Ca 2+ -calmodulin signalling at the host-pathogen interface.

Multiple eukaryotic cell processes are modulated by calcium ions (Ca). As such, Ca is emerging as a crucial regulator of innate immunity in multicellular organisms. In particular, recent studies have identified roles of Ca signalling at the host-bacteria interface. Following microbial exposure, Ca signals mobilised from the extracellular milieu or intracellular stores are transduced into cell physiological responses. However, during infection with host-adapted pathogens, Ca signals are often atypical, due to the activities of virulence factors, with varied consequences for both the pathogen and the host cell. In this review, we describe the Ca-dependent host factors regulating antibacterial immunity, in addition to bacterial effectors that promote, inhibit, or co-opt Ca-calmodulin signalling to promote infection.