Abstract
It is now widely accepted that siderophores play a role in marine iron biogeochemical cycling. However, the mechanisms by which siderophores affect the availability of iron from specific sources and the resulting significance of these processes on iron biogeochemical cycling as a whole have remained largely untested. In this study, we develop a model system for testing the effects of siderophore production on iron bioavailability using the marine copiotroph Alteromonas macleodii ATCC 27126. Through the generation of the knockout cell line ΔasbB::kmr, which lacks siderophore biosynthetic capabilities, we demonstrate that the production of the siderophore petrobactin enables the acquisition of iron from mineral sources and weaker iron-ligand complexes. Notably, the utilization of lithogenic iron, such as that from atmospheric dust, indicates a significant role for siderophores in the incorporation of new iron into marine systems. We have also detected petrobactin, a photoreactive siderophore, directly from seawater in the mid-latitudes of the North Pacific and have identified the biosynthetic pathway for petrobactin in bacterial metagenome-assembled genomes widely distributed across the global ocean. Together, these results improve our mechanistic understanding of the role of siderophore production in iron biogeochemical cycling in the marine environment wherein iron speciation, bioavailability, and residence time can be directly influenced by microbial activities.
Highlights
Iron (Fe) is an essential micronutrient for marine microorganisms, serving as a cofactor in enzymes facilitating fundamental processes such as photosynthesis, respiration, and nitrogen fixation
In summary, we have utilized A. macleodii ATCC 27126 as an effective model organism in order to demonstrate experimentally that the acquisition of iron from specific sources in the marine environment, it was not searched for in this environment is facilitated by the production of a siderophore, in dataset
The bioavailability of colloidal from seawater is a significant step in understanding the cycling of and particulate mineral iron and iron associated with weaker this class of siderophores in the natural marine environment ligand pools was increased through the production of petrobactin. which has the potential to act as a unique control on iron This demonstrates the significant role that heterotrophic bacteria availability [95]
Summary
Iron (Fe) is an essential micronutrient for marine microorganisms, serving as a cofactor in enzymes facilitating fundamental processes such as photosynthesis, respiration, and nitrogen fixation. In oxygenated seawater at pH ~8, inorganic dissolved iron is most thermodynamically stable in the form of Fe (III) hydroxide complexes These hydroxide complexes have the tendency to be scavenged by sinking particulate matter and are in equilibrium with Fe(III) oxyhydroxide particulates which are characterized by low solubility [1]. With a significant iron requirement [3,4,5], marine heterotrophic bacteria are impacted by this iron scarcity and have developed multiple pathways for acquiring sufficient iron from their environment [6]. One such pathway is through the production, exudation, and uptake of siderophores. Several structural classes of siderophores have been isolated directly from seawater [19,20,21,22]
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