Isolation and characterisation of ethoprophos-degrading bacteria

Abstract

An enrichment culture technique was used to isolate bacteria responsible for the enhanced biodegradation of ethoprophos in a soil from Northern Greece. Restriction fragment length polymorphism patterns of the 16S rRNA gene, partial 16S rRNA sequence analysis, and sodium dodecylsulfate–polyacrylamide gel electrophoresis total protein profile analysis were used to characterise the isolated bacteria. Two of the three ethoprophos-degrading cultures were pure and both isolates were classified as strains of Pseudomonas putida (epI and epII). The third culture comprised three distinct components, a strain identical to P. putida epI and two strains with 16S rRNA sequence similarity to Enterobacter strains. Isolate epI effectively removed a fresh ethoprophos addition from both fumigated and non-fumigated soil when introduced at high inoculum density, but removed it only from fumigated soil at low inoculum density. Isolates epI and epII degraded cadusafos, isazofos, isofenphos and fenamiphos, but only at a slow rate. This high substrate specificity was attributed to minor (cadusafos), or major (isazofos, isofenphos, fenamiphos) structural differences from ethoprophos. Studies with 14C-labelled ethoprophos indicated that isolates epI and epII degraded the nematicide by removing the S-propyl moiety.