Bacterial Mg²⁺Homeostasis, Transport, and Virulence

Abstract

Organisms must maintain physiological levels of Mg2+ because this divalent cation is critical for the stabilization of membranes and ribosomes, 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 Mg2+ both outside and inside the cytoplasm. We examine how bacteria achieve Mg2+ homeostasis by adjusting the expression and activity of Mg2+ transporters, and by changing the composition of their cell envelope. We discuss the connections that exist between Mg2+ sensing, Mg2+ transport and bacterial virulence. Additionally, we explore the logic behind the fact that bacterial genomes encode multiple Mg2+ transporters and distinct sensing systems for cytoplasmic and extracytoplasmic Mg2+. These analyses may be applicable to the homeostatic control of other cations.

An RNA motif advances transcription by preventing Rho-dependent termination

“…2B, [105-125]). The modest decrease in affinity displayed by the RNA with mutations in a rut in the mgtCBR leader is in contrast to the effect of mutation of a rut site in the mgtA leader region (15,25), which decreased affinity for Rho eightfold [ , and Δ51-60), suggesting that this region serves as a genuine rut site. Cumulatively, our findings revealed two distinctive features of Rho interaction with the mgtCBR RNA.…”

An Essential Factor for High Mg2+ Tolerance of Staphylococcus aureus

“…Mg 2+ cannot diffuse freely through membranes and therefore has to be imported through dedicated channels, using the electrochemical gradient of this ion (Payandeh et al, 2013). On the molecular level this transport is best understood in prokaryotes, where import of Mg 2+ has been linked to four classes of transporters: CorA, MgtA/B, MgtE, and a recently described Nramp-related transporter (Kehres and Maguire, 2002; Groisman et al, 2013; Shin et al, 2014). Most bacteria possess several Mg 2+ transporters and sometimes several from one class.…”

When Too Much ATP Is Bad for Protein Synthesis

“…And fourth, the PhoP/PhoQ system governs expression of genes responsible for a variety of chemical modifications of the phosphate residues in the lipopolysaccharide (LPS) portion of the outer membrane [28,61-64]. These modifications would make the Mg 2+ ions normally neutralizing the phosphate residues available for other Mg 2+ -dependent functions [65]. …”

“…That the expression of the mgtA , mgtCBR and mgtE Mg 2+ transporter genes responds to cytosolic Mg 2+ suggests that the corresponding gene products help bacteria cope with low cytosolic Mg 2+ . In this context, the PhoP-dependent modification of the LPS is proposed to make the Mg 2+ ions that normally neutralize the LPS available for transport into the cytoplasm by the PhoP-dependent Mg 2+ transporter(s) [65]. It has been estimated that about one third of the total Mg 2+ content of E. coli is bound to the LPS, suggesting that the LPS serves as a Mg 2+ reservoir [28].…”