Community Analysis of Soil Microorganisms Capable of Enhanced EPTC and Atrazine Degradation.

EPTC (S-ethyldipropylthiocarbamate) and atrazine (2-chloro-4-(ethylamine)-6-(isopropylamine)-s-triazine) are widely used herbicides in the United States. Negative impacts of excess exposure of these herbicides, especially atrazine, are well documented and include environmental pollution and reduced animal/human health. Thus their rapid degradation after application is important to prevent negative impacts. Microorganisms naturally can degrade synthetic chemicals by mineralizing them and using the carbon and other elements as nutrient sources. Many pesticide-degrading microorganisms have been reported, but most have been studied using standard cultivation laboratory techniques. We used a culture independent approach to identify organisms capable of degrading these herbicides and also to follow the pathway and mechanism of their degradation. Studies have reported that the EPTC degradation pathway involves thc family of genes and the atrazine degradation pathway comprises the atz and trz family of genes. We used two different soils (Wooster silt loam and Luray silty clay loam) for this study. The soils were continuously exposed to the herbicides and soil subsamples were collected at different times during this exposure. A polymerase chain reaction (PCR) technique was used to monitor the appearance of the genes involved in the degradation to better understand the sequential pathway. We also used the PCR-DGGE method to characterize the bacterial diversity involved in the degradation of the herbicides. A polymerase chain reaction (PCR) was conducted using a set of universal bacterial primers that amplify the 338 to 518 region of the 16s rRNA gene of bacteria. Denaturing gradient gel electrophoresis (DGGE) analysis was used to separate the PCR products and to compare the microbial diversity among the two soil types. Amplification products were cloned and sequenced and compared to gene databases. Results show that soil microbial population is greatly influenced due to the exposure of EPTC and atrazine.