Irreducibly complex, too. Shortly after the new enzyme evolved, a series of mutation produced a regulator, so that the enzyme is only active when the substrate is present. As a result a three-part system evolved such that it only works if all three elements are present. Remove any one of them, and it doesn't work.
There are many sorts of bacteria, and many sorts of antibiotic resistance. Interestingly, Flemming, after discovering penicillin, predicted that overuse would result in the evolution of resistance in bacteria. Mutation and natural selection was all that was needed to do so.
God created nature so that it would bring forth all of that and much, much more. Pretty amazing, no?