However, in recent years, scientists have developed microbe-semiconductor biohybrids (Image shows how solar microbes turn CO2 into bioplastic) that combine the biosynthetic capabilities of living systems with the ability of semiconductors to receive light.
These microorganisms use solar energy to convert carbon dioxide (CO2) into value-added chemicals, such as bioplastics and biofuels. But how this energy transport occurs in such a small and complex system, and whether the process can be improved, is still unclear. Cornell researchers have developed a multimodal platform to image these biohybrids at single-cell resolution, to better understand how they function and how they can be optimized for more efficient energy conversion.
The team’s paper, “Single-Cell Multimodal Imaging Uncovers Energy Conversion Pathways in Biohybrids,” was published July 27 in Nature Chemistry. The lead researchers are postdoctoral researcher Bing Fu and former postdoctoral researcher Xianwen Mao.
Peng Chen, Professor of Chemistry Peter J.W. Debye and the College of Arts and Sciences led the project. This effort is the result of a broad collaboration – with Tobias Hanrath, a professor in the Smith School of Chemical and Biomolecular Engineering at Cornell Engineering, and Buz Barstow, Ph.D. ’09, assistant professor of environmental biology in the College of Agriculture and Environmental Sciences – funded by the US Department of Energy (DOE) to investigate microscopic imaging of microbes as a way to advance bioenergy research.
Biohybrid research is done on bacteria and macro – which are large cells in a bucket, Peng said – focusing on the accumulation of valuable chemicals and the collective behavior of the cells, rather than on the underlying system which allows complex chemical reactions.
“Theology is very diverse. Each cell is very different. Now, to better interrogate it, you really need to measure it at the single-cell level,” Chen said. “This is where we come in. We provide quantitative analysis of protein behavior and insight into electron transport processes from semiconductors to bacterial cells.
The new system combines multi-channel fluorescence imaging with current photoelectrochemical imaging to study the bacterium Ralstonia eutropha. The platform can simultaneously image, track, and measure multiple proteins within a cell while measuring electron flow, ultimately correlating the properties of cellular proteins and electron transport processes.
The researchers were successful in explaining the different functions of two types of hydrogenases – the one attached to the cell membrane and the other soluble in the cytoplasm – which help metabolize hydrogen and drive CO2 fixation. Although soluble hydrogenase is known to be essential for hydrogen metabolism, researchers have found that membrane-bound hydrogenase, although not essential, makes the process easier and makes it better.
In addition, the researchers obtained the first evidence that bacteria can receive large amounts of electrons from semiconductor photocatalysts. The team analyzed the electron and found it to be three orders of magnitude higher than scientists had previously thought, suggesting that bacteria could be designed in the future to improve the efficiency of energy conversion.
The researchers also found that membrane-bound and soluble hydrogenases play an important role in facilitating the transfer of electrons from the semiconductor to the cell. Meanwhile, not only can the cell accept electrons; it can also expand them in the other direction, without the help of hydrogenases.
The microscope is perfect for studying other biological and inorganic systems, including yeast, as well as for other processes, such as nitrogen fixation and pollutant removal.
Source: Cornell University
