Specific action of 4-nitropyridine 1-oxide on Excherichia coli K-12 pro+ strains leading to the isolation of proline-requiring mutants: isolation and characterization of pro-mutants.

A specific action of 4-nitropyridine 1-oxide on Escherichia coli K-12 Pro(+) strains leading to highly efficient, selective isolation of Pro(-) mutants is described. Incubation of Pro(+) cells with a sublethal concentration of 4-nitropyridine 1-oxide in Penassay broth gave Pro(-) mutants, which lacked either the biosynthetic pathway of proline from glutamic acid to glutamyl gamma-phosphate (proB(-)) or the pathway from glutamyl gamma-phosphate to glutamic gamma-semialdehyde (proA(-)) or both. Pro(-) mutants, which have the metabolic block between Delta(1) pyrroline-5-carboxylate (the cyclized dehydration product of glutamic gamma-semialdehyde) and proline (proC(-)) were not found among survivors. Treatment of Pro(+) cells with N-methyl-N'-nitro-N-nitrosoguanidine led to isolation of all three types of Pro(-) mutants, suggesting that the action of 4-nitropyridine 1-oxide on Pro(+) cells is apparently distinct from the action of N-methyl-N'-nitro-N-nitrosoguanidine. F-duction and interrupted mating experiments led to determination of the correlation between proline loci and the biosynthetic pathway of proline from glutamic acid.