Structure and Function of Bacterial Nanowires

细菌纳米线是由一些厌氧细菌（包括硫还原地杆菌）产生的自然存在的导电延伸。它们主要用于在环境中寻找电子受体，这样细菌就可以排出呼吸过程中产生的多余电子，这在没有氧气的情况下尤为重要。这些细菌菌株也可以形成生物膜，在这些生物膜中，纳米线连接成一个巨大的纳米线网络。在某些情况下，网络可以包括来自不同种类细菌的纳米线，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在用作微生物燃料电池方面具有很大的潜力，我们可以直接从生物那里获得电能。本研究的目的是阐明细菌纳米线在生物膜中的导电机制。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）的文章表明，关于蛋白质细丝中的传导分子机制还有很多需要了解。我们将解决的关键问题包括：存在多少种不同类型的导电丝？电是如何沿着毛传导的？当相邻的毛接触时，毛内的规则阵列是否被破坏，如果是这样，如何保持导电性？是生物膜产生了粗大的导电纳米线，还是这种网络是脱域的？我们将使用低温电子显微镜和单粒子分析分离的纳米线，以及聚焦离子束（FIB）研磨生物膜和电子断层扫描对生物膜进行原位研究，研究硫还原g纳米线作为细菌纳米线的代表系统。这项工作将帮助我们了解细菌如何在一个网络中协同工作，以及生物膜功能的固有局限性。我们期望通过对纳米线结构的一些修改，我们可以提高导电效率，从而设计出一种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，即细胞和细胞网络的分子细节原位成像。FIB铣削和低温电子断层扫描的结合被证明是非常强大的，将其引入加拿大研究界可能会产生强大的影响，并增加全国许多小组的工作。

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.