CLONING AND CHARACTERIZATION OF A BACILLUS-THURINGIENSIS HOMOLOG OF THE SPOIIID GENE FROM BACILLUS-SUBTILIS

The SpoIIID protein of Bacillus subtilis (Bs) is a small DNA-binding p rotein that is essential for gene expression of the mother cell compar tment during sporulation. We have cloned a DNA fragment from Bacillus thuringiensis (Bt) that showed a specific hybridization with the Bs sp oIIID gene. Sequence analysis found an open reading frame encoding 90 amino acids (aa), which are 89% identical to the deduced aa sequence o f Bs spoIIID. Upstream from the transcription start point (rsp), a nuc leotide sequence highly homologous to the consensus sequence motif for the sigma(35)-recognized promoters was found. Northern blot analysis has indicated that the expression of the gene is induced only at the m idsporulation stage, and that the gene constitutes an operon with a do wnstream gene, mreB. The Bs strain carrying the spoIIID Delta erm or s poIIID83 mutation completely restored sporulation ability upon introdu ction of the spoIIID homologous gene from Bt. These results strongly s uggest that the gene we have cloned is a Bt homolog of spoIIID.