Absence of acetohydroxy acid synthetase in a clinical isolate of Neisseria gonorrhoeae requiring isoleucine and valine

A clinical isolate of Neisseria gonorrhoeae with an unusual growth requirement for isoleucine and valine lacked the activity of acetohydroxy acid synthetase, one of the enzymes required for the biosynthesis of these amino acids. A spontaneous mutant which no longer required isoleucine and valine had acquired this enzymatic activity.