Kanoknit Sornkong, Poonsuk Prasertsan, and Vorasan Sobhon

pp. 103 - 110

Abstract

DDT is an organochlorine pesticide that can persist in the environment resulting in environmental problem with chronic effects on human and animal health. The determination of p,p′-DDT in soil samples from 23 agricultural areas in Songkhla Province found DDT residue in the ranges of 0.17-9.84 ng/g soil. After repeated culturing in mineral salts-yeast
extract medium (MSYM) with an addition of 25 ppm p,p′-DDT (DDT₂₅), 167 morphologically different bacterial strains were isolated. Out of 167 isolates, only 5 strains showed p,p′-DDT degrading ability as indicated by clear zone around the colony when grown on nutrient agar supplemented up to 100 ppm p,p′-DDT. These 5 isolates include SB1A01, SB2A02,
SB1A10, SB1A12 and SB1B05. Growth of these isolates in MSYM+DDT₂₅ after 10 days indicated reductions of p,p′-DDT
by 30.5, 20.3, 37.4, 30.4 and 32.2%, respectively. Based on the morphological characteristics and 16S rDNA analysis, isolate SB1A10 which showed the highest degradation ability was found to be 99% identical (1360/1362) to Staphylococcus haemolyticus.