Dynamic allocation of MurJ coordinates bacterial growth and division

Abstract

Rod-shaped bacteria grow by inserting peptidoglycan into the lateral cell wall during elongation and into the septal cell wall during division. These two modes of growth are driven by distinct peptidoglycan synthesis machineries that consume the shared precursor Lipid II and must be coordinated so that cell enlargement remains matched to division. However, how cells spatially allocate this shared precursor, and whether Lipid II translocation itself contributes to this coordi-nation, remain unclear. Here we show that the spatial distribution of the essential Lipid II flippase MurJ coordinates this balance in Escherichia coli. Increasing nonseptal MurJ abundance shifted cell-wall synthesis toward elongation and reduced septal synthesis. Single-molecule tracking revealed that MurJ diffuses throughout the membrane but is transiently captured at the division site, rather than stably incorporated into the septal synthesis machinery. This recruitment requires active septal cell-wall synthesis, but not ongoing Lipid II synthesis or flipping, indicating that MurJ recruitment is coupled to the active synthesis machinery rather than to substrate availability or transport. Thus, activation of septal synthesis creates transient MurJ capture at the division site, providing a mechanism to preferentially supply Lipid II for septal growth during cytokinesis. These findings reveal a capture-and-release mechanism that dynamically enriches MurJ at active division sites and thereby coordinates elongation and division in bacterial cells.