Evolution of metabolic diversity: Insights from microbial polyketide synthases

Modular polyketide synthases of microorganisms are multifunctional enzymes providing a molecular construction plan for the stepwise generation of polyketides of high structural complexity. The giant genes that are found in various groups of bacteria went through a complex evolutionary process involving multiple gene duplications, gene losses and horizontal gene transfer events. Phylogenetic data provide evidence that homologous recombination has led to exchange, loss, and gain of domains and domain fragments and hence to a natural “reprogramming” of the assembly lines.