Interactions between the nitrogen-fixing cyanobacterium and siderophore-producing cyanobacterium under iron limitation.

As diazotrophic cyanobacteria of tremendous biomass, continuously provide a nitrogen source for carbon-fixing cyanobacteria and drive the generation of primary productivity in marine environments. However, ocean iron deficiencies limit growth and metabolism of . Recent studies have shown the co-occurrence of and siderophore-producing in iron-deficient oceans, but whether siderophores secreted by can be used by to adapt to iron deficiency is not clear. We constructed a mutant strain unable to produce siderophores to explore this issue. filtrates with or without siderophores were added into a microbial consortium consisting of Trichodesmium erythraeum IMS 101 as the dominant microbe with chronic iron deficiency. By analyzing the physiological phenotype, metagenome, and metatranscriptome, we investigated the interactions between the nitrogen-fixing cyanobacterium and siderophore-producing cyanobacterium under conditions of iron deficiency. The results indicated that siderophores secreted by are likely to chelate with free iron in the culture medium of the consortium, reducing the concentration of bioavailable iron and posing greater challenges to the absorption of iron by . These findings revealed the characteristics of iron-competitive utilization between diazotrophic cyanobacteria and siderophore-producing cyanobacteria, as well as potential interactions, and provide a scientific basis for understanding the regulatory effects of nutrient limitation on marine primary productivity.