Cloning, sequencing, and characterization of the Bacillus subtilis biotin biosynthetic operon

A 10-kb region of the Bacillus subtilis genome that contains genes involved in biotin biosynthesis was cloned and sequenced. DNA sequence analysis indicated that B. subtilis contains homologs of the Escherichia coli and Bacillus sphaericus bioA, bioB, bioD, and bioF genes. These four genes and a homolog of the B, sphaericus bioW gene are arranged in a single operon in the order bioWAFDB and are followed by two additional genes, biol and orf2. biol and orf2 show no similarity to any other known biotin biosynthetic genes, Tht biol gene encodes a protein with similarity to cytochrome P-450s and was able to complement mutations in either bioC or bioH of E. coli. Mutations in biol caused B. subtilis to grow poorly in the absence of biotin. The bradytroph phenotype of biol mutants was overcome by pimelic acid, suggesting that the product of biol functions at a step prior to pimelic acid synthesis. The B. subtilis bio operon is preceded by a putative vegetative promoter sequence and contains just downstream a region of dyad symmetry with homology to the bio regulatory region of B. sphaericus. Analysis of a bioW-lacZ translational fusion indicated that expression of the biotin operon is regulated by biotin and the B. subtilis birA gene.