Abstract
Hydrothermal systems are ideal to understand how microbial communities cope with challenging conditions. Lirima, our study site, is a polyextreme, high-altitude, hydrothermal ecosystem located in the Chilean Andean highlands. Herein, we analyze the benthic communities of three nearby springs in a gradient of temperature (42–72 °C represented by stations P42, P53, and P72) and pH, and we characterize their microbial diversity by using bacteria 16S rRNA (V4) gene metabarcoding and 16S rRNA gene clone libraries (bacteria and archaea). Bacterial clone libraries of P42 and P53 springs showed that the community composition was mainly represented by phototrophic bacteria (Chlorobia, 3%, Cyanobacteria 3%, at P42; Chlorobia 5%, and Chloroflexi 5% at P53), Firmicutes (32% at P42 and 43% at P53) and Gammaproteobacteria (13% at P42 and 29% at P53). Furthermore, bacterial communities that were analyzed by 16S rRNA gene metabarcoding were characterized by an overall predominance of Chloroflexi in springs with lower temperatures (33% at P42), followed by Firmicutes in hotter springs (50% at P72). The archaeal diversity of P42 and P53 were represented by taxa belonging to Crenarchaeota, Diapherotrites, Nanoarchaeota, Hadesarchaeota, Thaumarchaeota, and Euryarchaeota. The microbial diversity of the Lirima hydrothermal system is represented by groups from deep branches of the tree of life, suggesting this ecosystem as a reservoir of primitive life and a key system to study the processes that shaped the evolution of the biosphere.
Highlights
Earth was characterized by high temperatures in primitive oceans, high UV radiation, low oxygen concentrations, acidic pH, intensive volcanic activity, and a reduced atmosphere with high hydrogen concentrations [1,2,3]
High altitude ecosystems around the Atacama Desert contain several hot springs that are characterized by extreme environmental factors such as those encountered in early earth, presenting extreme aridity, high UV radiation, and a wide daily temperature oscillation
The Lirima hydrothermal system is composed of several springs in a physicochemical gradient of temperature (42 to 72 ◦C) and pH (5.2 to 7.8) (Table 1; Figure 1)
Summary
Earth was characterized by high temperatures in primitive oceans, high UV radiation, low oxygen concentrations, acidic pH, intensive volcanic activity, and a reduced atmosphere with high hydrogen concentrations [1,2,3]. The geochemical composition of the water has been reported to be dominated by sodium sulfate, chloride, and arsenic [9] These unique environmental and geochemical conditions create peculiar niches for microbial life that are potentially similar to early Earth. Considering the above, we characterize the microbial diversity of three closely located hot springs in the Lirima hydrothermal system by using both 16S rRNA gene clonal (bacteria and archaea) and 16S rRNA (V4 region) gene metabarcoding analyses, and we determine the influence of physical and chemical environmental conditions on those microbial community structures. The results obtained in this study are discussed in the context of how hydrothermal systems are important reservoirs of unexplored microbial diversity and crucial systems to understand essential questions concerning the metabolisms, adaptations, and phylogenetic relationships of these microbial communities with deep branched lineages in the tree of life
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