Invited Paper BP-SuA1
Microbial Electron Conduits: Adventures at the Biotic-Abiotic Interface

Sunday, October 20, 2019, 3:00 pm, Room A120-121

In what has become an established pattern, however, our planet’s oldest and most versatile organisms are now challenging our current state of knowledge. With the discovery of bacterial nanowires, conductive biofilms, and multicellular bacterial cables, the length scales of microbial ET observations have jumped by 7 orders of magnitude, from nanometers to centimeters, during the last decade alone! This talk will take stock of where we are and where we are heading as we come to grips with the basic mechanisms and immense implications of microbial long-distance electron transport. We will focus on the biophysical and structural basis of long-distance, fast, extracellular electron transport by metal-reducing bacteria. These remarkable organisms have evolved direct charge transfer mechanisms to abiotic surfaces, allowing them to use abundant minerals as electron acceptors for respiration, instead of oxygen or other soluble oxidants that would normally diffuse inside cells. From a technological perspective, microbial extracellular electron transport is heavily pursued for interfacing redox reactions to electrodes in renewable energy technologies.

But how can an organism transfer electrons to a surface many cell lengths away? What molecules mediate this transport? And, from a physics standpoint, what are the relevant length, time, and energy scales? We will describe new experimental and computational approaches that revealed how bacteria organize heme networks on outer cell membranes, and along quasi-one-dimensional filaments known as bacterial nanowires, to facilitate long-range charge transport. Using electron cryo-tomography, in vivo fluorescent microscopy, and single molecule tracking, we are gaining new insight into the distribution of multiheme cytochromes along membranes. In addition, we will examine the fundamental limits of extracellular electron transport, down to single molecules and energy acquisition by individual cells. These findings are shedding light on one of the earliest forms of respiration on Earth while unraveling surprising biotic-abiotic interactions.