Model Atmospheric Aerosols Convert to Vesicles upon Entry into Aqueous Solution

Abstract

Aerosols are abundant on the Earth and likely played a role in prebiotic chemistry. Aerosol particles coagulate, divide, and sample a wide variety of conditions conducive to synthesis. While much work has centered on the generation of aerosols and their chemistry, little effort has been expended on their fate after settling. Here, using a laboratory model, we show that aqueous aerosols transform into cell-sized protocellular structures upon entry into aqueous solution containing lipid. Such processes provide for a heretofore unexplored pathway for the assembly of the building blocks of life from disparate geochemical regions within cell-like vesicles with a lipid bilayer in a manner that does not lead to dilution. The efficiency of aerosol to vesicle transformation is high with prebiotically plausible lipids, such as decanoic acid and decanol, that were previously shown to be capable of forming growing and dividing vesicles. The high transformation efficiency with 10-carbon lipids in landing solutions is consistent with the surface properties and dynamics of shortchain lipids. Similar processes may be operative today as fatty acids are common constituents of both contemporary aerosols and the sea. Our work highlights a new pathway that may have facilitated the emergence of the Earth's first cells.

Cyclophospholipids Enable a Protocellular Life Cycle

“…Since the final composition of the offspring protocell membranes reflects the ratio of total lipids in solution at equilibrium, multiple rounds of growth and division can be driven by feeding with vesicles of different composition . Potential prebiotic routes for one population of vesicles to encounter another could be the mixing of bodies of water through connecting streams, exchange through aqueous aerosols, or colocalization through convection and thermophoresis . Alternatively, osmotic pressures, potentially resulting from the replication of RNA, could drive the growth of cyclophospholipid-containing protocells …”

Motility of microscopic swimmers as protocells

“…Motile water droplets in oil could have been forerunners of vesicular protocells in the early ocean; a scenario that becomes plausible when considering the converging set of evidence that an oil slick could have covered the early ocean. 20,72 This oil slick could have been a source and a reservoir for lipids, would have introduced an interface in the prebiotic environment that could potentially promote the formation of vesicles, 73 and would furthermore trap particles, which would take on circular trajectories under confinement. 20,64 Besides the compositional challenge, we note that the motile behavior closest to modern life forms arises from the most complex supramolecular organizations.…”