[Isolation, degradation and phylogenetic analysis of methylparathion degradative strain X4]

The strain X4 was isolated from polluted wastes of Shandong Huayang Pesticide Chemical Industry Group Co., Ltd. It was cultured with methylparathion and p-nitrophenol, a kind of intermediate during methylparathion degrading process, and used them as the sole carbon source and decomposed them into carbon dioxide and wastes. It is identified as Arthrobacter sp. by means of a series of tests, and it has visible sphere-pole variable cycle. It is bacilliform when it is cultured in nutrient broth medium within 36h, then it become short gradually, and ultimately become uniform sphericity. Bacilliform strains array in "V" or "Y" shape. It has flagellum, moveable, no sporangium, oxidates glucose: The degradative ability to pesticides of X4 was determined by gas chromatography (GC) and spectrophotometer, and the degradative rate for methylparathion at 50mg/L and rho - nitrophenol at 50mg/L is above 99% within 7h. Moreover, X4 also can degrade other organophosphate pesticides quickly. The degradative rate for methamidophos, chlorpyrifos and carbofuran is 64%, 54% and 68%, respectively. The maximal tolerant concentration of X4 to MP, PNP, methamidophos, chlorpyrifos and carbofuran is 1700mg/L, 500mg/L, 500mg/L, 300mg/L and 300mg/L, respectively. All of the above tests were determined at 30 degrees C , pH7, with an inoculum of 30% . At the same time, 16S rRNA sequence of X4 is obtained, and the similar sequences to X4 were selected from GenBank by BLAST program and the phylogenetic tree with these sequences was constructed, the relationship between X4 and referenced strains was worked out. At present, methylparathion and p-nitrophenol degradative strains reported are mostly Pseudomonas sp., Flavobacterium, Alcaligenes sp. and so on. Furthermore, those strains can only degrade MP and PNP partially. It is reported firstly here that Arthrobacter sp. can degrade both MP and PNP to small molecule synchronously and effectively. Finally, the strain X4 shows a huge potential to be used in a bioremediation application for the treatment of methlparation residues, and further research may lead to an alternative route of disposal for use in agriculture or industry.