Genetic and Biochemical Analysis of the Biotin Loci ofEscherichia coliK-12

Abstract

Some 60 biotin auxotrophs of Escherichia coli K-12 were isolated and classified into four groups according to their cross-feeding patterns, excretion products, and their ability to show a growth response to various biotin vitamers. Since all the mutants could be transduced with Xdbio 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 Xdbio phages that carry portions of the bioA locus. A possible biochemical pathway for the biosynthesis of biotin in E. coli K-12 is discussed.

Mechanistic implications and family relationships from the structure of dethiobiotin synthetase

“…The bio operon of Escherichia. coli has been extensively studied and consists of five genes, bioA, B, F, C and D, which have been positioned at 17 min on the E. coli genetic map on the basis of deletion mapping and heteroduplex analysis of bio transducing phages [2][3][4][5][6][7][8]. On the basis of substrate studies it is known that at least four of the genes of the operon are definitely involved in the E. coli pathway -bioF, bioA, bioD and bioB -and that these encode the enzymes 8-amino-7-oxopelargonate synthase, 7,8-diaminopelargonate synthase, dethiobiotin synthetase (DTBS) and the bioB protein of biotin synthase, respectively [9].…”

Studies on Temperature‐Sensitive Mutants Affecting the Assimilatory Nitrate Reductase of Aspergillus nidulans

“…The precise size and nature of this molybdenum-containing cofactor in Aspergillus is still under investigation, but there are two possible ways in which the products of the five cnx genes could be involved in this formation. Firstly, a cnx gene could specify a small protein or peptide which was structurally part of the cofactor, and hence of the nitrate reductase molecule, or secondly a cnx gene could specify an enzyme which was responsible for the Enzymes ( synthesis of the cofactor from components of the metabolic pool, analogous to the biosynthesis of the coenzyme biotin [4].…”

Genetics of biotin biosynthesis in Bacillus subtilis

“…They could cross-feed strains K12-1, K12-26, and K12-22 of E. coli. The bioB mutants of E. coli, which lack biotin synthetase activity, have the same properties as those of group I mutants (18,24). The bioautographic techniques used to identify biotin precursors in culture supernatant fluids are not sensitive enough to detect DAP because of extremely low growth-promoting activity (18,20).…”

“…These mutant strains excreted 7-KAP in culture supernatant fluids and cross-fed E. coli strain K12-22 only. These are the characteristics of E. coli with a mutation in the bioA gene that codes for 7-KAP:DAP aminotransferase (18,24). Those mutant strains classified into group III grew on all of the compounds tested except pimelic acid.…”