Manganese-oxidizing photosynthesis before the rise of cyanobacteria
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Ono-Manganese-oxidizing.pdf
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Author(s)
Thomas, Katherine
Ono, Shuhei
Johnson, Jena E.
Webb, Samuel M.
Kirschvink, Joseph L.
Fischer, Woodward W.
Date Issued
June 2013
Journal
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences (U.S.)
Citation
Johnson, J. E., S. M. Webb, K. Thomas, S. Ono, J. L. Kirschvink, and W. W. Fischer. “Manganese-Oxidizing Photosynthesis before the Rise of Cyanobacteria.” Proceedings of the National Academy of Sciences 110, no. 28 (July 9, 2013): 11238–11243.
Version
Final published version
Abstract
The emergence of oxygen-producing (oxygenic) photosynthesis fundamentally transformed our planet; however, the processes that led to the evolution of biological water splitting have remained largely unknown. To illuminate this history, we examined the behavior of the ancient Mn cycle using newly obtained scientific drill cores through an early Paleoproterozoic succession (2.415 Ga) preserved in South Africa. These strata contain substantial Mn enrichments (up to ~17 wt %) well before those associated with the rise of oxygen such as the ~2.2 Ga Kalahari Mn deposit. Using microscale X-ray spectroscopic techniques coupled to optical and electron microscopy and carbon isotope ratios, we demonstrate that the Mn is hosted exclusively in carbonate mineral phases derived from reduction of Mn oxides during diagenesis of primary sediments. Additional observations of independent proxies for O[subscript 2]—multiple S isotopes (measured by isotope-ratio mass spectrometry and secondary ion mass spectrometry) and redox-sensitive detrital grains—reveal that the original Mn-oxide phases were not produced by reactions with O[subscript 2], which points to a different high-potential oxidant. These results show that the oxidative branch of the Mn cycle predates the rise of oxygen, and provide strong support for the hypothesis that the water-oxidizing complex of photosystem II evolved from a former transitional photosystem capable of single-electron oxidation reactions of Mn.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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DOI of Published Version
https://doi.org/10.1073/pnas.1305530110
