Characterization of acetanilide herbicides degrading bacteria isolated from tea garden soil.

Three different green manures were added to the tea garden soils separately and incubated for 40 days. After, incubation, acetanilide herbicides alachlor and metolachlor were spiked into the soils, separately, followed by the isolation of bacteria in each soil at designed intervals. Several bacterial strains were isolated from the soils and identified as Bacillus silvestris, B. niacini, B. pseudomycoides, B. cereus, B. thuringiensis, B. simplex, B. megaterium, and two other Bacillus sp. (Met1 and Met2). Three unique strains with different morphologies were chosen for further investigation. They were B. megaterium, B. niacini, and B. silvestris. The isolated herbicide-degrading bacteria showed optimal performance among three incubation temperatures of 30 degrees C and the best activity in the 10 to 50 microg/ml concentration of the herbicide. Each bacterial strain was able to degrade more than one kind of test herbicides. After incubation for 119 days, B. cereus showed the highest activity to degrade alachlor and propachlor, and B. thuringiensis to degrade metolachlor.