Ecological Genomics of Marine Picocyanobacteria

Abstract

SUMMARYMarine picocyanobacteria of the generaProchlorococcusandSynechococcusnumerically dominate the picophytoplankton of the world ocean, making a key contribution to global primary production.Prochlorococcuswas isolated around 20 years ago and is probably the most abundant photosynthetic organism on Earth. The genus comprises specific ecotypes which are phylogenetically distinct and differ markedly in their photophysiology, allowing growth over a broad range of light and nutrient conditions within the 45°N to 40°S latitudinal belt that they occupy.SynechococcusandProchlorococcusare closely related, together forming a discrete picophytoplankton clade, but are distinguishable by their possession of dissimilar light-harvesting apparatuses and differences in cell size and elemental composition.Synechococcusstrains have a ubiquitous oceanic distribution compared to that ofProchlorococcusstrains and are characterized by phylogenetically discrete lineages with a wide range of pigmentation. In this review, we put our current knowledge of marine picocyanobacterial genomics into an environmental context and present previously unpublished genomic information arising from extensive genomic comparisons in order to provide insights into the adaptations of these marine microbes to their environment and how they are reflected at the genomic level.