氧气、磷与地球早期生命

Two billion years ago Earth system was recovering from perhaps the single-most profound modification¹ of its surface environments: the oxygenation of the atmosphere and oceans. This led to a series of major changes in global biogeochemical cycles, as a team around Aivo Lepland of the Norwegian Geological Survey NGU reports in the latest online edition of Nature Geoscience. This also resulted in the distribution of one of life's key elements, phosphorus（磷）. Studies on the unique organic-rich Zaonega rock formation preserved in Carelia, NW Russia, with an age of around two billion years has revealed an astonishing result:"The formation of Earth's earliest phosphorites was influenced strongly, if not controlled completely, by the activity of sulfur² bacteria," says co-author Richard Wirth of the GFZ German Research Centre for Geosciences, who analyzed³ the rock samples with an electron microscope.   "This activity occurred in an oil field setting that had been influenced by active volcanism and associated venting⁵ and seeping⁷（渗出）." In the modern world, sulfur bacteria inhabit upwelling vent⁴ and seep⁶ areas known as "Black Smokers⁸" and mediate⁹ phosphorite formation.   The authors therefore conclude that the formation of the earliest worldwide phosphorites 2 billion years ago can be linked to the establishment of sulfur bacteria habitats, triggered by the oxygenation of Earth.