The catabolism of arginine by Pseudomonas aeruginosa

Mutants isolated from Pseudomonas aeruginosa strain PAO1632 (Hut-Ami) were unable to utilize L-arginine or L-ornithine as the carbon source for growth. Arginine deiminase (AD), catabolic ornithine carbamoyltransferase (cOTC) and N2-acetylornithine 5-aminotransferase (ACOAT) were present in the mutants but these enzymes were not induced to higher levels by exogenous L-arginine. One group of mutants could utilize L-ornithine but not L-arginine and in these strains L-arginine induced the synthesis of ACOAT but not AD or cOTC. The mutations of the arginine utilization-negative mutants were all in genes of the same transductional linkage group and mapped in the 45 to 50 min region of the chromosome. Revertants isolated on L-arginine or L-ornithine plates were derepressed for the synthesis of ACOAT. It is suggested that L-arginine is normally catabolized by the wild-type strain via the arginine deiminase pathway and requires a threshold level of ACOAT. The regulatory factors controlling the functioning of the divergent arginine deiminase and arginine carboxylase pathways are discussed.