The Bacillus subtilis genome sequencing project [Kunst et al., Nature 390 (1997) 249-256] identified ywhE as a gene that potentially encodes a high-molecular-weight class A penicillin-binding protein. Analysis of the expression of a translational ywhE-lacZ fusion showed that ywhE expression is sporulation-specific, and is controlled predominantly by the forespore-specific sigma factor sigma(F), and to a lesser extent by sigma(G). Primer extension analysis identified two transcription start sites located 26 and 27 nucleotides upstream of the ywhE translational initiation codon. Sequences located in the -10 and -35 regions relative to the transcription start sites showed good homology to the consensus sequences for promoter elements of sigma(F)-dependent genes. An insertional mutation in ywhE had no significant effect on growth, morphology, and sporulation, and ywhE spores had normal heat-resistance, cortex structure, and germination and outgrowth properties. However, overexpression of ywhE in Escherichia coli resulted in cell lysis.