The metals atlas

Alternative nitrogenase and microbial vanadium reduction

Vanadium illustrates two different ways a microbe can use an element: as part of an enzyme that fixes nitrogen, and as an external electron acceptor during anaerobic metabolism. Its importance is conditional. Availability of molybdenum helps determine when alternative nitrogen fixation matters, while vanadium speciation and culture chemistry influence reduction and growth.

Oxidative-stress defense and environmental manganese cycling

Manganese equips Staphylococcus aureus with defenses against superoxide. Host calprotectin can bind that manganese before the bacterium acquires it, weakening those defenses and helping neutrophils kill. This links metal withholding directly to immune attack. In a separate environmental metabolism, specialized bacteria obtain energy by oxidizing manganese and use it to support carbon fixation.

Siderophore capture, immune evasion, and iron-dependent metabolism

Siderophores capture iron that bacteria otherwise struggle to acquire. The host can intercept that delivery, while pathogens can modify the carrier to escape. This molecular contest helps determine microbial growth and virulence. Iron also supplies enzyme cofactors and respiratory substrates; its biological effect depends on which organism reaches which chemical pool.

Corrinoid sharing, vitamin B12 uptake, and metal interference

Cobalt sits at the center of vitamin B12 and related corrinoid cofactors, but the surrounding molecule determines who can use it. Microbial communities exchange, compete for, and chemically remodel these cofactors. This molecular ecology is distinct from exposure to free cobalt ions, which can interfere with essential cellular machinery.

Urease, [NiFe]-hydrogenases, and nickel-dependent glyoxalase I

For Helicobacter pylori, nickel helps turn stomach acidity into a survivable condition: nickel-loaded urease converts urea to ammonia, raising local pH. The bacterium also uses a nickel-containing hydrogenase. Storage and delivery proteins keep these enzymes supplied. Nickel use remains organism-specific: E. coli glyoxalase I provides a separate, biochemically established example.

Methane oxidation, copper acquisition, and metal toxicity

Copper can disable bacterial metabolism by stripping iron from exposed iron–sulfur enzyme clusters. In E. coli, that damage interrupts amino-acid production even without oxygen. Host cells can also deliver copper toward engulfed bacteria, while microbial exporters oppose the exposure. Copper's useful cofactor roles and destructive effects depend on where it is delivered.

Zinc capture, manganese-transport blockade, and host–microbial competition

Zinc can inhibit a bacterium by blocking its access to manganese. In Streptococcus pneumoniae, zinc occupies a metal-binding gateway and leaves the cell less able to resist oxidative attack. Elsewhere, high-affinity zinc uptake helps microbes compete under host zinc withholding. The local metal mixture and the acquisition machinery determine the outcome.

Molybdenum-cofactor respiration and nitrogen fixation

Molybdenum is incorporated into specialized cofactors that enable microbial redox reactions. Respiratory molybdenum cofactors are chemically distinct from the iron–molybdenum cofactor of nitrogenase. In the intestine, their importance depends on available electron donors and acceptors: inflammation can create a metabolic opportunity for organisms able to use these pathways.

Tungstoenzymes and competition with molybdenum

Tungsten is a genuine enzyme cofactor in some microbes, including cultured organisms associated with the human gut. Yet tungstate can inhibit other microbes by interfering with molybdenum-dependent metabolism. The direction of an effect therefore depends on the enzyme repertoire, the chemical substrate being processed, and the surrounding ecological conditions.

A laboratory mimic of the phosphate signal that switches regulators on

Beryllofluoride can make a bacterial signaling protein behave as though it has been phosphorylated. In NtrC, it stabilizes an active-state analogue and makes a normally transient regulatory switch easier to study. This is a chemically specific use of beryllium to probe signaling; beryllium sulfate has a separate record of inhibiting selected enzymes.

Organic-acid chemistry and strain-dependent sequestration

Microbial metabolism can change the ligands surrounding aluminum. Aluminum-stressed Pseudomonas fluorescens redirected organic-acid metabolism toward oxalate, including a signal consistent with complexed oxalate. Food- and gut-associated bacteria also differed in their ability to remove Al(III) from solution. These findings identify chemical handling as the starting point; they do not yet establish which route explains intestinal community changes in exposed animals.

Oxidation-state-dependent stress and reduction

Chromium is a case study in why both oxidation state and reaction mechanism matter. Bacteria can help convert chromate, Cr(VI), to Cr(III), but the products may remain soluble. A culture that reduces chromium is not necessarily removing it, and a protein associated with reduction is not automatically a dedicated chromate-reducing enzyme.

Ligand-dependent entry through a substrate-uptake pathway

The molecule carrying germanium can determine whether a bacterium accumulates it. Pseudomonas putida accumulated more germanium with catechol than with acetate alone, and a later uptake phase tracked catechol degradation. The investigators proposed entry of a germanium–catechol complex through an induced substrate-transport system. This makes ligand recognition a concrete mechanistic hypothesis, while the exact transporter remains unresolved.

Gut microbial chemistry changes the arsenic species encountered by the host

Gut microbes can modify arsenic before it is absorbed, adding methyl groups and forming sulfur-containing arsenicals. These reactions change the molecules present, and methylation is not automatically detoxification: a human-colon culture produced reactive MMA(III) as well as other products. Mouse experiments also show that an intact microbiota can protect against acute arsenic exposure. Transformation chemistry and host protection therefore need to be measured together.

An alternative carbon-acquisition cofactor in marine diatoms

A metal usually studied for toxicity can perform useful chemistry in the right enzyme. When zinc was scarce, the marine diatom Thalassiosira weissflogii used a cadmium-containing carbonic anhydrase to support inorganic-carbon acquisition and growth. Carbonic anhydrase interconverts carbon dioxide and bicarbonate, connecting the metal site to photosynthetic carbon supply. This specialized adaptation is separate from cadmium’s intestinal toxicity.

Organotin transformation and chemical-species dependence

Tin–microbe interactions are strongly compound dependent. Environmental bacteria can remove organic groups from tributyltin or add methyl groups to inorganic tin. Separately, organotin exposure can alter a mammalian gut community. Neither process can be generalized to all tin compounds, and transformation does not necessarily reduce toxicity.

Microbial redox transformations in contaminated environments

Antimony is a metalloid involved in microbial oxidation, reduction, and mineral formation. Its environmental fate depends on both the antimony species and the metabolism available in a particular setting. The strongest evidence here comes from isolates, genetic experiments, and sediment studies, rather than human microbiome research.

Tellurite toxicity and reductive resistance

Tellurium biology includes both toxicity and specialized respiration. Tellurite, Te(IV), challenges bacterial redox systems, while selected environmental isolates can conserve energy using tellurate, Te(VI). These are distinct chemical species and physiological outcomes; neither should stand in for all tellurium–microbe interactions.

Microbial methyl transfer changes mercury’s exposure hazard

Microbes change mercury’s biological consequences by changing its molecular form. HgcAB-dependent methylation converts inorganic mercury into methylmercury, using a cobalt-containing cobalamin cofactor and iron–sulfur chemistry. Intestinal demethylation is a separate process that can contribute to elimination after ingestion. The central question is which chemical conversion is occurring, where, and at what rate—not simply whether mercury and microbes coexist.

Experimental intestinal and soil-community stress

Thallium has three distinct microbial evidence streams: controlled intestinal exposure in mice, community surveys of contaminated soils, and experiments demonstrating microbial oxidation in freshwater. Together they show why thallium concentration alone is insufficient: chemical species, habitat, and biological activity change the interpretation.

Microbial binding and host handling change lead bioavailability

A gut community can change how much ingested lead reaches the host. Bacterial isolates differ greatly in their capacity to remove Pb(II) from solution, while germ-free mice absorbed and distributed more lead than conventional mice. Binding in the lumen and altered host metal-handling pathways are plausible contributors. The mouse comparison establishes a microbiota-dependent effect, but does not by itself separate those routes.

Particle contact, microbial spatial organization, and nutrient cycling

Titanium dioxide can change how microbes organize as well as which microbes are present. In culture, E171 particles clustered with bacteria and enhanced biofilm formation; in exposed mice, small compositional shifts accompanied changes in metabolites and intestinal markers. These observations motivate a physical-contact mechanism, but the causal link from particle-associated culture biofilms to effects inside the animal remains unresolved. Soil work separately connects nanoparticle exposure to impaired nitrification.

Iron mimic that turns microbial iron acquisition into a vulnerability

Gallium makes the distinction between acquiring a metal and using it impossible to miss. Its Ga³⁺ ion resembles ferric iron, Fe³⁺, but cannot perform iron’s redox chemistry. Siderophores—the molecules microbes release to scavenge iron—can therefore encounter a convincing chemical substitute that supplies no usable iron. The result depends on which siderophore binds it, where gallium goes, and which microbial functions lose access to working iron.

Oral biofilms on zirconia surfaces

Zirconium enters this literature mainly as zirconia, the solid zirconium oxide ceramic used in dental components. Its microbial relevance concerns colonization of a surface, not an established nutritional role or the antibacterial action of dissolved zirconium. Studies comparing zirconia with titanium have produced different adhesion results. Surface preparation, organism, time, and the endpoint being measured help explain why a single material ranking is inadequate.

Antimicrobial activity versus surface performance

Niobium antimicrobial research is strongly formulation-dependent. A niobium oxalate dispersion, niobium pentoxide nanoparticles, and a polymer-bound surface layer are different materials with different opportunities to contact bacteria. The most informative evidence includes an unsuccessful coating experiment: activity against cells in liquid did not automatically prevent a multispecies biofilm from growing on titanium.

Experimental antibacterial coordination complexes

Ruthenium antibacterial activity belongs to particular coordination compounds and delivery systems. Ligands determine how the metal-containing molecule interacts with cells, while a photosensitizing formulation also depends on illumination. The literature spans resistant Gram-positive isolates, experimental skin infections, and dental biofilms. These are distinct research settings, not interchangeable demonstrations that ruthenium itself is an antibiotic.

Antibacterial activity of valproate conjugates

Rhodium is being investigated through engineered coordination compounds whose ligands are part of the biological intervention. Two instructive approaches are valproate conjugation and exchangeable nitrogen-donor ligands. Both concern laboratory compound development. Neither demonstrates that exposure to rhodium alone produces the same effect or that a successful bacterial assay predicts a useful treatment.

Released silver ions disrupt bacterial proteins and membranes

Silver’s antimicrobial action depends on the chemical species that reaches a bacterium. Ag(I) can disrupt protein chemistry, iron homeostasis, metabolism, and membrane integrity; in tested nanoparticle preparations, oxidative release of Ag(I) explained the antibacterial activity. The particle can therefore act as an ion source, while its size and coating control delivery. Bacterial responses can also aggregate particles and reduce their activity.

Surface architecture and bacterial attachment

Hafnium research provides two very different antimicrobial examples: nanostructured oxide-coated surfaces and functionalized oxide nanoparticles. In the first, surface geometry is central; in the second, a targeting and polymeric formulation changes interaction with dental bacteria. Neither example supports treating bulk hafnium, dissolved ions, and engineered particles as interchangeable agents.

Host cells, bacteria, and implant surfaces

Tantalum highlights a distinction between killing bacteria directly and helping a host resist infection at an implant interface. Two preclinical studies reported favorable infection outcomes despite little or no intrinsic antibacterial advantage in isolated culture assays. Their proposed explanations involve host cells and local immunity, making the living tissue environment part of the material’s effect.

Structure-dependent antimicrobial candidates

Rhenium compounds show why coordination structure and activation conditions must accompany any antimicrobial claim. Closely related carbonyl complexes can be inactive or active, and illumination can change the bacterial spectrum. The evidence includes chemical screens, computational target hypotheses, and carefully controlled light-versus-dark susceptibility assays. It does not establish an antimicrobial property of elemental rhenium.

Ligand-dependent bacteriostasis

Osmium antimicrobial research spans growth-inhibitory organometallic complexes and a light-activated composite material. These interventions differ in ligand structure, delivery, and mechanism. The most useful evidence combines positive bacterial findings with explicit mammalian-cell comparisons: high potency alone does not establish a clinically useful therapeutic margin.

Experimental targeting of biofilm DNA

Iridium complexes are being developed for several distinct antibacterial strategies, including extracellular-DNA disruption, light-driven oxidation, and direct growth inhibition. Their ligands and physical conditions define the intervention. A biofilm-active compound, an imaging photosensitizer, and an anti-staphylococcal diamine complex cannot be treated as interchangeable evidence about iridium.

Replacing catalytic zinc to disable antibiotic resistance

Bismuth can disable a resistance enzyme by replacing the metal that makes it work. In tested metallo-β-lactamases, Bi(III) displaced catalytic Zn(II), stopping the enzymes from breaking open β-lactam antibiotics and restoring meropenem activity in bacterial assays and mice. This is metal substitution with a functional consequence: the antibiotic survives because the bacterial enzyme loses its chemistry. Bismuth also affects other targets in Helicobacter pylori.

Modulation of bacterial gene expression

Scandium can alter bacterial gene expression and the production of extracellular enzymes and secondary metabolites. It is a rare-earth element, but not a lanthanide. The evidence here concerns a culture condition that changes microbial behavior, rather than an established scandium-containing enzyme or a universal nutritional requirement.

Binding to microbial biomass

Yttrium has direct microbial evidence for biosorption and for recognition by a selective metal-binding protein. Neither observation establishes that bacteria require yttrium for growth. Although grouped with the rare-earth elements, yttrium is not a lanthanide, and its biology should be evaluated on its own evidence.

A catalytic metal for bacterial alcohol oxidation

Lanthanum can occupy an enzyme’s catalytic site rather than merely stick to a bacterium. In ExaF, La(III) works with the organic cofactor PQQ in alcohol oxidation; the lanthanum-containing enzyme efficiently processed ethanol, whereas the preparation obtained with calcium alone had little activity. Acquiring this metal can therefore unlock useful substrate chemistry for a bacterium.

Enabling the methanol-oxidation step in methane metabolism

Cerium is part of the machinery that lets selected bacteria use methane. After methane is converted to methanol, a cerium-containing XoxF methanol dehydrogenase carries out the next oxidation step. In Methylacidiphilum fumariolicum SolV, lanthanide availability was required for growth and the metal was located in the enzyme. That links an environmental metal supply to a defined carbon-processing reaction.

Cofactor supporting alcohol oxidation

Praseodymium has direct experimental support as a usable metal in bacterial alcohol oxidation. Evidence comes from a nonmethylotrophic soil bacterium and from comparative studies of methylotrophs. This is an element-specific experimental role, rather than an inference based only on the better-known lanthanum and cerium examples.

A PQQ-associated enzyme metal whose acquisition controls access to catalysis

Neodymium can be built directly into a working methanol-oxidation enzyme. Structure and activity measurements place Nd in the PQQ-containing active site of XoxF1. The biological challenge starts earlier: poorly soluble neodymium must first be made accessible, and a secreted metallophore called methylolanthanin contributes to acquisition. Uptake and catalysis are two distinct links in the same metal-dependent pathway.

Strain-dependent use and bioaccumulation

Gadolinium illustrates three different microbial outcomes: use after laboratory adaptation, binding to microbial biomass, and cellular stress in yeast. These should not be conflated. A bacterium able to grow with gadolinium has a particular physiological solution; it does not demonstrate a general nutrient role or a beneficial effect in a host microbiome.

Comparative enzyme chemistry and evidence gaps

Samarium, europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium belong in the atlas, but their evidence is uneven. Comparative enzyme assays cover the series; europium also has direct structural and growth evidence, and samarium has experimental biomineralization evidence. No single “rare-earth effect” should be assigned to every member.

Urease changes water chemistry so growing minerals capture strontium

Strontium can be captured because bacteria build a different chemical environment. Urea breakdown releases ammonium and bicarbonate and raises pH, favoring calcium-carbonate formation. Dissolved Sr can then enter or associate with the growing mineral. The microbe drives the precipitation chemistry; strontium is transferred into a solid rather than consumed as food.

Direct and indirect radionuclide reduction

Technetium connects microbial electron transfer to radionuclide mobility. Dissolved Tc(VII), commonly studied as pertechnetate, can be reduced to less soluble Tc(IV). Microbes may catalyze that change directly or generate iron minerals that do the reducing chemistry outside the cell.

Electron-transfer-driven nanoparticle formation

Palladium is a useful example of microbial metal recovery. Bacteria can reduce soluble Pd(II) to elemental Pd(0), forming particles associated with biomass. The reaction links metabolism to materials synthesis, but it does not mean palladium is a nutrient or that every palladium compound behaves alike.

Bioleaching electronic waste

Acid-producing microbial communities can release indium from discarded displays. They create a leaching environment; the evidence does not imply an indium-dependent metabolism or nutritional requirement.

Competition with potassium uptake

Cesium uptake can overlap with potassium transport, while resistance may depend on maintaining other intracellular ions. Uptake, tolerance, and useful environmental capture are distinct outcomes.

Symbiont-associated biomineralization

Marine bacteria and extracellular polymers can concentrate barium and promote barite formation. A sponge symbiont also mineralizes barium internally, demonstrating a distinct host-associated route.

Microbial reduction of metal complexes

Platinum profiles need to separate microbial reduction, resistance, and engineered recovery. Fungi and bacteria can convert soluble platinum species into particles, while resistant cells can alter their physiology under exposure. None of these observations makes platinum an ordinary microbial cofactor.

Detoxification through biomineralization

Gold is biologically active when encountered as soluble complexes, even though bulk metallic gold appears inert. Gold-associated bacteria can convert those complexes into less accessible forms. Their chemistry connects detoxification, extracellular molecules, and the formation of elemental gold.

Cell-associated sequestration

Thorium can be sequestered by bacterial biomass and can alter biofilm communities. These are separate chemical and ecological findings.

Respiratory reduction and immobilization

Some metal-reducing bacteria conserve energy while converting soluble U(VI) into less soluble U(IV). This respiratory process can immobilize uranium, but its effectiveness depends on the organisms and surrounding geochemistry.

Coupled microbial reduction and precipitation

Microbial Np(V) reduction and removal from water are distinct achievements. Mineral partners and phosphate chemistry influence whether reduced neptunium becomes effectively immobilized.

Microbial reduction of oxidized plutonium

Microbes can reduce Pu(V/VI) to particle-associated Pu(IV), yet further reduction can produce soluble Pu(III) when suitable ligands are present. Reduction therefore does not invariably immobilize plutonium.

Microbial accumulation and biosorption

Americium research in microbes is mainly about binding and partitioning rather than a demonstrated biological redox cycle. Bacteria, fungal biomass, and dissolved microbial products can change how americium distributes between water, cells, and mineral surfaces.

RNA sensing and cation export

Lithium is a light alkali metal included for its value in understanding bacterial ion sensing and tolerance. The most direct evidence here concerns RNA switches and cation export. These mechanisms help cells respond to an unwanted ion; they do not establish lithium as a broadly required microbial nutrient.

Broader metal context: sodium gradients, salinity, and gut ecology

Sodium belongs to microbial metallomics as an alkali-metal ion with roles in membrane energetics and environmental adaptation. Salt also changes host-associated communities through ecological and host-mediated routes. Sodium gradients, dietary sodium chloride, and circulating microbial metabolites are related but different measurements, and the evidence is clearest when those levels are kept distinct.

Broader metal context: ribosome function and magnesium sensing

Magnesium is a major cellular ion that links ribosome stability, energy metabolism, and environmental sensing. Bacteria can monitor magnesium outside the cell through proteins and inside the cell through RNA-based systems. These separate control points help explain why total magnesium is a poor substitute for knowing the available pool at a particular molecular target.

Broader metal context: ion homeostasis and biofilm signaling

Potassium is a major intracellular ion whose movement can influence both an individual bacterium and its neighbors. In Bacillus subtilis, uptake is regulated by the second messenger cyclic di-AMP, while channel-mediated potassium release supports coordinated biofilm behavior. These are physiological signaling mechanisms demonstrated in laboratory systems, with their wider ecological prevalence still an open question.

Biofilm architecture, biomineralization, and calcium-responsive signaling

Calcium can shape microbial communities as a mineral-building component, a matrix-associated ion, and an environmental signal. Bacillus subtilis and Pseudomonas aeruginosa illustrate different mechanisms. These roles place calcium in broader microbial metallomics, although it is an alkaline-earth metal rather than a heavy metal in conventional usage.

Trace-element nutrition and microbial respiration

Selenium is a nonmetal included because microbial cofactor chemistry, environmental respiration, and host nutrient competition intersect. The chemical form and metabolic role are crucial: selenium incorporated into a protein is different from selenate used as a respiratory electron acceptor. Evidence from cultures and mice supports several such roles without establishing a general benefit from increasing selenium exposure.

Transport through potassium-handling systems

Rubidium is useful for understanding how bacteria distinguish chemically similar alkali-metal ions. It can enter through potassium-handling systems and can partly substitute for potassium under some culture conditions. Transportability, however, is not the same as physiological equivalence: the transporter, strain, and potassium background change the result.