Sprecher
Beschreibung
Carbonate lakes on the early Earth may have concentrated RNA precursors and membrane-forming fatty acids. Here, we show that natural carbonate lakes provide compatible conditions for nonenzymatic RNA assembly, ribozyme activity, and encapsulation by prebiotic membranes. Carbonate lakes contain at most ~1 mM divalent cations because carbonate salts of divalent cations are relatively insoluble. We collected water from Last Chance lake and Goodenough lake in British Columbia, Canada, which have some of the highest phosphate concentrations of any lake in the world. Because we sampled these lakes after seasonal evaporation, the lake water contained ~1 M Na+ plus ~1 mM Mg2+ at pH10. We investigated the nonenzymatic, RNA-templated extension of RNA primers by 2-aminoimidazole activated ribonucleotides. We find that the initial rate of primer extension is comparable in lake water and standard laboratory conditions (50 mM MgCl2 at pH 8). After 72 hours, we observe lower yields of extended product in lake water than in laboratory conditions, although the yield is increased by supplying a higher initial concentration of activated nucleotides. We also demonstrate that a ligase ribozyme that uses 2-aminoimidazole activated oligonucleotides as substrate is active when the natural lake water is adjusted to pH 9. Finally, we show that vesicles composed of 1:1 decanoic acid: decanol encapsulate aqueous solutes despite salt-induced flocculation in natural lake water. By identifying compatible conditions for both nonenzymatic and ribozyme-catalyzed RNA assembly, and for encapsulation by fatty acid membranes, our results suggest that natural carbonate lakes could have enabled the emergence of cellular life on the early Earth.
