Gene-Enzyme Relationships in Histidine Biosynthesis in Bacillus subtilis

Mutants for 9 of the 10 steps in histidine biosynthesis have been isolated and identified by enzyme assay. Each locus has been mapped in relation to the aro cluster and to other histidine loci by deoxyribonucleic acid-mediated transformation. The genes which code for enzymes 3, 6, and 8 of the pathway are linked to the aro cluster. A major histidine linkage group is composed of the genes which specify enzymes 1, 2, 5, 7, and 10. The locus which codes for step 9 of the pathway is unlinked to any other identified his loci. The major histidine cluster is loosely linked to cysB and is unlinked to any of the loci concerned with aromatic amino acid biosynthesis.