Drinking regular milk will not only give kittens diarrhea, but will also cause them to slowly starve to death if their diet isn't properly supplemented [source: Kitten Rescue]. The ratio of caseins and whey in cow's milk is nowhere near sufficient to support a growing kitten [source: Fries].
One of the significant adaptions occurred in one strain of E. coli. In general, this bacteria is known for not being able to use citrate in an aerobic environment as an energy source, even though it could use citrate under anaerobic conditions because it already has the machinery to process citrate.
E. coli (Escherichia coli) is one of several types of bacteria that normally inhabit the intestine of humans and animals (commensal organism). Some strains of E. coli are capable of causing disease under certain conditions when the immune system is compromised or disease may result from an environmental exposure.