Smith M J, Sheehan P E, Perry L L, O'Connor K, Csonka L N, Applegate B M, Whitman L J
Chemistry Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA.
Biophys J. 2006 Aug 1;91(3):1098-107. doi: 10.1529/biophysj.106.085167. Epub 2006 May 19.
Magnetotactic bacteria are characterized by the production of magnetosomes, nanoscale particles of lipid bilayer encapsulated magnetite, that act to orient the bacteria in magnetic fields. These magnetosomes allow magneto-aerotaxis, which is the motion of the bacteria along a magnetic field and toward preferred concentrations of oxygen. Magneto-aerotaxis has been shown to direct the motion of these bacteria downward toward sediments and microaerobic environments favorable for growth. Herein, we compare the magneto-aerotaxis of wild-type, magnetic Magnetospirillum magneticum AMB-1 with a nonmagnetic mutant we have engineered. Using an applied magnetic field and an advancing oxygen gradient, we have quantified the magnetic advantage in magneto-aerotaxis as a more rapid migration to preferred oxygen levels. Magnetic, wild-type cells swimming in an applied magnetic field more quickly migrate away from the advancing oxygen than either wild-type cells in a zero field or the nonmagnetic cells in any field. We find that the responses of the magnetic and mutant strains are well described by a relatively simple analytical model, an analysis of which indicates that the key benefit of magnetotaxis is an enhancement of a bacterium's ability to detect oxygen, not an increase in its average speed moving away from high oxygen concentrations.
趋磁细菌的特征是产生磁小体，即由脂质双分子层包裹的纳米级磁铁矿颗粒，其作用是使细菌在磁场中定向。这些磁小体实现了磁趋氧性，即细菌沿着磁场并朝着适宜的氧气浓度移动。磁趋氧性已被证明能引导这些细菌向下朝着有利于生长的沉积物和微需氧环境移动。在此，我们比较了野生型趋磁嗜磁螺菌AMB-1与我们构建的非磁性突变体的磁趋氧性。利用外加磁场和前进的氧气梯度，我们将磁趋氧性中的磁优势量化为向适宜氧气水平的更快迁移。在施加磁场中游动的磁性野生型细胞比零磁场中的野生型细胞或任何磁场中的非磁性细胞更快地从前进的氧气中迁移开。我们发现，磁性菌株和突变菌株的反应可以用一个相对简单的分析模型很好地描述，对该模型的分析表明，趋磁的关键益处是增强了细菌检测氧气的能力，而不是提高了其远离高氧浓度的平均速度。
