Background: El Chichón volcano is one of the most active volcanoes in Mexico. Previous studies have described the poly-extreme conditions of the lake crater but its bacterial composition and the functional features of the complete microbiome have not been characterized yet.Methods: This study integrated two approaches to explain the microbiology diversity and abundance, one focused on the environmental genomic potential by metagenomics approach, and other culturomics of enrichment of bacteria and archaea. The microbial diversity of the anaerobic consortia cultivated in was carried out by metabarcoding analysis, the metabolic capacity by metabolomics uxes of carbon and enzymologic techniques for the analysis of sulfate reduction in laboratory-grown prokaryotic cells.Results: This work provides new information on the taxonomic and functional diversity of the Archea representative phyla Crenarchaeota and Euryarchaeota as well as the phyla Thermotogales and Aqui cae for Bacteria. Through the analysis of microbial consortia cultivation and the genetic information collected from the natural environment sampling, metabolic interactions were identi ed between the microorganisms that support the life of the microbiome under multi-extreme conditions. A close relationship is proposed between the cycles of carbon and sulfur in an active volcano.Conclusions: This research contributes to the understanding of microbial metabolism under extreme conditions and potential knowledge of "microbial dark matter" that can be applied in biotechnological processes and evolutionary studies.

The crater lake of El Chichón active volcano represents one of the most important extreme ecosystems in the world due to its high temperatures, low pH and the appearance of high concentrations of heavy metals because of volcanic activity. The latter is of great importance in nearby volcano sites due to heavy metal pollution, which is one of the worst types of environmental problems in the world. In this study, the concentration of heavy metals was evaluated in soils and sediments from different sections in the crater lake of El Chichón volcano. Representative samples were collected from four sediments and soils in 2015 and 2017. These samples were analyzed for 20 metals by inductively coupled plasma-optical emission spectrometry (ICP-OES). The most abundant elements in sediments of the crater lake of "El Chichón" volcano were Fe, Na, Si, Ca, K and Al and not found in soil samples. Be and Tl were more abundant in the soil, but the concentration of Se was higher in soil without showing statistically significant differences. Principal component analysis (PCA) showed that the abundance of metals was influenced by sample type. That is, a higher concentration of heavy metals and trace elements was found in volcanic sediments as compared to soil samples. This difference may be related to metals originating from the magma, which is partially transported in the water stream that gives way to the volcano lake. The most toxic heavy metals identified and quantified in high concentrations in crater soils and sediments were As and Cd. This study suggests that sediments and soils of El Chichón crater lake could be an important source of heavy metals and toxic elements such as As and Cd.

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Background: El Chichón volcano is one of the most active volcanoes in Mexico. Previous studies have described the poly-extreme conditions of the lake crater but its bacterial composition and the functional features of the complete microbiome have not been characterized yet. Methods: This study integrated two approaches to explain the microbiology diversity and abundance, one focused on the environmental genomic potential by metagenomics approach, and other culturomics of enrichment of bacteria and archaea. The microbial diversity of the anaerobic consortia cultivated in was carried out by metabarcoding analysis, the metabolic capacity by metabolomics fluxes of carbon and enzymologic techniques for the analysis of sulfate reduction in laboratory-grown prokaryotic cells. Results: This work provides new information on the taxonomic and functional diversity of the Archea representative phyla Crenarchaeota and Euryarchaeota as well as the phyla Thermotogales and Aquificae for Bacteria. Through the analysis of microbial consortia cultivation and the genetic information collected from the natural environment sampling, metabolic interactions were identified between the microorganisms that support the life of the microbiome under multi-extreme conditions. A close relationship is proposed between the cycles of carbon and sulfur in an active volcano. Conclusions: This research contributes to the understanding of microbial metabolism under extreme conditions and potential knowledge of "microbial dark matter" that can be applied in biotechnological processes and evolutionary studies.