Safe haven under constant attack-The Chlamydia-containing vacuole

Chlamydia belong to the group of obligate intracellular bacteria that reside in a membrane bound vacuole during the entire intracellular phase of their life cycle. This vacuole called inclusion shields the bacteria from adverse influences in the cytosol of the host cell like the destructive machinery of the cell-autonomous defence system. The inclusion thereby prevents the digestion and eradication in specialised compartments of the intact and viable cell called phagolysosomes or autophagolysosomes. It is becoming more and more evident that keeping the inclusion intact also prevents the onset of cell intrinsic cell death programmes that are activated upon damage of the inclusion and direct the cell to destruct itself and the pathogen inside. Chlamydia secrete numerous proteins into the inclusion membrane to protect and stabilise their unique niche inside the host cell. We will focus in this review on the diverse attack strategies of the host aiming at the destruction of the Chlamydia-containing inclusion and will summarise the current knowledge on the protection mechanisms elaborated by the bacteria to maintain the integrity of their replication niche.