Background and Purpose

Heavy hydrocarbons such as toluene are one of the main petrochemical and oil products that due to high toxicity and carcinogenic properties, are now considered as a widespread contaminant. Meantime, the capabilities of some micro-organisms to change or degrade oil products are proven. The purpose of this study as the first step of our Bioremediation plan is the identification of hydrocarbon degrading bacteria from the contaminated soil Shiraz oil refinery site.

Materials and Methods

After sampling the refinery contaminated soil at three points from three stations in spring and summer, determining the distribution of toluene-degrading bacteria was performed through microbial count test by variable plate count method as an indicator of microbial activity. Toluene-degrading bacteria in MSM saline medium with toluene as a carbon source were isolated. After screening and identification of superior strains through biochemical and molecular detection method (16SrRNA), the growth curve of various concentrations of toluene was studied during 8 days.


The numbers of bacteria per cfu / ml per gram of soil were 6.4 ×106, 3.4× 106, 3.2×106 in spring and 3.3×108, 5.4×108, 6.4×109 in summer, respectively. Identified strains belonged to the Klebsiella, Kluyvera, Staphylococcus and Pseudomonas genus. Klebsiella had the highest growth in concentrations of 1, 2, 3, 4 mol per liter over 8 days. Statistical analysis between strains by ANOVA and DUNCAN tests indicated a meaningful difference at the 0.05 level.


The results of this study indicated the capability of the local mentioned strains as the first aim in degrading heavy hydrocarbons. In addition Identification of diversity and efficiency of the local micro-organism for the next stage of bioremediation plan was considered.

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