Prokaryotic communities of the cryoconite holes from the glaciers of the Arctic, Antarctic, and Central Caucasus

Cryoconites are the deposits on the surface of glaciers that create specific ecological niches for the development of communities of microorganisms. The sediment material can vary in origin, structure, and nutrient content, creating local variations in the growth conditions. An additional factor of variability is the location of the glaciers, as they are found in different climatic zones in the high mountain regions and closer to the poles. Here we studied the common and specific features of the microbial communities from five glaciers representing different parts of the world, including Arctic (Mushketova in Severnaya Zemlya, IGAN in Polar Ural), Antarctic (Pimpirev on Livingstone Island) and Caucasus (Shkelda und Garabashi in Central Caucasus). According to the chemical parameters of the cryoconites, each region had characteristic properties: Arctic cryoconites had higher nitrates and microelements content, Antarctic - organic carbon, ammonium and potassium, Caucasus - alkaline pH and high phosphorus content. Analysis of data from high-throughput sequencing of the 16S rRNA gene showed that although cryoconite microbiomes are composed of similar bacterial phyla (Pseudomonadota, Cyanobacteria, Bacteroidota, Acidobacteriota and Actinobacteriota), at a low taxonomic level they comprised of dissimilar representatives: only several common phylotypes were identified for the entire dataset. The WGSNA analysis revealed three groups of microorganisms corresponding with the three geographical locations that significantly change with different chemical parameters of cryoconites. Our work demonstrates that cryoconite creates a specific ecological niche that facilitates growth of predominantly autotrophic microorganisms, but local factors and physical isolation creates specific patterns for each of such diversity hotspots.