DETECTION AND QUANTIFICATION OF DEGRADATIVE GENES IN SOILS CONTAMINATED BY TOLUENE

A method based on the polymerase chain reaction (PCR) was developed fo r a rapid and specific detection of toluene degradative genes in soil The xylE gene coding for catechol 2,3-dioxygenase was chosen as a targ et gene. The detection threshold was evaluated in microcosms using a s terilized standard soil inoculated with various amounts of a degradati ve strain of Pseudomonas putida (mX). The extracted DNA was used as a template to amplify the xylE gene. PCR followed by hybridization with an internal probe allowed us to detect 10(2) bacteria per g of soil. I n polluted soils, quantification of target DNA by competitive PCR was compared with enumeration of degradative microflora. This molecular me thod appeared;to be rapid, sensitive and more suitable than the microb iological approach to estimate the biodegradative potential of a pollu ted soil.