Uptake,metabolism and effects of DDT,fenitrothion and chlorpyrifos on Tetrahymena pyriformis

The uptake and metabolism of DDT, fenitrothion and chlorpyrifos were studied in cultures of the ciliate protozoan Tetrahymena pyriformis. When cultures were treated with DDT in concentrations varying from 0.01 to 0.5 μg ml^?1, concentrations found in T. pyriformis were 3.8 to 335 μg g^?1 dry weight. The accumulation of fenitrothion ranged from 28.7 μg g^?1 in cultures treated with 1 μg ml^?1 to 2260 μg g^?1 in cultures treated with 10 μg ml^?1. Under similar experimental conditions chlorpyrifos was accumulated from 24.7 to 15400 μg g^?1. The patterns of uptake were dependent on the growth cycle, the ability of the organism to metabolise insecticide and the type of the insecticide used. Maximum accumulation of DDT, fenitrothion and chlorpyrifos occurred in 2, 4 and 6 h respectively. Tetrahymena metabolised DDT to DDD and DDE but failed to metabolise fenitrothion and chlorpyrifos. The effects on growth and morphology of T. pyriformis were studied over a period of 5 days. Higher concentrations (10, 50 and 100 μg ml^?1) of DDT inhibited only the growth of the organisms and did not change cell morphology. Fenitrothion was extremely toxic to the organisms and at 5 and 10 μg ml^?1 cells became more or less spherical and died after 48 h. However, concentrations of 0.5, 1 and 2.5 μg ml^?1 fenitrothion caused growth inhibition, but only at 2.5 μg ml^?1 was this permanent. Chlorpyrifos inhibited the growth of the organisms at 1, 5 and 10 μg ml^?1 but the morphology was affected only at 5 and 10 μg ml^?1.