BIODEGRADATION OF ATRAZINE BY AGROBACTERIUM-RADIOBACTER J14A AND USE OF THIS STRAIN IN BIOREMEDIATION OF CONTAMINATED SOIL

We examined the ability of a soil bacterium, Agrobacterium radiobacter J14a, to degrade the herbicide atrazine under a variety of cultural c onditions, and we used this bacterium to increase the biodegradation o f atrazine in soils from agricultural chemical distribution sites. J14 a cells grown in nitrogen-free medium with citrate and sucrose as carb on sources mineralized 94% of 50 mu g of [C-14-U-ring] atrazine ml(-1) in 72 h with a concurrent increase in the population size from 7.9 x 10(5) to 5.0 x 10(7) cells ml(-1). Under these conditions cells minera lized the [ethyl-C-14] atrazine and incorporated approximately 30% of the C-14 into the J14a biomass, Cells grown in medium without addition al carbon and nitrogen sources degraded atrazine, but the cell numbers did not increase. Metabolites produced by J14a during atrazine degrad ation include hydroxyatrazine, deethylatrazine, and deethyl-hydroxyatr azine. The addition of 10(5) J14a cells g(-1) into soil with a low ind igenous population of atrazine degraders treated with 50 and 200 mu g of atrazine g(-1) soil resulted in two to five times higher mineraliza tion than in the noninoculated soil. Sucrose addition did not result i n significantly faster mineralization rates or shorten degradation lag times. However, J14a introduction (10(5) cells g(-1)) into another so il with a larger indigenous atrazine-mineralizing population reduced t he atrazine degradation lag times below those in noninoculated treatme nts but did not generally increase total atrazine mineralization.