Isolation, Identification And Characterization Of A New Synthetic Pyrethroids Degrading Bacterium Gordonia Sp.D2 And Its Phylogenetic Analysis

The most widely used pesticides mostly in the classes of organochlorines, organophosphates, carbamates and synthetic pyrethroids in terms of the chemical structures. Synthetic pyrethroids (SPs) ranks the second insecticides, account for 20% of the world insecticide market, and cover up about one third in our country. Extensive and long term usage has given rise to much public concern about its residues and harmful effects; microbial degradation has been an interesting field under investigation in recent years.From the activated sludge sample collected from Shandong Dacheng Pesticides Co. Ltd., one bacterium D2 that could use cypermethrin as the sole carbon source was isolated and identified as Gordonia sp. Strain D2 has an obvious rod-ball transformation phenomenon; it was a long rod at first when cultured and transformed to ball at last. All chemotaxonomic and physiological characteristics are coinciding with Gordonia sp. After analyzed by gas chromatography, the degradation rate of strain D2 was 25% in 4d, 42% in 7d and 52.3% in 8d. When inoculated at 30% level, the degradation rate was better, reaches 73.7% in 8d. The optimum biodegradation was at pH 7, 30℃; addition of extra carbon source could greatly improve the degrading ability.Strain D2 could also degrade p-nitrophenol, methyl parathion, endosulfan, fenpropathrin, and methamidophos. The maximum enduring concentrations are: 1200mg/L for cypermethrin, 800mg/L for fenpropathrin, 200mg/L for p-nitrophenol, 300mg/L endosulfan, and 150mg/L for methamidophos. Strain D2 was sensitive to mostly used antibiotics, when released to the environment for bioremediation; it won't be prevalent among the autochthon bacteria without resistance factor.The nucleotide sequence data were deposited in the GenBank nucleotide sequence database with the following accession numbers: DQ787430 (16S rDNA gene) and DQ913892 (gyrB gene). The phylogenetic analysis using 16S rRNA, gyrB and GyrB sequences shows that 16S rRNA gene is suit for identifying the isolate to the genus level, gyrB gene and GyrB amino acid sequences are more adapted for phylogenetic analysis.