Characterization of Electrogenic Gut Bacteria

Abstract

While electrogenic, or electricity-producing, Gram-negative bacteria predominantly found in anaerobic habitats have been intensively explored, the potential of Gram-positive microbial electrogenic capability residing in a similar anoxic environment has not been considered. Because Gram-positive bacteria contain a thick non-conductive cell wall, they were previously believed to be very weak exoelectrogens. However, with the recent discovery of electrogenicity by Gram-positive pathogens and elucidation of their electron-transfer pathways, significant and accelerated attention has been given to the discovery and characterization of these pathways in the members of gut microbiota. The discovery of electrogenic bacteria present in the human gut and the understanding of their electrogenic capacity opens up possibilities of bacterial powered implantable batteries and provide a novel biosensing platform to monitor human gastrointestinal health. In this work, we characterized microbial extracellular electron-transfer capabilities and capacities of five gut bacteria: Staphylococcus aureus, Enterococcus faecalis, Streptococcus agalactiae, Lactobacillus reuteri, and Lactobacillus rhamnosus. A 21-well paper-based microbial fuel cell array with enhanced sensitivity was developed as a powerful yet simple screening method to accurately and simultaneously characterize bacterial electrogenicity. S. aureus, E. faecalis, and S. agalactiae exhibited distinct electrogenic capabilities, and their power generations were comparable to that of the well-known Gram-negative exoelectrogen, Shewanella oneidensis. Importantly, this system was used to begin a large-scale transposon screen to examine the genes involved in electrogenicity by the human pathobiont S. aureus.

Electrochemical Microwell Plate to Study Electroactive Microorganisms in Parallel and Real-Time

“…The ec-MP presented here will allow a true parallelization of the microbial electrochemical screening and microbial electrochemically driven selection. This will open the door to perform microbial resource mining in habitats that are already well known for harbouring EAM like wastewater and soil ( Koch and Harnisch 2016a ; Logan et al, 2019 ) but also recently discovered ones like the oral ( Naradasu et al, 2020 ) or gut ( Tahernia et al, 2020b ; Rago et al, 2021 ) microbiome and especially to explore new habitats as resources. Further, we foresee that already exploited EAM, for instance, for microbial electrosynthesis of chemical building blocks ( Mayr et al, 2019 ; Wu et al, 2019 ), can be further improved using concepts and tools that are well established (for non-electrochemical means) like site directed mutagenesis, CRISPR-CAS, and techniques beyond in high-throughput ( Alves et al, 2017 ; Fan et al, 2020 ).…”

Electrogenic Bacteria Promise New Opportunities for Powering, Sensing, and Synthesizing

“…characterized microbial extracellular electron transfer capabilities and capacities of five gut bacteria: Staphylococcus aureus , Enterococcus faecalis , Streptococcus agalactiae , Lactobacillus reuteri , and Lactobacillus rhamnosus ( Figure a). [ 103 ] From the study, S. aureus, E. faecalis , and S. agalactiae exhibited distinct electrogenic capabilities, and their power generations were comparable to that of well‐known Gram‐negative exoelectrogen, S. oneidensis . This work demonstrated that many Gram‐positive gut bacteria can transfer electrons to the exterior of their cells and this finding has enormous upside potential for the fields of biosensing, biocomputing, and biosynthesis.…”

“…Electrogenic bacteria are a promising element for biosensing because they produce quantifiable electricity by sensing and responding to a wide variety of external signals including [103] Copyright 2020, American Chemical Society. b) A wearable microbial fuel cell using human skin bacteria.…”

“…a) Conceptual image for ingestible microbial fuel cells. Reproduced with permission [103]. Copyright 2020, American Chemical Society.…”

Spatial Engineering of Microbial Consortium for Long‐Lasting, Self‐Sustaining, and High‐Power Generation in a Bacteria‐Powered Biobattery

“…[10,11] Wearable or implantable biobatteries have been proposed that use human skin or gut bacteria and feed off sweat or other organics available in the human body. [12,13] However, because these biobatteries use heterotrophs that feed and generate power from organic Bacteria-powered biobatteries using multiple microbial species under well-mixed conditions demonstrate a temporary performance enhancement through their cooperative interaction, where one species produces a resource that another species needs but cannot synthesize. Despite excitement about the artificial microbial consortium, those mixed populations cannot be robust to environmental changes and have difficulty generating long-lasting power because individual species compete with their neighbors for space and resources.…”