Unifying Geochemical Scenario for the Origin of a High Cellular Potassium to Sodium Ratio in Living Cells

Potassium ion is the most common compound in all living organisms, with intercellular [K+]:[Na+] ratios greater than 1 across all domains of life. While most natural aquifers are rich in sodium, it is believed that localized potassium-rich environments were crucial for initiating prebiotic reaction networks leading to the origin of life. Several current hypotheses, based on modern geochemical observations, suggest that hydrothermal fields and their associated clays could have provided such environments. My work expands on current prebiotic theories regarding the origins of high potassium concentrations by providing a geochemical basis for the empirical observations proposed by other authors. Here, I show how abiotic enrichment in potassium can occur during the acidic alteration of a wide range of aluminum silicate rocks through the formation of alum salts (KAl(SO4)2•12H2O). I further propose how simple and well-known alum chemistry can lead to the accumulation of important biological molecules, such as phosphates, ammonia, and carboxylic acids. I provide a general thermodynamic model, proof-of-concept experiments, and a chemical rationale for the plausibility and importance of potassium-rich environments in the origin of life. This work suggests that potassium enrichment could have been one of the earliest steps in the origins of life, defining the reaction conditions where most prebiotic reactions took place. Since potassium is both the most common and simplest component in all living organisms on Earth, understanding the geochemical conditions that lead to potassium enrichment is valuable for comprehending the origins of life on Earth and the search for life elsewhere in the universe, including on our closest neighbor, Mars.