Chlamydia trachomatis

Cell structure and metabolism

Chlamydia trachomatis is structurally gram negative and is one of three bacterial species in the genus Chlamydia. It was once thought to be a virus because it could have not been cultured in an artificial medium. C. trachomatis is an obligate intracellular pathogen that lives within human cells and cannot make its own ATP. This means that they are unable to replicate outside of a host cell. The pathogens have evolved a unique biphasic life cycle. They alternate between two functionally and morphologically distinct forms; elementary body and reticular body. Elementary body (EB) is infectious, but metabolically inert (chemically inactive). EB is taken up by host cells, primarily byreceptor-mediated endocytosis. the bacteria prevent fusion of the endosome and lysosome, but the mechanism of this is not known. Inside the endosome, the EB differentiates into a metabolically active but non-infectious form, reticulate body (RB) using energy sources and amino acids from the host cell. RB replicates and ultimately forms new EBs that are capable of infecting additional cells. C. trachomatis has a glycolytic pathway and a linked tricarboxylic acid cycle. Glycogen synthesis and use of glucose derivatives plays a supporting role in chlamydial metabolism.