Abstract
The mechanism of iron acquisition was studied in nitrogen-fixing Azomonas macrocytogenes. Spent solid agar plating medium samples from Fe-deficient and Fe-sufficient cultures were subjected to the high voltage paper electrophoresis siderophore assay. A yellow-green fluorescent peptide was elicited only under conditions of iron deficiency, whereas a novel dark blue fluorescent, Arnowpositive phenolic compound was detected under both Fe-deficient and Fe-sufficient conditions. Both compounds formed colored complexes with ferric iron. SDS-PAGE analysis of outer envelope protein preparations revealed the hyperproduction of an 83 kDa protein under iron-limiting conditions. Chemical analysis indicated that the phenolate was 3,4-dihydroxybenzoic acid (protocatechuic acid), a compound previously unreported as an extracellular product of a diazotroph.
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