In this study, we isolated and characterized bacterial strains from ancient (Neogene) permafrost sediment that was permanently frozen for 3.5 million years. The sampling site was located at Mammoth Mountain in the Aldan river valley in Central Yakutia in Eastern Siberia. Analysis of phospolipid fatty acids (PLFA) demonstrated the dominance of bacteria over fungi; the analysis of fatty acids specific for Gram-positive and Gram-negative bacteria revealed an approximately twofold higher amount of Gram-negative bacteria compared to Gram-positive bacteria. Direct microbial counts after natural permafrost enrichment showed the presence of (4.7 ± 1.5) × 10⁸ cells g⁻¹ sediment dry mass. Viable heterotrophic bacteria were found at 0 °C, 10 °C and 25 °C, but not at 37 °C. Spore-forming bacteria were not detected. Numbers of viable fungi were low and were only detected at 0 °C and 10 °C. Selected culturable bacterial isolates were identified as representatives of Arthrobacter phenanthrenivorans, Subtercola frigoramans and Glaciimonas immobilis. Representatives of each of these species were characterized with regard to their growth temperature range, their ability to grow on different media, to produce enzymes, to grow in the presence of NaCl, antibiotics, and heavy metals, and to degrade hydrocarbons. All strains could grow at −5 °C; the upper temperature limit for growth in liquid culture was 25 °C or 30 °C. Sensitivity to rich media, antibiotics, heavy metals, and salt increased when temperature decreased (20 °C > 10 °C > 1 °C). In spite of the ligninolytic activity of some strains, no biodegradation activity was detected.

Permafrost is widely distributed in the Northern Hemisphere and arrives after hundreds of thousands and millions of years. Permafrost contains live microorganisms, which are not frozen due to the relatively high ambient temperatures (from −2 to −8°C) but are immobilized; thus, their age seems to be close to the age of the permafrost. The longevity of relict microbial cells is obviously related to their mechanism of protection against heat, radiation, free radicals, and other damaging agents. A strain of Bacillus sp. was isolated from the permafrost aged about 3 million years and its 16S rDNA sequence was identified, followed by preliminary testing of the bacterial culture in Drosophila melanogaster and mice. The experiments showed immune stimulation and improvement of the physical condition. This fact, together with the age of microbial cells, suggests the consideration of relict microorganisms as objects of gerontology.

Saline frozen rocks of the Arctic coast require detailed study, since they are characterized by a low bearing capacity and low resistance to technogenic impacts. The currently known mechanisms of salinization of permafrost due to the effect of marine transgression (marine salinity) and cryogenic concentration, as well as due to the concentration of salts as a result of dehydration of rocks (continental salinity), do not always enable us to explain the presence of saline deposits on the Arctic coast of the Arctic Ocean. The purpose of this work is to present new mechanisms of salinity formation in permafrost that can explain the development of salinization at significant altitudes above sea level. Possible hypotheses of the formation of saline frozen rocks at high altitudes above sea level are given for the first time: the upsurge in sea level and tsunamis in the recent geological past, the latest tectonics, and biogenic salinization. The applied approach, taking into account the mechanisms of salinization formation in rocks, enables us to present graphically a new variant of the map of the distribution pattern of frozen saline rocks in the Northern Hemisphere. The boundary of the marine type of salinization was determined by the maximal boreal transgression, and the boundary of the continental type of salinity was drawn by analyzing and comparing the map of atmospheric precipitation and the map of evaporation (the areas where evaporation predominates over precipitation were isolated). A significant increase in the areas with the marine and continental salinity types on the Arctic coast of the Arctic Ocean is shown. It has been revealed that the maximal transgression did not reach such high levels in high-altitude regions in the Quaternary Period; in addition, the climate of these sites is far from the continental one.

The rheological behavior of a pile-frozen soil interface can accelerate pile settlement in pile foundation engineering and deteriorate the bearing capacity of the pile in cold regions. This is the core basis for guiding the design of pile engineering and judging the service life of pile foundations. However, it is unclear how the rheological process is affected by the factors which determine the ad-freeze strength at the pile-frozen soil interface. In this paper, based on a series of Multistage Loading Creep Test (MLCT) for pile-frozen Qinghai-Tibet clay soil interface and microscopic observations of frozen soil, the rheological process and the cryo-mechanism of the interface were analyzed. The results showed that the decrease in soil temperature reduce the interface’s instantaneous deformation value and creep rate, which results from the temperature-dependent rheological behavior of ice. The trend also occurs in the soil with coarser particles and the pile with a rough surface. The presence of massive ice in frozen soil benefits the bearing capacity of the interface at a high temperature of -1°C. However, it can considerably increase the interface’s creep rate due to the influence of the rheological properties of ice at a relatively low temperature of -5°C. Either thick lenticular ice lens or chaotic reticulate cryo-structures in the frozen soil surrounding a pile will enhance the interface’s rheological properties. The interface exhibits the lowest instantaneous deformation value and the slowest creep rate for frozen soil with the massive cryo-structure, which is formed with optimum moisture content. From an engineering viewpoint, the settlement of a pile foundation can be reduced by controlling its instantaneous deformation or restraining its creep rate.