Although it seems like evolutionary determinism, there’s some weight to the idea that cells are constrained to a certain evolutionary path, no matter the environment they appear in. Certainly, the charge-transfer reactions central to metabolism on Earth, more broadly known as reduction/oxidation (redox) reactions, are known to produce electric current even in the absence of biology. Take for example the galvanic cell, invented in the 1700s by Alessandro Volta. The redox reactions central to his invention remain vital to the ubiquitous modern-day battery. What biologists have found since his discovery is that similar redox reactions are at the center of metabolism. Except instead of the charge being derived from metals, nature provides a wide range of different substances that can be eaten and breathed.
Thousands of meters down, bacteria electrify themselves by eating simple geofuels.
All kinds of compounds, everything from hydrogen gas to sulfate—can serve as the terminals of a metabolic circuit. Despite this flexibility, the depth of structural and functional similarity in the ETC across a multitude of life forms suggests only a few degrees of freedom during the system’s evolution. Annette Rowe is head of the Electromicrobiology Laboratory at the University of Cincinnati, where she studies the often unusual ways that organisms power their metabolic circuits. Some of her research has focused on bacteria capable of breathing current carried by electrodes.2 Reached by phone, Rowe points out that while the metabolic systems of two organisms may “have protein architecture that looks really similar, most of them are uniquely derived, evolutionarily speaking.” This means that the same solution to the problem of distributing the electric harvest throughout the cell has appeared over and over again throughout history. The name of that solution? Adenosine triphosphate.
Adenosine triphosphate, ATP for short, is one of those incredible pieces of biology that appears to be universal. There is no exception to the rule that to live is to work, and no exception to the rule that all known cells use electrochemical gradients to do work.
Anastasia Bendebury & Michael Shilo Delay, “Uncovering the Spark of Life” at Nautilus
Biology is beginning to sound more like physics all the time. Laws and all.