Investigating the potential of bioremediation in aged oil-polluted hypersaline soils in the south oilfields of Iran.

To date, studies for bioremediation of oil-polluted hypersaline soils have been neglected or limited to specific spots. Hence, in this study, ten samples of oil field soils in the Khuzestan province of Iran were collected to evaluate bioremediation's feasibility. These samples were analyzed for their physicochemical properties as well as the most probable number of total and hydrocarbon-degrading bacteria. Thirty-nine hydrocarbon-degrading bacteria were isolated from these soils over a 1-month incubation in an MSM medium enriched with diesel oil as the sole source of carbon. As revealed by 16S-rRNA analysis, the identified strains belonged to the genera Ochrobactrum, Microbacterium, and Bacillus with a high frequency of Ochrobactrum species. Additionally, by using degenerate primers, the third group of alkB gene was detected in Ochrobactrum and Microbacterium isolates through the touchdown nested PCR method for the first time. Ochrobactrum species possessing the alkB gene showed the highest population, and therefore, the highest adaptation to harsh environmental conditions. Most isolates showed outstanding results in the ability to grow with crude and diesel oil and tolerate high salt percentages, biosurfactant production, and emulsification activity, which are considered the most effective factors in bioremediation of such environments. Considering the soil analysis, limiting factors in bioremediation like available phosphorous, and the abundance of bacteria with remediation traits in these soils, these extremely polluted environments can be refined.