[Characteristics of a 3-phenoxybenzoic acid degrading-bacterium and the construction of a engineering bacterium]

A bacterium capable of utilizing 3-phenoxybenzoic acid (3-PBA) as sole carbon source was isolated from petroleum-contaminated soil. This bacterium, designated as BA3, was identified as Sphingobium sp. according to its physiological & biochemical characteristic and the similarity analysis of its 16S rDNA sequence. Strain BA3 was able to degrade 99% of 100 mg x L(-1) 3-phenoxybenzoic acid within 60 h. The optimal pH and temperature for the degradation were 7.0 and 30 degrees C, respectively. The degradation efficiency was related positively to initial inoculum size. The pyrethroid hydrolase gene (pytH) gene was amplified from the genomic DNA of Sphingobium sp. JZ-2 by PCR. Recombinant plasmids pPYTH was constructed by ligating pytH gene into the broad host vector pBBRMCS- 5. Under the help of plasmid RK600, pPYTH was transferred into Sphingobium sp. BA3 to construct engineering strain BA3-pytH; Fenpropathrin degradation experiments showed that strain JZ-2 was able to degrade only 60% of 50 mg x L(-1) fenpropathrin in 48 h while engineering strain BA3-pytH was able to degrade over 95% of 50 mg x L(-1) fenpropathrin under the same conditions. Even more, BA3-pytH could rapidly degrade 3-PBA, metabolic products of pyrethroid insecticides, eliminating the inhibition of 3-PBA to pyrethroid hydrolase. Therefore, in contrast to strain JZ-2, engineering strain BA3-pytH had more advantages in bioremediation of pyrethroid insecticides contaminated environment.