PDF(Pubmed)
Abstract：
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 Proteobacteria, Firmicutes, Acidobacteria, Actinobacteria, and Bacteroidetes, 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.
摘要：
地球上的一些自然环境以高水平的辐射为特征，包括法国地块中部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，用于了解这些泉水中的细菌种群如何长期适应高水平的天然和慢性放射性。这项研究的目的是分析法国地块中部五个天然放射性矿泉沉积物的细菌群落，2019年秋季和2020年春季采样，并观察放射性核素是否，与其他物理化学参数相比，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，两个弹簧，Dourioux和Montagne的放射性元素浓度/活性很高（铀，钍和氡)。分析细菌群落的结构，通过基于16SrRNA基因测序的下一代测序，表明在Dourioux和Montagne中存在放射性核素，与其他弹簧相比，没有导致细菌多样性和丰富度的减少。然而,Dourioux和Montagne的特征是特定的细菌种群，其存在与这些弹簧中测量的放射性元素浓度/活性相关。这表明放射性元素可以部分解释这些泉水中细菌群落的结构。此外,其中一些特定于Dourioux和Montagne的操作分类单位(OTU)，主要隶属于变形杆菌，Firmicutes,酸杆菌,放线菌,和拟杆菌,可以通过不同的机制(生物吸附，生物矿化，生物蓄积性,和生物还原)，这将允许开发对这些金属/放射性元素敏感的其他细菌物种。特别是,硫酸盐和/或铁还原细菌的共存，能够生物还原铀，发酵细菌，释放有机碳的来源，反映了具有互补功能的细菌的关联，使它们能够在这种特殊的环境中生长并在这些极端环境中保持高度的多样性。这项研究为在自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提供了更好的理解。
