Functional diversity of Archaea in Brazilian Pantanal soda lakes and their role in nutrient cycling

• Ano de defesa: 2025
• Autor(a) principal: Feitosa, Yara Barros
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: 16S rRNA; Archaea; Arqueias; Biogeochemical cycling; Ciclos biogeoquímicos; Metagenômica; Metagenomics; Metanogênese; Methanogenesis
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/64/64133/tde-11092025-161133/

Wetlands are home to great biodiversity, but these areas are also sources of greenhouse gas emissions. The Pantanal is the worlds largest wetland and comprises about 900 soda lakes, extreme environments that provide a unique habitat for haloalkaliphilic organisms. Despite the harsh conditions, the microbiome of soda lakes play crucial roles in biogeochemical cycling and ecosystem functioning. Previous studies about microbiota have focused on bacterial communities, and Archaea have not yet garnered significant attention, even though they dominate the biogenic production of methane, the most important greenhouse gas after carbon dioxide. In this context, this thesis focuses on establishing the archaeal diversity and its functional potential in Pantanal soda lakes through 16S rRNA amplicon sequencing and metagenome-assembled genomes (MAGs) from environmental samples. Water, sediment, and soil from the surrounding vegetation were collected from six soda lakes during both dry and wet seasons. Bioinformatics and meta-analyses were performed to correlate the 16S rRNA profiles with environmental variables. Sample type has a primary effect on the abundance, composition, and structure of the archaeal communities, depending on the presence of flooding. The pH level appears to be the main environmental variable driving differences in the communities across lakes. Archaeal diversity increased in sediments from inside the lake during the dry season, likely as a coping mechanism to thrive under extreme conditions. The most abundant taxa found in the sediment are methanogens, whereas in the water, the most abundant group are known to form a consortium with methanogens in anaerobic environments. In the soil, ammonia-oxidizing archaea were the most prevalent. The MAGs analysis also provided valuable insights into taxonomic diversity and functional potential, highlighting the importance of archaea in biogeochemical cycling. The presence of genes associated with methanogenesis and arsenic resistance pathways underscores the adaptability of Archaea to extreme conditions. Furthermore, genes associated with pigment production and secondary metabolite biosynthesis suggest their potential for biotechnological applications. These discoveries expand our understanding of archaeal contributions to soda lakes functioning and open new opportunities to harness their unique metabolic capabilities for industrial and environmental biotechnology