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Carbon isotope evidence for the global physiology of Proterozoic cyanobacteria.

ABSTRACT: 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 (?-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 ?-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 ?-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.

SUBMITTER: Hurley SJ

PROVIDER: S-EPMC7787495 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Carbon isotope evidence for the global physiology of Proterozoic cyanobacteria.

Hurley Sarah J SJ Wing Boswell A BA Jasper Claire E CE Hill Nicholas C NC Cameron Jeffrey C JC

Science advances 20210106 2

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 (α-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 β-cyanobacterium (<i>Synechococcus</i> sp. PCC 7002), a ...[more]

PMID: 33523966

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Carbon isotope evidence for the global physiology of Proterozoic cyanobacteria.

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Carbon isotope evidence for the global physiology of Proterozoic cyanobacteria.

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