生物谷报道：以往我们的常识告诉我们只有具备完整神经系统的生物才可以主动预知环境的改变而作好应变准备。可是美国普林斯顿大学的科学家近日研究表明细菌也具有某种形式的学习记忆能力，能够预先判断环境的变化而做出反应。
研究人员利用计算机模型模拟了细菌的进化，并在实验室中培育大肠杆菌：首先将温度从25摄氏度提高到37摄氏度，然后将氧含量从20%降低到零。研究人员监控了几百代细菌的反应，结果发现，几周之后，细菌已经可以预料氧气的下降，即温度一改变它们就会调整自己的代谢。这说明，大肠杆菌能够发展出将高温（如人类口腔内）与缺氧（如人类肠道内）建立联系的能力。
近百年来，关于细菌行为的流行观点是动态平衡（homeostasis），即认为细菌对环境刺激的反应是以一种作用-反作用的方式进行的。这一研究结果则颠覆了以往的认知。这是细菌具有联想学习的首个证据，这种反应与巴甫洛夫条件反射作用（条件反射训练后，狗闻铃声便分泌过量唾液）相似。当然，这并不是说单细胞的细菌与狗或人具有相同的学习方式。研究医院表示，人或狗的联想学习跨越整个生命周期，并且包括对脑部神经元之间连接强度的修正；而细菌的学习要经过很长时间的进化过程，包括基因网络之间连接的改变。
此次研究对于处理细菌感染和抗药性具有潜在的意义。另外，预见细菌的行为可能还有助于指导酿造等依赖它们的工业过程。这项研究的报告5月8日在线发表于Science杂志。（生物谷www.bioon.com）
生物谷推荐原始出处：
Science，DOI: 10.1126/science.1154456，Ilias Tagkopoulos，Saeed Tavazoie
Anticipatory Behavior Within Microbial Genetic Networks
Ilias Tagkopoulos 1, Yir-Chung Liu 2, Saeed Tavazoie 2*
1 Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA.; Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA.
2 Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA.; Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
* To whom correspondence should be addressed.
Saeed Tavazoie , E-mail: tavazoie@genomics.princeton.edu
These authors contributed equally to this work.
We question whether homeostasis alone adequately explains microbial responses to environmental stimuli, and explore the capacity of intra-cellular networks for predictive behavior in a fashion similar to metazoan nervous systems. We show that in silico biochemical networks, evolving randomly under precisely defined complex habitats, capture the dynamical, multi-dimensional structure of diverse environments by forming internal models that allow prediction of environmental change. We provide evidence for such anticipatory behavior by revealing striking correlations of Escherichia coli transcriptional responses to temperature and oxygen perturbations—precisely mirroring the co-variation of these parameters upon transitions between the outside world and the mammalian gastrointestinal-tract. We further show that these internal correlations reflect a true associative learning paradigm, since they show rapid de-coupling upon exposure to novel environments.
