ANALYSIS OF THE BIOTIN BIOSYNTHESIS PATHWAY IN CORYNEFORM BACTERIA - CLONING AND SEQUENCING OF THE BIOB GENE FROM BREVIBACTERIUM-FLAVUM

The biotin biosynthetic pathway of three coryneform bacteria, Brevibac terium flavum, Brevibacterium lactofermentum, and Corynebacterium glut amicum were analysed by cross-feeding experiments using several Escher ichia coil biotin-requiring mutants. The three strains of coryneform b acteria tested were able to convert 7-keto-8-aminopelargonic acid to b iotin, through a biotin synthetic pathway identical to that from E. co il. The biotin biosynthetic gene, bioB, of B. flavum was cloned by phe notypic complementation of E. coil bioB mutants. The bioB gene was loc ated on a 1.7 kb HindIII-SacI DNA fragment. Nucleotide sequence analys is of this fragment revealed that the bioB gene of B. flavum consists of a 1005 bp open reading frame. Its deduced amino acid sequence is 35 .7% and 31.5% identical to that of the E. coil and Bacillus sphaericus bioB gene products, respectively. B. flavum mutants obtained by in vi vo disruption of the bioB gene lost their ability to grow on minimal m edium containing dethiobiotin, indicating that the bioB gene product i s necessary for the conversion of dethiobiotin to biotin.