Microbial diversity in wetlands from Biosphere Reserve in Calakmul Mexico
Background: The Calakmul Biosphere Reserve (CBR) is the second most extended tropical forest after the Amazonas. Besides the richness in some animal and plant species that have been described in CBR, many other aspects of the biodiversity in this important natural protected area have not been studied. The microbial communities are largely unknown. Due to the great permeability of the karst substrate, the soils do not retain humidity, hence, no permanent surface water bodies exist. However, depressions associated with faults and fractures allow water to accumulate in the rainy season, forming water holes. The upcoming threats over the Yucatan peninsula with the Maya train make it necessary to urgently describe its biodiversity and value it as a source of goods to avoid mismanagement of this forest. Results: To increase the knowledge about the microbial communities living in the subaquatic soils of the Calakmul wetlands, we characterize the microbiota from three waterholes, two belonging to the core zone without human disturbances: Ag-C1 and Ag-C2, and one collected in the buffer zone: Ag-B3. Samples were collected in three different years (2017, 2018, and 2019) to monitor spatiotemporal changes in bacterial communities' diversity. The composition of microbiomes was addressed by 16S rRNA metabarcoding, while shotgun metagenomics assessed the genomic potential of some samples. Alpha diversity analyses of the three zones from 16S rRNA metabarcoding show a lower diversity in Ag-C1 in contrast to Ag-C2 and Ag-B3, although the Ag-C2 zone presents a higher abundance of species. Regarding beta diversity, Ag-C1 bacterial community intra-diversity is more conserved than in the other sites. In addition, when compared at the zone level, they are observed to be far apart, suggesting that the territorial location of the sample marks this behavior. The bacterial communities from CBR waterholes mainly comprise genera from phyla Proteobacteria, Acidobacteria, and Actinobacteria. Conclusion: This characterization allowed us to identify the composition of microbial communities and a preliminary picture of the metabolic capacities of the microbiomes that inhabit the wetlands from different conservation zones. The three sites have a unique composition of microorganisms; therefore, the chemical composition, natural and anthropogenic disturbances, vegetation and fauna of the sites could determine the microbial structure of these sites. Knowing the microbial communities' composition establishes a baseline to assess the impact of climatic factors, soil types, and human intervention in environments as necessary as wetlands.