Pan Yongxin, Lin Wei, Li Jinhua, Wu Wenfang, Tian Lanxiang, Deng Chenglong, Liu Qingsong, Zhu Rixiang, Winklhofer Michael, Petersen Nikolai
Biogeomagnetism Group, Key Laboratory of the Earth's Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.
Biophys J. 2009 Aug 19;97(4):986-91. doi: 10.1016/j.bpj.2009.06.012.
Magnetotactic bacteria are microorganisms that orient and migrate along magnetic field lines. The classical model of polar magnetotaxis predicts that the field-parallel migration velocity of magnetotactic bacteria increases monotonically with the strength of an applied magnetic field. We here test this model experimentally on magnetotactic coccoid bacteria that swim along helical trajectories. It turns out that the contribution of the field-parallel migration velocity decreases with increasing field strength from 0.1 to 1.5 mT. This unexpected observation can be explained and reproduced in a mathematical model under the assumption that the magnetosome chain is inclined with respect to the flagellar propulsion axis. The magnetic disadvantage, however, becomes apparent only in stronger than geomagnetic fields, which suggests that magnetotaxis is optimized under geomagnetic field conditions. It is therefore not beneficial for these bacteria to increase their intracellular magnetic dipole moment beyond the value needed to overcome Brownian motion in geomagnetic field conditions.
趋磁细菌是一类能够沿着磁力线定向移动和迁移的微生物。极性趋磁的经典模型预测，趋磁细菌沿磁场方向的迁移速度会随着外加磁场强度的增加而单调增加。我们在此对沿螺旋轨迹游动的趋磁球状细菌进行了该模型的实验测试。结果表明，随着磁场强度从0.1毫特斯拉增加到1.5毫特斯拉，沿磁场方向的迁移速度的贡献会降低。在磁小体链相对于鞭毛推进轴倾斜的假设下，这一意外观察结果可以在数学模型中得到解释和重现。然而，磁劣势仅在比地磁场更强的磁场中才会显现，这表明趋磁在地球磁场条件下是优化的。因此，对于这些细菌来说，将其细胞内磁偶极矩增加到超过在地磁场条件下克服布朗运动所需的值是没有益处的。
