Da bi izboljšali razumevanje mikrobiologije hitro izginjajočih arktičnih ledenikov, smo vzorčili ledeniška okolja na območjih, ki veljata za žarišče polarnih mikrobioloških raziskav, na Svalbardu in Grenlandiji. V vzorcih površinskega in podledeniškega ledu, kriokonitov, snega, ledeniške vode in vode na površini ledenikov smo analizirali mikrobno raznolikost in zastopanost s kombinacijo metod gojenja in molekularnih metod. Z gojenjem smo osamili okrog 500 čistih kultur gliv, ki so pripadale 77 vrstam (62 rodovom) in več kot 200 bakterijskih kultur, ki smo jih uvrstili v 27 vrst (23 rodov). Najpogosteje osamljeni bakterijski rodovi, skupni vzorcem tako Grenlandije kot Svalbarda, so bili Cryobacterium, Massilia, Pseudomonas in Sphingomonas. Pri glivah so bili skupni rodovi psihrofilnih bazidiomicetnih kvasovk Mrakia, Phenoliferia, Callizyma ter psihrotolerantni filamentozni Penicillium in Cladosporium. Callizyma je nov rod, izoliran z Grenlandije in Svalbarda, ki obsega dve novi oligotrofni in psihrofilni vrsti Callizyma psychrophila in Callizyma arctica. Sekvenciranje pomnožkov taksonomskih označevalcev je odkrilo večjo glivno raznolikost ledeniških habitatov v primerjavi s kulturomiko, vključno z nekaterimi nepričakovanimi najdbami, kot sta bili prisotnost dermatofitske glive Malassezia restricta in izjemno halotolerantne črne kvasovke Hortaea werneckii. Poleg tega smo s pomočjo sekvenciranja v vseh vzorcih odkrili prisotnost zgodnjih filogenetskih skupin gliv (Chytridiomycota in Rozellomycota). Tako v ledu baze ledenikov na Svalbardu, kot v površinskem ledu ledenikov na Grenlandiji, so večino gliv predstavljale bazidiomicete (večinoma iz razreda Microbotryomyecets). Najpogostejša bakterijska debla, ki smo jih odkrili s sekvenciranjem, so bile Proteobacteria, Cyanobacteria, Chroloflexi, Armatimonadetes, Actinobacteria in Bacteroidetes. Z iskanjem lastnosti, ki so običajno povezane s patogenostjo za človeka, smo med okoljskimi arktičnimi glivami in bakterijami našli več termotolerantnih in hemolitičnih sevov, ki so bili pogosto odporni tudi proti antimikotikom ali antibiotikom. Interakcije med izbranimi vrstami gliv in ledeniškimi algami, ki s cvetenjem v površinskem ledu grenlandskega ledenega pokrova pospešujejo taljenje ledu, so nakazale ugoden in ne škodljiv vpliv gliv v začetku sezone taljenja ledu, z možnim prehodom v bolj saprofitsko obliko rasti, ko se kasneje v sezoni stanje alge začne slabšati. Iste vrste gliv so proizvajale protimikrobne spojine, ativne proti preizkušenim klinično pomembnim in okoljskim bakterijskim vrstam, kar kaže na njihovo sposobnost modulacije rasti drugih mikroorganizmov. In order to advance our understanding of the microbiology of the quickly disappearing Arctic glaciers, sampling campaigns in two regions considered as the “hot spots” of polar microbiological research, Svalbard and Greenland, were performed. Samples of supra- and subglacial ice, cryoconite, snow, glacial meltwater, and supraglacial water were analysed for microbial diversity, with a combination of culture dependent and independent methods, and for microbial abundance. Cultivation allowed the isolation of around 500 pure cultures of fungi, belonging to 77 species (62 genera), and more than 200 bacterial cultures belonging to 27 species (23 genera). Most frequent cultivated bacterial genera, common to both Greenland and Svalbard samples, were Cryobacterium, Massilia, Pseudomonas, and Sphingomonas. For fungi, the common genera were the psychrophilic basidiomycetous yeasts Mrakia, Phenoliferia, Callizyma, and the psychrotolerant filamentous Penicillium and Cladosporium. Callizyma is a novel genus isolated from Greenland and Svalbard, comprising two novel oligotrophic and psychrophilic species Callizyma psychrophila and Callizyma arctica. Amplicon sequencing of taxonomic markers uncovered a larger fungal diversity of glacial habitats compared to culturomics, and included some unexpected findings, such as the presence of the dermatophytic fungus Malassezia restricta and the extremely halotolerant black yeast Hortaea werneckii. Additionally, the sequencing revealed the presence of early-lineages fungi (Chytridiomycota and Rozellomycota) in all the collected samples. In both, Svalbard subglacial and Greenland Ice Sheet supraglacial habitats, fungal diversity was mainly composed of Basidiomycota (the majority belonging to the Microbotryomycetes class). The most common bacterial phyla recovered with NGS techniques were Proteobacteria, Cyanobacteria, Chroloflexi, Armatimonadetes, Actinobacteria, and Bacteroidetes. Screening for the expression of phenotypes commonly associated with human pathogenicity in environmental Arctic fungi and bacteria, highlighted the presence of thermotolerant and hemolytic strains, which were often also resistant to antifungals or antibiotics. Interactions between selected fungal species and glacier algae blooming on the surface ice of the Greenland Ice Sheet, contributing to its faster melting, indicated that fungi have a beneficial rather than detrimental impact at the beginning of the melting season. Their behaviour possibly switch to saprophytic later in the season when glacier algae start deteriorating. The same fungal species produced antimicrobial compounds active against tested clinically relevant and environmental bacterial species, pointing to their ability to modulate the growth of other microorganisms.