Evolutionary radiation of lanthipeptides in marine cyanobacteria

Lanthipeptides are a large family of microbial natural products of ribosomal origin. Prochlorosins are a group of unusually diverse lanthipeptides found in strains of the marine cyanobacteria Prochlorococcus and Synechococcus—the most abundant photosynthetic microorganisms on Earth. By analyzing the prochlorosin biosynthesis genes from cultured strains and wild cyanobacteria, we show that the global collective of these microorganisms has evolved thousands of structurally distinct lanthipeptides via a process of evolutionary radiation favoring the sustained emergence of new structures over refinement of an existing one. The evolutionary history of prochlorosins suggests a fundamentally different structure-to-function relationship compared with other lanthipeptides and opens the question of how structural diversification contributes to their function and mode of action in the marine environment.