Recent Theoretical Approaches to Minimal Artificial Cells

Fabio Mavelli,Luigi Cassidei,Emiliano Altamura,Pasquale Stano

doi:10.3390/e16052488

Abstract

Minimal artificial cells (MACs) are self-assembled chemical systems able to mimic the behavior of living cells at a minimal level, i.e. to exhibit self-maintenance, self-reproduction and the capability of evolution. The bottom-up approach to the construction of MACs is mainly based on the encapsulation of chemical reacting systems inside lipid vesicles, i.e. chemical systems enclosed (compartmentalized) by a double-layered lipid membrane. Several researchers are currently interested in synthesizing such simple cellular models for biotechnological purposes or for investigating origin of life scenarios. Within this context, the properties of lipid vesicles (e.g., their stability, permeability, growth dynamics, potential to host reactions or undergo division processes…) play a central role, in combination with the dynamics of the encapsulated chemical or biochemical networks. Thus, from a theoretical standpoint, it is very important to develop kinetic equations in order to explore first—and specify later—the conditions that allow the robust implementation of these complex chemically reacting systems, as well as their controlled reproduction. Due to being compartmentalized in small volumes, the population of reacting molecules can be very low in terms of the number of molecules and therefore their behavior becomes highly affected by stochastic effects both in the time course of reactions and in occupancy distribution among the vesicle population. In this short review we report our mathematical approaches to model artificial cell systems in this complex scenario by giving a summary of three recent simulations studies on the topic of primitive cell (protocell) systems.

Highlights

IntroductionA minimal artificial cells (MACs) is a self-assembled chemical system that exhibits self-maintenance (i.e. autopoiesis), self-reproduction and the capability of evolution
The chemical implementation of minimal artificial cells (MACs) from scratch is attracting the interest of a growing number of researchers in the fields of synthetic biology and origin of life studies [1,2,3,4,5,6], who are becoming aware of the potential of microcompartments and lipid vesicle technologies to uncover biologically relevant phenomena, as well as plausible prebiotic processes and evolutionary transitions
This formula will be applied to the simple case of enzymatic self-producing vesicle, a short name to indicate those lipid-synthesizing vesicles that are capable of growth and division due to the enzyme-catalysed conversion of a molecular precursor in the membrane-forming molecule L

Summary

Introduction

A MAC is a self-assembled chemical system that exhibits self-maintenance (i.e. autopoiesis), self-reproduction and the capability of evolution. This property stems from their autopoietic organization, but requires that metabolic production of their components overcome their spontaneous degradation. Self-reproducing (proliferating) organisms may exhibit evolution capability in a Darwinian sense as a collective trait due to the transmission, generation by generation, of operational instructions in a coded form. Because reproduction is often imperfect, self-reproducing organisms generate “diversity” and evolve in a Darwinian sense, i.e., owing to the interplay between the generation of genotypic diversity and selection/competition processes in a world of limited resources. While self-reproduction and evolution are typical features of living cellular forms as we know them, it is reasonable to focus on autopoietic self-maintenance for determining the core feature that characterizes minimal “living” entities

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