This phylum consists of intracellular parasites that get vitamins, amino acids, ATP, and other vital cellular molecules from their host cell. Chlamydia trachomatis, a species within this phylum, causes a venereal disease in humans that is commonly referred to as "chlamydia" or "trachoma," and Chlamydophila pneumoniae causes a type of pneumonia that creates chest infections. Chlamydia and Clhamydophila are just two of the five genera in the phylum, the other three are Parachlamydia, Simkania, and Waddlia.