These studies, however, are still mainly centered on genes and the proteins they encode, somehow neglecting the small organic chemicals that support life processes. Modern statistical bioinformatic approaches targeted to the comparative analysis of genomes are being used to detect signatures of natural selection at the gene and population level, as an attempt to understand the origin of primordial metabolism and its expansion. These results have implications in choosing biochemical pathways and enzymes for engineered or combinatorial biosynthesis.Evolution of metabolism is a longstanding yet unresolved question, and several hypotheses were proposed to address this complex process from a Darwinian point of view. Because the underlying enzymes exhibit broad substrate tolerance, discrete exchange of substrates and enzymes between Prochloron strains leads to the rapid generation of chemical novelty. The module exchange leads to gain or loss of discrete chemical functional groups. We observe that Prochloron exchanges discrete functional genetic modules for cyanobactin secondary metabolite biosynthesis in an otherwise conserved genetic background. We show that tunicates and their symbiotic Prochloron cyanobacteria share congruent phylogenies, indicating that Prochloron phylogeny is related to host phylogeny and not to external habitat or geography. Here, by examining a marine symbiosis, we provide a precise evolutionary model of how nature generates a family of novel chemicals, the cyanobactins.
Diversity-generating metabolism leads to the evolution of many different chemicals in living organisms.
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