Holub Guillaume, Sergeant Claire, Bailly Céline, Beauger Aude, Breton Vincent, Chardon Patrick, Montavon Gilles, Vesvres Marie-Hélène, Mallet Clarisse
University of Bordeaux, CNRS, LP2iB, UMR5797, Gradignan, France.
IMT Atlantique, University of Nantes, CNRS, SUBATECH, UMR 6457, Nantes, France.
Front Microbiol. 2024 Jul 23;15:1423342. doi: 10.3389/fmicb.2024.1423342. eCollection 2024.
Some natural environments on Earth are characterised by high levels of radiation, including naturally radioelement enriched mineral springs in the French Massif Central. Therefore, naturally radioactive mineral springs are interesting ecosystems for understanding how bacterial populations in these springs have adapted to high levels of natural and chronic radioactivity over the very long term. The aim of this study was to analyse the bacterial communities of sediments from five naturally radioactive mineral springs in the French Massif Central, sampled in autumn 2019 and spring 2020, and to observe whether radionuclides, compared to other physicochemical parameters, are drivers of the bacterial community structuring in these extreme environments. Physicochemical measurements showed that two springs, Dourioux and Montagne had high radioelement concentrations/activities (uranium, thorium and radon). Analysis of the structure of the bacterial communities, by next generation sequencing based on 16S rRNA gene sequencing, showed that the presence of radionuclides in Dourioux and Montagne, did not lead to a reduction in bacterial diversity and richness compared to the other springs. However, Dourioux and Montagne were characterised by specific bacterial populations, whose presence correlates with the radioelement concentrations/activities measured in these springs. This suggests that radioelements could partly explain the structuring of bacterial communities in these springs. In addition, several of these operational taxonomic units (OTUs) specific to Dourioux and Montagne, mainly affiliated to , , , , and , could be involved in the biogeochemistry of radionuclides through different mechanisms (biosorption, biomineralisation, bioaccumulation, and bioreduction), which would allow the development of other bacterial species sensitive to these metals/radioelements. In particular, the co-occurrence of sulphate and/or iron-reducing bacteria, capable of bioreducing uranium, with fermentative bacteria, releasing sources of organic carbons, reflects associations of bacteria with complementary functions that allow them to grow in this peculiar environment and maintain a high diversity in these extreme environments. This study has provided a better understanding of the structuring of bacterial communities exposed to ionising radiation for thousands of years in naturally radioactive environments.
地球上的一些自然环境具有高辐射水平的特征，包括法国中央地块富含天然放射性元素的矿泉。因此，天然放射性矿泉是有趣的生态系统，有助于理解这些泉水中的细菌种群如何在长期内适应高水平的天然和慢性放射性。本研究的目的是分析2019年秋季和2020年春季采集的法国中央地块五个天然放射性矿泉沉积物中的细菌群落，并观察与其他物理化学参数相比，放射性核素是否是这些极端环境中细菌群落结构的驱动因素。物理化学测量表明，杜里奥克斯和蒙塔涅这两个泉具有高放射性元素浓度/活度（铀、钍和氡）。通过基于16S rRNA基因测序的下一代测序分析细菌群落结构，结果表明，与其他泉相比，杜里奥克斯和蒙塔涅中放射性核素的存在并未导致细菌多样性和丰富度降低。然而，杜里奥克斯和蒙塔涅的特征是有特定的细菌种群，其存在与这些泉中测得的放射性元素浓度/活度相关。这表明放射性元素可能部分解释了这些泉中细菌群落的结构。此外，杜里奥克斯和蒙塔涅特有的几个操作分类单元（OTU），主要隶属于、、、、和，可能通过不同机制（生物吸附、生物矿化、生物积累和生物还原）参与放射性核素的生物地球化学过程，这将有利于其他对这些金属/放射性元素敏感的细菌物种的生长。特别是，能够生物还原铀的硫酸盐还原菌和/或铁还原菌与释放有机碳源的发酵菌同时存在，反映了具有互补功能的细菌之间的关联，使它们能够在这种特殊环境中生长并在这些极端环境中保持高多样性。本研究更好地理解了在天然放射性环境中暴露于电离辐射数千年的细菌群落的结构。
