On the way towards basic autonomous systems: stochastic simulations of minimal lipid-peptide cells

In this paper, we apply a recently developed stochastic simulation platform to investigate the dynamic behaviour of minimal ‘self-(re-)producing’ cellular systems. In particular, we study a set of preliminary conditions for appearance of the simplest forms of autonomy in the context of lipid vesicles (more specifically, lipid–peptide vesicles) that enclose an autocatalytic/proto-metabolic reaction network. The problem is approached from a ‘bottom-up’ perspective, in the sense that we try to show how relatively simple cell components/processes could engage in a far-from-equilibrium dynamics, staying in those conditions thanks to a rudimentary but effective control of the matter-energy flow through it. In this general scenario, basic autonomy and, together with it, minimal agent systems would appear when (hypothetically pre-biological) cellular systems establish molecular trans-membrane mechanisms that allow them to couple internal chemical reactions with transport processes, in a way that they channel/transform external materialenergetic resources into their own means and actively regulate boundary conditions (e.g., osmotic gradients, inflow/outflow of different compounds, . . .) that are critical for their constitution and persistence as proto-metabolic cells. The results of our simulations indicate that, before that stage is reached, there are a number of relevant issues that have to be carefully analysed and clarified: especially the immediate effects that the insertion of peptide chains (channel precursors) in the lipid bilayer may have in the structural properties of the membrane (elasticity, permeability, . . .) and in the overall dynamic behaviour of the cell.