The host cytosol: front-line or home front?

Intracellular pathogens replicate in modified vacuolar compartments or in the cytosol of host cells. Many pathogenic bacterial species have evolved to modify the host vacuolar environment, but little is known about the mammalian cytosol as a medium for bacterial growth. Recent studies indicate that the cytosol is restrictive for the growth of bacteria other than cytosolic pathogens in contrast to earlier research that provided evidence that any bacteria with access to the cytosol can replicate there. Comparison of these studies suggests that the cytosolic contents of various host cell types can be differentially permissive for bacterial growth, and that both host and bacterial factors are important in determining the ability of particular bacteria to replicate in the cytosol.