Molecular Diversity and Network Complexity in Growing Protocells

TL;DR

This paper models protocell molecular diversity and network complexity, revealing how resource limitations drive diversity, and how catalytic networks evolve from parasitic to mutualistic species, shedding light on primitive cell origins.

Contribution

It introduces a model showing how resource constraints promote molecular diversity and the evolution of complex catalytic networks in protocells.

Findings

Diversity increases with resource limitation.

Molecular species evolve from parasitic to host roles.

Complex catalytic networks develop through evolution.

Abstract

A great variety of molecular components is encapsulated in cells. Each of these components is replicated for cell reproduction. To address an essential role of the huge diversity of cellular components, we study a model of protocells that convert resources into catalysts with the aid of a catalytic reaction network. As the resources are limited, it is shown that diversity in intracellular components is increased to allow the use of diverse resources for cellular growth. Scaling relation is demonstrated between resource abundances and molecular diversity. We then study how the molecule species diversify and complex catalytic reaction networks develop through the evolutionary course. It is shown that molecule species first appear, at some generations, as parasitic ones that do not contribute to replication of other molecules. Later, the species turn to be host species that support the replication of other species. With this successive increase of host species, a complex joint network evolves. The present study sheds new light on the origin of molecular diversity and complex reaction network at the primitive stage of a cell.