Marine picocyanobacteria

Abstract

Summary: Picocyanobacteria of the genera Prochlorococcus and Synechococcus numerically dominate vast tracts of the world's oceans and contribute a significant proportion of primary production, particularly in oligotrophic regions. The ecological success of these two genera suggests they possess sophisticated strategies to respond to variations in their environment. Indeed, it appears that it is the in situ community structure of these organisms which underlies this success, with the existence of specific ecotypes or lineages occupying different niches to populate the world's oceans. For Prochlorococcus there is now excellent physiological and genomic data for defining the basis of this niche partitioning particularly with respect to its vertical distribution down a water column. The situation for Synechococcus is more complex probably due to the larger spatial distribution of marine Synechococcus in oceanic ecosystems. This has led to extensive phylogenetic and physiological variation within the Synechococcus genus but the genomic basis for this phenotypic variation, and hence niche adaptation is less well understood. This chapter seeks to give an overview of the knowledge gained on these organisms over the last three decades focusing on aspects of ecology, physiology and molecular biology that are pertinent to this niche adaptation process.