The response of the mammal to varying dietary protein intake under conditions in which amino acid and energy requirements are adequately satisfied is a form of adaptation involving the utilization of varying proportions of carbohydrate and amino acids as sources of energy, and is therefore analogous to the adaptation seen in bacteria on change in form of energy source (1). The amino nitrogen re...

A mutation, s, of Neurospora, leads to a 98% reduction in ornithine transcarbamylase (OTC) activity without imposing an arginine requirement. It has been found that the enzyme present in the s strain is different from the normal enzyme in its affinities for ornithine and carbamyl phosphate. The affinity of the mutant enzyme for carbamyl phosphate is much greater than in the case of the wild typ...

Auxotrophic mutants of Rhizobium meliloti 104A14 were isolated using nitrous acid mutagenesis followed by penicillin enrichment. Mutants in ornithine transcarbamylase, argininosuccinate synthetase or serine-glycine biosynthesis formed nitrogen-fixing (Fix+) nodules on the roots of alfalfa (Medicago sativa). Mutants with defects in ornithine, pyrimidine, purine, asparagine, leucine, methionine o...