Bioremediation potential of indigenous gram-positive bacteria isolated from contaminated soil with polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) were extensively spread in the environment and are regarded as one of the mutagenic and carcinogenic agents on living creatures. Among the vast variety of procedures for the elimination of contamination, biological removal is capable of transmuting pollutants into innocuous and nontoxic substances using less amount of energy, chemicals and time. The study was aimed at evaluating the possibility of growth of the indigenous bacteria isolated from oil-polluted soils, in the presence of PAH compounds in the laboratory, and also identifying them by using the method of PCR. Specimens of the research were isolated from environmental gasoline and oil-polluted soils from the Isfahan City refinery. Initially, the native bacteria were separated from the contaminated soil with such compounds by utilizing a basic medium containing the concentration of 12.8 mg/l in 16 PAH compounds. Then, those bacteria which were able to grow and reproduce in the presence of the compounds identified through biochemical experiments and determination of genome sequence and consequently registered as new species. The results obtained in the study substantiated that approximately 13.3% of the total heterotrophic bacteria possess a degradable ability of the hydrocarbons. After the evaluation of biochemical tests and gene sequencing, it was disclosed that the isolated indigenous bacteria belonged to Bacillus licheniformis ATHE9, Bacillus mojavensis ATHE13 and a particular species of Bacillus (ATHE10). The results of the present research verify the importance and proficiency of the native bacteria in the terms of the elimination of PAHs pollutions in contaminated areas.