Global Regulators in a Bacterial Pathogen and Virulence

细菌几乎占据了地球上的每一个生态位，它们已经繁衍了数十亿年。生物学家认为，地球上细菌生命的“成功”是由于细菌能够在正确的时间表达正确的基因，从而充分利用它们生长的特定环境。为了做到这一点，它们在任何情况下都有选择性地表达必要的基因，它们这样做的主要方法之一是使用转录因子。这是一组特殊的蛋白质，它们对来自环境的特定信号作出反应，在特定基因的调控区域相互作用，从而开启或关闭它们的表达。一些细菌能够在人类身上定居，其中一小部分会导致疾病。对细菌来说，人类宿主“只是”另一个环境，因此，在人类环境中繁殖需要某些基因的表达，这些基因的表达受转录因子的调节。大多数转录因子只影响少数基因的表达，然而，少数转录因子影响数百个基因的表达，其中最著名的转录因子之一是CRP。通过研究导致人类疾病的常见细菌病原体，我们发现CRP控制着一些导致疾病的基因。我们的主要目标之一是跟进这一观察结果，并确定这些病原体中受CRP调节的基因的完整目录。我们希望找到数百个目标，所以第二个目标是了解CRP在这些目标之间是如何分布的，以及它如何随着环境的变化而变化。最近的一些研究表明，存在其他蛋白质与CRP相互作用，并改变其在某些基因调控区域的活性。我们将特别关注使细菌对人类有害的基因。抗生素通常用于治疗由细菌引起的有害感染，但众所周知，由于抗生素不能杀死的耐药细菌的出现，目前存在很大的问题。因此，有必要寻找不依赖抗生素的新抗菌策略。在之前对CRP的研究中，我们已经能够构建一种版本的CRP (CRP-0)，它失去了调节基因表达的能力，但能够干扰有害细菌中“好”CRP的活性。一些初步数据表明，我们可以使用CRP-0“解除”有害细菌菌株的武装，使其无害。我们计划开发一种载体来传递CRP-0，因为CRP在细菌中如此广泛，这将提供一种选择，通过“解除”而不是杀死它们来“中和”许多不同的细菌病原体，从而提供一种治疗选择。先前的研究表明，大多数含有CRP的细菌也含有第二种非常相似的转录因子，称为FNR。FNR对于让细菌适应缺氧的生长很重要，我们发现，对于一些细菌病原体来说，缺氧有助于感染。因此，我们计划采用与FNR并行的方法，并确定其目标。有害细菌和无害细菌之间的目标比较应该告诉我们为什么缺氧会促进毒性。此外，FNR衍生物，如CRP-0，在调节基因表达的能力方面存在缺陷，将为我们提供干扰细菌基因表达的第二种选择，这些基因表达是成功感染所必需的。因此，我们的总体策略是发现CRP和FNR对细菌感染的贡献，并利用我们的发现开拓一种不依赖抗生素的抗菌策略。

Bacteria colonise almost every niche on earth and they have been thriving for billions of years. Biologists believe that the 'success' of bacterial life on earth is due to the ability of bacteria to express the right gene at the right time, thereby making the most of the particular environment where they are growing. To do this, they selectively express the necessary genes in any situation, and one of the main ways they do this is by the use of transcription factors. These are a specialised group of proteins, which, in response to a particular signal from the environment, interact at the regulatory region of specific genes, and either turn on or turn off their expression. Some bacteria are able to colonise humans and a small number of these cause disease. To a bacterium, a human host is "just" another environment, and, hence, thriving in a human environment requires the expression of certain genes whose expression is regulated by transcription factors. Most transcription factors affect the expression of just a handful of genes, however a small number affect hundreds of genes, one of the most well-known being the transcription factor called CRP. Working with common bacterial pathogens that cause human disease, we have found that CRP controls some of the genes responsible for disease. One of our main aims is to follow up on this observation and identify the full catalogue of genes that are regulated by CRP in these pathogens. We expect to find hundreds of targets, and so a second aim is to understand how CRP is distributed between these targets, and how this alters in response to changes in the environment. Some very recent research suggests the existence of other proteins that interact with CRP and alter its activity at the regulatory region of certain genes. We will pay particular attention to the genes that make bacteria dangerous to humans. Antibiotics are commonly used to treat harmful infections due to bacteria, but it is well-known that there is currently a big problem due to the appearance of resistant bacteria that are not killed by antibiotics. Hence, there is a need to find new antibacterial strategies that do not rely on antibiotics. In previous work with CRP, we have been able to construct a version of CRP (CRP-0) that has lost its ability to regulate gene expression, but is able to interfere with the activity of 'good' CRP in harmful bacteria. Some preliminary data has shown that we can use CRP-0 to 'disarm' a harmful bacterial strain and make it harmless. We plan to develop a vector for the delivery of CRP-0 and, because CRP is so widespread in bacteria, this will provide an option to 'neutralise' many different bacterial pathogens by 'disarming' them rather than killing them, thereby providing a therapy option. Previous research has shown that most bacteria that contain CRP also contain a second very similar transcription factor called FNR. FNR is important to allow bacteria to adapt to growth in the absence of oxygen, and we have found that, for some bacterial pathogens, infection is aided by the absence of oxygen. Hence, we plan to take a parallel approach with FNR, and identify its targets. Comparison of targets between harmful and harmless bacteria should tell us why the lack of oxygen promotes virulence. In addition, FNR derivatives which, like CRP-0, are handicapped in their ability to regulate gene expression, will provide us with a second option to interfere with the expression of bacterial genes that are needed for successful infection. Hence, our overall strategy is to discover the contribution of CRP and FNR to bacterial infections and to exploit what we find to pioneer an anti-bacterial strategy that does not depend on antibiotics.