The ability of Neisseriae to use lactoferrin as an iron source depends on the presence of a lactoferrin binding site

Abstract

We investigated whether the property of Neisseriae to use human lactoferrin (hLf) as an iron source was mediated by the presence of lactoferrin binding sites on the surface of the bacteria. Therefore we iodinated 100% Fe-saturated hLf (^{1 2 5}I-hLf) and incubated various strains of meningococci, gonococci and commensal Neisseria species with the ligand. All meningococci, but only a part of the gonococcal and commensal strains tested were able to bind ^{1 2 5}I-hLf. The binding was mediated by a time-dependent, saturable and reversible process. Bovine Lf, but not human transferrin, inhibited the binding of lactoferrin, indicating that the binding sites were specific for lactoferrin. The expression of Lf binding sites on the surface of the Neisseriae was higly correlated with their ability to use Lf for growth. This finding strongly suggests that the presence of lactoferrin binding sites is a prerequisite for using this iron-binding protein as an iron source.