Overview Chlamydia and Rickettsia are 2 groups of Gram-negative bacteria Both bacteria are obligate intracellular parasites they must steal host ATP to live Chlamydia cannot make any ATP whatsoever Rickettsia can make some (but not enough) they cannot be cultured on non-living artificial media instead, they are innoculated into living cells for culture about the size of large viruses (i.e. quite small) however, they are not viruses because they have both DNA and RNA viruses have only one or the other synthesize their own proteins are sensitive to antibiotics Important differences between the 2 groups include Differences between Chlamydia and Rickettsia Chlamydia Rickettsia Transmission Person-to-person Arthropod vector Site of replication Endosomes Cytoplasm Type of cell attacked Columnar epithelium Endothelium