Acetogenic bacteria utilize light-driven electrons as an energy source for autotrophic growth

Abstract

Acetogenic bacteria use cellular redox energy to convert CO2 to acetate using the Wood–Ljungdahl (WL) pathway. Such redox energy can be derived from electrons generated from H2 as well as from inorganic materials, such as photoresponsive semiconductors. We have developed a nanoparticle-microbe hybrid system in which chemically synthesized cadmium sulfide nanoparticles (CdS-NPs) are displayed on the cell surface of the industrial acetogen Clostridium autoethanogenum. The hybrid system converts CO2 into acetate without the need for additional energy sources, such as H2, and uses only light-induced electrons from CdS-NPs. To elucidate the underlying mechanism by which C. autoethanogenum uses electrons generated from external energy sources to reduce CO2, we performed transcriptional analysis. Our results indicate that genes encoding the metal ion or flavin-binding proteins were highly up-regulated under CdS-driven autotrophic conditions along with the activation of genes associated with the WL pathway and energy conservation system. Furthermore, the addition of these cofactors increased the CO2 fixation rate under light-exposure conditions. Our results demonstrate the potential to improve the efficiency of artificial photosynthesis systems based on acetogenic bacteria integrated with photoresponsive nanoparticles.

Faster growth enhances low carbon fuel and chemical production through gas fermentation

“…Exploring the physiological boundaries of acetogens has been informative for understanding regulation of their energy-limited metabolism (Valgepea et al, 2017a; Mahamkali et al, 2020; Jin et al, 2021; Klask et al, 2020). Additionally, various bioprocess approaches, multi-omics analysis, construction of metabolic models, and development of genetic tools are being pursued for development of cell factories with enhanced substrate conversion, product distribution, and expanded product spectrum (Valgepea et al, 2018; Lemgruber et al, 2019; Heffernan et al, 2020; Smith et al, 2020; Fackler et al, 2021; Jin et al, 2021; Bourgade et al, 2021; Diender et al, 2021; Molitor et al, 2019; Pavan et al, 2022). Notably, the effects of μ on acetogen metabolism and the gas fermentation bioprocess have not been established.…”

Pushing the methodological envelope in understanding the photo/electrosynthetic materials-microorganism interface

“…In a complementary direction, understanding the effects of the inorganic component on the function of the microbe is key toward approaching the rational design of materials-microbe interfaces. To this end, biohybrids consisting of Clostridium autoethanogenum with CdS particles on their surfaces that converted CO 2 to acetate under illumination were investigated ( Jin et al., 2021 ). Transcriptional analysis illustrated activation of genes in Wood–Ljundahl pathway, as well as metal ion and flavin-binding proteins, indicating that likely involvement of flavins in a mediated EET route between CdS and the microbe.…”

Panoramic insights into semi-artificial photosynthesis: origin, development, and future perspective

“…163,164 Besides, a chemically synthesized CdS was closely attached to the acetogen Clostridium autoethanogenum for solar-power to CO 2 to acetate conversion, in which the transcriptional analysis was applied to reveal the underlying electron transfer mechanism. 165 In addition to CdS, other materials have also been integrated with bacterial cells. For example, M. thermoacetica was covalently bonded with metal-organic frameworks (MOF) for fixation of CO 2 in aerobic conditions, which extended the application field of anaerobic bacteria.…”