Magnetotactic Bacteria In The Amb-1 Culture Conditions Optimization And Magnetic Bodies Change Process

Magnetotactic bacteria research is hot spot in microbiology field. Magnetotactic bacteria have nano single-domain magnetite/greigite (Fe3O4/Fe3S4), which are called magnetosome. There are problems in culturing magnetotactic bacteria bacause they need chemo-autolithotrophic and microaerobic growth conditions.Growth conditions of Magnetospirillum magneticum AMB-1 were optimized by orthogonal experimental design. When culture conditions were chosen with ferric quinine 0.02 mmol/L, 75% volume, pH 6.7 and 25℃, OD600 values reached 0.440 (1.166×109 cells/ml). AMB-1 cells were all collected by magnet before inoculation. After magnetic enrichment and cultivation for several times, Cmag values of AMB-1 reached 1.9-2.0 steadily.The process of magnetosome assembling was studied after optimization, that AMB-1 had high production with many magnetosomes. During cultivating process, magnetosomes were characterized by Transmission Electron Microscope (TEM). As a result, smaller crystals (average 27 nm, n=188) were observed in bacteria after 24 h incubation. Over 48 h, the size of crystals increased (43 nm, n=203) and MS formed several chains arranging along major axes. After 72 h, crystals maturated (50 nm, n=191) and after 168 h, part-autolyzing bacteria with magnetosomes can be detected. Over 192 h, the bacteria autolyzed and magnetosomes were released to the media.There were tow ways of magnetosome chain separating modes in dividing AMB-1 cells. One is symmetric separation into the daughter cells. The other is asymmetric separation and only one daughter cell was heritor of the magnetosomes. Part of non-magnetosome daughter cells might produce magnetosomes later. These phenomena explained why magnetism of magnetotactic bacteria decreased with more multiplications (Cmag value decreased).Method of deleting some kind of genes was usually used in research of magnetosomes synthesis. Comparing wild strain with gene mutation strain can find out the function of the gene. However, this method need many steps and the strain of mutation can not inherit stably. Special method of magnetic cells collected to inoculation was used to screen out strains with and without magnetosomes. Such kind of strains was obtained, and they could inherit stably.Magnetosomes have applying valve in medical treatment, environmental protecting etc. However, it is a long way to put magnetosomes to application. Because magnetotactic bacteria are difficult to culture, and costs of pure magnetosomes are high. During the investigating process of magnetosome assembling, magnetosomes were set free after 192 h culture.