Genome rearrangement shapes Prochlorococcus ecological adaptation

Abstract

Prochlorococcus is the most abundant and smallest known free-living photosynthetic microorganism and is a key player in marine ecosystems and biogeochemical cycles. Prochlorococcus can be broadly divided into high-light-adapted (HL) and low-light-adapted (LL) clades. In this study, we isolated two low-light-adapted clade I (LLI) strains from the western Pacific Ocean and obtained their genomic data. We reconstructed Prochlorococcus evolution based on genome rearrangement. Our results showed that genome rearrangement might have played an important role in Prochlorococcus evolution. We also found that the Prochlorococcus clades with streamlined genomes maintained relatively high synteny throughout most of their genomes, and several regions served as rearrangement hotspots. Backbone analysis showed that different clades shared a conserved backbone but also had cladespecific regions, and the genes in these regions were associated with ecological adaptations.