Magnetosome Assembling and Optimization of Growth Conditions of the Magnetospirillum Magneticum AMB-1 Strain

Growth conditions of Magnetospirillum magneticum AMB-1 were optimized by orthogonal experimental design. When culturing conditions were chosen with ferric quinine 0.02 mmol/L, 75% volume, pH 6.7 and 25degC, the OD₆₀₀ values reached 0.440 (1.166times10⁹ 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. During cultivating process, magnetosomes (MS) were characterized by Transmission Electron Microscope (TEM). As a result, smaller crystals (average 27.87 nm, n=188) were observed in bacteria after 24 h incubation. Over 48 h, the size of crystals increased (43.45 nm, n=203) and MS formed several chains arranging along major axes. After 72 h, crystals maturated (50.31 nm, n=191) and after 168 h, part-autolyzing bacteria with MS can be detected. Over 192 h, the bacteria autolyzed and MS were released to the media. It was also observed that two kinds of MS 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 MS. Part of non-magnetosome daughter cells might produce MS later.