Analysis of Bacterial Diversity during Bioremediation of Gasoil-contaminated Soils with Different Salinities

Bioremediation is a proven technology for treatment of contaminated soils. Soil physico-chemical properties and microbial composition are key factors for the successful implementation of this technology. In this study, we evaluated the bacterial diversity during bioremediation of gasoil-contaminated soils with different salinities. The results of TPH analysis indicated an inverse relationship between soil salinity and TPH degradation extent, so that TPH removal decreased from 61% in the non-saline soil to 33% in hypersaline soil (8% NaCl) from the Hoze Soltan salt lake. Culture-independent analysis of soil bacterial diversity during bioremediation process showed that Xanthomonas was dominant in the microcosm of Hoze Soltan (8% salinity), Marinobacter and KSA1 were dominant in microcosm of the Rudeshur (5% salinity) and Achromobacter, Iamia and Xanthomonas had the highest frequency in microcosm of the Khorshid-Abad farmland (0% salinity) during bioremediation. The results of culture-dependent analysis showed that Bacillus genus was dominant in the microcosms of Hoze Soltan and Rudeshur. However, Proteobacteria including the genera Microvirga, Brevundimonas, and Hyphomonas were dominant in microcosm of the Khorshid-Abad. The obtained results suggest that the soil salinity has a considerable effect on the microbial flora and bioremediation success of gasoil-contaminated soil and accordingly the simultaneous application of both culture-dependent and independent methods can provide a better comprehension about petroleum hydrocarbon biodegradation.