The gamma isomer of hexachlorocyclohexane (HCH), also known as lindane, is a carcinogenic persistent organic pollutant. Lindane was used worldwide as an agricultural insecticide. Soil and groundwater contamination with lindane and other HCH isomers is a worldwide concern. Through this project, we studied the complete biotransformation of lindane to non-toxic end products using a sequential treatment approach with three mixed anaerobic microbial cultures. Illumina 16S rRNA gene amplicon sequencing was used during the various stages of the experiments to monitor the microbial community linked to a specific phase in the biotransformation and to help identify key microorganisms that carry out these reactions.