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.

Mutations designated gtaC and gtaE that affect ␣-phosphoglucomutase activity required for interconversion of glucose 6-phosphate and ␣-glucose 1-phosphate were mapped to the Bacillus subtilis pgcA (yhxB) gene. Backcrossing of the two mutations into the 168 reference strain was accompanied by impaired ␣-phosphoglucomutase activity in the soluble cell extract fraction, altered colony and cell morphology, and resistance to phages 29 and 11. Altered cell morphology, reversible by additional magnesium ions, may be correlated with a deficiency in the membrane glycolipid. The deficiency in biofilm formation in gtaC and gtaE mutants may be attributed to an inability to synthesize UDP-glucose, an important intermediate in a number of cell envelope biosynthetic processes.Peptidoglycan and wall teichoic acids (WTAs) are major constituents of the cell wall in many gram-positive bacteria. It has been proposed that lipoteichoic acids (LTAs), polymers anchored in the membrane, and WTAs contribute to the cell wall electrolyte properties, modulate the activity of peptidoglycan-degrading enzymes, and maintain cation homeostasis (24). The biology of WTAs and LTAs has been reviewed recently (17,24).In Bacillus subtilis 168, poly(glycerolphosphate) [poly(Gro-P)], known as the major WTA, is glucosylated and D-alanylated at the C-2 position of the 1,3-phosphodiester-linked glycerol units (17,24). Absence of either of these substituents does not affect cell viability, whereas the polymer backbone is an essential cell constituent (20). Glucosylation of poly(Gro-P) plays an essential role in the attachment of phage 29 to B. subtilis 168 (34). Mutations associated with a 29-resistant phenotype were mapped to three loci, gtaA, gtaB, and gtaC (35). Subsequently, analyses of gtaB-deficient mutants established that gtaB is the structural gene of the UTP:␣-glucose-1-phosphate uridylyltransferase (28, 31), the enzyme that catalyzes the formation of UDP-glucose (UDP-Glc) from ␣-glucose 1-phosphate (␣-Glc 1-P) and UTP. gtaA (rodD), which has been renamed tagE, encodes the enzyme for the transfer of glucosyl groups from UDP-Glc to the poly(Gro-P) moiety of the major WTA (10, 19). In addition, UDP-Glc is required for the polymerization of poly(glucosyl N-acetylgalactosamine phosphate), the minor WTA (17), as well as for the YpfP-governed synthesis of diglucosyldiacylglycerol, the membrane anchor for poly(Gro-P) which forms the main chain of LTA (12).Mutations leading to an ␣-phosphoglucomutase (␣-PGM) deficiency (i.e., mutations associated with the inability to convert glucose 6-phosphate [Glc 6-P] to ␣-Glc 1-P) were mapped to the gtaC locus at 77°on the B. subtilis genome (1, 28). The gtaC mutants were, however, split into two subgroups; the PBSZ-sensitive mutants retained the designation gtaC, whereas the PBSZ-resistant mutants were renamed gtaE (28). Inspection of the B. subtilis 168 chromosome sequence (16) In the present study we found that gtaC and gtaE mutations map to yhxB (designated pgcA in this paper). Below we present evidence that the...