Characterization of the mbl determinant and cloning of the spoIIID gene from Bacillus cereus ATCC 10987

To examine the transcriptional start site of the putative Bacillus cereus m bl gene, we have cloned and sequenced the upstream region of the previously reported B. cereus mbl determinant, which showed sequence similarity to th e mreB morphogene from Escherichia coli. Primer extension analysis revealed the transcriptional start site of mbl to 259 bp upstream of the putative t ranslational start site and showed that the mbl gene was expressed at 3, 6, and 10 h of growth after inoculation. Antibodies against B, cereus Mbl sho wed that even though mbl mRNA was present in amounts detectable with Northe rn blot analysis exclusively in the early logarithmic growth phase, the amo unt of protein was constant during the cell cycle. Immunogold labeling cryo -transmission electron microscopy indicates that B. cereus Mbl is a cytopla smic protein. The upstream sequence of mbl revealed two open reading frames , spoIIID and orf1. The amino acid sequence of B. cereus SpoIIID is identic al to the SpoIIID sequence from Bacillus thuringiensis. Primer extension sh owed that mbl is not cotranscribed with spoIIID.