More than 5 decades of work support the idea that cell envelope synthesis, including the inward growth of cell division, is tightly coordinated with DNA replication and protein synthesis through central metabolism. Remarkably, no unifying model exists to account for how these fundamentally disparate processes are functionally coupled. Recent studies demonstrate that proteins involved in carbohydrate and nitrogen metabolism can moonlight as direct regulators of cell division, coordinate cell division and DNA replication, and even suppress defects in DNA replication. In this minireview, we focus on studies illustrating the intimate link between metabolism and regulation of peptidoglycan (PG) synthesis during growth and division, and we identify the following three recurring themes. (i) Nutrient availability, not growth rate, is the primary determinant of cell size. (ii) The degree of gluconeogenic flux is likely to have a profound impact on the metabolites available for cell envelope synthesis, so growth medium selection is a critical consideration when designing and interpreting experiments related to morphogenesis. (iii) Perturbations in pathways relying on commonly shared and limiting metabolites, like undecaprenyl phosphate (Und-P), can lead to pleotropic phenotypes in unrelated pathways.KEYWORDS FtsZ, MreB, UDP-glucose, cell division, gluconeogenesis, metabolism, morphogenesis, peptidoglycan, phosphoenolpyruvate, undecaprenyl phosphate T o accurately partition chromosomes and other cell contents during reproduction, cells must possess mechanisms to organize repeated cycles of cell growth, chromosome replication, and division. Eukaryotes orchestrate this coordination using the cell cycle and separate growth, DNA synthesis, and cytokinesis into distinct, temporally sequestered phases. Bacteria, by contrast, simultaneously increase in cell size and replicate DNA before (or concurrently with) cell division. Elucidating the molecular mechanisms prokaryotes employ to achieve spatiotemporal organization of these intertwined yet functionally disparate processes is of considerable interest to scientists seeking to understand bacterial reproduction, and many outstanding questions remain to be answered. For example, how is DNA replication kept in sync with changing growth and division rates? How are cell dimensions maintained or actively rearranged in response to environmental or developmental cues? What signals do cells sense to switch between increasing in cell size and dividing during the cell cycle? Relatedly, how are these signals transduced to activate/deactivate the distinct machineries required for each process?Perhaps one of the biggest mysteries remaining in bacterial cell biology relates to understanding the regulatory cross talk that must occur to integrate central metabolism with macromolecular biosynthesis. Nutrients are converted into stored energy and precursors used to synthesize macromolecules like DNA and peptidoglycan (PG), so it is no surprise that nutrient availability has a profound impac...

Many bacteria utilize actin-like proteins to direct peptidoglycan (PG) synthesis. MreB and MreB-like proteins are thought to act as scaffolds, guiding the localization and activity of key PG-synthesizing proteins during cell elongation. Despite their critical role in viability and cell shape maintenance, very little is known about how the activity of MreB family proteins is regulated. Using a Bacillus subtilis misexpression screen, we identified two genes, yodL and yisK, that when misexpressed lead to loss of cell width control and cell lysis. Expression analysis suggested that yodL and yisK are previously uncharacterized Spo0A-regulated genes, and consistent with these observations, a ⌬yodL ⌬yisK mutant exhibited reduced sporulation efficiency. Suppressors resistant to YodL's killing activity occurred primarily in mreB mutants and resulted in amino acid substitutions at the interface between MreB and the highly conserved morphogenic protein RodZ, whereas suppressors resistant to YisK occurred primarily in mbl mutants and mapped to Mbl's predicted ATP-binding pocket. YodL's shape-altering activity appears to require MreB, as a ⌬mreB mutant was resistant to the effects of YodL but not YisK. Similarly, YisK appears to require Mbl, as a ⌬mbl mutant was resistant to the cell-widening effects of YisK but not of YodL. Collectively, our results suggest that YodL and YisK likely modulate MreB and Mbl activity, possibly during the early stages of sporulation. IMPORTANCEThe peptidoglycan (PG) component of the cell envelope confers structural rigidity to bacteria and protects them from osmotic pressure. MreB and MreB-like proteins are thought to act as scaffolds for PG synthesis and are essential in bacteria exhibiting nonpolar growth. Despite the critical role of MreB-like proteins, we lack mechanistic insight into how their activities are regulated. Here, we describe the discovery of two B. subtilis proteins, YodL and YisK, which modulate MreB and Mbl activities. Our data suggest that YodL specifically targets MreB, whereas YisK targets Mbl. The apparent specificities with which YodL and YisK are able to differentially target MreB and Mbl make them potentially powerful tools for probing the mechanics of cytoskeletal function in bacteria. Bacterial cell growth requires that the machineries directing enlargement and division of the bacterial cell envelope be coordinated in both time and space (1). The cell envelope is comprised of membranes and a macromolecular mesh of peptidoglycan (PG) that possesses both rigid and elastic properties (2, 3). PG is highly cross-linked, allowing bacteria to maintain shapes and avoid lysis, even in the presence of several atmospheres of internal turgor pressure. PG rearrangements are required during the inward redirection of growth that occurs at the time of cell division, but they are also necessary when cells insert new PG and dynamically modify their morphologies in response to developmental or environmental signals (4, 5). To avoid lysis during PG rearrangements, bacteria must c...