Structure and Function of Bacterial Nanowires

细菌纳米线是由一些厌氧细菌（包括硫还原地芽孢杆菌）产生的天然存在的导电延伸物。它们主要用于在环境中寻找电子受体，因此细菌可以释放在呼吸过程中产生的过量电子，这在氧气不可用时特别相关。这些相同的细菌菌株也可以形成生物膜，在这些生物膜中，纳米线连接成一个大型的纳米线网络。 在某些情况下，网络可以包括来自不同物种的细菌的纳米线，这增加了找到电子受体的可能性。这种天然的电子发射细菌纳米线网络具有作为微生物燃料电池的巨大潜力，我们可以直接从生物体中获得电能。 这项研究的目的是阐明生物膜中细菌纳米线的导电机制。我们最近发表的关于一种以前未知的基于细胞色素的纳米线（OmcS）的文章证明了关于蛋白质细丝中传导的分子机制还有多少要了解。我们将解决的关键问题包括：有多少不同类型的导电丝存在？电流是如何沿着菌毛传导的？当相邻的菌毛接触时，菌毛内的规则排列是否被破坏？如果是，导电性是如何保持的？生物膜产生的是导电纳米线的粗电缆，还是网络的离域性？ 我们将从G. sulfurreducens作为细菌纳米线的代表性系统，使用低温电子显微镜和单颗粒分析孤立的纳米线，以及聚焦离子束（FIB）研磨的生物膜和电子断层扫描原位研究的生物膜。 这项工作将帮助我们了解细菌如何在网络中共同工作，以及生物膜功能的固有局限性。我们希望通过对纳米线结构的一些修改，我们可以提高导电效率，从而设计出改进的微生物燃料电池。此外，这项研究将有助于在加拿大首次建立一种重要的科学方法，即用分子细节对细胞和细胞网络进行原位成像。FIB研磨和低温电子断层扫描的结合被证明是非常强大的，它引入加拿大研究界可能会产生强大的影响，并加强全国许多团体的工作。

Bacterial nanowires are naturally occurring electrically conductive extensions produced by some anaerobic bacteria, including Geobacter sulfurreducens. They are primarily used to find electron acceptors in the environment so the bacteria can shed excess electrons produced during respiration, which is particularly relevant when oxygen is not available. These same bacterial strains can also form biofilms, and in these biofilms the nanowires link into a large network of nanowires. Networks can in some cases include nanowires from bacteria of a different species, which increases the likelihood of finding an electron acceptor. This network of natural electron-emitting bacterial nanowires has great potential for use as a microbial fuel cells, where we can gain electrical energy directly from the organisms. The goal of the proposed research is to elucidate the mechanism of electrical conduction through bacterial nanowires in biofilms. Our recent publication on a previously unknown cytochrome-based nanowire (OmcS) demonstrates how much is to be learned about the molecular mechanisms of conduction in protein filaments. Key questions we will address include: How many different types of conductive filaments exist? How is electricity conducted along a pilus? Is the regular array within the pilus disrupted when a neighbouring pilus makes contact, and if so, how is conductivity maintained? Do biofilms produce thick cables of conductive nanowires, or is the network delocalised? We will study nanowires from G. sulfurreducens as a representative system of bacterial nanowires using cryoelectron microscopy and single particle analysis for isolated nanowires, as well as focused ion beam (FIB)-milled biofilms and electron tomography for in situ studies of biofilms. This work will help us understand how bacteria work together in a network, and what limitations are inherent to the function of a biofilm. We expect that with some modifications to the structure of the nanowires, we can improve efficiency of electric conduction, leading to the design of an improved microbial fuel cell. Additionally, this research will help establish an important scientific method in Canada for the first time, in situ imaging of cells and cellular networks with molecular detail. The combination of FIB milling and cryo-electron tomography is proving to be very powerful, and its introduction into the Canadian research community is likely to have a strong impact and augment the work of many groups across the country.