Abstract
The pTiC58 plasmid noc genes of A. tumefaciens C58 code for nopaline oxidase (nocC), the inducible periplasmic protein n1 (nocB) and a function(s) required for ornithine catabolism (nocA). Strains C58 and Ach-5 of A. tumefaciens have chromosomal ornithine catabolism genes. The chromosomal orc gene codes for ornithine dehydrogenase. Strain C58 is normally orc, but orc+ mutants can be selected. Chromosomal orc and pTiC58 nocA plasmid genes were characterized. Complementation of most chromosomal orc mutants by pTiC58 restored growth on nopaline and L-ornithine but did not restore ornithine dehydrogenase activity. Ornithine is an intermediate of nopaline degradation and the Ti plasmid and chromosomes code for ornithine-degradative enzymes. A model for nopaline catabolism is presented.