In the present research investigation, 13 indigenous bacteria (from CQ1 to CQ13) were isolated from soil collected from Changqing oil field of Xi'an, China.

In the present study, 12 indigenous diesel‐oil‐degrading bacteria were isolated from the petroleum‐contaminated soils of the Changqing oil field (Xi’an, China). Measurement of the diesel‐oil degradation rates of these strains by the gravimetric method revealed that they ranged from 42% to 66% within 2 weeks. The highest degradation rates were observed from strains CQ8‐1 (66%), CQ8‐2 (62.6%), and CQ11 (59%), which were identified as Bacillus thuringiensis, Ochrobactrum anthropi, and Bordetella bronchialis, respectively, based on their 16S rDNA sequences. Moreover, the physiological and biochemical properties of these three strains were analyzed by Gram staining, catalase, oxidase, and Voges–Proskauer tests. Transmission electron microscopy showed that all three strains were rod shaped with flagella. Gas chromatography and mass spectrometric analyses indicated that medium‐ and long‐chain n‐alkanes in diesel oil (C11–C29) were degraded to different degrees by B. thuringiensis, O. anthropi, and B. bronchialis, and the degradation rates gradually decreased as the carbon numbers increased. Overall, the results of this study indicate strains CQ8‐1, CQ8‐2, and CQ11 might be useful for environmentally friendly and cost‐effective bioremediation of oil‐contaminated soils.

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