Frankel R B, Bazylinski D A, Johnson M S, Taylor B L
Physics Department, California Polytechnic State University, San Luis Obispo, California 93407, USA.
Biophys J. 1997 Aug;73(2):994-1000. doi: 10.1016/S0006-3495(97)78132-3.
Magnetotactic cocci swim persistently along local magnetic field lines in a preferred direction that corresponds to downward migration along geomagnetic field lines. Recently, high cell concentrations of magnetotactic cocci have been found in the water columns of chemically stratified, marine and brackish habitats, and not always in the sediments, as would be expected for persistent, downward-migrating bacteria. Here we report that cells of a pure culture of a marine magnetotactic coccus, designated strain MC-1, formed microaerophilic bands in capillary tubes and used aerotaxis to migrate to a preferred oxygen concentration in an oxygen gradient. Cells were able to swim in either direction along the local magnetic field and used magnetotaxis in conjunction with aerotaxis, i.e., magnetically assisted aerotaxis, or magneto-aerotaxis, to more efficiently migrate to and maintain position at their preferred oxygen concentration. Cells of strain MC-1 had a novel, aerotactic sensory mechanism that appeared to function as a two-way switch, rather than the temporal sensory mechanism used by other bacteria, including Magnetospirillum megnetotacticum, in aerotaxis. The cells also exhibited a response to short-wavelength light (< or = 500 nm), which caused them to swim persistently parallel to the magnetic field during illumination.
趋磁球菌沿着局部磁场线持续游动，其偏好的方向对应于沿着地磁场线向下迁移。最近，在化学分层的海洋和咸淡水生境的水柱中发现了高细胞浓度的趋磁球菌，而并不总是如预期的那样在沉积物中发现，因为沉积物是持续向下迁移的细菌的栖息地。在此，我们报告称，一种海洋趋磁球菌的纯培养物（命名为MC-1菌株）的细胞在毛细管中形成了微需氧带，并利用趋氧性在氧气梯度中迁移至偏好的氧气浓度。细胞能够沿着局部磁场在两个方向上游动，并结合趋氧性利用趋磁性，即磁辅助趋氧性或磁趋氧性，更有效地迁移至其偏好的氧气浓度并维持在该位置。MC-1菌株的细胞具有一种新颖的趋氧性传感机制，该机制似乎起到双向开关的作用，而不是其他细菌（包括趋磁螺菌）在趋氧性中使用的时间传感机制。这些细胞还对短波长光（≤500 nm）有反应，光照期间它们会沿着磁场持续平行游动。
