Siderophore-Mediated Aluminum Uptake by Bacillus megaterium ATCC 19213.

The bacterium Bacillus megaterium ATCC 19213 is known to produce two hydroxamate siderophores, schizokinen and N-deoxyschizokinen, under iron-limited conditions. In addition to their high affinity for ferric ions, these siderophores chelate aluminum. Aluminum was absorbed by B. megaterium ATCC 19213 through the siderophore transport receptor, providing an extra pathway for aluminum accumulation into iron-deficient bacteria. At low concentrations of the metal, siderophore-mediated uptake was the dominant process for aluminum accumulation. At high concentrations of aluminum, passive transport dominated and siderophore production slowed the passive transport of aluminum into the cell. Siderophore production was affected by the aluminum content in the media. High concentrations of aluminum increased production of siderophores in iron-limited cultures, and this production continued into stationary phase. Aluminum did not stimulate siderophore production in iron-replete cultures. The production of siderophores markedly affected aluminum uptake. This has direct implications on the toxicity of heavy metals under iron-deficient conditions.