Molecular cloning and preliminary genetic analysis of the men gene cluster of Bacillus subtilis

The Bacillus subtilis chromosomal locus that contains the genes encoding the menaquinone biosynthetic enzymes (the men genes) was cloned by using an integrable plasmid vector. The men cluster was reconstituted on three overlapping recombinant plasmids, and a tentative gene order was derived. Evaluations of the direction of transcription and of transcriptional boundaries suggested that the men genes are expressed in the form of at least one polycistronic message. In addition, a spectrum of Men phenotypes resulting from the integration of different internal fragments of the cluster indicate transcriptional complexities, possibly including an internal promoter. The size of cloned DNA fragments required to encompass the transcription unit, as well as the locations of known men mutations within these fragments, suggests that a gene(s) not previously identified with the men system is also located within the cluster. The cloned men sequences make available probes to examine the patterns of transcription from the men locus in response to changing environmental conditions and during the developmental sequence represented by endospore formation.