Thomas Gavin H
Department of Biology, Wentworth Way, University of York, York, UK, YO10 5DD.
Mol Microbiol. 2017 Jun;104(6):883-888. doi: 10.1111/mmi.13691. Epub 2017 May 12.
Bacteria have evolved many routes for taking up nutrients, demonstrating great versatility in the types and mechanism of uptake used in different physiological conditions. The discovery of a single transporter in the bacterium Advenella mimigardefordensis for the uptake of five different sugars, including L-glucose and D-xylose, is described in this issue (Meinert et al., ), providing yet another example of the surprising adaptability of bacterial transport strategies. The transporter identified is a tripartite ATP-independent (TRAP) transporter, not previously associated with sugar transport, and in fact does not transport the sugars directly at all, rather requiring them to be converted in the periplasm to their respective sugar acid forms before transport through what appears to be a novel general sugar acid transporter. In this commentary, I describe how this process is consistent with the known mechanisms of TRAP transporters and consider how the role of sugar oxidation, or oxidative fermentation, operates with multiple hexose and pentose sugars. Finally I suggest that the periplasmic conversion of nutrients acquired across the outer membrane, before transport across the inner membrane, could have potentially useful biological functions in Gram negative bacteria.
细菌已经进化出多种摄取营养物质的途径，在不同生理条件下所采用的摄取类型和机制方面展现出极大的多样性。本期介绍了在模仿花园地小杆菌（Advenella mimigardefordensis）中发现的一种单一转运蛋白，它能够摄取包括L-葡萄糖和D-木糖在内的五种不同糖类（迈纳特等人），这为细菌转运策略惊人的适应性提供了又一个例证。所鉴定出的转运蛋白是一种不依赖ATP的三方转运蛋白（TRAP转运蛋白），此前未发现其与糖类转运有关，实际上它根本不直接转运糖类，而是需要糖类在周质中先转化为各自的糖酸形式，然后通过一种看似全新的通用糖酸转运蛋白进行转运。在这篇述评中，我阐述了这一过程如何与TRAP转运蛋白的已知机制相符，并探讨了糖氧化或氧化发酵在多种己糖和戊糖中的作用机制。最后，我提出在外膜摄取的营养物质在内膜转运之前先在周质中进行转化，这在革兰氏阴性菌中可能具有潜在的重要生物学功能。
