Comparative genomic and physiological analysis provides insights into the role of Acidobacteria in organic carbon utilization in Arctic tundra soils

Acidobacteria are among the most abundant bacterial phyla found in terrestrial ecosystems, but relatively little is known about their diversity, distribution and most critically, their function. Understanding the functional activities encoded in their genomes will provide insights into their ecological roles. Here we describe the genomes of three novel cold-adapted strains of subdivision 1 Acidobacteria. The genomes consist of a circular chromosome of 6.2Mbp for Granulicella mallensis MP5ACTX8, 4.3Mbp for Granulicella tundricola MP5ACTX9, and 5.0Mbp for Terriglobus saanensis SP1PR4. In addition, G.tundricola has five mega plasmids for a total genome size of 5.5Mbp. The three genomes showed an abundance of genes assigned to metabolism and transport of carbohydrates. In comparison to three mesophilic Acidobacteria, namely Acidobacterium capsulatum ATCC 51196, Candidatus Koribacter versatilis Ellin345, and Candidatus Solibacter usitatus Ellin6076, the genomes of the three tundra soil strains contained an abundance of conserved genes/gene clusters encoding for modules of the carbohydrate-active enzyme (CAZyme) family. Furthermore, a large number of glycoside hydrolases and glycosyl transferases were prevalent. We infer that gene content and biochemical mechanisms encoded in the genomes of three Arctic tundra soil Acidobacteria strains are shaped to allow for breakdown, utilization, and biosynthesis of diverse structural and storage polysaccharides and resilience to fluctuating temperatures and nutrient-deficient conditions in Arctic tundra soils.