Accumulation of iron by yersiniae

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Abstract
Escherichia coli, Bacillus megaterium, and 3 spp. of yersiniae grew rapidly without significant production of soluble siderophores in a defined Fe sufficient medium (20 .mu.M Fe3+). In Fe-deficient medium (0.1-0.3 .mu.M Fe3+) all organisms showed reduced growth, and there was extensive production of siderophores by E. coli and B. megaterium. Release of soluble siderophores by Yersinia pestis, Y. pseudotuberculosis or Y. enterocolitica in this medium was not detected. Citrate (1 mM) inhibited growth of yersiniae in Fe-deficient medium, indicating that the organisms lack an inducible Fe3+-citrate transport mechanism. Uptake of 59Fe3+ by all yersiniae was an energy-dependent saturable process, showing increased accumulation after adaptation to Fe-deficient medium. Growth of Y. pseudotuberculosis and Y. enterocolitica but not Y. pestis on Fe-limited solid medium was enhanced to varying degrees by exogenous siderophores (desferal, schizokinen, aerobactin and enterochelin). Only hemin (0.1 pmol) or a combination of inorganic iron plus protoporphyrin IX promoted growth of Y. pestis on agar rendered highly Fe deficient with egg white conalbumin (10 .mu.M). Growth of Y. pseudotuberculosis and Y. enterocolitica was stimulated on this medium by Fe3+ or hemin. Apparently, hemin can serve as a sole source of Fe for yersiniae and the organisms possess an efficient cell-bound transport system for Fe3+.