Manganese-oxidizing photosynthesis before the rise of cyanobacteria

Johnson J.E.; Web S.M.; Thomas K.Ono S.Kirschvink J.L.Fischer W.W.

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Manganese-oxidizing photosynthesis before the rise of cyanobacteria

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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 scientifi c 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_2 - multiple S isotopes (measured by isotope-ratio mass spectrometry and secondary ion mass spectrometry) and redoxsensitive detrital grains - reveal that the original Mn-oxide phases were not produced by reactions with O_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.

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《Proceedings of the National Academy of Sciences of the United States of America》 |2013年第28期|11238-11243|共6页
作者
Johnson J.E.; Web S.M.; Thomas K.Ono S.Kirschvink J.L.Fischer W.W.;
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作者单位

Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States;

Stanford Synchrotron Radiation Lightsource, Stanford University, Menlo Park, CA 94025, United States;

Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, United States;

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收录信息美国《科学引文索引》(SCI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
原文格式 PDF
正文语种英语
中图分类自然科学总论;
关键词
Great oxidation event; Pyrite; Water oxidation; X-ray absorption spectroscopy;

Manganese-oxidizing photosynthesis before the rise of cyanobacteria

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