Achievements

Cells compute with chemistry and semiconductors compute with transistors – but both operate by controlling the flow of electrons. Biochemistry typically allows electron flow in proteins only over a few nanometers whereas semiconductors use wires that can conduct quickly over long distances. What if cells have designed biomolecules that behave like wires? To breathe, living cells typically use oxygen-like soluble, membrane-ingestible molecules to dump electrons generated in metabolism. But I have found that to “breathe” in hot, anoxic environments that mimic early earth, soil bacteria, Geobacter have evolved nanowires, made up of polymerized cytochrome proteins, to export electrons to extracellular acceptors that could be hundreds of cell lengths away (Cell 2019, Nature Chem.Bio. 2020, Nature 2021). Rather than waiting for oxygen-like molecules to form and be taken up by cells, life can instead employ cytochrome nanowires to grow in harsh environments. These nanowire-forming cytochromes are widespread in diverse microbes and are essential for extracellular respiration. This discovery was made possible with methods I have developed for imaging protein structure and function. This was a very surprising discovery, because thousands of papers since 2002 thought that these nanowires are made up of pili protein, not cytochromes, as cytochromes usually stay monomeric. However, my work showed that Geobacter have evolved a polymeric assembly of cytochromes and therefore, can perform micrometer long electron transfer.