WikiBiomeThe human microbiome encyclopediaAn alphabetical index of host defenses in the public WikiBiome knowledge base.
Antimicrobial metals are metal ions and metal-based materials that kill or inhibit microorganisms. Copper, silver, zinc, and gallium are the principal agents, each exploiting different aspects of microbial metal biology. What makes this field particularly relevant to Wi…
Autoimmunity occurs when the immune system attacks the body's own tissues. What has emerged over the past two decades is that the gut microbiome is not merely associated with autoimmune disease -- it is a mechanistic driver of immune tolerance breakdown. Metals add a se…
Structured microbial communities encased in a self-produced extracellular polymeric substance (EPS) matrix. Biofilms are the predominant mode of bacterial and fungal growth in chronic infections, device-associated infections, and the gut. From a metallomics perspective,…
A heterodimer of S100A8 and S100A9 calcium-binding proteins that constitutes approximately 60% of the cytosolic protein content of neutrophils. Calprotectin is a central effector of nutritional immunity, sequestering essential transition metals from invading pathogens a…
Cysteine is a sulfur-containing amino acid whose thiol (-SH) group makes it the primary metal-binding residue in biology. It is the rate-limiting precursor for glutathione (the master intracellular antioxidant), a key residue in metallothioneins (metal-binding proteins)…
iron occupies a unique position among dietary metals: it is both an essential nutrient and a selective pressure that shapes the gut microbial ecosystem. The form, quantity, and bioavailability of dietary iron determines which microbes thrive and which are competitively …
The pathological disruption of normal metal homeostasis — the tightly regulated balance of essential trace elements (iron, zinc, copper, manganese, selenium, cobalt) and the effective exclusion of toxic metals (cadmium, lead, mercury, arsenic). Dyshomeostasis is a conve…
The primary intracellular iron storage protein, capable of sequestering up to 4,500 iron atoms in a single molecule as a mineralized ferric oxyhydroxide core. Ferritin is one of the most elegant solutions evolution has produced for the iron paradox: iron is essential fo…
The only known cellular iron exporter in mammals. Encoded by the SLC40A1 gene, ferroportin (FPN) sits on the basolateral membrane of enterocytes, the surface of macrophages, and the membrane of hepatocytes, controlling the flow of iron from these cells into the bloodstr…
The most abundant intracellular thiol and the master antioxidant of mammalian cells. Glutathione is a tripeptide (gamma-glutamyl-cysteinyl-glycine) whose sulfhydryl (-SH) group makes it both a critical antioxidant and a primary target for heavy metal binding. GSH deplet…
The master regulator of systemic iron homeostasis. Hepcidin is a 25-amino-acid peptide hormone produced primarily by hepatocytes that controls iron absorption, recycling, and distribution by binding to and degrading ferroportin (SLC40A1/FPN) -- the only known cellular i…
Interferon gamma (IFN-γ) is the signature Th1 cytokine and the primary activator of macrophage antimicrobial functions. In the WikiBiome framework, IFN-γ is critical for two reasons: it drives nutritional immunity (iron restriction against intracellular pathogens) and i…
Innate immunity is the body's first-line, non-specific defense against pathogens — comprising physical barriers (epithelium, mucus), antimicrobial molecules (calprotectin, lactoferrin, defensins), pattern recognition receptors (TLRs, NOD-like receptors), and phagocytic …
Microbial communities do not acquire and use metals in isolation. Within biofilms, polymicrobial infections, and the gut microbiome, microbes engage in complex cooperative and competitive relationships mediated by metals -- sharing metallophores, concentrating metals in…
An iron-binding glycoprotein of the transferrin family that sequesters iron (and potentially other metals) from pathogens at mucosal surfaces and sites of inflammation. Lactoferrin is a key effector of nutritional immunity, complementing calprotectin's role in metal res…
Lipocalin-2 (also known as NGAL — neutrophil gelatinase-associated lipocalin, or siderocalin) is a 25 kDa secreted protein produced by activated neutrophils, epithelial cells, and other innate immune cells. Its primary antimicrobial function is to sequester bacterial si…
The biological processes by which organisms maintain proper intracellular and systemic concentrations of essential metals -- importing what is needed, storing excess safely, and exporting or sequestering surplus. Both host and microbial systems have evolved elaborate me…
Transition metals serve as essential cofactors for pathogen virulence factors across virtually all domains of microbial life. The dependence of pathogens on metals they must scavenge from the host environment creates a fundamental tension at the heart of infectious dise…
Inflammation is a broad concept, but in the metallomics context it has a specific character: heavy metals and pathogens activate overlapping inflammatory pathways, creating convergent pathology where distinguishing the metal contribution from the microbial contribution …
Microbial metallomics is the study of how metals and microorganisms interact at the systems level — how metal availability shapes microbial communities, how microbes acquire and weaponize metals for virulence, and how this bidirectional metal-microbe interface drives di…
N-acetylcysteine (NAC) is the acetylated form of the amino acid L-cysteine and serves as the rate-limiting precursor for glutathione synthesis — the body's primary intracellular antioxidant and a critical cofactor for phase II detoxification of heavy metals. In the micr…
The strategy by which mammalian hosts withhold essential metals from invading pathogens to limit their growth. Well-established for iron and zinc; underexplored but potentially powerful for nickel.
Pathogens deploy dedicated cellular machinery to import, store, regulate, and when necessary export transition metals. These systems complement the extracellular siderophores metallophores that scavenge metals from the host environment by providing the membrane transpor…
Reactive oxygen species — superoxide (O2•−), hydrogen peroxide (H2O2), and hydroxyl radical (OH•) — are chemically reactive molecules generated during normal metabolism and massively amplified by heavy metal exposure. ROS are both weapons (the host uses them to kill pat…
Small, high-affinity iron-chelating molecules secreted by bacteria and fungi to scavenge ferric iron (Fe3+) from the environment. Siderophore competition is a fundamental ecological force in the gut microbiome: organisms with superior iron acquisition systems gain a dec…
Siderophores are small, high-affinity iron-chelating molecules secreted by bacteria, fungi, and some plants to scavenge ferric iron (Fe3+) from their environment. In the context of infection, siderophores are the molecular weapons pathogens deploy to break through nutri…
Siderophores and metallophores are small-molecule chelators secreted by pathogens to scavenge metals from the metal-scarce host environment. They represent the extracellular arm of pathogen metal acquisition -- how pathogens reach out into the surrounding milieu to capt…
Superoxide dismutases are metalloenzymes that catalyze the dismutation of superoxide radical (O2-) into hydrogen peroxide (H2O2) and molecular oxygen -- the first line of defense against oxidative damage in all aerobic organisms. What makes SOD uniquely important in mic…
Transferrin is a glycoprotein (β₁-globulin, ~80 kDa) synthesized primarily by the liver that functions as the principal iron-transport protein in blood plasma. It binds ferric iron (Fe³⁺) with extraordinarily high affinity (Kd ~10⁻²³ M) and delivers it to cells via tran…