A variant form of a gene. If you read the page at my source, you will find a discussion of bacteria that eat nothing but Nylon. Find that in your pre-existing genes.
Pilgrims had nothing about eating corn in their genes either, yet they managed just fine after landing at Plymouth Rock.
I think those nylon-eating bacteria live in my hosiery drawer.
Compared to most plastic like things nylon is easy. It is a polyamide and finding an enzyme that can cleave a polyamide is not too tough (natural amides are very common). If you like this kind of thing and have a university library close, read the papers of E.C.C. Lin on enzyme recruitment. They date back to the 60's and 70's, before the cloning rage, but they will explain in great detail the natural modification of existing enzymes to use unnatural substances as substrates.
The bugs that eat halogenated hydrocarbons are even more interesting!