Abstract 1042 Evolution of a minimal cell

The cell is the simplest independent functional unit of life.However, even unicellular model organisms that are touted for their tractability are complex, possessing thousands of genes and proteins, many of which remain uncharacterized even after decades of in-depth investigation.The quest for the simplest organism has been aided by advances in synthetic biology, which involve the redesign or novel construction of biological parts and modules.Using such tools, a minimal cell was constructed with a genome derived from the bacterium Mycoplasma mycoides, which contains only the smallest set of genes required for autonomous cellular life.I will discuss experiments used to test whether genome minimization constrained cellular evolution.Mutation rates were the highest among all reported bacteria but were not affected by genome minimization.And while synthetic streamlining of the genome was initially costly, the minimal cell rapidly regained fitness in just 2000 generations of evolution.The only apparent constraint associated with genome minimization involved the evolution of cell size.Our findings demonstrate that natural selection can rapidly increase the fitness of one of the simplest autonomously growing organisms.Understanding how species with small genomes overcome evolutionary challenges provides critical insights into the persistence of host-associated endosymbionts, the stability of streamlined chassis for biotechnology, and the targeted refinement of synthetically engineered cells.