Polaroinonas sp. strain JS666 is the first aerobic organism isolated capable of growth-coupled cis-dichloroethene (cDCE) degradation. Because of this, JS666 may be a promising bioaugmentation agent at cDCE-contaminated sites where the common groundwater contaminant has migrated into an aerobie zone. Laboratory experiments revealed two distinct degradation patterns by J5666 (i.e. growth-linked cDCE degradation vs. apparently cometabolic degradation), depending upon how the organism is cultured. Growths-linked degradation was obtained by repeatedly transferring a small fraction of actively degrading culture to fresh media. Apparently cometabolic degradation was obtained by centrifuging cells grown-up on cDCE with succinate as a cosubstrate and reususpending them into fresh media with cDCE as the sole carbon source. Upon resuspension, these cultures showed a decrease in biomass concentration and rates of cDCE degradation over time. In addition, cDCE degradation was not sustainable without the addition of an alternative carbon source besides cDCE. The presence of two distinct degradation patterns suggests that multiple pathways may be involved in cDCE degradation by JS666. The current paradigm is that aerobic degradation of chlorinated ethenes involves a monooxygenase, which adds oxygen to the double bond forming an epoxide. In these experiments, 2-D gel electrophoresis was used to identify proteins involved in the cDCE degradation pathway/s of JS666 to determine if a monooxygenase is involved and to investigate the possibility of the presence of alternative pathways.