Sp. K172, a strain of Flavobacterium, is a species of nylon-eating bacteria discovered in ponds that contained factory waste. What made this bacteria significant was that the enzymes they used to digest the factory waste (now known as nylonase) were unique to the particular strain. An analysis of the genome suggests that the mutation that created this strain was a frame shift (for example mutating the word 'mutate' to 'mtate') and gene duplication.
Since that time, Sp. K172 has been a central point of contention between the supporters of evolution and critics such as proponents of intelligent design and creationism. Evolutionary scientists have pointed it out as an example of how mutations can create new information and new functions. Some Creation scientists and intelligent design proponents contend that the bacteria in question cannot be adequately explained by the evolutionary view and instead claim that the bacterial plasmids were designed to be able to accommodate new food sources. 
It should be pointed out that the bacterium in question has lost the ability to process regular bacteria food sources, and only processes nylon at 1/50th the efficiency that regular bacteria are able to process food consumption. Due to this fact, some Creationists view this as genetic breakdown that just happened to hit on an odd niche during the degrading process, but would have no future as a precursor of any positive evolutionary change.
- Kinoshita, S., Kageyama, S., Iba, K., Yamada, Y. and Okada, H. 1981
- Batten, Don, "The adaptation of bacteria to feeding on nylon waste", Journal of Creation 17(3):3–5, December 2003 HTML, PDF.