Microbial Iron Oxidation in Aquatic Ecosystems

Microbial iron oxidation is a pivotal process in both freshwater and marine environments, driving the transformation of soluble ferrous iron (Fe2+) into insoluble ferric iron (Fe3+) minerals. This biogeochemical reaction is primarily mediated by specialised bacteria and archaea that harness energy from the Fe2+/Fe3+ redox couple to fix carbon dioxide, thereby linking iron cycling to primary production and organic carbon turnover. In stratified water bodies and sediments, iron‐oxidising microorganisms inhabit narrow oxic–anoxic transition zones, where they form characteristic iron‐rich mats and encrust biofilms. These structures influence nutrient sequestration, trace‐metal mobility and contaminant attenuation, and leave morphological and chemical biosignatures that inform studies of early Earth and astrobiology. At the molecular level, electron transfer is facilitated by periplasmic and outer‐membrane multiheme cytochromes, while extracellular biomineral scaffolds such as stalks and sheaths aid in waste‐product removal and colony architecture. The ecological distribution of neutrophilic iron oxidisers (for example, members of the Gallionellaceae in freshwater and Zetaproteobacteria in marine settings) reflects adaptations to oxygen concentration, pH and competing abiotic oxidation. Advances in genomics, meta-omics and in situ imaging have deepened our understanding of iron‐oxidation pathways, community interactions and the role of these microbes in global iron and carbon cycles. Practical applications range from bioremediation of metal‐contaminated waters to the development of biosensors and bioinspired materials for pollutant capture.

Research from Nature Portfolio

No recent Nature Portfolio content available.

Microbial Iron Oxidation in Aquatic Ecosystems publication trend

The graph below shows the total number of articles in microbial iron oxidation in aquatic ecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Chemolithotrophy: Metabolic process by which organisms derive energy from the oxidation of inorganic compounds, here ferrous iron, to fix carbon.

Microaerophilic: Characteristic of organisms that require oxygen at concentrations lower than atmospheric levels, typical of iron‐oxidising bacteria at redox interfaces.

Multiheme cytochrome: Electron‐transfer protein containing multiple haem cofactors, facilitating extracellular electron transport during iron oxidation.

Exopolysaccharide: Extracellular polymeric carbohydrate matrix produced by microbes, often forming stalks or sheaths that support biomineral growth and community structure.

Biomineralisation: Biological process of mineral formation, in this context the deposition of ferric oxyhydroxides around microbial cells or extracellular filaments.

Redox gradient: Spatial variation in oxidation–reduction potential, creating niches where iron oxidisers localise to access both Fe2+ and O2.

References

1. Gallionellaceae pangenomic analysis reveals insight into phylogeny, metabolic flexibility, and iron oxidation mechanisms. mSystems (2023).
2. Microbial community response to hydrocarbon exposure in iron oxide mats: an environmental study. Frontiers in Microbiology (2024).
3. FeGenie: A Comprehensive Tool for the Identification of Iron Genes and Iron Gene Neighborhoods in Genome and Metagenome Assemblies. Frontiers in Microbiology (2020).