biostudies-literatureUnknown17(8)Ward LMagouron institutesimons foundationWhile most productivity on the surface of the Earth today is fueled by oxygenic photosynthesis, for much of Earth history it is thought that anoxygenic photosynthesis-using compounds like ferrous iron or sulfide as electron donors-drove most global carbon fixation. Anoxygenic photosynthesis is still performed by diverse bacteria in niche environments today. Of these, the Chlorobi (formerly green sulfur bacteria) are often interpreted as being particularly ancient and are frequently proposed to have fueled the biosphere during late Archean and early Paleoproterozoic time before the rise of oxygenic photosynthesis. Here, we perform comparative genomic, phylogenetic, and molecular clock analyses to determine the antiquity of the Chlorobi and their characteristic phenotypes. We show that contrPloS onee0270187https://www.ebi.ac.uk/biostudies/studies/S-EPMC9342728biostudies-literaturePhototrophy and carbon fixation in Chlorobi postdate the rise of oxygen.PMC9342728Ward LMShih PMfalsePhototrophy and carbon fixation in Chlorobi postdate the rise of oxygen.While most productivity on the surface of the Earth today is fueled by oxygenic photosynthesis, for much of Earth history it is thought that anoxygenic photosynthesis-using compounds like ferrous iron or sulfide as electron donors-drove most global carbon fixation. Anoxygenic photosynthesis is still performed by diverse bacteria in niche environments today. Of these, the Chlorobi (formerly green sulfur bacteria) are often interpreted as being particularly ancient and are frequently proposed to have fueled the biosphere during late Archean and early Paleoproterozoic time before the rise of oxygenic photosynthesis. Here, we perform comparative genomic, phylogenetic, and molecular clock analyses to determine the antiquity of the Chlorobi and their characteristic phenotypes. We show that contr2022-01-01T00:00:00Z20222026-03-17T16:16:34.938Z2024-10-17T18:59:44.937ZS-EPMC93427283591391110.1371/journal.pone.0270187