Ability of bacteroides species to obtain iron from iron salts, haem-compounds and transferrin

Abstract

Of the five Bacteriodes species of the ‘fragilis group’ only Bacteroides fragilis was able to grow in human plasma. Therefore the capacity of several iron sources to stimulate to growth of Bacteroides species under iron restricted conditions in vitro was tested. The iron chelator bipyridyl was used for the restriction of iron in the media. Ferrous sulphate, ferric ammonium sulphate and ferric citrate stimulated the growth of all five Bacteroides species tested to the same extent. B. fragilis, and to a lesser extent B.thetaiotaomicron and B. distasonis were better able than B. vulgatus and B. ovatus to use haem-compounds as an iron source in the presence of the iron chelator bipyridyl. All five Bacteroides species tested could use 30% iron-saturated transferrin. There was no correlation between the ability of the strains to grow in human plasma and the ability to use either haem-compounds of transferrin as a source of iron.