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.

Relatively little is known about the microbial communities present in natural environments that meet physico-chemical conditions for the development of potential leaching microorganisms such as thermal ecosystems from the Chilean Altiplano. Thermophilic leaching enrichments were obtained and identified from a high altitude solfataric pound in Lirima hot springs in the Chilean Altiplano. This ecosystem is characterized by hot underground freshwaters, enriched in sulfur compounds showing pH from neutral to acidic. Microbial diversity has been scarcely explored here, and preliminary results demonstrate that hydrothermal pounds are represented by thermophilic anaerobic and acidophilic taxa. Thermophilic leaching cultures in shake flasks were obtained using ferrous iron and pyrite as energy source. The presence of Bacteria and Archaea in oxidizing enrichments was determined by PCR amplification of 16S rRNA genes. A preliminary analysis of microbial diversity using massive sequencing revealed that Bacteria were more abundant than Archaea in both enrichments. Specifically for the iron-oxidizing culture, the majority of the sequences clustered within the Proteobacteria phylum (79%). Among Proteobacteria, the proportion of Betaproteobacteria (42.2%) and Gammaproteobacteria (21.27%) was much higher than that of Alphaproteobacteria (15.5%). Within the Betaproteobacteria class, the most frequent genus was Leptothrix-like. Similar results were obtained for the pyrite oxidizing culture. Interestingly, this study shows the presence of microorganisms close to the Leptothrix genus under low pH conditions (1.7-2.8) and their capacity to grow at high temperatures with ferrous iron or pyrite as sole energy source