Steady state analysis of a vesicle bioreactor with mechanosensitive channels

An intermediate step between simple models of protocells having no membrane structure and the current, complex membrane organization of modern cells considers simple forms of membrane change that interact with the protocell dynamics in predictable ways. Here we analyse a kinetic model of a simple protocell system: a bioreactor vesicle involving mechanosensitive channels. This is a closed lipid bilayer which hosts a minimal metabolism X +E →W +E inside its internal (variable volume) water pool, and with channels anchored in the membrane. The reactor can swell, opening the channels, which in turn allow enhanced passive diffusion of solutes X and W into and out of the reactor. We calculate under what external conditions and parameter regimes the reactor is able to maintain a far from equilibrium steady state, and what behaviours are possible in this reduced complexity scenario. This study is just a preliminary step in modelling the bigger question of how osmotic force sensing devices in early membranes could couple with early metabolisms, enhancing the stability of protocells in changing environments.