Evolutionary Genomics of Marine Bacteria and Archaea

The ocean harbors an enormous diversity of bacteria and archaea whose metabolic activities have global biogeochemical impacts. Evolutionary genomic studies play an important role in marine microbiology by providing insights into the selective pressures that influence the diversity and functioning of marine microbial lineages, shedding light on their niche specialization, and helping to define their broader ecological roles. The scope of evolutionary genomic studies in the ocean has dramatically expanded in recent years owing to advances in sequencing technology, metagenomics, and single-cell sequencing. Historically the collection of sequenced genomes has been composed of a small number of cultured microbes, but recent advances have opened a window into the genomics of a broad diversity of lineages throughout the biosphere. This broad genomic representation of lineages across the tree of life has enabled comparative genomic analyses that help to identify the ecological and evolutionary forces that drive the diversification of microorganisms in the ocean. In this chapter, we review some of the salient themes that have emerged in the last few decades of these studies. We discuss the main findings of these evolutionary genomic studies and their implications for our understanding of the diversity and functioning of microbial life in the ocean.