Aer and Tsr guide Escherichia coli in spatial gradients of oxidizable substrates
Aer and Tsr guide Escherichia coli in spatial gradients of oxidizable substrates
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DOI：
10.1099/mic.0.26304-0
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发表时间：
2003-09-01
期刊：
影响因子：
2.8
通讯作者：
Zhulin, IB
中科院分区：
文献类型：
--
作者：
Greer-Phillips, SE;Alexandre, G;Zhulin, IB
大肠杆菌中的Aer和Tsr化学感受器控制对氧和氧化还原电位的策略反应，这些反应是称为能量趋化性的整体行为的一部分。他们还建议调解响应迅速利用的碳源，甘油和琥珀酸，通过能源的士机制。在这项研究中，Aer和Tsr蛋白分别在大肠杆菌的“全换能器敲除”菌株中表达，并在各种可氧化碳源的梯度中分析了趋化性。除了已知的对甘油和琥珀酸的反应之外，发现Aer指导对核糖、半乳糖、麦芽糖、苹果酸、脯氨酸和丙氨酸以及磷酸转移酶系统（PTS）碳水化合物葡萄糖、甘露醇、甘露糖、山梨醇和果糖的趋化性，但不指导对天冬氨酸、谷氨酸、甘氨酸和阿拉伯糖的趋化性。Tsr将出租车引向糖（包括由PTS运输的糖），但不引向有机酸或氨基酸。当突变的Aer蛋白不能结合FAD辅因子在无受体菌株中表达时，趋化性不能恢复到任何底物。Aer似乎介导快速氧化底物的反应，无论它们是否是有效的生长底物，而Tsr似乎介导的士基板，支持最大的增长，无论它们是否是快速氧化。这与Aer和Tsr分别感知氧化还原和质子动力的假设相关。两者合计，结果表明，Aer和Tsr介导的反应，以广泛的化学品和他们的引诱物库重叠的专门的化学感受器，即Trg（核糖，半乳糖）和焦油（麦芽糖）。
The Aer and Tsr chemoreceptors in Escherichia coli govern tactic responses to oxygen and redox potential that are parts of an overall behaviour known as energy taxis. They are also proposed to mediate responses to rapidly utilized carbon sources, glycerol and succinate, via the energy taxis mechanism. In this study, the Aer and Tsr proteins were individually expressed in an 'all-transducer-knockout' strain of E coli and taxis was analysed in gradients of various oxidizable carbon sources. In addition to the known response to glycerol and succinate, it was found that Aer directed taxis towards ribose, galactose, maltose, malate, proline and alanine as well as the phosphotransferase system (PTS) carbohydrates glucose, mannitol, mannose, sorbitol and fructose, but not to aspartate, glutamate, glycine and arabinose. Tsr directed taxis towards sugars (including those transported by the PTS), but not to organic acids or amino acids. When a mutated Aer protein unable to bind the FAD cofactor was expressed in the receptor-less strain, chemotaxis was not restored to any substrate. Aer appears to mediate responses to rapidly oxidizable substrates, whether or not they are effective growth substrates, whereas Tsr appears to mediate taxis to substrates that support maximal growth, whether or not they are rapidly oxidizable. This correlates with the hypothesis that Aer and Tsr sense redox and proton motive force, respectively. Taken together, the results demonstrate that Aer and Tsr mediate responses to a broad range of chemicals and their attractant repertoires overlap with those of specialized chemoreceptors, namely Trg (ribose, galactose) and Tar (maltose).