Ability of Neisseria gonorrhoeae, Neisseria meningitidis, and commensal Neisseria species to obtain iron from transferrin and iron compounds.

The ability of Neisseria species to use iron compounds and to compete with iron-binding proteins was examined with deferrated defined medium and the iron chelator deferoxamine. All Neisseria species were able to assimilate a variety of ferric and ferrous iron salts. They were not able to efficiently solubilize an inorganic iron salt such as ferric nitrate, but were able to use iron chelated by citrate, oxalacetate, pyrophosphate, or nitrilotriacetate. Each of the 95 Neisseria isolates examined was able to use hemin as a sole source of iron, and most, but not all, of the isolates were able to obtain iron from hemoglobin. Heated human serum stimulated growth of all gonococci, meningococci, and some commensal Neisseria species in iron-deficient medium. All gonococci and meningococci were able to scavenge iron from 25% saturated transferrin, whereas most commensal organisms were inhibited by this iron-binding protein. The ability to compete with transferrin was specific, since partially saturated conalbumin was bacteriostatic for all Neisseria species. Although the pathogenic Neisseria species were able to compete more efficiently with transferrin for iron than were the nonpathogenic Neisseria species, no correlation was observed between the virulence of different strains or colony types of gonococci and the ability to scavenge iron in vitro from transferrin or other chelators.