Genetic, Biophysical, and Behavioral Characterization of Microbial Extracellular Electron Transport in Human and Animal Systems
Abstract
While all respiring organisms must breathe, the terminal electron acceptors for an organism can be very different. For humans, animals, and many other organisms, including some microbes, the terminal electron acceptor is oxygen. However, many microbes can grow in the absence of oxygen as the terminal electron acceptor, including virtually all microbes that inhabit the human gut. Our team showed definitively that human gut microbes can dispose of electrons using a process called extracellular electron transport, or EET, where electrons are transferred across cellular membranes to solid state terminal electron acceptors, soluble electron acceptors, and-or other living cells. While we have identified several organisms capable of EET, isolated directly from the human digestive tract, and have shown that those microbes communicate with each other to optimize ETT-generated electrical currents, we still do not have a comprehensive understanding of which microbes are capable of EET and what the physiological effects of this process are in human or animal systems. In this proposal we will characterize the mechanism(s) and role(s) of EET by- (1) Fully characterizing the species of microbes in the human gut capable of performing EET and developing gut-derived microcosm communities for in vitro and in vivo analyses; (2) Determining the mechanisms of EET at the biophysical, biochemical, and molecular genetic levels in both organisms in our proxy communities, and developing in situ electrochemical techniques that interrogate fresh human-derived samples and the gut of animal models; (3) Establishing a mouse model system to define the role of EET-capable microbes in gut communities, where the effects of EET active vs. inactive microbes on animal behavior, metabolic metrics, and tress tolerances will be determined. As part of our initial pilot project, four bacterial species capable of EET have been isolated directly from human fecal material. Further, we have demonstrated that these microbes are capable of cellto-cell communication where electricity generation of two species grown together far exceeds the current generation produced by either species in monoculture. We will now fully characterize the members of the human gut EET community from additional human gut samples. Newly identified species will then be characterized in vitro for their ability to conduct electricity to eletroactive surfaces, establish redox synergy with other microbes, and-or perform EET using soluble acceptor molecules. A variety of biophysical, physiological and molecular genetic-genomic tools will allow us to identify the components of the EET apparatus in each microbe. In order to identify a role for EET-capable microbes in the mammalian digestive system, a humanized mouse model is being developed, where we replace the mouse microbiome with human-derived microbiotas. The effect on mouse behavior and physiology will be determined as a function of their EET capabilities. Assays will include learning behaviors, thermal and mechanosensation.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 29, 2024
- Source ID
- FA95502310287
Entities
People
- Steven E. Finkel
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Southern California