To estimate the minimal gene set required to sustain bacterial life in nutritious conditions, we carried out a systematic inactivation of Bacillus subtilis genes. Among Ϸ4,100 genes of the organism, only 192 were shown to be indispensable by this or previous work. Another 79 genes were predicted to be essential. The vast majority of essential genes were categorized in relatively few domains of cell metabolism, with about half involved in information processing, one-fifth involved in the synthesis of cell envelope and the determination of cell shape and division, and one-tenth related to cell energetics. Only 4% of essential genes encode unknown functions. Most essential genes are present throughout a wide range of Bacteria, and almost 70% can also be found in Archaea and Eucarya. However, essential genes related to cell envelope, shape, division, and respiration tend to be lost from bacteria with small genomes. Unexpectedly, most genes involved in the Embden-Meyerhof-Parnas pathway are essential. Identification of unknown and unexpected essential genes opens research avenues to better understanding of processes that sustain bacterial life.

The process of sporulation in the bacterium Bacillus subtilis proceeds through a well-defined series of morphological stages that involve the conversion of a growing cell into a two-cell-chamber sporangium within which a spore is produced. Over 125 genes are involved in this process, the transcription of which is temporally and spatially controlled by four DNA-binding proteins and five RNA polymerase sigma factors. Through a combination of genetic, biochemical, and cell biological approaches, regulatory networks have been elucidated that explicitly link the activation of these sigma factors to landmark events in the course of morphogenesis and to each other through pathways of intercellular communication. Signals targeting proteins to specific subcellular localizations and governing the assembly of macromolecular structures have been uncovered but their nature remains to be determined.

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Sporulation in Bacillus subtilis is a model for how cells of one type generate other differentiated cell types. During sporulation two cellular compartments arise that differ from each other and from the progenitor cell. Differential gene expression between the two is governed by the successive appearance of four transcription factors whose activities are coordinated in crisscross fashion between the two cells.

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Cell fate is determined by cell-specific activation of transcription factor sigma F after asymmetric division during sporulation by Bacillus subtilis. The activity of sigma F is governed by SpoIIAA, SpoIIAB, and SpoIIE, a membrane protein localized at the polar septum. SpoIIAB binds to and inhibits sigma F, and SpoIIAA inhibits SpoIIAB, which prevents SpoIIAB from binding to sigma F. SpoIIAB is also a serine kinase that inactivates SpoIIAA. Here, it is demonstrated that SpoIIE dephosphorylates SpoIIAA-P and overcomes SpoIIAB-mediated inhibition of sigma F. The finding that SpoIIE is a serine phosphatase links asymmetric division to the pathway governing cell-specific gene transcription.