De novo fatty acid synthesis is required for establishment of cell type-specific gene transcription during sporulation in Bacillus subtilis

A hallmark of sporulation of Bacillus subtilis is the formation of two distinct cells by an asymmetric septum. The developmental programme of these two cells involves the compartmentalized activities of sigma(E) in the larger mother cell and of sigma(F) in the smaller prespore. A potential role of de novo lipid synthesis on development was investigated by treating B. subtilis cells with cerulenin, a specific inhibitor of fatty acid biosynthesis. These experiments demonstrated that spore formation requires de novo fatty acid synthesis at the onset of sporulation. The transcription of the sporulation genes that are induced before the formation of two cell types or that are under the exclusive control of sigma(F) occurred in the absence of fatty acid synthesis, as monitored by spo-lacZ fusions. However, expression of lacZ fusions to genes that required activation of sigma(E) for transcription was inhibited in the absence of fatty acid synthesis. The block in sigma(E)-directed gene expression in cerulenin-treated cells was caused by an inability to process pro-sigma(E) to its active form. Electron microscopy revealed that these fatty acid-starved cells initiate abnormal polar septation, suggesting that de novo fatty acid synthesis may be essential to couple the activation of the mother cell transcription factors with the formation of the differentiating cells.