Screening, identification and degrading gene assignment of a chrysene-degrading strain
A predominant chrysene-degrading strain named CT was isolated from the activated sludge of Zhenjiang coking plant. The strain was initially identified as Paracoccus aminovorans by the results of morphological observation, physio-biochemical test and 16S rDNA gene sequence analysis. Under the conditions of initial chrysene concentration of 40 mg/l, inoculation amount of 10% (V/V) at pH 7.0 and temperature of 35°C, the degradation efficiency of chrysene by the strain CT reached 85.2% within 8 days. Alkaline lysis was applied to the extract plasmids from strain CT to confirm the location of chrysene-degrading genes. A plasmid, greater than 15 kb, was detected. The transformants obtained the ability to degrade chrysene when the plasmid of strain CT was transformed to competent cell of Escherichia coli DH10B, and could remove 43% of chrysene in the solutions with concentration of 30 mg/l within 8 days. But the mutation lost the ability to degrade chrysene when its plasmid was eliminated by sodium dodecyl sulfonate (SDS) and high temperature. This indicated that the plasmid of strain CT carried chrysene-degrading genes.
Key words: Chrysene, degrading strain, Paracoccus, degrading gene, plasmid.