Let me be more specific. At the molecular level, what kind of event, required by evolution, are you asserting cannot happen or has not been observed to happen?
At the molecular level? Do you mean the chemical level?
DNA doesn’t change from it’s basic coding, if that’s what you’re asking.
The DNA that makes a strain of bacteria into that strain remains. (that is, unless you expose the organism to a chemical like alcohol).
For all the adaptive genetic testing of the mutations and natural selection of E coli, it is still readily identifiable as E coli. No new bacteria have been produced. Similiar to breeds of dogs, just different mechanisms.