The Construction Of Surface Display System Of Magnetosomes

Magnetosomes are membrane-enclosed magnetite nanocrystals, synthesized by magnetotactic bacteria(MTB). Specific transmembrane proteins are sorted to the magnetosome membrane(MM). Mam C is the most abundant MM protein of Magnetospirillum gryphiswaldense strain MSR-1. Mam F is the second most abundant MM protein and forms stable oligomers. Magnetosome possesses a single magnetic domain and exhibits strong ferrimagnetism, have a great potential for application.Surface modification is the key strategy for magnetosome application. Biotin or streptavidin carrying magnetosomes would be a great help for their appliction. In this study, “surface display” technique was employed for fusion expression of biotin carboxyl carrier protein or streptavidin with the N terminal of Mam C or Mam F, expectively. Several recombination bacterial strains were constructed, including MSR-ΔF-BF, MSR-ΔC-BC, MSR-ΔF-SF and MSR-ΔC-SC. The recombination magnetosomes displaying biotin(BMP-ΔF-BF, BMP-ΔC-BC), or displaying streptavidin(BMP-ΔF-SF, BMP-ΔC-SC) were synthesized by these strains.The growth status and magnetic responses of the recombinant strains fell in between wild type strain and the mam C or mam F mutant, which indicated partial functional complementation. The surface expression of the fusion proteins were confirmed by western blotting. No impact on the magnetosome synthesis and morphology were found by transmission electron microscope(TEM). The hydrated radii and zeta potential of recombinant magnetosomes detected by Zeta PLAS were 30 nm to 90 nm larger than wild type. But, as all zeta potentials were less than-30 m V, no influence on the dispersibility and stability was found. The amount of fusion proteins was reduced as the increasing of times and duration of sample extraction, the standard procedure of extraction was established. Moreover, keeping in the liquid nitrogen was found the best method for magnetosome storage.The conjugation of streptavidin and biotin carrying magnetosome, BMP-ΔF-BF and BMP-ΔC-SC, were also confirmed by TEM. The further experiments are going on, which will lay important foundation for the appiliction of magnetosome surface display system.