PrkC modulates MreB filament density and cellular growth rate by monitoring cell wall precursors

How bacteria link their rate of growth to the external nutrient conditions is not known. To explore how Bacillus subtilis modulates the rate cells expand their encapsulating cell wall, we compared the single-cell growth rate to the density of moving MreB filaments under different conditions. MreB filament density scales with the growth rate, and is modulated by the mur genes that create the cell wall precursor lipid II. Lipid II is sensed by the serine/threonine kinase PrkC, which, among other proteins, phosphorylates RodZ. Phosphorylated RodZ then increases MreB filament density, increasing growth. Strikingly, increasing the activity of this pathway results in cells elongating far faster than wild type in nutrient-poor media, indicating slow-growing bacteria contain spare growth capacity. Overall, this work reveals that PrkC functions as a cellular rheostat, tuning the activities of cellular processes in response to lipid II, allowing cells to grow robustly across a broad range of nutrient conditions. One-sentence summaryThe serine/threonine kinase PrkC modulates both MreB filament density and cellular growth rate by sensing lipid II in Bacillus subtilis.