High bacterial microdiversity within an Antarctic wetland complex

QUIROGA M.V.; MATALONI G.; COWAN, D.A.; LEBRE, P.H.; VALVERDE, ANGEL

Bogotá -Online

Congreso; II ISME Latin American Congress; 2021

Universidad de los Andes

The discrimination of amplicon sequence variants (ASVs), which can be further clustered into 97% similarity operational taxonomic units (OTUs, species proxy), allows the identification of strains or ecotypes within species and therefore the study of intra-species microdiversity. The study of microdiversity is key to understanding the ecological and evolutionary processes shaping the distributional patterns of microorganisms. Here, we studied bacterial microdiversity at one specific sampling time (summer 2018) and a relatively small spatial scale (1 square kilometer) encompassing the Punta Cierva wetland complex. This area has been long recognized as a macro-biodiversity hotspot within the Antarctic Peninsula. The analysis of high-throughput 16S rRNA gene amplicons uncovered 17 dominant OTUs (78% total reads), each containing from 17 to 460 ASVs. These dominant OTUs were ubiquitously distributed across the wetland complex. In contrast, most ASVs were specific to one wetland type. Accordingly, we observed significantly different ASV-community structures for each wetland type (Bray-Curtis based PERMANOVA, all pairwise comparison P < 0.05). Using rarefaction to decouple dominant OTU characteristics from their global abundance, we found that the increase of OTU effective microdiversity (i.e., number of ASVs) favored their persistence and reduced their abundance variability across samples. Studying the degree of diversification among dominant OTUs (i.e., OTU-population structure: Bray Curtis dissimilarities of ASV composition for each OTU) and the environmental distribution of their most abundant ASVs, two contrasting patterns were observed. Highly diversified OTUs appear to achieve their ubiquity through many specialist ASVs inhabiting specific wetland types, while less diversified OTUs may be ubiquitous due to a small number of ASVs inhabiting a broader range of wetland types. Overall, several bacterial taxa at Punta Cierva showed high intra-species microdiversity, which might ensure the survival of these taxa under changing environmental conditions.