By siderophore production, iron becomes easily available to plants and human beings that reduce the deficiency of essential micro nutrient which results in maximum yield production and more survival against epidemic diseases respectively.
Iron deficiency affects the economy of many countries and in developing countries, it causes 4% loss of gross domestic production (GDP). The deficiency of micro nutrient particularly Fe leading to loss of billions of dollars.
Living organism require iron as an essential element for different cellular processes. As iron is the fourth most abundant element in earth crust, but it is not easily available to organism because iron at aerobic condition and biological pH become oxidized to insoluble compounds.
Most aerobic microbes require iron as an essential element in different metabolic processes including oxygen transport, DNA synthesis, synthesis of ATP, formation of heme and electron transport. In these metabolic processes a number of enzymes are involved that consist of iron containing cofactors, which are more than hundred. Microbes have been adopted different ways for iron scavenging. Through transport system and receptor here is away to acquisition of iron is siderophores.
Siderophore: a way of Iron Acquisition
Siderophores (Greek; sidero-iron phores-carrier) are small, relatively low molecular weight iron chelating compounds secreted under iron deficient environment by different microbes such as bacteria, fungi and by some plants also. Latest, it is reported some siderophore also produced by mammalian. Among the most facultative and aerobic microbes one types of siderophore has been stated. Siderophore help in iron acquisition from insoluble hydroxide forms, it also help in its acquisition from ferric phosphate, ferric citrate and ferric transferrin.
Iron acquisition begins by binding of secreted siderophore with available ferric ion form a ferri-siderophore complex and after this complex bind with a definite receptor protein. Iron concentration increases with decrease of siderophore production. Report suggest, siderophore production of Gram- positive bacteria such as Micrococcus luteus and Bacillus silvestrishas strongly affect by Fe(III) concentration. Instead of their own siderophore microorganism namely Escherichia coli also use other siderophores secreted by fungi.
Siderophore as Plant Growth Promoters
Many siderophore secreting fungal and bacterial strains have their role in plant growth because soil is abundant with iron but it is not available to plant due to its low solubility. Secreted siderophores will chelate the iron and form it accessible to plant. Yellow green siderophores that are soluble in water were produced by pseudomonas fluorescens in succinate medium. Siderophores extend the length of root and shoot and enhance number of leaves in iron limited conditions. Biofertilizers are used with siderophores to enhance the yield of crops. It is also a biocontrol agent hinder the growth of many phytopathogenic fungi like as phytophthora parasitica.
Role of siderophore under heavy metals stress
Heavy metals presence causes destruction of membrane bound Fe(III) reductase enzyme which reduce iron uptake in plant. This iron deficiency shows as chlorosis of young leaf. Iron deficiency prevented by plant inoculation with bacterial siderophore in heavy metal stress. Vigna radiate, plant inoculation with bacterial siderophore Pseudomonas sp. showed increase of chlorophyll level and chlorotic symptoms reduction, even though bio available iron present in higher amount.
Relationship between siderophore and plant growth hormone
Indole acetic acid (IAA) is a plant growth hormone, secreted by microbes and plant, which play important role in development of plant. Against indole acetic acid, heavy metal possesses negative effect cause IAA destruction and plant growth inhibition. Plant under metal stress affected by IAA destruction. Siderophore production reduces IAA destruction. Siderophore increase plant ability against the stress of heavy metal. Detailed study carried out siderophore effect in toxic metal presence on auxin synthesis. Siderophore increase plant ability against the stress of heavy metal due to its capability of secondary metabolites production.
Auxin production was negatively affected by metal cation such as Ni2+, Cu2+, Al3+, Cd2+ or combination of Ni2+ and Cd2+ with Fe3+. By chelation, in the presence of Cu2+, Ni2+, Cd2+, and Al3+ siderophore enhance the synthesis of auxin. The ability of metals to hinder the synthesis of auxin is reduces due to chelation.
Human Health Care by Siderophore
Iron play important role in human body, its deficiency leads to iron deficiency anemia (type of anemia). Anemia is a condition which is characterized by inadequate hemoglobin or red blood cells. In human body due to lack of iron sufficient amount, production of hemoglobin protein is reduced. Untreated iron deficiency anemia leads to irregular or fast heartbeat, pregnancy complication, delayed growth in children and infants. Siderophore based medicine are used for treatment of anemia. We can eliminate the use of medicine by using iron rich foods that are produced by agricultural resources. Some plants that are good source of iron are cashews, beans, lentils and dark green leafy vegetables specially spinach.
Chemotherapies by Iron Chelators
Siderophore potential utilize as iron chelators in the treatment of cancer. Siderophore used for non-transferrin constrain iron clearance in serum which takes place in cancer therapy.
Anti-malarial Siderophore
Plasmodium falciparum induce malaria is treated by some siderophore. Klebsiella pneumoniae produced siderophore operate as antimalarial agent. Siderophore causes depletion of intra-cellular iron by entering inside the P. falciparum cell. K. pneumoniae also inhibit Trypanosoma brucei growth, which is protozoic parasite induces sleeping sickness in the bloodstream of human.
Siderophore as Magnetic Resonance Imaging (MRI)
Varieties of paramagnetic ions as Fe3+, Mn2+ and Gd3+ used to enhance the improved contrast for magnetic resonance imaging. In MRI Gd3+ is known as appropriate contrast agent due to its favorable electronic rate of relaxation and strong magnetic movement but it is highly toxic at required concentration of MRI. So, for prevention of free cation release in vivo, chelators are required. Synthetic analogs and siderophores for such chelators serve as principal model.
Trojan Horse Antibiotics
Siderophores are used to deliver the antibiotics in bacteria that are resistant to antibiotics. It is powerful applications which use capabilities of siderophores to transfer iron by convey drugs into cell through formation of conjugates between antimicrobial agents and siderophore. Naturally, siderophore- antibiotics are albomycins, salimycins and ferrimycins.
Transuranic Element Removal from Human Body
Siderophore are able to remove transuranic element like aluminum which exposure is increase to human by the use of nuclear energy in progression of electricity generation. By the use of siderophore, these elements can be removed from human body because it relive disease symptoms and lower the aluminum level in the body.
Conclusion
As microorganisms are being used in different biofertilizer, bio-pesticides and pro-biotic, now a days, it is becoming an emerging sector for application of microbes to produce iron chelating siderophores that necessary to meet the basic requisites of nutritional needs along with other applications. There is a gigantic scope for the implication of microbial siderophores for the sustainability of plants and humans. Recently, the applications of siderophores in agricultural and environmental sector are reported to combat with pathogenic and heavy metal stress, and elemental geochemical cycling as well as mineral weathering processes, but this research is not initiated in various field of microbiology at all.
Siderophore application in advanced medical field is reported for different technique of infectious disease diagnose and treatment of epidemic diseases e.g. malaria along with chemotherapies. So, there is an urgency to develop siderophores from normal and also extreme-philes in the ecosystems like saline soils, degraded area, deep sea, desert, forest and medical to exploit their applications for welfare of all living beings as well as for environment.