Understanding the Role of Peptidoglycan Metabolism in Bacterial Predation

我们正在研究一种天然的、友好的细菌--细小芽孢杆菌--大致翻译为“吃水蚤的细菌”--它能够杀死其他不那么友好的细菌。细菌种群的控制在人类生存的许多领域都很重要--即解决医疗保健(例如超级细菌)、作物瘟疫、食品安全、生物污染和水质管理中不受欢迎的病原体物种。有可能以治疗的方式利用：i)从蛭弧菌研究中获得的知识，ii)蛋白质产品(酶生物制剂)或iii)整个细胞/培养物。与其他捕食性细菌不同，蜈蚣弧菌从内部杀死目标--进入它们，分解它们，在里面繁殖，然后破裂它们释放子细胞，重新开始循环。蜈蚣弧菌来自一种非捕食性的祖先细菌，因此开发了专门的工具，使它能够进入并杀死其他细菌。这些工具是蛋白质酶--我们的目标是研究它们的形式和功能，以便我们更好地了解杀死过程，甚至可能增强蛭弧菌作为抗菌剂的潜力。这些蛋白质可以非常有用地让我们针对病原体细胞的入侵，并以受控的方式破坏它们。我们实验室之前的研究表明，其中一种酶(Bd3459)针对猎物，并作用于改变猎物的形状。我们发现，Bd3459通过切割猎物壁的特定区域(称为肽聚糖)实现了这一点，导致壁部分坍塌，从而改变了它以前支持的细菌的形状--就像锯掉房子的支撑墙一样！形状的改变是为了给被捕食者提供最佳的空间，这也向其他入侵者发出信号，这个特定的“家”已经被占领，再进入将是浪费的。还有更多在细菌猎物的细胞壁“被蚕食”的“特殊”蜈蚣弧菌酶--我们想对这些酶进行研究，以便更全面地了解虱弧菌开始杀死猎物时发生了什么，并允许人们将这些酶用于生物技术。我们将研究这些酶本身的原子细节(称为x射线结晶学)，使用酶的荧光版本来跟踪它们发挥作用的位置(它们是“咀嚼”宿主还是防止不必要的自我破坏？)，监测功能的精确性质(称为酶分析)。还测试了酶：位置：功能关系，通过构建细菌突变株(缺乏酶)来证实/消除出现的假设。肽聚糖靶向酶的研究具有非常实际的应用-完整的壁对于大多数医学相关细菌是必不可少的，并形成了几种非常成功的抗生素(例如青霉素、万古霉素)的作用基础。我们的研究结果可能对这一过程有所启发，也对微生物生理学(形态和功能)具有普遍意义。

We are studying the natural, friendly bacterium Bdellovibrio bacteriovorus - roughly translated as "leech-like bacteria-eater" - which is able to kill other less-friendly bacteria. The control of bacterial populations is important in many areas of human existence - namely tackling undesirable pathogenic species in healthcare (e.g. superbugs), crop pestilence, food safety, biofouling and water quality management. The potential exists to use i)knowledge gained from Bdellovibrio study, ii)protein products (enzybiotics) or iii)whole cells/cultures in a therapeutic manner. Unlike other predatory bacteria, Bdellovibrio kills its targets from within - entering them, breaking them down, reproducing inside and then bursting them to release daughter cells and begin the cycle anew.Bdellovibrio arose from a non-predatory ancestor bacterium, and thus developed specialized tools that allow it to enter and kill other bacteria. These tools are protein enzymes - we aim to investigate the form and function of these so that we understand the killing process better, and perhaps even enhance the potential of Bdellovibrio as an antibacterial agent. Such proteins can be very useful to let us target the invasion of pathogen cells and break them in a controlled way.Prior investigation by our laboratories revealed that one such enzyme (Bd3459) was targeted to the prey, and acted to change prey shape. We showed that Bd3459 achieved this by cutting particular regions of the prey wall (known as peptidoglycan), causing the wall to partially collapse and so alter the shape of the bacterium that it previously supported - much like sawing away at the support walls of a house! The shape change serves to provide the optimal space for Bdellovibrio invasion of prey, which also signals to fellow invaders that this particular "home" is occupied and that further entry would be wasteful. There are more "special" Bdellovibrio enzymes that "chip away" at the cell walls of bacterial prey- we would like to work on these to develop a fuller picture of what goes on when Bdellovibrio starts to kill its prey and to allow people to use these for biotechnology.We will look at the enzymes themselves in atomic detail (known as x-ray crystallography), using fluorescent versions of the enzymes to track where they exert their effects (do they "chew up" the host or prevent unwanted destruction of self?), monitoring the precise nature of the function (known as enzyme assays), and also testing the enzyme:location:function relationship by constructing mutant strains of bacteria (lacking the enzymes) to confirm/dispel the hypotheses arising.The investigation of peptidoglycan-targeting enzymes has a very practical application - an intact wall is essential to most medically-relevant bacteria, and forms the basis of action of several very successful antibiotics (e.g. penicillin, vancomycin). Results from our study may inform on this process, and also have implications for microbial physiology (form and function) in general.