Glucose controls manganese homeostasis through transcription factors regulating known and newly identified manganese transporter genes in Bacillus subtilis

Mn(2+) is an essential nutrient whose concentration is tightly controlled in bacteria. In Bacillus subtilis, the Mn(2+)-activated transcription factor MntR controls Mn(2+) transporter genes. However, factors regulating intracellular Mn(2+) concentration are incompletely understood. Here, we found that glucose addition induces an increase in intracellular Mn(2+) concentration. We determined this upshift was mediated by glucose induction of the major Mn(2+) importer gene mntH by the transcription factor AhrC, which is known to be involved in arginine metabolism and to be indirectly induced by glucose. In addition, we identified novel AhrC-regulated genes encoding the Mn(2+) importer YcsG and the ABC-type exporter YknUV. We found the expression of these genes was also regulated by glucose and contributes to the glucose induction of Mn(2+) concentrations. ycsG expression is regulated by MntR as well. Furthermore, we analyzed the interaction of AhrC and MntR with the promoter driving ycsG expression and examined the Mn(2+)-dependent induction of this promoter to identify the transcription factors responsible for the Mn(2+) induction. RNA-Seq revealed that disruption of ahrC and mntR affected the expression of 502 and 478 genes, respectively (false discovery rate, <0.001, log(2)[fold change] ≥ |2|. The AhrC- and/or MntR-dependent expression of twenty promoters was confirmed by LacZ analysis, and AhrC or MntR binding to some of these promoters was observed via EMSA. The finding that glucose promotes an increase in intracellular Mn(2+) levels without changes in extracellular Mn(2+) concentrations is reasonable for the bacterium, as intracellular Mn(2+) is required for enzymes and pathways mediating glucose metabolism.