Isolation and Characterization of Novel Butachlor-Degrading Bacteria from Rice Paddy Soils

Four different bacteria capable of degrading butachlor, as well as five different syntrophic pairs of bacteria able to break down butachlor, were isolated from rice paddy soils in Korea. Genetic and phenotypic analyses were conducted to better understand their characteristics and behavior. All single isolates and syntrophic pairs were able to utilize butachlor as a sole carbon and energy source. Analysis of the 16S rRNA sequence showed that the isolates were related to members of the genus Rhodococcus and a new type of butachlor-degrading genus Sphingobium. The chromosomal DNA fingerprinting patterns of the butachlor-degrading bacteria and syntrophic pairs were analyzed using a technique called repetitive-sequence-based PCR (REP-PCR). The results showed that there were two different REP-PCR patterns found among the four independent butachlor-degrading bacteria, and ten strains of five different syntrophic pairs produced a total of eight distinct DNA fingerprints. Through the use of gas chromatography-mass spectrometry (GC-MS) analysis, it was observed that the syntrophic pair was capable of breaking down butachlor using various chemical pathways, such as 2-chloro-N-(2,6-diethylphenyl) acetamide (CDEPA), 2,6-diethylphenyl isocyanate, 2,6-diethylaniline (DEA), and 2-ethylaniline.