Chlamydiae is a bacterial phylum whose members are obligate intracellular pathogens. Many Chlamydiae coexist in an asymptomatic state within specific hosts, and it is widely believed that these hosts provide a natural reservoir for these species. All Chlamydiae grow by infecting eukaryotic host cells. They are as small or smaller than many viruses. Inside the cells Chlamydiae take on an intracellular replicative form; outside of cells they survive only in...