Siderophores are small, high-affinity iron chelating agents, and many microorganisms have the ability to secrete them for the acquisition of iron under iron deficiency conditions (because the iron is solid in the general natural environment with very low concentration of iron ions) and transport through membrane transporter. Siderophore is one of the strongest soluble ferric chelators known in the world. The structure and properties of siderophore produced by different organisms vary widely. The types include: catechins, hydroxamates and carboxylates. Belonging to catechins, enterobactin is the strongest siderophore known, binding to the Fe3+ with high affinity (K=1052 M), so we will develop our project based on the siderophore system of E. coli.
The natural siderophore producing is affected by the concentration of iron ions. Through the regulation mechanism of Fur, when the iron ion concentration is high, the siderophore gene is inhibited, and thus the siderophore is no longer produced. Therefore, we need to modify the natural siderophore system to initiate the expression of the siderophore gene when the quorum sensing signal molecule HSL is present.
Chorismic acid, an aromatic amino acid precursor, is converted to 2,3-dihydroxybenzoic acid (DHB) by a series of enzymes, EntA, EntB and EntC. An amide linkage of DHB to L-serine is then catalyzed by EntD, EntE, EntF and EntB. Three molecules of the DHB-Ser formed undergo intermolecular cyclization, yielding enterobactin.
First, we made a standard curve of removal rust using the siderophore.
1 g of sodium molybdate and 1 g of sodium nitrite were weighed and dissolved in 10 ml of deionized water. 0.5 mol/l of HCL, and 1 mol/L of NaOH were prepared. Set 2,3-dihydroxybenzoic acid(DHB) with different concentration gradients was set. 1 ml of each of the above four solutions was mixed, and the mixed solution ‘s absorbance was measured at 510 nm. The standard curve for of removal rust was obtained.
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