Acquisition of iron by Gardnerella vaginalis

Abstract

Six Gardnerella vaginalis strains were examined for the ability to utilize various iron-containing compounds as iron sources. In a plate bioassay, all six strains acquired iron from ferrous chloride, ferric chloride, ferrous sulfate, ferric ammonium citrate, ferrous ammonium sulfate, bovine and equine hemin, bovine catalase, and equine, bovine, rabbit, and human hemoglobin. All six strains also acquired iron from human lactoferrin, but not from human transferrin, as determined by a liquid broth growth assay. Siderophore production was detected in eight G. vaginalis strains by the chrome azurol S universal chemical assay. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the cytoplasmic membrane proteins isolated from G. vaginalis 594 grown under iron-replete and iron-restricted conditions revealed several iron-regulated proteins ranging in molecular mass from 33 to 94 kDa. These results indicate that G. vaginalis may acquire iron from iron salts and host iron compounds.

FIG. 1

Utilization of iron sources by G. vaginalis 594 as determined by the plate bioassay. G. vaginalis cells were inoculated onto a PSD plate containing 100 μM deferoxamine mesylate as described in Materials and Methods. Filter disks were spotted with dH₂O (a), ferric chloride (b), ferrous chloride (c), catalase (d), bovine hemin (e), or bovine hemoglobin (f).

FIG. 2

Iron-regulated proteins of G. vaginalis 594. Equal amounts of protein (50 μg) were loaded onto each lane. Membrane protein profiles of G. vaginalis 594 cells grown under iron-replete (lane 1) and iron-restrictive (lane 2) conditions are shown. MW, molecular weight markers (in thousands).