Evolutionary transitions in bacterial symbiosis

TLDR

Bacterial lineages form beneficial infections with eukaryotic hosts, and the origins, evolution, and breakdown of these mutualisms—occurring repeatedly throughout history—constitute key evolutionary transitions. The study synthesizes data across bacterial–eukaryote interactions to examine evolutionary events and develops a framework to test hypotheses about the forces shaping bacterial symbiosis. The authors investigate five key evolutionary transitions—origin of bacterial associations, stable maintenance of mutualism, evolution of strict vertical transmission, and breakdown of mutualism—across the bacterial domain and construct a framework to analyze these events.

Abstract

Diverse bacterial lineages form beneficial infections with eukaryotic hosts. The origins, evolution, and breakdown of these mutualisms represent important evolutionary transitions. To examine these key events, we synthesize data from diverse interactions between bacteria and eukaryote hosts. Five evolutionary transitions are investigated, including the origins of bacterial associations with eukaryotes, the origins and subsequent stable maintenance of bacterial mutualism with hosts, the capture of beneficial symbionts via the evolution of strict vertical transmission within host lineages, and the evolutionary breakdown of bacterial mutualism. Each of these transitions has occurred many times in the history of bacterial-eukaryote symbiosis. We investigate these evolutionary events across the bacterial domain and also among a focal set of well studied bacterial mutualist lineages. Subsequently, we generate a framework for examining evolutionary transitions in bacterial symbiosis and test hypotheses about the selective, ecological, and genomic forces that shape these events.