Sulphur nutrition and metabolism in various species of Neisseria.

Most Neisseria strains are able to grow with sulphate as a unique source of sulphur. Nevertheless, a cysteine requirement was present in a few strains of N. meningitidis and in 30% of N. flava strains isolated in our laboratory. All strains of N. gonorrhoeae exhibited such a requirement. In every strain tested, the need for cysteine (which can be satisfied by thiosulphate) was linked to the lack of sulphite-reducing-activity. The implications of these findings for the taxonomy and identification of Neisseria are discussed.