Sporulation and time course expression of sigma-factor homologous genes in Clostridium acetobutylicum.

The gene for the vegetative sigma factor A of Clostridium acetobutylicum was constitutively transcribed during growth and formed an operon together with dnaE. Sporulation-specific sigma factors E, G, and K were sequentially induced shortly before mature endospores could be detected. Maximal transcription in the course of spore formation was found to be in the order sigE-sigG-sigK, thus matching the pattern described for Bacillus subtilis. From primer extension experiments promoter structures could be deduced with high homology to the Bacillus consensus. Upstream of the spoIIGA-sigE operon a gene with significant similarity to ftsZ could be detected.