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qgaoamtf至尊木虫 (职业作家)
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【分享】微生物的主动应对行为
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乍一看，微生物似乎受其环境以及该环境中可能发生的任何变化支配。它们的命运似乎只能是对所发生的事件做出反应。所以，关于细菌和酵母在一系列变化遵从一个重复模式的环境中都能够将一个刺激与对某种未来环境的适当反应联系起来的发现，有点儿出乎意料。在一个与巴甫洛夫条件反射在某些方面有相似之处、但却依赖于调控网络和自然选择而非认知的过程中，穿过肠道的大肠杆菌及经过不同发酵阶段的酵母会“预测”它们下面要经历什么，并对代谢通道进行组织，来应对其所要经历的东西。大肠杆菌此后会仅仅重复暴露于一系列环境中的第一个，甚至“忘记”它们所受过的训练并失去条件反射。（转帖自：生物谷Bioon.com，2009-7-9） 生物谷推荐原始出处： Nature 460, 220-224 (9 July 2009) | doi:10.1038/nature08112 Adaptive prediction of environmental changes by microorganisms Amir Mitchell1, Gal H. Romano2, Bella Groisman1, Avihu Yona1, Erez Dekel3, Martin Kupiec2, Orna Dahan1,5 & Yitzhak Pilpel1,4,5 1 Department of Molecular Genetics, Weizmann Institute of Science Rehovot 76100, Israel 2 Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv 69978, Israel 3 Department of Molecular Cell Biology, Weizmann Institute of Science Rehovot 76100, Israel 4 Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, USA 5 These authors contributed equally to this work. Natural habitats of some microorganisms may fluctuate erratically, whereas others, which are more predictable, offer the opportunity to prepare in advance for the next environmental change. In analogy to classical Pavlovian conditioning, microorganisms may have evolved to anticipate environmental stimuli by adapting to their temporal order of appearance. Here we present evidence for environmental change anticipation in two model microorganisms, Escherichia coli and Saccharomyces cerevisiae. We show that anticipation is an adaptive trait, because pre-exposure to the stimulus that typically appears early in the ecology improves the organism's fitness when encountered with a second stimulus. Additionally, we observe loss of the conditioned response in E. coli strains that were repeatedly exposed in a laboratory evolution experiment only to the first stimulus. Focusing on the molecular level reveals that the natural temporal order of stimuli is embedded in the wiring of the regulatory network—early stimuli pre-induce genes that would be needed for later ones, yet later stimuli only induce genes needed to cope with them. Our work indicates that environmental anticipation is an adaptive trait that was repeatedly selected for during evolution and thus may be ubiquitous in biology. http://www.51xuewen.com/group/1952/topic_23076.htm |
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