Bioleaching is the extraction or liberation of metals from their ores through the use of living organisms. Bioleaching is one of several applications within biohydrometallurgy and several methods are used to treat ores or concentrates containing copper, zinc, lead, arsenic, antimony, nickel, molybdenum, gold, silver, and cobalt.
Siderophores (Greek: "iron carrier") are small, high-affinity iron-chelating compounds that are secreted by microorganisms such as bacteria and fungi. They help the organism accumulate iron. Although a widening range of siderophore functions is now being appreciated, siderophores are among the strongest (highest affinity) Fe3+ binding agents known. Phytosiderophores are siderophores produced by plants.
Iron–sulfur proteins are proteins characterized by the presence of iron–sulfur clusters containing sulfide-linked di-, tri-, and tetrairon centers in variable oxidation states. Iron–sulfur clusters are found in a variety of metalloproteins, such as the ferredoxins, as well as NADH dehydrogenase, hydrogenases, coenzyme Q – cytochrome c reductase, succinate – coenzyme Q reductase and nitrogenase. Iron–sulfur clusters are best known for their role in the oxidation-reduction reactions of electron transport in mitochondria and chloroplasts. Both Complex I and Complex II of oxidative phosphorylation have multiple Fe–S clusters. They have many other functions including catalysis as illustrated by aconitase, generation of radicals as illustrated by SAM-dependent enzymes, and as sulfur donors in the biosynthesis of lipoic acid and biotin. Additionally, some Fe–S proteins regulate gene expression. Fe–S proteins are vulnerable to attack by biogenic nitric oxide, forming dinitrosyl iron complexes. In most Fe–S proteins, the terminal ligands on Fe are thiolate, but exceptions exist.
Chorismic acid, more commonly known as its anionic form chorismate, is an important biochemical intermediate in plants and microorganisms. It is a precursor for:
In enzymology, a 2,3-dihydro-2,3-dihydroxybenzoate dehydrogenase (EC 1.3.1.28) is an enzyme that catalyzes the chemical reaction
Aerobactin is a bacterial iron chelating agent (siderophore) found in E. coliand other Enterobacteriaceae species. It is a virulence factor enabling E. coli to sequester iron in iron-poor environments such as the urinary tract.
2,3-Dihydroxybenzoic acid is a natural phenol found in Phyllanthus acidus and in the aquatic fern Salvinia molesta. It is also abundant in the fruits of Flacourtia inermis. It is a dihydroxybenzoic acid, a type of organic compound.
Ferrichrome is a cyclic hexa-peptide that forms a complex with iron atoms. It is a siderophore composed of three glycine and three modified ornithine residues with hydroxamate groups [-N(OH)C(=O)C-]. The 6 oxygen atoms from the three hydroxamate groups bind Fe(III) in near perfect octahedral coordination.
Rhodotorulic acid is the smallest of the 2,5-diketopiperazine family of hydroxamate siderophores which are high-affinity chelating agents for ferric iron, produced by bacterial and fungal phytopathogens for scavenging iron from the environment. It is a tetradentate ligand, meaning it binds one iron atom in four locations (two hydroxamate and two lactam moieties), and forms Fe2(siderophore)3 complexes to fulfill an octahedral coordination for iron.
Yersiniabactin (Ybt) is a siderophore found in the pathogenic bacteria Yersinia pestis, Yersinia pseudotuberculosis, and Yersinia enterocolitica, as well as several strains of enterobacteria including enteropathogenic Escherichia coli and Salmonella enterica. Siderophores, compounds of low molecular mass with high affinities for ferric iron, are important virulence factors in pathogenic bacteria. Iron—an essential element for life used for such cellular processes as respiration and DNA replication—is extensively chelated by host proteins like lactoferrin and ferritin; thus, the pathogen produces molecules with an even higher affinity for Fe3+ than these proteins in order to acquire sufficient iron for growth. As a part of such an iron-uptake system, yersiniabactin plays an important role in pathogenicity of Y. pestis, Y. pseudotuberculosis, and Y. entercolitica.
Many bacteria secrete small iron-binding molecules called siderophores, which bind strongly to ferric ions. FepA is an integral bacterial outer membrane porin protein that belongs to outer membrane receptor family and provides the active transport of iron bound by the siderophore enterobactin from the extracellular space, into the periplasm of Gram-negative bacteria. FepA has also been shown to transport vitamin B12, and colicins B and D as well. This protein belongs to family of ligand-gated protein channels.
Ferric-chelate reductase (NADPH) (EC 1.16.1.9, ferric chelate reductase, iron chelate reductase, NADPH:Fe3+-EDTA reductase, NADPH-dependent ferric reductase, yqjH (gene)) is an enzyme with systematic name Fe(II):NADP+ oxidoreductase. This enzyme catalyses the following chemical reaction
Ascorbate ferrireductase (transmembrane) (EC 1.16.5.1, cytochrome b561) is an enzyme with systematic name Fe(III):ascorbate oxidorectuctase (electron-translocating). This enzyme catalyses the following chemical reaction
N2-citryl-N6-acetyl-N6-hydroxylysine synthase (EC 6.3.2.38, N(alpha)-citryl-N(epsilon)-acetyl-N(epsilon)-hydroxylysine synthase, iucA (gene)) is an enzyme with systematic name citrate:N6-acetyl-N6-hydroxy-L-lysine ligase (ADP-forming). This enzyme catalyses the following chemical reaction
Bacillibactin is a catechol-based siderophore secreted by members of the genus Bacillus, including Bacillus anthracis and Bacillus subtilis. It is involved in the chelation of ferric iron (Fe3+) from the surrounding environment and is subsequently transferred into the bacterial cytoplasm via the use of ABC transporters.
Siderocalin(Scn), lipocalin-2, NGAL, 24p3 is a mammalian lipocalin-type protein that can prevent iron acquisition by pathogenic bacteria by binding siderophores, which are iron-binding chelators made by microorganisms. Iron serves as a key nutrient in host-pathogen interactions, and pathogens can acquire iron from the host organism via synthesis and release siderophores such as enterobactin. Siderocalin is a part of the mammalian defence mechanism and acts as an antibacterial agent. Crystallographic studies of Scn demonstrated that it includes a calyx, a ligand-binding domain that is lined with polar cationic groups. Central to the siderophore/siderocalin recognition mechanism are hybrid electrostatic/cation-pi interactions. To evade the host defences, pathogens evolved to produce structurally varied siderophores that would not be recognized by siderocalin, allowing the bacteria to acquire iron.
The iron/lead transporter (ILT) family is a family of transmembrane proteins within the lysine exporter (LysE) superfamily. The ILT family includes two subfamilies, the iron-transporting (OFeT) family and the lead-transporting (PbrT) family. A representative list of the proteins belonging to these subfamilies of the ILT family can be found in the Transporter Classification Database.
Rebecca Abergel is a professor of nuclear engineering and of chemistry at University of California, Berkeley. Abergel is also a senior faculty scientist in the chemical sciences division of Lawrence Berkeley National Laboratory, where she directs the Glenn T. Seaborg Center and leads the Heavy Element Chemistry research group. She is the recipient of several awards for her research in nuclear and inorganic chemistry.
Vibriobactin is a catechol siderophore that helps the microbial system to acquire iron. It was first isolated from Vibrio cholerae.
Mirubactin is a siderophore produced by the bacterium Actinosynnema mirum.A.mirum was first isolated from the Raritan River in New Jersey in 1976, and its full genome sequence was published in 2009. In 2012, mirubactin was isolated and characterized, and the biosynthesis was connected with the gene cluster Amir_2714-Amir_2728, since renamed mrbA-mrbO.
