obligate intracellular bacteria

Obligate intracellular bacteria proliferate only within host cells, although some may survive outside of cells.

These organisms are well adapted to the intracellular environment, with pumps to capture amino acids and adenosine triphosphate (ATP) for energy in their membranes.

Some are unable to synthesize ATP at all (e.g., Chlamydia), while others synthesize at least some of their own ATP (e.g., the Rickettsiae).