Understanding and manipulating a conserved and essential transcription factor to activate antibiotic production in Streptomyces species

几乎所有用于人类医学的抗生素都是在50多年前发现的，大多数致病细菌现在对这些药物中的一种或多种具有耐药性。这意味着人类正面临着回到前抗生素时代，这是一种被描述为“抗生素末日”的令人担忧的情况。政府委托奥尼尔对抗生素耐药性（AMR）进行的审查估计，如果我们现在不启动抗生素发现工作，那么到2050年，耐药感染将比癌症杀死更多的人，估计每年有1000万人。我们目前使用的大多数抗生素都是来自土壤细菌次级代谢产物的天然产物，其中最重要的一组被称为链霉菌，占所有已知抗生素的50%。链霉菌对人类非常重要，尽管科学家已经从这些细菌中发现了许多抗生素，但我们现在知道他们只发现了真正容易找到的化合物，即低挂水果。过去15年的基因组测序显示，在实验室条件下，链霉菌细菌只能产生约25%的次级代谢产物，这意味着从1940-60年，即所谓的抗生素发现的黄金时代，科学家们几乎没有对其能力进行采样。其余的被称为“沉默的”次级代谢产物，因为它们不在实验室中产生。好消息是，这意味着我们比世纪的科学家有很大的优势-如果我们能找到方法来启动600多个已知物种中所有沉默的次级代谢产物的生产，我们将发现许多新的抗生素，可以进入临床试验管道。这是抗生素发现的最早阶段，我们现在加大努力至关重要，因为药物通过临床试验并批准用于人类需要10-15年的时间。可能<1%的抗生素将适用于治疗疾病，因此我们在未来几十年内从链霉菌中发现的天然产物越多越好。激活沉默次生代谢产物产生的一种方法是了解控制其在土壤中产生的天然信号和信号通路，这是我们研究的重点。如果我们能够操纵这些信号通路，我们就可以迫使细菌在实验室中制造所有的抗生素。理想情况下，我们希望在所有600多种已知的链霉菌中鉴定影响抗生素生产的信号通路，这是我们建议的主题。我们已经确定了一个信号通路由两个蛋白质称为MtrA和MtrB，并发现这是唯一的保守和必要的途径在链霉菌属。这意味着这种MtrAB双组分系统存在于每一个测序的链霉菌菌株中！MtrA是一种DNA结合蛋白，其活性受信号感应蛋白MtrB控制。如果我们通过删除mtrA基因来破坏这条通路，它是致命的。如果我们删除mtrB基因，它就不需要环境信号来激活该途径，并导致活性MtrA蛋白的过量产生，从而启动通常在野生型菌株中沉默的抗生素的产生。然而，简单地过度生产MtrA是行不通的，我们必须删除MtrB以及。在这个项目中，我们将分析MtrAB在两个模式物种称为S。coelicolor和S.委内瑞拉。我们将确定MtrB如何控制MtrA活性，为什么MtrA在没有MtrB的情况下是活跃的，为什么以及MtrA如何激活沉默次级代谢产物的产生。我们还将尝试获得总是活跃的MtrA蛋白的功能，看看我们是否可以用它们来开启我们的模型菌株和我们已经分离和基因组测序的两种新的天才链霉菌物种中的抗生素生产。我们称它们为天才，因为它们似乎编码许多新的次级代谢产物，而MtrA可能使我们能够从这些菌株中发现新的抗生素。

Almost all the antibiotics used in human medicine were discovered >50 years ago and most disease-causing bacteria are now resistant to one or more of these drugs. This means humans are facing a return to the pre-antibiotic era, an alarming situation that has been described as 'antibiotic Armageddon'. The government commissioned O'Neill review on AntiMicrobial Resistance (AMR) estimates that if we do not kick-start antibiotic discovery efforts now then by 2050 drug resistant infections will kill more people than cancer, an estimated 10 million a year. Most of the antibiotics we currently use are natural products derived from the secondary metabolites of soil bacteria and the most important group are called Streptomyces, which make 50% of all known antibiotics. Streptomyces are incredibly important to humans and although scientists have already discovered lots of antibiotics from these bacteria we now know that they only found the really easy to find compounds, the low hanging fruit. Genome sequencing over the last 15 years has revealed that Streptomyces bacteria only make about 25% of their secondary metabolites under laboratory conditions which means that from 1940-60, the so-called golden age of antibiotic discovery, scientists were barely sampling their capability. The rest are called 'silent' secondary metabolites because they do not make them in the lab. The good news is this means we have a big advantage over scientists working in the 20th century - if we can find ways to switch on production of all the silent secondary metabolites in the >600 known species we will find lots of new antibiotics that can enter the clinical trials pipeline. This is the earliest stage in antibiotic discovery and it is vital that we increase our efforts now because it takes 10-15 years to get drugs through clinical trials and approved for use in humans. Probably <1% of antibiotics will be suitable for treating disease so the more natural products we can discover from Streptomyces in the next few decades the better. One way to activate the production of silent secondary metabolites is to understand the natural signals and signalling pathways that control their production in the soil and this is the focus of our research. If we can manipulate those signalling pathways we can force the bacteria to make all of their antibiotics in the laboratory. Ideally we want to identify signalling pathways which effect antibiotic production in all 600+ known Streptomyces species and this is the subject of our proposal. We have identified a signalling pathway consisting of two proteins called MtrA and MtrB and found this is the only conserved and essential pathway in the genus Streptomyces. This means this MtrAB two-component system is found in every single sequenced Streptomyces strain! MtrA is a DNA binding protein and its activity is controlled by the signal sensing protein MtrB. If we disrupt the pathway by deleting the mtrA gene it is lethal. If we delete the mtrB gene it removes the need for an environmental signal to activate the pathway and results in over-production of active MtrA protein which switches on production of antibiotics that are usually silent in the wild-type strains. However, simply over-producing MtrA does not work, we HAVE to remove MtrB as well. In this project we will analyse MtrAB in two model species called S. coelicolor and S. venezuelae. We will determine how MtrB controls MtrA activity, why MtrA is active in the absence of MtrB and why and how MtrA activates the production of silent secondary metabolites. We will also try to make gain of function MtrA proteins that are always active and see if we can use them to switch on antibiotic production in our model strains and in two new talented Streptomyces species that we have isolated and genome sequenced. We call them talented because they appear to encode many novel secondary metabolites and MtrA may allow us to discover new antibiotics from these strains.