Colorimetric assay for Lindane dechlorination by bacteria

A colorimetric microtitre plate-based assay that detects haloalkane dehalogenase activity was modified to detect dechlorination of gamma-hexachlorocyclohexane (Lindane). Dechlorination is indicated by the colour change of phenol red from red to yellow, in a weakly buffered solution, as the solution becomes acidic due to HCl formed during dechlorination. Enzyme activity can be monitored by reading the absorbance of each well at 540 nm. Positive controls for the assay were the known Lindane-degrading microorganisms, Rhodanobacter lindaniclasticus and Sphingomonas paucimobilis UT26. Dechlorination in a scaled-up version of the assay was confirmed by GC/ECD detection of known metabolites of the test microorganisms from which the enzyme extracts were prepared. The assay was used to measure the rate of dechlorination in cell-free extracts of R. lindaniclasticus. It was also used to screen the cell-free extracts of 24 bacterial isolates, from a Lindane-contaminated soil, for Lindane dechlorination activity. Although no isolates tested positive, the assay represents a new inexpensive and rapid screening tool for the detection of Lindane-degrading microorganisms.