Compartmentation plays a multiple role in allowing the evolutionary persistence of artificial cells. There are two key aspects:
a) containment of beneficial local impact of genetic material, and
b) protection against exploitation by foreign genetic material.
The former is primary, and allows critical concentrations of nutrients and building blocks to be accrued, and appropriate chemical conditions (e.g. pH, buffer and ion concentrations) to be maintained independently of those in the environment. There are two immediate negative consequences of containment: the free uptake of resources is likely to be inhibited and likewise the removal of waste products. Either active transport mechanisms across the container for selective substances must be achieved, or the disadvantages of slowed accrual and increased levels of waste must be offset by the benefits of containment listed above. In artificial environments it is possible to supply high concentrations of nutrients and ideal buffer conditions, so that containment for its beneficial local impact may be unnecessary.
Protection against exploitation by foreign genetic material takes two forms: in the first case the foreign material arise by mutation from the organism itself, in the second it comes from other organisms. In the former case, the threat is from within, and the ongoing process of cell division, creating new boundaries each generation, can isolate the foreign material stochastically, as analysed in many population genetic models. It is not clear that boundaries improve the situation, in this case, compared with a reaction-diffusion mechanism such as with replicating spots. If the exploitation comes from foreign material, strong containment, allowing limited passage of foreign genes, would appear to be inevitably advantageous, but then the negative impact of strong containment on resource accumulation, waste removal and on the ease of self-reproduction of the cell need to be considered. Finally, a limited amount of foreign genetic material may be useful in providing stronger innovative potential in times of changing environments.
On the other hand, it is clear, that some defined degree of spatial genetic isolation is essential, and for many environments resource isolation is necessary for achieving an effective metabolism. So if containment can be modulated and tuned by multiphase systems such as membranes, then an optimal situation for the cell can be achieved. In this section, we investigate the complementation of compartmentation using microsystems which allows: