Colorimetric assay for Lindane dechlorination by bacteria

A colorimetric microtitre plate-based assay that detects haloalkane dehalog enase activity was modified to detect dechlorination of gamma -hexachlorocy clohexane (Lindane). Dechlorination is indicated by the colour change of ph enol red from red to yellow, in a weakly buffered solution, as the solution becomes acidic due to HCl formed during dechlorination. Enzyme activity ca n be monitored by reading the absorbance of each well at 540 rim. Positive controls for the assay were the known Lindane-degrading microorganisms, Rho danobacter lindaniclasticus and Sphingomonas paucimobilis UT26. Dechlorinat ion in a scaled-tip version of the assay was confirmed by GC/ECD detection of known metabolites of the test microorganisms from which the enzyme extra cts were prepared. Die assay was used to measure the rate of dechlorination in cell-free extracts of R. lindaniclasticus. It was also used to screen t he cell-free extracts of 24 bacterial isolates, from a Lindane-contaminated soil, for Lindane dechlorination activity. Although no isolates tested pos itive, the assay represents a new inexpensive and rapid screening tool for the detection of Lindane-degrading microorganisms. (C) 2001 Published by El sevier Science B.V.