A Modular 3D-Printed Design to Investigate Prebiotic Chemical Systems in Hot Spring Pools

The emergence of protocells, membranous compartments with encapsulated genetic material, was a crucial step in life's origin and evolution. The hot spring hypothesis for the origin of life suggests that protocells with the capacity to encapsulate organic matter could have formed in hot spring pools during wet-dry (WD) cycling of hydrothermal fluids. Previous investigations have focused on mimicking WD cycles within a single pool, which precludes simulation of many hydrothermal field conditions, such as different mineralogies and variable temperature, pH, and water flow within and between multiple hot spring pools. Here, we present a modular 3D-printed hydrothermal field simulator that mimics many more aspects of the complex nature of hot spring fields by controlling the temperature, pH, and mineralogical variability of a series of linked pools. Furthermore, the pools can be programmed to experience fluid mixing between proximal pools and periodic WD cycling events. Results with the prototype hot spring field design demonstrate the ability to spontaneously form lipid vesicles that encapsulate organic matter within membranous compartments comprised of decanoic acid:decanol (4:1) or the phospholipids POPC:POPG (1:1). We observed that the vesicles formed during multiple WD cycles in the simulator pools displayed variation in their size distribution and differences in the number of membrane layers. Cargo encapsulation was favored in giant unilamellar vesicles and oligolamellar vesicles. Overall, the hot spring simulator offers a novel and customizable approach for studying multiple processes within hydrothermal field dynamics that include prebiotic chemical reactions, mineral surface catalysis, and the complexities of fluid mixing between proximal hot spring pools.