M. N. Poglazova

Microflora in the basal strata at Antarctic ice core above the Vostok lake

The microbiological investigations of the Antarctic ice core at the Vostok station become especially important in connection with the discovery of an subglacial lake in this region. This lake is considered by the world-wide scientific community to be an important object for searching for relict forms of life on the Earth and also as a model for solving a number of problems of exobiology--for instance for development of methods to penetrate into underice sea at Europe--Jupiters satellite. For the first time the Antarctic ice core samples were taken from the horizons which correspond to the basal zone (3534-3541 m) and to the accreation ice zone (3555-3611 m) above the subglacial lake Vostok. As a result of the microbiological investigations it was shown that the total number of microbial cells have been in the same range of quantities as at the upper, younger horizons and varied from 1.3 x 10(2) up to 9.6 x 10(2) cl/ml. Some periodicity in the cell concentration and in their morphological diversity was revealed along the core. The maximal number and the greatest morphological variety were detected at horizons with the depth of 3534, 3555 and 3595 m. A drop in the cell concentration two or three times as much was found in ice layers under each of the above mentioned horizons. The discovered stratification is apparently connected with the periodicity of the lake water interactions with the basal ice layer and obviously depends on the complex natural events which took place in the geological history of our planet.

Microbiological Characterization of the Accreted Ice of Subglacial Lake Vostok, Antarctica

The accreted ice of subglacial Lake Vostok extends upward from the lake water level (a depth of 3750 m) to the bottom surface of the overlying Antarctic ice sheet. All of the accreted ice samples, taken from depths between 3541 and 3611 m, were found to contain pro- and eukaryotic microorganisms, whose number and diversity varied in different ice horizons and correlated, to a certain degree, with the occurrence of organic and inorganic impurities in a given horizon. Some biological objects found in the accreted lake ice, including bacteria, microalgae, and the pollen of higher plants, were morphologically similar to those found earlier in the glacier ice bulk. The others were not. It is suggested that the microorganisms found in the lake ice may come from different locations—the bottom layer of the glacier ice, the bedrock underlying the glacier, and the lake water.

Antarctic ice sheet as an object for solving some methodological problems of exobiology

Abstract Icy formations are often found in the cosmos: there are comets nuclei, polar caps of Mars and of other planets and Europa, the Jupiters satellite covered with icy crust. Various inclusions of mineral and organic compounds have been permanently accumulated in the ice thickness which protects them from subsequent environmental influence and ensures their reliable and long-term preservation. So icy bodies are unique objects for searching microorganisms and studying ancient ecological events that occurred during formation of icy layers. Complex microbiological and glaciological investigations at Vostok station carried out during a number of years resulted in the discovery of well-preserved cells of microorganisms of different taxonomic groups, as well as plant pollen and unicellular algae in the ice sheet horizons the age of which exceeds 300,000 years. Upon incubation of some samples with radiocarbon labeled organics an evidence of the preservation of some viable microorganisms has been provided. The investigation of ice bodies in an attempt to find any possible form of microscopical life has an advantage over analogous studies of other cosmic solids because the cells of microorganisms and other inclusions can be released from the melted ice without destruction and can be studied unambiguously by different methods of microscopy.

Antarctic ice sheet as a model in search of life on other planets

Abstract This paper concerns the problem of search of life on other planets due to similarities of some conditions in polar ice caps of Earth and Mars. Viable microbes were isolated from layers of the Antarctic ice sheet that dates back about 200 000 years. Their morphological variability and gradual restoration of some physiological functions in favourable conditions were described. The relation of microbes distribution at different horizons of ice to considerable fluctuations of Earths climate in ancient geological epochs was revealed. Those fluctuations of climate brought to the sharp variations of intensity of microparticles and microbes transfer with intercontinental aerial streams to polar caps of neighbouring planets.

Microorganisms found in the basal horizons of the Antarctic glacier above Lake Vostok.

The Antarctic ice sheet, whose thickness in the central part reaches 4000 m, keeps information on the changes in the climate and composition of the Earth atmosphere over hundreds of thousands of years [1, 2]. Along with the bubbles of ancient air and particles of atmospheric dust that were brought to the surface of the glacier by the air streams, its layers also contain microorganisms, some of which retain viability after the long-term anabiosis [3].

Time machine: Ancient life on Earth and in the cosmos

The discovery more than 30 years ago of the unique superlong anabiosis phenomenon (deep sleep/dormancy) for ancient microorganisms buried in Antarctic ice deposits created the experimental and theoretical basis for the fields of cryomicrobiology and astrobiology related to searching for life or its evidence in the universe. This discovery is of special interest in light of the upcoming International Polar Year (IPY 2007–2008) and the creation of the U.S. Subglacial Antarctic Lake Environments program (http://salepo.tamu.edu/us_sale). Abysov et al. [1977, 1978] discovered superlong anabiosis for microorganisms in deep Antarctic ice cores above Lake Vostok when his group found and revived ancient microbes frozen for more than 500,000 years (Figure 1). Previously, only science fiction writers had contemplated a deep sleep/dormancy phenomenon that might allow humans to postpone their deaths by freezing and thus travel in time into the future.

Endospore formation by Streptomyces avermitilis in submerged culture

The ability of streptomycetes to form endospores during their life cycle was studied in submerged cultures of Streptomyces avermitilis. Submerged S. avermitilis spores were most intensely formed (1) during the culture development cycle on synthetic medium CP1 with glucose under phosphate limitation and (2) in autolysing cell suspensions of high density obtained by tenfold concentration in phosphate buffer (pH 7.2) with 0.2% CaCl2 of stationary-phase cells grown in synthetic medium. Endospores of S. avermitilis formed in submerged cultures shared the major characteristics of specialized microbial resting forms: heat resistance, resistance to lysozyme, ability to retain the main species-specific features, and ultrastructural organization characteristic of endospores. They can be considered a resting form of streptomycetes alternative to the spores formed exogenously on aerial mycelium in surface cultures.

Microorganisms and unicellular algae in the ice sheet of Antarctica

Institute of Microbiology RAS have carried out during several years the microbiological investigations at the Central Antarctic in the region of Vostok station. The special technics of aseptic sampling from ice sheet have been used.

Long-term conservation of viable microorganisms in the ice sheet of Central Antarctica

Many investigators regard Antarctica as a model for solution of such problems as search of life on other planets, the quarantine in planets, and at the Earth during interplanetary contacts. It is also a good natural experiment for studying the phenomenon of microbial long- term anabiosis. Remoteness from the regions of intensive anthropogenic effects, low stable temperature and reliable protection of ancient ice horizons against subsequent environmental changes make Antarctic ice sheet an ideal object for methodological works necessary for investigation of various problems of exobiology. Investigations of ice bodies in attempts to find there any possible form of life has an advantage over similar studies of other cosmic solids because microorganisms, spores, plant pollen, unicellular algae, and other inclusions rather easily release from the melted ice and their investigation by different methods depends only on the well thought-out techniques. Special techniques of aseptic sampling while drilling at Vostok station and analysis of these samples by different methods have provided evidence for the existence of viable microorganisms in very ancient layers of the ice sheet. The relationship between quantitative distribution of microbes at different horizons of the ice column with the Earths climate fluctuations at the time of these layers formation was also demonstrated.

Development of cytology at the Institute of Microbiology, Russian Academy of Sciences (1934-2004)

Cytological investigations of microorganisms have been the main line of research carried out at the Laboratory of Microbiology, USSR Academy of Sciences (1930–1934), headed by Academician G.A. Nadson, and at the Institute of Microbiology, USSR Academy of Sciences (INMI), founded on the basis of this laboratory in 1934. Within this line of research, morphology, fine structure, modes of reproduction, and developmental cycles of microbial cells were investigated and concepts of microbial evolution and classification were developed. The preference given by Nadson and his colleagues to this research line is obvious and justified: facing the enormous variety of microscopic creatures, researchers endeavored first of all to understand the nature, origin, evolution, and variability of microorganisms and their position in the system of the known kingdoms of the organic world. On the background of extremely scant information concerning the biochemical composition and physiology of microbial cells, cytological investigations performed in the 1920s and 1930s were really at the front of biology and played a role similar to that currently played by molecular biology. The discovery and description of cellular structures, organelles, and organoids (nuclei, chromosomes, cell walls, membranes, vacuoles, mitochondria, etc.) initiated the emergence of new large branches of biology.