Siderophores


Also found in: Medical.

Siderophores

Low-molecular-mass molecules that have a high specificity for chelating or binding iron. Siderophores are produced by many microorganisms, including bacteria, yeast, and fungi, to obtain iron from the environment. More than 500 different siderophores have been identified from microorganisms. Some bacteria produce more than one type of siderophore. See Bacteria, Fungi, Yeast

Iron is required by aerobic bacteria and other living organisms for a variety of biochemical reactions in the cell. Although iron is the fourth most abundant element in the Earth's crust, it is not readily available to bacteria. Iron is found in nature mostly as insoluble precipitates that are part of hydroxide polymers. Bacteria living in the soil or water must have a mechanism to solubilize iron from these precipitates in order to assimilate iron from the environment. Iron is also not freely available in humans and other mammals. Most iron is found intracellularly in heme proteins and ferritin, an iron storage compound. Iron outside cells is tightly bound to proteins. Therefore, bacteria that grow in humans or other animals and cause infections must have a mechanism to remove iron from these proteins and use it for their own energy and growth needs. Siderophores have a very high affinity for iron and are able to solubilize and transport ferric iron (Fe3+) in the environment and also to compete for iron with mammalian proteins such as transferrin and lactoferrin. The majority of bacteria and fungi use siderophores to solubilize and transport iron. Microorganisms can use either siderophores produced by themselves or siderophores produced by other microorganisms. See Iron metabolism

The many different types of siderophores can generally be classified into two structural groups, hydroxamates and catecholate compounds. Despite their structural differences, all form an octahedral complex with six binding coordinates for Fe3+.

Siderophores have potential applications in the treatment of some human diseases and infections. Some siderophores are used therapeutically to treat chronic or acute iron overload conditions in order to prevent iron toxicity in humans. Individuals who have defects in blood cell production or who receive multiple transfusions can sometimes have too much free iron in the body. However, in order to prevent infection during treatment for iron overload, it is important to use siderophores that cannot be used by bacterial pathogens.

A second clinical application of siderophores is in antibiotic delivery to bacteria. Some gram-negative bacteria are resistant to antibiotics because they are too big to diffuse through the outer-membrane porins. However, siderophore-antibiotic combination compounds have been synthesized that can be transported into the cell using the siderophore receptor. See Antibiotic, Drug resistance

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Generally these mechanism includes indole acetic acid production (Lee et al., 2004), phosphate solubilization activity (Verma et al., 2001; Wakelin et al., 2004), production of a siderophores (Pandey et al., 2015).
Extraction of siderophores from the secondary metabolites of cell-free supernatant was carried out by following the method of Meyer and Abdallah (24).
The formation of a clear zone around the colonies was considered positive (adapted from Cattelan, 1999); c) production of siderophores: the isolates were grown in King B medium, then centrifuged and Chromium Azurol S (CAS) indicator solution was added to the supernatant.
The coexistence of virulence factors such as the rmpA gene, siderophores and biofilm production with hvKP strains carrying genes for K1 and K2 indicate a high virulence of these strains.
They also found that higher concentrations of siderophores predicted hypervirulence.
graminis BgA1IPS, which was isolated in the present study; however, BgA1IPS also produces siderophores. Phylobacterium sp.
On the other hand, 12 isolates of endophytic bacteria showed qualitative capacity to produce siderophores. It has been shown that endophytic bacteria have various indirect mechanisms for promoting the growth of plants, which include: the production of antimicrobial metabolites and lytic enzymes, the induction of systemic resistance, competition for nutrients (production of siderophores) and the saturation of ecological niches (20).
Szaniszlo, "Evidence for direct utilization of a siderophore, ferrioxamine B, in axenically grown cucumber," Plant, Cell & Environment, vol.
Siderophores are low molecular weight organic molecules that are produced by microorganisms under iron-stress conditions.
fluorescens strains have the ability to compete for iron with the pathogen by producing siderophores [26, 35], as the content of iron in fruits is limited, though fruit wounds are nutrient rich [21].
Examples of direct growth promotion mechanisms include nitrogen fixation [16]; phosphate solubilization or iron mobilization by microbial siderophores [17]; and provision of hormones such as indole acetic acid, cytokinin, and gibberellin [18-21].