Characterization and catabolic genes detection of three oil-degrading Rhodococcus spp.北大核心CSCD

Oil pollution is one of the major factors causing environmental deterioration. Bioremediation of oil contaminated environments by microorganisms attracts much research attention. This study aimed to screen efficient oil-degrading bacteria from oil contaminated soil and analyze their characteristics and catabolic genes. Oil-degrading bacteria were screened from oil contaminated soil in minimal medium containing crude oil and identified by morphological, physiological and biochemical characteristics and 16S rDNA sequence analysis. Their growth and degradation characteristics were studied with ultraviolet spectroscopy and GC-MS analysis. The surfactant production was studied by adopting culture method. The major oil-degrading related genes were detected by t he PCR a mplification. As a result, t hree oil-degrading bacteria strains named KB1, 2182 and JC3-47 were isolated from the oil contaminated soil samples. The strains could use crude oil as the sole carbon source to degrade oil with a degrading rate of 41.02%, 32.26% and 55.90%, respectively, when cultured in minimal medium containing crude oil for 3 days. The bacteria were identified to belong to genus Rhodococcus. With 100% similarity of 16S rDNA sequences of the three strains with known ones of Rhodococcus, KB1 was preliminarily identified as Rhodococcus erythropolis, 2182 as Rhodococcus equi, and JC3-47 as Rhodococcus qingshengii. They grew well at 10-50 °C, with the initial pH of 3-9 and the NaCl concentration of 0-5%. The optimal temperature for bacterial growth was 35 °C, 35 °C and 30 °C respectively. KB1 and 2182 could grow at pH 2 and 9.0% of NaCl. The bacteria grew well in broth containing different organic substrates as sole carbon source, such as n-dodecane, n-octadecane, benzene, methylbenzene, xylene and naphthaline. KB1 and JC3-47 could grow well in broth containing pyrene. GC-MS analysis revealed that the bacteria could effectively degrade medium- and long-chain alkane components in crude oil. The bacteria produced biosurfactants and decreased the surface tension of the culture broth. They also showed adhesion activities to n-hexadecane. The oil-degrading related genes such as alkane monooxygenase, aromatic-ring-hydroxylating dioxygenase and catechol dioxygenase genes were detected in all the three strains. Besides, biphenyl dioxygenase genes were detected in KB1 and 2182. The isolated Rhodococcus spp. strains could effectively degrade petroleum hydrocarbons with high adaptabilities to extreme environments such as high salt and low temperature. They are supposed to be applied broadly in the bioremediation of oil contaminated soil in such environments.