Abstract: Pseudomonas putida S3A was isolated in previous study and selected for its good ability to degrade nylon 6, nylon 66 and nylon 6 film as a sole source of carbon and nitrogen. Thus, plasmid profile of this bacterium was studied. Results showed that this isolate harbored small plasmid DNA bands. In order to study the role of its plasmid in degradation of nylon 6 film, curing experiment was performed using Sodium Dodecyl Sulfate (SDS) and showed that two colonies had lost their ability to degrade nylon 6 film as a sole source of carbon and nitrogen. Plasmid DNA extraction from one of these colonies indicated the loss of plasmid DNA bands and this referred that the plasmid DNA bands could be responsible for degrading of nylon 6 film in P. putida S3A.