Nylon is:
[-CO-R-CO-NH-R'-NH-]n
The researchers used nylon hexamer (n=6) as a substrate, but real nylon has n>6. So this bug, while it can eat nylon waste and small pieces from manufacture cannot handle the large polymer. It also has a very high Km = 6x10-3M meaning that it has very poor affinity for the nylon hexamer. However, selective mutation should be able to reduce the Km and they also should be able to gradually increase the size of the oligomer substrate. This is the kind of thing that nature would do under natural conditions. The tough part of nylon isn't that an organism cannot hydrolyze the amide bond - that's a piece of cake, but the enzyme cannot get to the amide bond in a water insoluble polymer.
MRM - I think your original point is well taken and this is a nice example of evolution and some of the processes that can be involved. But this bug doesn't really degrade nylon, yet.
RWP - what's the usual "n" for nylon (my Merck Index doesn't say exactly)?
Don't know, but fairly high.
Eventually, I imagine, nylonase will bind to insoluble nylon and hydrolyse it on the fiber. The difficulty in hydrolysing insoluble polymers is the primary reason cellulases are rather rare.