Characterization of Microbacterium sp. F10a and its role in polycyclic aromatic hydrocarbon removal in low-temperature soil.

A polycyclic aromatic hydrocarbon degrading bacterium isolated from oil-polluted soil was identified as Microbacterium sp. F10a based on 16S rDNA gene sequence analysis. Plant growth promoting characteristics of the strain, degradation rate of phenanthrene and pyrene, and cell surface hydrophobicity characteristics of the strain were further characterized. The strain was also evaluated for promoting the growth of wheat and phenanthrene and pyrene removal from soil artificially contaminated with a mixture of phenanthrene (200 mg.kg-1) and pyrene (150 mg.kg-1) in pot experiments. The strain had the plant growth promoting characteristics of producing indole acetic acid, siderophore, and 1-aminocyclopropane-1-carboxylate deaminase activity and solubilizing inorganic phosphate. The strain also has a cell surface hydrophobicity that could increase the aqueous polycyclic aromatic hydrocarbon solubility. High-performance liquid chromatographic analysis showed that the degradation rates of phenanthrene (50 mg.L-1) and pyrene (20 mg.L-1) were 98% and 65%, respectively, under 28 degrees C after 7 days. Inoculation with the strain was found to significantly increase (p < 0.05) the growth of wheat and phenanthrene and pyrene removal in the unplanted or planted soils in a low-temperature environment. There were no significant differences in culturable bacterial numbers between live bacterial inoculation and dead bacterial inoculation controls in the unplanted and planted soils. However, the numbers of polycyclic aromatic hydrocarbon degrading bacteria were significantly greater in the inoculated planted or unplanted soils compared with the dead bacterial inoculation controls.