Llirós Marc, García-Armisen Tamara, Darchambeau François, Morana Cédric, Triadó-Margarit Xavier, Inceoğlu Özgül, Borrego Carles M, Bouillon Steven, Servais Pierre, Borges Alberto V, Descy Jean-Pierre, Canfield Don E, Crowe Sean A
Laboratory of Freshwater Ecology, Research Unit in Environmental and Evolutionary Biology, University of Namur, B-5000 Namur, Belgium.
Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, E-08913 Bellaterra, Catalonia, Spain.
Sci Rep. 2015 Sep 8;5:13803. doi: 10.1038/srep13803.
Iron-rich (ferruginous) ocean chemistry prevailed throughout most of Earth's early history. Before the evolution and proliferation of oxygenic photosynthesis, biological production in the ferruginous oceans was likely driven by photoferrotrophic bacteria that oxidize ferrous iron {Fe(II)} to harness energy from sunlight, and fix inorganic carbon into biomass. Photoferrotrophs may thus have fuelled Earth's early biosphere providing energy to drive microbial growth and evolution over billions of years. Yet, photoferrotrophic activity has remained largely elusive on the modern Earth, leaving models for early biological production untested and imperative ecological context for the evolution of life missing. Here, we show that an active community of pelagic photoferrotrophs comprises up to 30% of the total microbial community in illuminated ferruginous waters of Kabuno Bay (KB), East Africa (DR Congo). These photoferrotrophs produce oxidized iron {Fe(III)} and biomass, and support a diverse pelagic microbial community including heterotrophic Fe(III)-reducers, sulfate reducers, fermenters and methanogens. At modest light levels, rates of photoferrotrophy in KB exceed those predicted for early Earth primary production, and are sufficient to generate Earth's largest sedimentary iron ore deposits. Fe cycling, however, is efficient, and complex microbial community interactions likely regulate Fe(III) and organic matter export from the photic zone.
在地球早期历史的大部分时间里，富含铁（铁质）的海洋化学环境盛行。在含氧光合作用进化和扩散之前，铁质海洋中的生物生产可能是由光铁营养细菌驱动的，这些细菌将亚铁离子{Fe(II)}氧化，以利用阳光中的能量，并将无机碳固定为生物量。因此，光铁营养菌可能为地球早期的生物圈提供了能量，在数十亿年的时间里推动了微生物的生长和进化。然而，在现代地球上，光铁营养活动在很大程度上仍然难以捉摸，使得早期生物生产模型未经检验，生命进化所必需的生态背景缺失。在这里，我们表明，在东非（刚果民主共和国）卡布诺湾（KB）光照充足的铁质水域中，活跃的远洋光铁营养菌群落占微生物群落总数的比例高达30%。这些光铁营养菌产生氧化铁{Fe(III)}和生物量，并支持一个多样化的远洋微生物群落，包括异养铁（III）还原菌、硫酸盐还原菌、发酵菌和产甲烷菌。在适度的光照水平下，KB中的光铁营养速率超过了早期地球初级生产的预测速率，足以形成地球上最大的沉积铁矿床。然而，铁循环是高效的，复杂的微生物群落相互作用可能调节了铁（III）和有机物从光合层的输出。
