Understanding extracellular electron transfer in electromicrobiology: from electromethanogens to cable bacteria

TY - GEN

T1 - Understanding extracellular electron transfer in electromicrobiology: from electromethanogens to cable bacteria

AU - Wang, Bo

PY - 2024/2

Y1 - 2024/2

N2 - Extracellular Electron Transfer (EET) in electroactive microorganisms (EAMs) is a beneficial process facilitating microbe communication with the external environment, electron release, and energy recharge. One significant application, called electromethanogenesis (EM) leverages EAMs interacting with electrodes, enhancing electron transfer rates, addressing electron shortages, and concurrently yielding value-added chemicals and fuels. External power is required to overcome thermodynamical barriers, but the prolonged electricity input is not environmentally friendly, and is a big challenge in remote areas lacking enough electrical access. Natural solar light as a green driving-power, however, is constrained in day/night intermittence. Multicellular filamentous cable bacteria composed of conductive periplasmic fibers play a pivotal role in biogeochemical cycling and exhibit promising potential in developing bioelectronic materials. However, the underlying conductor compositions, conduction mechanisms, interaction with electrodes, and many other basic metabolic and molecular features of cable bacteria remain elusive. To address if natural solar-intermittent power can effectively drive EM, a natural solar-intermittent bioelectrocatalysis system was successfully established to boost EM and recover bioenergy from wastewater (organic source) and waste (inorganic carbon source, exhausted gas, CO2). This was achieved through long-term monitoring of bioreactor indicators such as electrical current, gas production, and basic chemistry parameters. In-depth mechanism investigations encompassed electrochemistry, biofilm visualization, microbial community structures, functional genes, and more. On a complementary front, a fundamental exploration delved into understanding the long-distance electron transfer (LDET) mechanism in cable bacteria, along with identifying compound candidates for conductive periplasmic fibers. To that end, I developed a proteomics protocol for sequential protein extraction, which indicated that PilA, a major subunit of type IV pili (T4P), cannot be part of the fibers. Instead, it hinted towards another, potentially metal-binding, protein candidate. Further, I developed an anti-PilA nanobody for PilA localization in native cable bacteria. Preliminary data corroborate the absence of PilA from the fibers and suggest a role in gliding motility rather than conductivity.Together, by the investigation of applications and fundamental directions in EAMs, the development of a carbon-neutral technology utilizing solar power for bioenergy recovery, and the integration of multiple molecular toolboxes to understand LDET, will pave the way for broader applications in the field of electromicrobiology.

AB - Extracellular Electron Transfer (EET) in electroactive microorganisms (EAMs) is a beneficial process facilitating microbe communication with the external environment, electron release, and energy recharge. One significant application, called electromethanogenesis (EM) leverages EAMs interacting with electrodes, enhancing electron transfer rates, addressing electron shortages, and concurrently yielding value-added chemicals and fuels. External power is required to overcome thermodynamical barriers, but the prolonged electricity input is not environmentally friendly, and is a big challenge in remote areas lacking enough electrical access. Natural solar light as a green driving-power, however, is constrained in day/night intermittence. Multicellular filamentous cable bacteria composed of conductive periplasmic fibers play a pivotal role in biogeochemical cycling and exhibit promising potential in developing bioelectronic materials. However, the underlying conductor compositions, conduction mechanisms, interaction with electrodes, and many other basic metabolic and molecular features of cable bacteria remain elusive. To address if natural solar-intermittent power can effectively drive EM, a natural solar-intermittent bioelectrocatalysis system was successfully established to boost EM and recover bioenergy from wastewater (organic source) and waste (inorganic carbon source, exhausted gas, CO2). This was achieved through long-term monitoring of bioreactor indicators such as electrical current, gas production, and basic chemistry parameters. In-depth mechanism investigations encompassed electrochemistry, biofilm visualization, microbial community structures, functional genes, and more. On a complementary front, a fundamental exploration delved into understanding the long-distance electron transfer (LDET) mechanism in cable bacteria, along with identifying compound candidates for conductive periplasmic fibers. To that end, I developed a proteomics protocol for sequential protein extraction, which indicated that PilA, a major subunit of type IV pili (T4P), cannot be part of the fibers. Instead, it hinted towards another, potentially metal-binding, protein candidate. Further, I developed an anti-PilA nanobody for PilA localization in native cable bacteria. Preliminary data corroborate the absence of PilA from the fibers and suggest a role in gliding motility rather than conductivity.Together, by the investigation of applications and fundamental directions in EAMs, the development of a carbon-neutral technology utilizing solar power for bioenergy recovery, and the integration of multiple molecular toolboxes to understand LDET, will pave the way for broader applications in the field of electromicrobiology.

M3 - PhD thesis

PB - Aarhus University

ER -