Carbon Isotope Evidence for the Global Physiology of Proterozoic Cyanobacteria: Article No. eabc8998

Sarah Hurley, Boswell Wing, Claire Jasper, Nicholas Hill, Jeffrey Cameron

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25 Scopus Citations


Ancestral cyanobacteria are assumed to be prominent primary producers after the Great Oxidation Event [˜2.4 to 2.0 billion years (Ga) ago], but carbon isotope fractionation by extant marine cyanobacteria (a-cyanobacteria) is inconsistent with isotopic records of carbon fixation by primary producers in the mid-Proterozoic eon (1.8 to 1.0 Ga ago). To resolve this disagreement, we quantified carbon isotope fractionation by a wild-type planktic ß-cyanobacterium (Synechococcus sp. PCC 7002), an engineered Proterozoic analog lacking a CO2-concentrating mechanism, and cyanobacterial mats. At mid-Proterozoic pH and pCO2 values, carbon isotope fractionation by the wild-type ß-cyanobacterium is fully consistent with the Proterozoic carbon isotope record, suggesting that cyanobacteria with CO2-concentrating mechanisms were apparently the major primary producers in the pelagic Proterozoic ocean, despite atmospheric CO2 levels up to 100 times modern. The selectively permeable microcompartments central to cyanobacterial CO2-concentrating mechanisms (“carboxysomes”) likely emerged to shield rubisco from O2 during the Great Oxidation Event.
Original languageAmerican English
Number of pages9
JournalScience Advances
Issue number2
StatePublished - 2021

NREL Publication Number

  • NREL/JA-2800-79023


  • carbon dioxide
  • cyanobacteria
  • isotopes


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