Iron Transport in Microalgae: the Isolation and Biological Activity of a Hydroxamate Siderophore from the Blue-Green Alga Agmenellum quadruplicatum

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Abstract
Supernatants from Fe-deficient cultures of the marine, coccoid blue-green alga A. quadruplicatum strain PR-6 contained a chloroform-soluble Fe-binding hydroxamate which was stimulatory of the growth of Arthrobacter flavescens JG-9. Production of this material was maximal at 1 .mu.M Fe, was temperature dependent and was increased by adding NH4+. At the absorption maximum of 430 nm the .**GRAPHIC**. of the purified ferric complex was 32. The Fe-free compound yielded nitroso dimers on periodate oxidation and was 60% as active on a weight basis for growth of A. flavescens as ferrioxamine B. At concentrations as low as 1 ng ml-1 the purified hydroxamate stimulated growth of Fe-depleted A. quadruplicatum in a chemically defined medium. Growth factor activity for A. flavescens JG-9 was also found in the supernatants and/or cell extracts of other blue-green algae and several diatoms grown under low-Fe conditions.

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