Bacterial phylotypes associated with rock-dwelling Umbilicaria Lichens from Arctic/Subarctic areas in North America and Northern Europe

Abstract

The diversity of bacteria associated with lichens has received increasing attention. However, studies based on next-generation sequencing of microbiomes have not yet been conducted in the Arctic and Subarctic regions. In this study, rock-dwelling lichens belonging to the Umbilicariaceae family were sampled from the Arctic and Subarctic biological zones. The primary research purpose was to undertake a comparative investigation of the bacterial composition and diversity, identify potential indicators, and explore their potential metabolic pathways. 18S rRNA gene sequences of the fungal partner belonging to the genus Umbilicaria (Ascomycota) and the algal partner affiliated with the lineage Trebouxia (Chlorophyta). Comparing Umbilicaria spp. with a previous study in the Antarctic zone, the fungal partners were more inclined to cluster by sampling region. Operational taxonomic units (OTUs) were established based on a predetermined similarity threshold for V3-V4 sequences, which were ascribed to 19 bacterial phyla, and ten of them were consistently present in all samples. The most distinct zonal indicator genera based on OTU frequencies from Arctic and Subarctic lichens were Capsulimonas (Armatimonadota) and Jatrophihabitans (Actinomycota), respectively. Although the Subarctic zone had higher biodiversity and species richness based on alpha-diversity, the beta-diversity showed that the main species of bacterial communities were not significantly different, and the predictions of metabolic pathways based on the bacterial microbiome in lichen samples from the two zones were similar. These findings provide evidence that the geographical and/or bioclimatic environment and the different lichen-forming fungal species mainly and partially influence bacterial microbiomes and metabolic pathways.

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