Bacterial communities of Antarctic lichens explored by gDNA and cDNA 16S rRNA gene amplicon sequencing

Recently, lichens came once more into the scientific spotlight due to their unique relations with Prokaryotes. Several temperate region lichen species have been thoroughly explored in this regard using state-of-the-art meta-omic technologies. However, the information on Antarctic lichens and their associated bacteriobiomes is somewhat lacking, despite the regions large phylogenetic and ecophysiological diversity of lichen species. In this paper we assessed the phylogenetic structure of the whole and active fractions of bacterial communities housed by Antarctic lichens growing in different environmental conditions by targeted 16S rRNA gene amplicon sequencing based on gDNA, as well as cDNA. Bacterial communities associated with lichens procured from a nitrogen enriched site (Penguin rookery) were very distinct from the communities isolated from lichens of a nitrogen depleted site (inland plateau). The former were characterized by substantial contributions of Bacteroidetes phylum members and the elusive Armatimonadetes. At the nutrient-poor site the lichen-associated bacteriobiome structure was unique for each lichen species, with chlorolichens being occupied largely by Proteobacteria. Lichen species with a pronounced discrepancy in diversity between the whole and active fractions of their bacterial communities were those regarded as having a wide ecological amplitude, hinting that the non-active part of the community is a reservoir of stress coping mechanisms activated during environmental condition changes. This is the first investigation to make use of transcriptomics to infer the bacterial biodiversity in Antarctic lichens, thus highlighting the role of prokaryotic symbionts in the adaptability and consequently the evolution of lichens in this harsh and intriguing ecosystem