Browsing by Author "Rutanen, Aino"

Global warming caused by the warming effect of greenhouse gases (GHGs) induces permafrost thaw, which could alter Arctic ecosystems from prominent carbon sinks to potential sources of GHG emissions when polar microorganisms become metabolically more active and have access to carbon compounds that were previously largely unavailable. Polar microbes can have significant contributions to the growing emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) and therefore, studies on their metabolism are important. The aim of my study was to investigate polar microbial community composition and diversity as well as functional potential that was related to GHG-cycling in a subarctic environment with genome-resolved metagenomics. Soil cores were collected at the Rásttigáisá fell that is located in Northern Norway. After DNA extraction, ten mineral soil samples were sequenced. Metagenome-assembled genomes (MAGs) were reconstructed using either the combination of human-guided binning and automatic binning or human-guided binning only. Taxonomy was assigned to the MAGs and the functional potential of the MAGs was determined. I recovered dozens of good-quality MAGs. Notably, the MAGs from the mostly unknown phyla Dormibacterota (formerly candidate phylum AD3) and Eremiobacterota (formerly candidate phylum WPS-2) were reconstructed. There were MAGs from the following bacterial phyla as well: Acidobacteriota, Actinobacteriota, Chloroflexota, Gemmatimonadota, Proteobacteria and Verrucomicrobiota. In addition to the bacterial MAGs, MAGs from the group of ammonia-oxidizing archaea were recovered. Most of the MAGs belonged to poorly studied phylogenetic groups and consequently, novel functional potential was discovered in many groups of microorganisms. The following metabolic pathways were observed: CO2 fixation via the Calvin cycle and possibly via a modified version of 3-hydroxypropionate/4-hydroxybutyrate cycle; carbon monoxide oxidation to CO2; CH4 oxidation and subsequent carbon assimilation via serine pathway; urea, ammonia and nitrite oxidation; incomplete denitrification as well as dissimilatory nitrate reduction to ammonium. My study demonstrates how genome-resolved metagenomics provides a valuable overview of the microbial community and its functional potential.