The conserved transcriptional regulator CdnL is required for metabolic homeostasis and morphogenesis inCaulobacter

Bacterial growth and division require regulated synthesis of the macromolecules used to expand and replicate components of the cell. Transcription of housekeeping genes required for metabolic homeostasis and cell proliferation is guided by the sigma factor σ70. The conserved CarD-like transcriptional regulator, CdnL, associates with promoter regions where σ70localizes and stabilizes the open promoter complex. However, the contributions of CdnL to metabolic homeostasis and bacterial physiology are not well understood. Here, we show thatCaulobacter crescentuscells lacking CdnL have severe morphological and growth defects. Specifically,ΔcdnLcells grow slowly in both rich and defined media, and are wider, more curved, and have shorter stalks than WT cells. These defects arise from transcriptional downregulation of most major classes of biosynthetic genes. Notably, we find thatΔcdnLcells are severely limited in glutamate synthesis, rendering them auxotrophic for that amino acid. Moreover,ΔcdnLcells produce low amounts of the cell wall precursor lipid II, andΔcdnLis synthetic lethal with other genetic perturbations that limit lipid II production.ΔcdnLcells also have aberrant localization of MreB and CtpS, cytoskeletal proteins required for maintaining proper cell width and curvature. Interestingly, the localization of CtpS is dependent on availability of CTP, which is predicted to be low inΔcdnLcells. Our findings implicate CdnL as a global regulator of genes required for metabolic homeostasis that impacts morphogenesis through availability of lipid II and through metabolite-mediated changes in localization of cytoskeletal regulators of cell shape.