title: Crown group Oxyphotobacteria postdate the rise of oxygen.
abstract: The rise of oxygen ca. 2.3 billion years ago (Ga) is the most distinct environmental transition in Earth history. This event was enabled by the evolution of oxygenic photosynthesis in the ancestors of Cyanobacteria. However, long-standing questions concern the evolutionary timing of this metabolism, with conflicting answers spanning more than one billion years. Recently, knowledge of the Cyanobacteria phylum has expanded with the discovery of non-photosynthetic members, including a closely related sister group termed Melainabacteria, with the known oxygenic phototrophs restricted to a clade recently designated Oxyphotobacteria. By integrating genomic data from the Melainabacteria, cross-calibrated Bayesian relaxed molecular clock analyses show that crown group Oxyphotobacteria evolved ca. 2.0 billion years ago (Ga), well after the rise of atmospheric dioxygen. We further estimate the divergence between Oxyphotobacteria and Melainabacteria ca. 2.5-2.6 Ga, which-if oxygenic photosynthesis is an evolutionary synapomorphy of the Oxyphotobacteria-marks an upper limit for the origin of oxygenic photosynthesis. Together, these results are consistent with the hypothesis that oxygenic photosynthesis evolved relatively close in time to the rise of oxygen.
authors.affiliation: Joint BioEnergy Institute, Emeryville, CA, USA.|Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: P M
authors.initials: PM
authors.lastname: Shih
authors.affiliation: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
authors.forename: J
authors.initials: J
authors.lastname: Hemp
authors.affiliation: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Ward
authors.affiliation: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville, TN, USA.
authors.forename: N J
authors.initials: NJ
authors.lastname: Matzke
authors.affiliation: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
authors.forename: W W
authors.initials: WW
authors.lastname: Fischer
mesh_terms: D005075:Biological Evolution; D000458:Cyanobacteria / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010788:Photosynthesis
chemical_list: D010100:Oxygen