Transport within protocell-nanotube networks and its implications for communication of primitive cells

Abstract

Protocells are self-organized primitive compartments which are thought to be precursors to first living cells at the origin of life. Several different types of model protocell structures have been proposed; among them, the most recently identified protocell nanotube networks (PNNs). A PNN consists of tens of surface adhered lipid compartments physically connected via lipid nanotubes. In this work, it is shown for the first time using differential interference contrast (DIC) microscopy that the PNNs can successfully form by using lipid compositions that are completely label-free. It has also been shown via confocal microscopy that the lipid nanotubes allow the transport of fluorescently labeled water soluble compounds, RNA and DNA among the compartments in the network. By employing fluorescence recovery after photobleaching (FRAP) technique, the diffusive redistribution of encapsulated fluorophores among compartments that are not in direct contact with each other, has been depicted. Results show that the transportation of the compounds in PNNs is possible due to the interconnecting nanotubes, which is proposed as a plausible chemical communication and replication mechanism between the protocells on the early Earth.