Colorimetric assay for Lindane dechlorination by bacteria

Area of Science:

• Environmental Microbiology
• Bioremediation
• Biocatalysis

Background:

• Lindane (gamma-hexachlorocyclohexane) is a persistent organochlorine pollutant.
• Microbial dechlorination is a key process in Lindane bioremediation.
• Efficient screening methods are needed to identify Lindane-degrading microorganisms.

Purpose of the Study:

• To modify and validate a colorimetric microtitre plate-based assay for detecting haloalkane dehalogenase activity specific to Lindane dechlorination.
• To assess the assay's utility in measuring dechlorination rates and screening bacterial isolates for Lindane degradation capabilities.

Main Methods:

• Adaptation of a colorimetric microtitre plate assay using phenol red indicator for HCl production during dechlorination.
• Validation using known Lindane-degrading bacteria (Rhodanobacter lindaniclasticus, Sphingomonas paucimobilis UT26).
• Confirmation of dechlorination in scaled-up assays using GC/ECD analysis of metabolites.
• Screening of cell-free extracts from 24 bacterial isolates from Lindane-contaminated soil.

Main Results:

• The assay successfully detected Lindane dechlorination, indicated by a color change from red to yellow due to HCl formation.
• Enzyme activity was quantifiable by measuring absorbance at 540 nm.
• Dechlorination was confirmed in scaled-up assays via GC/ECD.
• No Lindane dechlorination activity was detected in the 24 screened bacterial isolates.

Conclusions:

• The modified colorimetric assay is a sensitive, inexpensive, and rapid tool for detecting Lindane dechlorination activity.
• This assay facilitates the screening and identification of microorganisms with potential for Lindane bioremediation.
• Further application of this assay can aid in discovering novel Lindane-degrading microbial strains.