Genetic and biochemical analysis of the biotin loci of Escherichia coli K-12.

Some 60 biotin auxotrophs of Escherichia coli K-12 were isolated and classified into four groups according to their cross-feeding patterns, excertion products, and their ability to show a growth response to various biotin vitamers. Since all the mutants could be transduced with lambdadbio phages known to carry the entire bioA locus, it was concluded that all of the mutation sites were located in this locus. It was also possible to derive a gene order for the different mutant groups on the basis of transduction studies with various lambdadbio phages that carry portions of the bioA locus. A possible biochemical pathway for the biosynthesis of biotin in E. coli K-12 is discussed.