Mechanism And Optimization Of Magne-Some Formation In A. Ferrooxidans

The magnetic nanoparticles produced by the biomineralization, which are perfect magnetic biomaterials, have unique characters such as narrow size scale, few crystal defect, single magnetic domain and little cytotoxicity.Magnetotactic bacteria are a collection of prokaryote which could biominerilize and produce magnetic nanoparticles in vivo. The magnetic nanoparticles enveloped with bilayer lipid membrane, are named as magnetosomes which are mainly made of different forms of ferrum such as magnetite (Fe3O4), greigite (Fe3S4) and pyrite (FeS2). According to the studies so far, the biomineralization of Acidithiobacillus ferrooxidans is similar to that of magnetotactic bacteria, and could produce magnetosomes, although its magnetism is weaker. Compared to the studies on the magnetotactic bacteria, there are fewer studies on the mechanism of magnetosome and optimization of magnetosome production of Acidithiobacillus ferrooxidans.With the addition of citrate to the9K medium and the domestication of A. ferrooxidans with citrate, we studied the effect of citrate at different concentration level on the iron uptake and biomass of A. ferrooxidans. The results showed that the addition of citrate could improve the biomass of A. ferrooxidans. Meanwhile, it could also improve the iron concentration inner the cell. The growth and magnetosome formation of A. ferrooxidans are also studied by orthogonal design, and then it was analyzed with Response Surface Regression Analysis (RSREG) by SAS statistics software. Finally, the model were analyzed with Genetic Algorithms by Matlab software. The results demonstrated that the optimal condition for growth of A. ferrooxidans is195.68mM FeSO4,1.272g/L (NH4)2SO4,6.276mM citrate, initial pH1.87,21.1%of storage. The optimal condition for magnetosome formation by A. ferrooxidans is135.43mM FeSO4,2.325g/L (NH4)2SO4,16.412mM citrate, initial pH1.70,58.1%of storage. We also studied the effect of citrate on the expression of genes which involved in FeoABC ferrous uptake system and TonB ferric uptake system, and the relationship between iron uptake and magnetosome formation. The qPCR results showed that the addition of citrate would inhibit the ferrous uptake, but the ferric uptake would be enhanced, meanwhile, the magnetosome formation could be enhanced. The magnetosome extracted from A. ferrooxidans BY-3is also being studied the load capacity, and the results showed that the amount of doxorubicin loaded with1mg of magnetosome is was0.94mg, which is almost the same as the magnetosome extracted from the magnetotactic bacteria M. gryphiswaldense MSR-1. With the studies on the magnetosome formation mechanism and the optimization of A. ferrooxidans, the production of magnetosome by A. ferrooxidans is enhanced, which made the A. ferrooxidans be more suitable for the biomedicine application and so on.