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The role of bacteria in the origin of iron formations (IF) remains unclear because no direct evidence for their involvement exists. This study shows that spherical siderite in deep-water IF represents a biosignature for photoferrotrophy, whereas massive siderite reflects high cyanobacterial biomass in shallow-water.

Precambrian banded iron formations contain thin alternating layers of iron- and silica-rich minerals. Microbial culture experiments show that these alternations could be caused by changes in the relative dominance of microbial iron oxidation and abiotic silica precipitation driven by fluctuating ocean temperature.

To understand the network of reactions within the biogeochemical (iron) Fe cycle, it is necessary to determine which abiotic or microbially mediated reactions are dominant under various environmental conditions. Kappler and colleagues review the major biotic and abiotic reactions in the biogeochemical Fe cycle.

In this Review, Kappler and colleagues highlight recent advances in our understanding of the biogeochemical iron cycle, exploring the great complexity of the processes involved and novel mechanistic insights that have been gained.

Twisted iron-rich stalks provide evidence for iron-oxidizing bacteria in sedimentary deposits. Picard et al. show experimentally the persistence of such structures exposed to temperatures and pressures typical of diagenetic conditions, providing spectroscopic signatures to aid their reliable identification.

Biochar promotes plant growth via a slow release of nutrients; however, a mechanistic understanding of nutrient storage in biochar is lacking. Here, using high-resolution spectromicroscopy and mass spectrometry, the authors identify an organic coating on co-composted particles that enhances nutrient retention.

A directional long-distance ET chain from reduced to oxidized zones occurs in the subsurface, which reaches the distance of over centimeter scale. This implicates an overlooked contribution of “remote” electron sources/sinks for local biogeochemical processes.

An investigation using various methods reports an association between adeno-associated virus 2 and paediatric hepatitis of unknown aetiology.

Banded iron formation deposition by photoferrotrophic organisms in the early Earth’s oceans may have been inhibited by competition for iron and toxicity from nitrate-reducing microorganisms, according to a microbial incubation and numerical modelling study.

Analyses of genomes from 914 children, adolescents, and young adults provide a comprehensive resource of genomic alterations across a spectrum of common childhood cancers.

Humic substances make up a significant fraction of the natural organic matter in terrestrial and aquatic environments. Laboratory experiments suggest that humic substances serve as fully regenerable electron acceptors in recurrently anoxic environments such as peatlands.

Earth’s initial oxygenation took several hundred million years. Experiments and geochemical modelling suggest that early photosynthetic marine microbes may have been repeatedly stressed by Fe(II) delivered by submarine volcanism.

The decay of soil and sedimentary organic matter yields organic compounds with a high molecular weight, termed humic substances. Sediment-incubation experiments suggest that microbial reduction of solid-phase humics can accelerate iron(III) oxide reduction in wetland soils.

In ice-rich Siberian permafrost sediments deposited during the Pleistocene, 33-74% of the organic carbon is mineral-bound favoured by the presence of reactive iron, which can reduce microbial CO₂ production after thawing

A case–control study investigating the causes of recent cases of acute hepatitis of unknown aetiology in 32 children identifies an association between adeno-associated virus infection and host genetics in disease susceptibility.

The impacts of a melting Arctic on the biogeochemistry of marine ecosystems are unknown. Here, the authors investigate glacial input of iron to Svalbard fjords finding that reworking of glacial iron in fjord sediment is important to make iron bioavailable, but could be susceptible to glacial retreat.

The means by which planktonic cyanobacteria were able to persist through the Archean despite high fluxes of UV radiation are unclear. Here, the authors show that Fe(III)-Si rich precipitates in the Archean photic zone could have provided early planktonic cyanobacteria an effective shield against UV-C radiation.

The coupling of anaerobic oxidation of methane and arsenate reduction is an important pathway of releasing arsenic from soils, according to incubation experiments of arsenate-contaminated wetland soils.

Iron minerals trap carbon in permafrost, preventing microbial degradation and release to the atmosphere as CO₂, but the stability of this carbon as permafrost thaws is unclear. Here the authors use nanoscale analyses to show that thaw conditions stimulate Fe-reducing bacteria that trigger carbon release.

Methane can increase groundwater arsenic contamination by triggering the dissolution of arsenic-bearing iron oxide minerals by methane-oxidizing microorganisms, according to microcosm experiments on arsenic-bearing sediments from the Red River Delta, Vietnam.

Thawing of permafrost in peatlands decreases the immobilization and retention of phosphate with Fe oxides and releases initially sorbed phosphate, according to incubation experiments with Fe-rich sediments in soil along a permafrost thaw gradient.

Complex interactions between future climate, soil microbiome, and soil cadmium negatively impact microbial activity and nutrient cycling in soil with pH below 7, which potentially affects crop production, groundwater quality, and climate feedback, according to a series of laboratory experiments conducted with sampled soil.

In this Review, Philippot et al. explore how soil microorganisms can affect the physical and chemical properties of soil and discuss the ecological and evolutionary consequences of these microbially driven shifts in soil properties. They also explore how microbially mediated changes in soil properties can be used to combat threats to soil health and other environmental challenges.

Coupled Fe–C cycles are important considerations for carbon sequestration, soil fertility and ecosystem functions. This Review explores the role of Fe minerals in stabilizing and degrading organic matter and the role of organic matter in enhancing reactivity of Fe minerals under different conditions.

Framboidal-like pyrite may not only fingerprint microbial sulfur cycling but also record microbial iron cycling in hydrothermal sulfide systems, according to experimental work with biogenic and abiogenic magnetite and electron microscopy observations.

Microbial reduction and dissolution of reactive iron (III) mobilizes mineral-bound organic carbon, which contributes to carbon dioxide production and promotes methanogenesis and methane emission before complete permafrost thaw, according to an observational study along collapsing palsa hillslopes in Sweden.