Biodegradation And Regulation Of The S-Triazine Herbicides

Four new aerobic bacteria, which could degrade and mineralize atrazine and other s-triazine dericatives were isolated from the different locations impacted by herbicide spills. Their isolation, characterization and degradation on s-triazines were studied under a variety of cultural conditions.1. Based on Biolog tests and 16S rRNA sequence analysis, four strains were identified as a Agrobacterium sp. strainROl, Pseudomonas sp. strain R02, Agrobacterium sp. strain R03 and Pseudomonas sp. strain R04, respectively. They were gram-negative motile rods, able to use atrazine as a sole source of carbon or nitrogen.2. Four strains were able to catalyze atrazine side-chain removal and ring cleavage, had the broader substrate range. They were capable of metabolizing several s-triazine herbicide with different degradative rates. Strain R02 was capable of metabolizing atrazine at very high concentrations (>1000ppm).3. In comparative growth experiments, the consortium performed significantly better, both in attaining maximal cell density and inremoving atrazine from growing cultures.4. Sorption of CIET onto cells of Agrobacterium sp. strain R01 was studied with autoclaved and 0.2%(wt/vol) sodium azide-containing cell suspensions. Using the same low concentration of cell but autoclaved or treated with sodium azide, approximately 83% of 0.5um CIET adsorbed within 3 to 5 min. Sorption of CIET to R01 seem to be passive, since dead cell sorbed as well as live cells. Soil particles were capable of adsorbing CIET, CIET adsorption to soil particles and bacterial cells could decrease in metabolism and mineralization of CIET.5. Cell-free protein supernatants of strain R02 transformed 90% of the atrazine to water-soluble materials in 1 h. The crude extract could be stored at -70癈 for several months with no loss of activity. Boiled cell fractions failed to metabolize atrazine. These data suggested that atrazine was transformed by solube enzymes from strain R02.6. The addition of strain R04 was somewhat effective,indicating that this organism can survive and metabolize atrazine in a soil environment. In laboratory studies, solium citrate was an excellent carbon source for supporting atrazine metabolism. The effectiveness of sodium citrate alone suggests that indigenous bacteria are present and require only the proper conditions to stimulate the metabolism of atrazine.7. With the fixed-bed reactors used in this study we were able to demonstrate the practicability of eliminating atrazine in water through biological degradation. The proper conditions might improve reactor performance.