Antibiotic-resistant bacteria. Flesh eating bacteria. E.Coli contaminated hamburgers, strawberries, and ice cream. Tuberculosis, the greatest infectious killer of all time, is again rearing its head. Everywhere we look, we seem to encounter these ubiquitious, often useful, but occcasionaly pathogenic organisms. It was once thought that bacterial disease was conquered (with the advent of the antibiotic era.), but people professing that belief hadn't studied Darwin and evolutionary biology. Not only do we routinely read about the above problems, but scientist are finding more evidence to link bacteria to the development of other human illnesses, including peptic ulcers, cardiovascular disease, and possibly even psychiatric illness such as obsessive-compulsive diorder.