Berg H C, Turner L
Rowland Institute for Science, Cambridge, MA 02142.
Proc Natl Acad Sci U S A. 1995 Jan 17;92(2):477-9. doi: 10.1073/pnas.92.2.477.
Chemotactic cells of the bacterium Escherichia coli were marked asymmetrically by growth on a rich medium containing tetrazolium red. When this dye is reduced, it tends to form a refractile granule near one end of the cell, readily visualized by dark-field microscopy. In smooth-swimming cells, the marker was found with equal probability in front or behind. In wild-type cells, tumbles changed the cell orientation nearly as often as not. Some cells formed flagellar bundles at one end more frequently than at the other, but the run-interval distributions were the same either way. We conclude that the sensory system does not favor one end of the cell over the other. Thus, chemoreceptors that appear in patches at only one pole do not serve as a nose.
通过在含有四氮唑红的丰富培养基上生长，大肠杆菌的趋化细胞被不对称标记。当这种染料被还原时，它倾向于在细胞一端附近形成一个折光颗粒，通过暗视野显微镜很容易观察到。在平滑游动的细胞中，标记物出现在前端或后端的概率相等。在野生型细胞中，翻滚几乎总是会改变细胞方向。一些细胞在一端比在另一端更频繁地形成鞭毛束，但无论哪种方式，游动间隔分布都是相同的。我们得出结论，感觉系统并不偏向细胞的一端而不是另一端。因此，仅在一极以斑块形式出现的化学感受器并不充当鼻子。
