Biosynthesis of Riboflavin, Biotin, Folic Acid, and Cobalamin

This chapter reviews current knowledge of the bio-synthetic pathways for four vitamins (riboflavin, bio-tin, folic acid, and cobalamin) in Bacillus spp. Biosynthesis of these vitamins has been studied in Bacillus subtilis, Bacillus sphaericus, and Bacillus megaterium. Riboflavin, also called vitamin B2, is unique among the vitamins because more is known about the riboflavin (rib) biosynthetic genes in B. subtilis than is known for any other bacterium. The chapter discusses the organization and regulation of the riboflavin biosynthetic genes and presents results from laboratory on how this information can be used to enhance vitamin production by B. subtilis. The molecular genetics and enzymology of the biosynthesis of biotin, also called vitamin B8 or vitamin H, in bacteria have been studied extensively. Enzymatic steps in the biosynthesis of folic acid in enteric bacteria have been extensively are outlined. The chapter focuses on recently characterized B. subtilis genes known to be involved in folic acid biosynthesis. Vitamin B12, a complex organic molecule, is the largest of all the vitamins. Most current knowledge of genetic pathways involved in vitamin B12 or cobalamin biosynthesis comes from studies of Salmonella typhimurium.