SPORULATION AND PRIMARY SIGMA-FACTOR HOMOLOGOUS GENES IN CLOSTRIDIUM-ACETOBUTYLICUM

Using a PCR-based approach, we have cloned various a factor homologous genes from Clostridium acetobutylicum DSM 792. The nucleotide sequenc e of the dnaE-sigA operon has been determined and predicts two genes e ncoding 69- and 43-kDa proteins. The deduced DnaE amino acid sequence has approximately 30% amino acid identity with protein sequences of ot her primases. The putative sigA gene product shows high homology to pr imary a factors of various bacteria, most significantly to Bacillus su btilis and Staphylococcus aureus. Northern (RNA) blot analysis reveale d that both genes form an operon, which is clearly expressed under con ditions that allow for cell division. A promoter sequence with signifi cant homology to the sigma(H)-dependent Bacillus promoters preceded th e determined transcriptional start point, 182 bp upstream of the GUG s tart codon of dnaE. The homologous genes to Bacillus spp. sporulation sigma factors G, E, and K have been cloned and sequenced. Indirect evi dence for the existence of sigma(F) was obtained by identification of a DNA sequence homologous to the respective Bacillus consensus promote r. Southern hybridization analysis indicated the presence of sigma(D) and sigma(H) homologous genes in C. acetobutylicum. A new gene group c onserved within the eubacteria, but with yet unspecified functions, is described. The data presented here provide strong evidence that at le ast some of the complex regulation features of sporulation in B. subti lis are conserved in C. acetobutylicum and possibly Clostridium spp.