Unveiling Taxonomic Diversity and Functional Composition Differences of Microbial Mat Communities Through Comparative Metagenomics

Abstract

Microbial mats are stratified systems of microorganisms that have served as models to study diverse ecological functions. Comparing the unique and shared characteristics between different microbial mats could shed new light on the biodiversity, functionality and genetic potential of these habitats. In this study, the taxonomic diversity of a microbial mat from the Araro hot springs (Trans-Mexican volcanic belt) was explored and compared with the metagenomes of microbial mats from Cuatro Ciénegas (Mexico), Guerrero Negro (Mexico), Shark Bay (Australia), Yellowstone (USA), and Diamond Fork (USA). The thermal Araro microbial mat was dominated by the phyla Chloroflexi (particularly Chloroflexus), Cyanobacteria, and Proteobacteria. Chlorobium was abundant at Diamond Fork; whereas Thermus, Synechococcus, and Bacillus were found at the remaining locations together with less abundant microbial groups. Alpha diversity indices were highest in Araro, Cuatro Ciénegas, and Shark Bay. Principal component analysis and hierarchical clustering separated Araro from the remaining microbial mats. SEED subsystems revealed carbohydrate metabolism, amino acids, and derivatives to be dominant functions in most mats, while protein and DNA metabolism were prevalent in Araro. Sequences related to biogeochemical cycles of N, Fe, C, O, and S were observed in all mats except Yellowstone (O cycle only), suggesting the presence of different trophic groups. In summary, the six metagenomes exhibit important taxonomic and functional differences, which could be related to their environmental and physicochemical adaptations.