BACKGROUND: In Bacillus mycoides, as well as in other members of the B. cereus 
group, the tubulin-like protein of the division septum FtsZ is encoded by the 
distal gene of the cluster division and cell wall (dcw). Along the cluster the 
genes coding for structural proteins of the division apparatus are intermingled 
with those coding for enzymes of peptidoglycan biosynthesis, raising the 
possibility that genes with this different function might be coexpressed. 
Transcription of ftsZ in two model bacteria had been reported to differ: in B. 
subtilis, the ftsZ gene was found transcribed as a bigenic mRNA in the AZ 
operon; in E. coli, the transcripts of ftsZ were monogenic, expressed by 
specific promoters. Here we analyzed the size and the initiation sites of RNAs 
transcribed from ftsZ and from other cluster genes in two B. mycoides strains, 
DX and SIN, characterized by colonies of different chirality and density, to 
explore the correlation of the different morphotypes with transcription of the 
dcw genes.
RESULTS: In both strains, during vegetative growth, the ftsZ-specific RNAs were 
composed mainly of ftsZ, ftsA-ftsZ and ftsQ-ftsA-ftsZ transcripts. A low number 
of RNA molecules included the sequences of the upstream murG and murB genes, 
which are involved in peptidoglycan synthesis. No cotranscription was detected 
between ftsZ and the downstream genes of the SpoIIG cluster. The monogenic ftsZ 
RNA was found in both strains, with the main initiation site located inside the 
ftsA coding sequence. To confirm the promoter property of the site, a B. 
mycoides construct carrying the ftsA region in front of the shortened ftsZ gene 
was inserted into the AmyE locus of B. subtilis 168. The promoter site in the 
ftsA region was recognized in the heterologous cellular context and expressed as 
in B. mycoides.
CONCLUSIONS: The DX and SIN strains of B. mycoides display very similar RNA 
transcription specificity. The ftsZ messenger RNA can be found either as an 
independent transcript or expressed together with ftsA and ftsQ and, in low 
amounts, with genes that are specific to peptidoglycan biosynthesis.