Searching for heritability in prebiotically realistic membrane-bound systems

Membrane-bound compartments are ubiquitous in modern organisms meaning that they evolved early in Earth history. Vesicles composed of short-chain amphiphile molecules are some of the simplest prebiotically-plausible compartments and are capable of growth and division. Here we investigate the capacity of vesicle properties to transition between multiple metastable states in a historically contingent manner, thus implying heritability. We prepared 1:1 decanoic acid : decylamine vesicles in water or a mixture of organic compounds as might have been present on early Earth (EPS: enriched prebiotic soup). In some samples we added a detergent Triton X-100, which tends to increase vesicle size heterogeneity and promote vesicle remodeling. All four vesicle-containing mixtures were subjected to transfer-with-dilution: after a 24-hour incubation (one generation) we transferred 10% of the mix into 9X volume of a fresh, vesicle-containing mixtures. Sample with a history of transfer were compared to no-transfer controls (NTCs), which were initiated each generation using the same fresh vesicle-containing mixture but did not receive 10% of the prior generation. We compared transfer samples to NTCs for Nile Red fluorescence, vesicle size, and overall chemical composition, as measured by liquid chromatography/mass spectrometry (LC/MS). In samples with Triton, but not those without, we observe oscillation-like changes in Nile Red fluorescence, with significant temporal autocorrelation. In all samples, we observe non-linear changes in vesicle size over the course of 30 generations. Overall chemical composition did not change significantly due to transfers. These findings, while not definitive, suggest the possible presence of heritability in vesicles composed of short-chain amphiphiles.