title: Transferrin as a source of iron for Campylobacter rectus.
abstract: OBJECTIVE
  Campylobacter rectus is considered as one of the bacterial species of etiological importance in periodontitis. Iron-containing proteins such as transferrin are found in periodontal sites and may serve as a source of iron for periodontopathogens. The aim of this study was to investigate the capacity of C. rectus to assimilate transferrin-bound iron to support its growth.
  
  
  METHODS
  Growth studies were performed in broth media pretreated with an iron-chelating resin and supplemented with various iron sources. The uptake of iron by C. rectus was monitored using (55)Fe-transferrin. Transferrin-binding activity was assessed using a microplate assay while the degradation of transferrin and iron removal was evaluated by polyacrylamide gel electrophoresis. A colorimetric assay was used to determine ferric reductase activity.
  
  
  RESULTS
  Holotransferrin (iron-saturated form) but not apotransferrin (iron-free form) was found to support growth of C. rectus in an iron-restricted culture medium. Incubation of holotransferrin with cells of C. rectus resulted in removal of iron from the protein. A time dependent intracellular uptake of iron by C. rectus cells from (55)Fe-transferrin was demonstrated. This uptake was significantly increased when bacteria were grown under an iron-limiting condition. Cells of C. rectus did not show transferrin-binding activity or proteolytic activity toward transferrin. However, a surface-associated ferric reductase activity was demonstrated.
  
  
  CONCLUSIONS
  To survive and multiply in periodontal sites, periodontopathogens must possess efficient iron-scavenging mechanisms. In this study, we showed the capacity of C. rectus to assimilate iron from transferrin to support its growth. The uptake of iron appears to be dependent on a ferric reductive pathway.
authors.affiliation: Groupe de Recherche en Écologie Buccale, Faculté de Médecine Dentaire, Université Laval, Québec, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Grenier
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Tanabe