Screening And Identification Of Prometryn-degrading Bacterium DY-1 And Its Characteristics

Prometryn, also named Gesagard and Prometrex, was created by Swiss company Geigy in1959. With chemical name 2-Methylmercapto-4,6-Bis(isopropylamino)-1,3,5-triazine, prometryn belongs to sym-triazine selective herbicides, and is one of the most typical sym-triazine herbicides. Prometryn has a stable structure so it doesn’t tend to be hydrolyzed, photolyzed or naturally degraded under general conditions, and can persistently exist in nature. With the wide use of prometryn and the expansion of its using scope, prometryn can be delivered to underground water system by rainfall, surface water and the osmosis effect of roots of plants, and accumulate there. Then following the food chain, prometryn is first passed on to plants and animals, then continues to be transmitted through animal migration and predation, and finally is passed to human beings and do harm to the health of human beings.Making use of enrichment culture method, this experiment filtered out a strain that could degrade prometryn efficiently from the rice fields in Beilin District of Suihua, which have been given prometryn constantly, and named the strain DY-1. This strain could survive taking prometryn as its only carbon source. Tested by high performance liquid chromatography(HPLC),DY-1 was able to degrade the prometryn with concentration of 50 mg/L in the medium within 48 hours. With a degradation rate of 99.1%, it showed excellent degradation performance. After the strain growed for 48 hours, one factor(temperature, pH or the original concentration) was changed while the other two factors were kept the same. By testing its OD600 value, the optimal growth conditions for degrading bacterium DY-1 was concluded: the temperature should be 30 degrees Celsius, pH should be 7.0, and the original concentration should be 3%-5%. Its most suitable carbon source is sucrose and the most suitable nitrogen source is ammonium nitrate. The strain was identified as Pseudomonas sp. based on its morphological, biochemical and physiological characteristics as well as 16 S rDNA sequence homology. The 16 S rDNA gene sequence of degrading bacterium DY-1 was registered in GenBank with accession number KU054384. This research has provided the theoretical basis for the biodegradation of prometryn in soils as well as the bioremediation of soils contaminated by prometryn.