Bacterial Mg2+ Homeostasis, Transport, and Virulence

Organisms must maintain physiological levels of Mg 2+ because this divalent cation is critical for the stabilization of membranes and ribosomes, for the neutralization of nucleic acids, and as a cofactor in a variety of enzymatic reactions. In this review, we describe the mechanisms that bacteria utilize to sense the levels of Mg 2+ both outside and inside the cytoplasm. We examine how bacteria achieve Mg 2+ homeostasis by adjusting the expression and activity of Mg 2+ transporters and by changing the composition of their cell envelope. We discuss the connections that exist between Mg 2+ sensing, Mg 2+ transport, and bacterial virulence. Additionally, we explore the logic behind the fact that bacterial genomes encode multiple Mg 2+ transporters and distinct sensing systems for cytoplasmic and extracytoplasmic Mg 2+ . These analyses may be applicable to the homeostatic control of other cations.