Bacterial and fungal contributions to chlorothalonil degradation in soil

Abstract

The contributions of bacteria and fungi to the degradation of a chloroaromatic fungicide, chlorothalonil, in soil were evaluated quantitatively by a selective inhibition method. A mixture of ampicillin, chloramphenicol, and tetracycline was used to estimate the bacterial capacity, and cycloheximide to estimate the fungal capacity. A mixture of nutrient broth and yeast extract (NB + YE) was added to the soil to minimize the partial sterilization effect by antibiotics. The degradation of chlorothalonil was measured for a period of 6 h when the degradation rate and the carbon dioxide evolution rate were constant. The contribution rates estimated with the addition of NB + YE showed the same trend as the estimates with the addition of the dried powders of chlorothalonilsusceptible microorganisms, indicating the validity of NB + YE as a substrate for the chlorothalonil-degrading microorganisms. The contribution of the degrading fungi increased in the soils receiving farmyard manure (FYM). It was suggested that the accelerated biodegradation of chlorothalonil in FYMamended soils was due to the activation of the degrading fungi. © 1998, Taylor & Francis Group, LLC.