Biochemical and genetic studies with arginine and proline auxotrophs of Neisseria gonorrhoeae

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Abstract
The prevalence of specific arginine biosynthesis gene defects was studied for 319 arginine-requiring clinical isolates of Neisseria gonorrhoeae by using the ability of the strains to utilize intermediates of arginine biosynthesis. Only 11 % of the uracil-requiring strains defective in the carbamylation of ornithine to yield citrulline had a defective carbamoylphosphate synthetase gene (carAB). Strains defective in carAB were of auxotype CUH. The other strains (89%) having a dual requirement for citrulline and uracil, which were mostly of auxotype PCU, were defective in the ornithine transcarbamoylase gene (argF). Over 90% of the strains were defective either in argJ (174 strains) or in argF (126 strains). Three argininosuccinate-requiring strains (i.e., defective in argG) of auxotype PAU were identified. Some of the arginine auxotrophs of N. gonorrhoeae defective in carAB, argJ, argF, or argG were complemented by genetic transformation with DNA from recombinant bacteriophages carrying characterized gonococcal arginine biosynthesis genes. Gene defects in proA (five strains) and in proB (six strains) were identified by gonococcal transformation assays with recombinant bacteriophages or plasmids carrying proline biosynthesis genes from N. gonorrhoeae. None of the 11 proline-requiring strains tested was defective in proC.Key words: Neisseria gonorrhoeae, arginine biosynthesis, proline biosynthesis, gene defect, marker rescue.