortium of bacteria to combat oil pollution in the environment. This will be done by determining the identity of bacteria that are responsible for degrading blended crude oil. Also determining the effectiveness of the bacteria in the degradation of higher molecular weight hydrocarbons. The test was carried out by preparing flasks containing 100g sterilized sediment material along with 1g of crude oil, and adding to them the bacterial population. Bacteria were identified using direct 16S rDNA sequencing. Data analysis consisted of non-parametric analysis when data was not normally distributed and parametric analysis when data was normally distributed. A biodegradation rate was formulated and these were tested using an ANOVA test and Tukey’s test.

The results show that, under optimal conditions, the bacteria responsible for the degradation of the crude oil, P. pseudoalcaligenes, degraded 583.3mgkg^-1 of the blended crude oil from 1000mgkg^-1 oil contaminated sediment over a period of 10 days.

The identified bacteria consisting of P. pseudoalcaligenes, was found to drastically increase the degradation rate of the blended crude oil in the sediment. A symbiotic relationship was observed between the P. pseudoalcaligenes and E. citreus when the two populations are present, the degradation rate is further increased and allowed for the degradation of polycyclic aromatic hydrocarbons. These symbiotic relationships can be used to formulate bacterial consortias for degradation of crude oil compounds, these can be mixed with other isolated bacteria from different locations, however the symbiotic relationships are highly species dependent and will not be universal.