Missed this one and my apologies:
The frame shift producing the nylong-ingesting bacteria results in a less specific folding of a protein. There is a loss of specificity and that is all. And, by the way, a frame SHIFT is not the addition of information, but the misplacing of it, if you will. In most cases it is deleterious. In this case there was something we find useful that happened. BUT, if you put any of these nylon-eaters in a wild population they would be most unfit and die out entirely in a very short time. Either that or back mutate at that place and become 'normal' again.
Most mutations, by the way, are not inheritable. That does not make them any the less mutations. A mutation is any change in the genetic code. I thank God that most are not heritable! For instance, I have an adopted daughter with amnionic band syndrome. It is not heritable. It is just 'one of those things' mutations that can happen. In her case it means the ends of some fingers and toes did not develop, she is missing her right big toe and some muscle mass in her left thigh. Definitely a mutation, and never seen to be heritable.