Institute of Biology, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil; SAGE-COPPE, UFRJ, Rio de Janeiro, Brazil.
Center for Weather Forecasting and Climate Studies (CPTEC), National Institute for Space Research (INPE), Cachoeira Paulista, Brazil; Gradutate Program on Geoscience (Geochemistry), Federal Fluminense University, Niterói, Brazil.
Sci Total Environ. 2020 Dec 1;746:140904. doi: 10.1016/j.scitotenv.2020.140904. Epub 2020 Jul 19.
In the late Quaternary, glacial-interglacial transitions are marked by major environmental changes. Glacial periods in the western equatorial Atlantic (WEA) are characterized by high continental terrigenous input, which increases the proportion of terrestrial organic matter (e.g. lignin, alkanes), nutrients (e.g. iron and sulphur), and lower primary productivity. On the other hand, interglacials are characterized by lower continental contribution and maxima in primary productivity. Microbes can serve as biosensors of past conditions, but scarce information is available on deep-sea sediments in the WEA. The hypothesis put forward in this study is that past changes in climate conditions modulated the taxonomic/functional composition of microbes from deep sediment layers. To address this hypothesis, we collected samples from a marine sediment core located in the WEA, which covered the last 130 kyr. This region is influenced by the presence of the Amazon River plume, which outputs dissolved and particulate nutrients in vast oceanic regions, as well as the Parnaiba river plume. Core GL-1248 was analysed by shotgun metagenomics and geochemical analyses (alkane, lignin, perylene, sulphur). Two clusters (glacial and interglacial-deglacial) were found based on taxonomic and functional profiles of metagenomes. The interglacial period had a higher abundance of genes belonging to several sub-systems (e.g. DNA, RNA metabolism, cell division, chemotaxis, and respiration) that are consistent with a past environment with enhanced primary productivity. On the other hand, the abundance of Alcanivorax, Marinobacter, Kangiella and aromatic compounds that may serve as energy sources for these bacteria were higher in the glacial. The glacial period was enriched in genes for the metabolism of aromatic compounds, lipids, isoprenoids, iron, and Sulphur, consistent with enhanced fluvial input during the last glacial period. In contrast, interglacials have increased contents of more labile materials originating from phytoplankton (e.g. Prochlorococcus). This study provides new insights into the microbiome as climatic archives at geological timescales.
在第四纪晚期，冰期-间冰期的转变标志着重大的环境变化。在西赤道大西洋（WEA）的冰期，陆地陆源输入较高，导致陆地有机质（如木质素、烷烃）、营养物质（如铁和硫）的比例增加，初级生产力降低。另一方面，间冰期的陆地贡献较低，初级生产力达到最大值。微生物可以作为过去条件的生物传感器，但在 WEA 的深海沉积物中，相关信息非常有限。本研究提出的假设是，过去气候条件的变化调节了来自深海沉积物层的微生物的分类/功能组成。为了验证这一假设，我们从 WEA 采集了一个海洋沉积物岩芯样本，该样本涵盖了过去 130000 年。该地区受亚马逊河羽流和帕纳伊巴河羽流的影响，这些羽流在广阔的海洋区域输出溶解和颗粒营养物质。对 GL-1248 岩芯进行了鸟枪法宏基因组学和地球化学分析（烷烃、木质素、并五苯、硫）。根据宏基因组的分类和功能谱，发现了两个聚类（冰期和间冰期-冰退期）。间冰期的 DNA、RNA 代谢、细胞分裂、趋化性和呼吸等多个子系统的基因丰度较高，表明过去的环境中初级生产力增强。另一方面，在冰期，Alcanivorax、Marinobacter、Kangiella 和芳香族化合物的丰度较高，这些化合物可能是这些细菌的能源。冰期富含芳香族化合物、脂质、异戊二烯、铁和硫的代谢基因，与末次冰期河流输入增加一致。相反，间冰期含有更多源自浮游植物的更不稳定物质（如原绿球藻）。本研究为地质时间尺度上的微生物组作为气候档案提供了新的见解。
