Budrene E O, Berg H C
Department of Cellular and Developmental Biology, Harvard University, Cambridge, Massachusetts 02138.
Nature. 1991 Feb 14;349(6310):630-3. doi: 10.1038/349630a0.
When chemotactic strains of the bacterium Escherichia coli are inoculated on semi-solid agar containing mixtures of amino acids or sugars, the cells swarm outwards in a series of concentric rings: they respond to spatial gradients of attractants generated by uptake and catabolism. Cells also drift up gradients generated artificially, for example by diffusion from the tip of a capillary tube or by mixing. Here we describe conditions under which cells aggregate in response to gradients of attractant which they excrete themselves. When cells are grown in semi-solid agar on intermediates of the tricarboxylic acid cycle, they form symmetrical arrays of spots or stripes that arise sequentially. When cells in a thin layer of liquid culture are exposed to these compounds, spots appear synchronously, more randomly arrayed. In either case, the patterns are stationary. The attractant is a chemical sensed by the aspartate receptor. Its excretion can be triggered by oxidative stress. As oxygen is limiting at high cell densities, aggregation might serve as a mechanism for collective defence.
当将趋化性大肠杆菌菌株接种在含有氨基酸或糖混合物的半固体琼脂上时，细胞会以一系列同心环的形式向外游动：它们对由摄取和分解代谢产生的引诱剂的空间梯度做出反应。细胞也会沿着人工产生的梯度向上漂移，例如通过从毛细管尖端扩散或混合。在这里，我们描述了细胞响应自身分泌的引诱剂梯度而聚集的条件。当细胞在半固体琼脂中在三羧酸循环的中间产物上生长时，它们会形成依次出现的对称斑点或条纹阵列。当薄层液体培养中的细胞暴露于这些化合物时，斑点会同步出现，排列更随机。在任何一种情况下，这些图案都是静止的。引诱剂是一种由天冬氨酸受体感知的化学物质。其排泄可由氧化应激触发。由于在高细胞密度下氧气有限，聚集可能是一种集体防御机制。
