Molecular characterization of the argJ mutation in Neisseria gonorrhoeae strains with requirements for arginine, hypoxanthine, and uracil.

Arginine auxotrophs are commonly encountered among clinical isolates of Neisseria gonorrhoeae. Arginine auxotrophs which also require hypoxanthine and uracil (AHU strains) compose a unique set of strains that are highly homogeneous and are believed to be clonally derived. The Arg- phenotype of these strains is due to a lesion in the argJ gene encoding ornithine acetyltransferase. We have cloned the mutant argJ gene from an AHU strain and compared the sequence of this gene to the wild-type argJ gene. The mutant gene contained a 3-bp deletion within a repetitive region of the argJ gene. This mutation was restored to the wild-type sequence in a naturally occurring Arg+ revertant of the AHU strain. This deletion was detected in a wide variety of other AHU strains but not in other ArgJ- strains or in ArgJ+ strains, supporting the theory that AHU strains are clonally derived.