Understanding antibiotic entry into bacteria

抗生素使治疗和治愈危及生命的细菌感染成为可能。不幸的是，抗药性“超级细菌”的崛起正在极大地破坏这些重要药物的有效性，这一问题是当前全球公共卫生面临的最大威胁之一。解决这个问题的一个关键方面将涉及发现和开发新的抗生素，这些抗生素对已经对我们现有的抗生素产生耐药性的细菌具有活性。然而，一个重大的科学挑战阻碍了这一目标的实现。虽然现在可以识别或制造新的化合物来干扰细菌生物机器的正确功能（任何潜在抗生素的必要特性），但这些化合物基本上无法穿过细菌周围的膜到达该机器。如果我们知道如何修饰这些化合物以有效地将它们输送到细菌中，它们将有潜力成为新的抗生素。这项建议旨在提供基本的科学知识，使这种方法成为可能。通过了解像抗生素这样的小分子如何进入细菌--目前我们对这一现象知之甚少--我们将获得必要的战略情报，使我们能够合理地生产新的抗生素。该项目将采取两种相辅相成的办法来实现这一目标。其中第一项将采用一种称为液相色谱-质谱（LC-MS）的技术，直接测量大量不同的小分子集合渗透到细菌中的能力。根据这项研究的结果，我们将能够确定小分子必须具有哪些物理和化学性质才能使其进入细菌，从而使我们能够制定一套规则，用于指导新抗生素的产生。第二种方法将研究已建立的抗生素实际上穿过细菌膜的机制或过程。目前的观点是，由于膜在本质上是流体，大多数这样的化合物只是漂移或扩散。然而，我们有证据表明，事实上大多数（也许是所有）抗生素都利用了细菌通常用来从环境中输入营养素等物质的膜中的蛋白质“泵”。通过研究人为改变细菌中这些泵的数量或水平对抗生素进入能力的影响，我们的目标是更清楚地证明这些泵在抗生素进入中的作用。抗生素通过这种泵进入细菌的想法的影响是相当大的。例如，这意味着抗生素要进入细菌，它们需要具有与细菌从环境中输入的“理想”化合物相似的物理或化学特征;这些特征允许它们“劫持”相应的泵。此外，它将提供一种策略，通过设计与细菌输入的天然化合物具有相似性的化合物来制造新的抗生素。

Antibiotics have made possible the treatment and cure of life-threatening bacterial infections. Unfortunately, the rise of antibiotic-resistant "superbugs" is dramatically undermining the effectiveness of these important drugs, a problem that represents one of the current greatest threats to global public health. A crucial aspect of addressing the problem will involve the discovery and development of novel antibiotics active against bacteria that have become resistant to our existing antibiotics. However, a major scientific challenge stands in the way of achieving this aim. Although it is now feasible to identify or make new chemical compounds that interfere with the correct functioning of the biological machinery of bacteria (a requisite property of any potential antibiotic), these compounds are in the main unable to cross the membrane(s) that surround bacteria to reach that machinery. If we knew how to modify these compounds to effectively deliver them into bacteria, they would have potential as new antibiotics. This proposal seeks to provide the fundamental scientific knowledge to make such an approach possible. By understanding how small molecules like antibiotics enter bacteria - a phenomenon about which we know very little at present - we will gain the necessary strategic intelligence to allow us to rationally generate new antibiotics. The project will take two complementary approaches to achieve this. The first of these will employ a technique known as liquid chromatography-mass spectrometry (LC-MS) to directly measure the ability of a large and diverse collection of small molecules to penetrate into bacteria. From the results of this study, we will be able to determine what physical and chemical properties a small molecule must have to allow it to enter bacteria, allowing us to formulate a set of rules that can be applied to guide the generation of new antibiotics. The second approach will investigate the mechanism or process by which established antibiotics actually cross the membrane(s) of bacteria. The current view is that, since membranes are fluid in nature, most such compounds simply drift or diffuse across. However, we have evidence to suggest that in fact most (perhaps all) antibiotics take advantage of protein 'pumps' in the membrane(s) that bacteria ordinarily use to import things such as nutrients from the environment. By examining what impact artificially altering the number or levels of these pumps in bacteria has on the ability of antibiotics to enter, we aim to more clearly demonstrate the role of these pumps in antibiotic entry. The implications of the idea that antibiotics enter bacteria via such pumps are considerable. For example, it would mean that for antibiotics to get into bacteria they need to have similar physical or chemical features to 'desirable' compounds that bacteria import from the environment; features that allow them to 'hijack' the corresponding pumps. Furthermore, it would offer a strategy to make new antibiotics by designing compounds that have regions of similarity to natural compounds that bacteria import.