A metagenomic study of the bacteria in snow algae microbiomes

The bacterial communities found in snow algae blooms have been described in terms of their 16S rRNA gene community profiles, but little information exists on their metabolic potential. Previously, we reported that several bacterial taxa are common across snow algae blooms in the southwestern mountains of the Coast Range in British Columbia, Canada. Here, we further this work by reporting a partial bacterial metagenome from the same snow algal microbiomes. Using shotgun metagenomic data, we constructed metagenomically assembled bacterial genomes (MAGs). Of the total 54 binned MAGs, 28 were bacterial and estimated to be at least 50% complete based on single copy core genes. The 28 MAGs fell into five classes: Actinomycetia, Alphaproteobacteria, Bacteroidia, Betaproteobacteria, and Gammaproteobacteria. All MAGs were assigned to a class, 27 to an order, 25 to a family, 18 to a genus, and none to species. MAGs showed the potential to support algal growth by synthesizing B-vitamins and growth hormones. There was also widespread adaptation to the low oxygen environment of biofilms, including synthesis of high-affinity terminal oxidases and anaerobic pathways for cobalamin synthesis. Also notable were the absence of N₂ fixation, and the presence of incomplete denitrification pathways suggestive of NO signalling within the microbiome.