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Observations of anthropogenic global warming

Papers on micro-organisms in permafrost

Posted by Ari Jokimäki on September 13, 2016

This is a list of papers on micro-organisms in permafrost. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Functional Characterization of Bacteria Isolated from Ancient Arctic Soil Exposes Diverse Resistance Mechanisms to Modern Antibiotics (Perron et al. 2015) [FULL TEXT]
Abstract: “Using functional metagenomics to study the resistomes of bacterial communities isolated from different layers of the Canadian high Arctic permafrost, we show that microbial communities harbored diverse resistance mechanisms at least 5,000 years ago. Among bacteria sampled from the ancient layers of a permafrost core, we isolated eight genes conferring clinical levels of resistance against aminoglycoside, β-lactam and tetracycline antibiotics that are naturally produced by microorganisms. Among these resistance genes, four also conferred resistance against amikacin, a modern semi-synthetic antibiotic that does not naturally occur in microorganisms. In bacteria sampled from the overlaying active layer, we isolated ten different genes conferring resistance to all six antibiotics tested in this study, including aminoglycoside, β-lactam and tetracycline variants that are naturally produced by microorganisms as well as semi-synthetic variants produced in the laboratory. On average, we found that resistance genes found in permafrost bacteria conferred lower levels of resistance against clinically relevant antibiotics than resistance genes sampled from the active layer. Our results demonstrate that antibiotic resistance genes were functionally diverse prior to the anthropogenic use of antibiotics, contributing to the evolution of natural reservoirs of resistance genes.”
Citation: Perron GG, Whyte L, Turnbaugh PJ, Goordial J, Hanage WP, Dantas G, et al. (2015) Functional Characterization of Bacteria Isolated from Ancient Arctic Soil Exposes Diverse Resistance Mechanisms to Modern Antibiotics. PLoS ONE 10(3): e0069533. doi:10.1371/journal.pone.0069533.

Molecular characterization of bacteria from permafrost of the Taylor Valley, Antarctica (Bakermans et al. 2014) [FULL TEXT]
Abstract: “While bacterial communities from McMurdo Dry Valley soils have been studied using molecular techniques, data from permafrost are particularly scarce given the logistical difficulties of sampling. This study examined the molecular diversity and culturability of bacteria in permafrost from the Taylor Valley (TV), Antarctica. A 16S rRNA gene clone library was constructed to assess bacterial diversity, while a clone library of the RNA polymerase beta subunit (rpoB) gene was constructed to examine amino acid composition of an essential protein-coding gene. The 16S rRNA gene clone library was dominated by Acidobacteria from Gp6 and Gemmatimonadetes. The rpoB gene clone library (created with primers designed in this study) was also dominated by Acidobacteria. The ability of sequence analyses to garner additional information about organisms represented by TV sequences was explored. Specifically, optimum growth temperature was estimated from the stem GC content of the 16S rRNA gene, while potential cold adaptations within translated rpoB sequences were assessed. These analyses were benchmarked using known psychrophiles and mesophiles. Bioinformatic analyses suggested that many TV sequences could represent organisms capable of activity at low temperatures. Plate counts confirmed that c. 103 cells per gram permafrost remained viable and were culturable, while laboratory respiration assays demonstrated that microbial activity occurred at −5 °C and peaked at 15 °C.”
Citation: Bakermans, C., Skidmore, M. L., Douglas, S. and McKay, C. P. (2014), Molecular characterization of bacteria from permafrost of the Taylor Valley, Antarctica. FEMS Microbiol Ecol, 89: 331–346. doi:10.1111/1574-6941.12310.

Bacterial growth at −15 °C; molecular insights from the permafrost bacterium Planococcus halocryophilus Or1 (Mykytczuk et al. 2013) [FULL TEXT]
Abstract: “Planococcus halocryophilus strain Or1, isolated from high Arctic permafrost, grows and divides at −15 °C, the lowest temperature demonstrated to date, and is metabolically active at −25 °C in frozen permafrost microcosms. To understand how P. halocryophilus Or1 remains active under the subzero and osmotically dynamic conditions that characterize its native permafrost habitat, we investigated the genome, cell physiology and transcriptomes of growth at −15 °C and 18% NaCl compared with optimal (25 °C) temperatures. Subzero growth coincides with unusual cell envelope features of encrustations surrounding cells, while the cytoplasmic membrane is significantly remodeled favouring a higher ratio of saturated to branched fatty acids. Analyses of the 3.4 Mbp genome revealed that a suite of cold and osmotic-specific adaptive mechanisms are present as well as an amino acid distribution favouring increased flexibility of proteins. Genomic redundancy within 17% of the genome could enable P. halocryophilus Or1 to exploit isozyme exchange to maintain growth under stress, including multiple copies of osmolyte uptake genes (Opu and Pro genes). Isozyme exchange was observed between the transcriptome data sets, with selective upregulation of multi-copy genes involved in cell division, fatty acid synthesis, solute binding, oxidative stress response and transcriptional regulation. The combination of protein flexibility, resource efficiency, genomic plasticity and synergistic adaptation likely compensate against osmotic and cold stresses. These results suggest that non-spore forming P. halocryophilus Or1 is specifically suited for active growth in its Arctic permafrost habitat (ambient temp. ~−16 °C), indicating that such cryoenvironments harbor a more active microbial ecosystem than previously thought.”
Citation: Nadia C S Mykytczuk, Simon J Foote, Chris R Omelon, Gordon Southam, Charles W Greer, Lyle G Whyte, The ISME Journal (2013) 7, 1211–1226; doi:10.1038/ismej.2013.8.

Climate change and zoonotic infections in the Russian Arctic (Revich et al. 2012) [FULL TEXT]
Abstract: “Climate change in the Russian Arctic is more pronounced than in any other part of the country. Between 1955 and 2000, the annual average air temperature in the Russian North increased by 1.2°C. During the same period, the mean temperature of upper layer of permafrost increased by 3°C. Climate change in Russian Arctic increases the risks of the emergence of zoonotic infectious diseases. This review presents data on morbidity rates among people, domestic animals and wildlife in the Russian Arctic, focusing on the potential climate related emergence of such diseases as tick-borne encephalitis, tularemia, brucellosis, leptospirosis, rabies, and anthrax.”
Citation: Boris Revich, Nikolai Tokarevich, Alan J. Parkinson, Int J Circumpolar Health 2012, 71: 18792 –

On the prospects of microbiological research on mammoth fauna in permafrost (Neustroev, 2012)
Abstract: “Research of mammoth microflora is of current interest in terms of psychrophiles, cryoanabiosis, and the peculiar properties of ecology and evolution of microorganisms. Recovered Bacillus bacteria strains of the mammoths express antagonistic activity against pathogenic and opportunistic microorganisms. Moreover, the strains are antibiotic resistant and salt tolerant. The obtained data is consistent with research on biocoenosis of domestic and wild animals, cryogenic soil, air, atmosphere precipitation, and plants. Having high biological activity, Bacillus bacteria are the dominant group in the microbiocenosis environment in permafrost.”
Citation: M.P. Neustroev, Quaternary International, Volume 255, 26 March 2012, Pages 139–140,

43. Global warming and expanding the range of feral conditions in Yakutia – The coldest region of the North-East Asia (Solomonov et al. 2012)
Abstract: “In Yakutia, there has long been a number of natural foci of infectious human and animal diseases such as tularemia, anthrax, rabies, brucellosis, leptospirosis and others. The circulation of pathogens in nature is closely connected with the peculiarities of natural ecosystems and their animal populations, especially the mass species of birds and mammals and their ecto-and endoparasites. Global warming has caused the expansion to the north of the range of many species of birds and their ectoparasites from the southern parts of the Asia–Pacific region. There was the possibility of the spread causative agent of avian influenza H5N1 dangerous to humans, in-line with those observed in recent decades, global warming and the expansion of the range of animal-carriers and custodians of infectious agents are expanding the range of feral diseases such as rabies, brucellosis,and encephalitis, stable foci of new diseases, including pseudotuberculosis, have appeared in our region. With further advancement of the classical forms of rabies in South Yakutia in the central and northern areas of the Arctic, the counter-propagation form of rabies may occur to the south, with the genetic restructuring of their agents as a result of recombination of genes and new mutations. Melting of permafrost soils and an irrigation of territories can promote “awakening” of the centres, previously widespread in the region, of a malignant anthrax and natural smallpox. There is concern has about the recently established detection of viable, including spore-forming, micro-organisms in the remains of the mammoth fauna of the natural burial sites in the Late Pleistocene permafrost sediments over time. The latter indicates that there is potential for the release of pathogens from the surface of especially dangerous infections from that era (epidemiological echo). Previously, Somov (1974), who worked many years in Chukotka and other regions of the Russian Far East, put forward a hypothesis on the preservation of psychrophilic pathogens infections at low temperatures of the environment in saprophytic state that only if it enters the human body become virulent. In this regard, we suggested in 1980 that “the further development of the northern territories may appear natural foci of new, perhaps previously unknown infectious diseases”. Thus, global warming contributes to increased incidence of especially dangerous infections by expanding the range of animal carriers and disseminators of infection due to possible preservation at low temperatures in the state of saprophytic pathogens in the active state.”
Citation: N.G. Solomonov, V.F. Chernyavskyy, B.M. Kerschengoltz, O.I. Nikiphorov, E.S. Khlebnyy, Cryobiology, Volume 65, Issue 3, December 2012, Pages 353,

Thawing of permafrost may disturb historic cattle burial grounds in East Siberia (Revich & Podolnaya, 2011) [FULL TEXT]
Abstract: “Climate warming in the Arctic may increase the risk of zoonoses due to expansion of vector habitats, improved chances of vector survival during winter, and permafrost degradation. Monitoring of soil temperatures at Siberian cryology control stations since 1970 showed correlations between air temperatures and the depth of permafrost layer that thawed during summer season. Between 1900s and 1980s, the temperature of surface layer of permafrost increased by 2–4°C; and a further increase of 3°C is expected. Frequent outbreaks of anthrax caused death of 1.5 million deer in Russian North between 1897 and 1925. Anthrax among people or cattle has been reported in 29,000 settlements of the Russian North, including more than 200 Yakutia settlements, which are located near the burial grounds of cattle that died from anthrax. Statistically significant positive trends in annual average temperatures were established in 8 out of 17 administrative districts of Yakutia for which sufficient meteorological data were available. At present, it is not known whether further warming of the permafrost will lead to the release of viable anthrax organisms. Nevertheless, we suggest that it would be prudent to undertake careful monitoring of permafrost conditions in all areas where an anthrax outbreak had occurred in the past.”
Citation: Boris A. Revich, Marina A. Podolnaya, Global Health Action 2011, 4: 8482 – DOI: 10.3402/gha.v4i0.8482.

Biogeochemistry of permafrost in Central Yakutia (Brouchkov et al. 2011) [FULL TEXT]
Abstract: “Permafrost is widespread in the Northern Hemisphere and is as old as hundreds of thousands to millions of years. Frozen ground stores living microorganisms which remain unfrozen in the relatively warm environment (–2…–8 °C) but are immobilized and may be about the age of the host permafrost. A strain of Bacillus sp. was isolated from ~3 Ma permafrost and its 16S rDNA sequence was identified. A large group of microorganisms including fungi was isolated from the wedge ice. Permafrost deposits contain invertase, urease, katalase and dehydrogenase.”
Citation: A.V. Brouchkov, V.P. Melnikov, M.V. Schelchkova, G.I. Griva, V.E. Repin, E.V. Brenner, M. Tanaka, EARTH CRYOSPHERE, 2011, Vol. XV, № 4, p. 79-87.

Multi-locus real-time PCR for quantitation of bacteria in the environment reveals Exiguobacterium to be prevalent in permafrost (Rodrigues & Tiedje, 2007) [FULL TEXT]
Abstract: “We developed a multi-locus quantitative PCR approach to minimize problems of precision, sensitivity and primer specificity for quantifying a targeted microbial group in nature. This approach also avoids a systematic error in population quantitation when 16S rRNA genes are used because of copy number heterogeneity. Specific primers were designed to assess the abundance of psychrotrophic and mesophilic Exiguobacterium spp. that excluded the thermophilic members of the genus. The chosen primers targeted genes for DNA gyrase B (gyrB), the beta subunit of the RNA polymerase gene (rpoB) and a hypothetical gene so far found only in this group. The results demonstrate that the multiple primer approach provides a more reliable estimate of population density; that the targeted Exiguobacterium group is found at a median density of 50 000 gene copies per μg of total community DNA in 27 of 29 permafrost soils but was found in only one of the four temperate and tropical soils tested.”
Citation: Rodrigues, D. F. and Tiedje, J. M. (2007), Multi-locus real-time PCR for quantitation of bacteria in the environment reveals Exiguobacterium to be prevalent in permafrost. FEMS Microbiology Ecology, 59: 489–499. doi:10.1111/j.1574-6941.2006.00233.x.

Diversity and distribution of alkaliphilic psychrotolerant bacteria in the Qinghai–Tibet Plateau permafrost region (Zhang et al. 2007)
Abstract: “The Qinghai–Tibet Plateau represents a unique permafrost environment, being a result of high elevation caused by land uplift. And the urgency was that plateau permafrost was degrading rapidly under the current predicted climatic warming scenarios. Hence, the permafrost there was sampled to recover alkaliphilic bacteria populations. The viable bacteria on modified PYGV agar were varied between 102 and 105 CFU/g of dry soil. Forty-eight strains were gained from 18 samples. Through amplified ribosomal DNA restriction analysis (ARDRA) and phylogenetic analyses, these isolates fell into three categories: high G + C gram positive bacteria (82.3%), low G + C gram positive bacteria (7.2%), and gram negative α-proteobacteria (10.5%). The strains could grow at pH values ranging from 6.5 to 10.5 with optimum pH in the range of 9–9.5. Their growth temperatures were below 37°C and the optima ranging from 10 to 15°C. All strains grew well when NaCl concentration was below 15%. These results indicate that there are populations of nonhalophilic alkaliphilic psychrotolerant bacteria within the permafrost of the Qinhai-Tibet plateau. The abilities of many of the strains to produce extracellular protease, amylase and cellulase suggest that they might be of potential value for biotechnological exploitation.”
Citation: Zhang, G., Ma, X., Niu, F. et al. Extremophiles (2007) 11: 415. doi:10.1007/s00792-006-0055-9.

Characterization of the microbial diversity in a permafrost sample from the Canadian high Arctic using culture-dependent and culture-independent methods (Steven et al. 2007) [FULL TEXT]
Abstract: “A combination of culture-dependent and culture-independent methodologies (Bacteria and Archaea 16S rRNA gene clone library analyses) was used to determine the microbial diversity present within a geographically distinct high Arctic permafrost sample. Culturable Bacteria isolates, identified by 16S rRNA gene sequencing, belonged to the phyla Firmicutes, Actinobacteria and Proteobacteria with spore-forming Firmicutes being the most abundant; the majority of the isolates (19/23) were psychrotolerant, some (11/23) were halotolerant, and three isolates grew at −5°C. A Bacteria 16S rRNA gene library containing 101 clones was composed of 42 phylotypes related to diverse phylogenetic groups including the Actinobacteria, Proteobacteria, Firmicutes, Cytophaga – Flavobacteria – Bacteroides, Planctomyces and Gemmatimonadetes; the bacterial 16S rRNA gene phylotypes were dominated by Actinobacteria- and Proteobacteria-related sequences. An Archaea 16S rRNA gene clone library containing 56 clones was made up of 11 phylotypes and contained sequences related to both of the major Archaea domains (Euryarchaeota and Crenarchaeota); the majority of sequences in the Archaea library were related to halophilic Archaea. Characterization of the microbial diversity existing within permafrost environments is important as it will lead to a better understanding of how microorganisms function and survive in such extreme cryoenvironments.”
Citation: Steven, B., Briggs, G., McKay, C. P., Pollard, W. H., Greer, C. W. and Whyte, L. G. (2007), Characterization of the microbial diversity in a permafrost sample from the Canadian high Arctic using culture-dependent and culture-independent methods. FEMS Microbiology Ecology, 59: 513–523. doi:10.1111/j.1574-6941.2006.00247.x.

Microbial ecology and biodiversity in permafrost (Steven et al. 2006) [FULL TEXT]
Abstract: “Permafrost represents 26% of terrestrial soil ecosystems; yet its biology, essentially microbiology, remains relatively unexplored. The permafrost environment is considered extreme because indigenous microorganisms must survive prolonged exposure to subzero temperatures and background radiation for geological time scales in a habitat with low water activity and extremely low rates of nutrient and metabolite transfer. Yet considerable numbers and biodiversity of bacteria exist in permafrost, some of which may be among the most ancient viable life on Earth. This review describes the permafrost environment as a microbial habitat and reviews recent studies examining microbial biodiversity found in permafrost as well as microbial growth and activity at ambient in situ subzero temperatures. These investigations suggest that functional microbial ecosystems exist within the permafrost environment and may have important implications on global biogeochemical processes as well as the search for past or extant life in permafrost presumably present on Mars and other bodies in our solar system.”
Citation: Steven, B., Léveillé, R., Pollard, W.H. et al. Extremophiles (2006) 10: 259. doi:10.1007/s00792-006-0506-3.

Characterization of potential stress responses in ancient Siberian permafrost psychroactive bacteria (Ponder et al. 2005) [FULL TEXT]
Abstract: “Past studies of cold-acclimated bacteria have focused primarily on organisms not capable of sub-zero growth. Siberian permafrost isolates Exiguobacterium sp. 255-15 and Psychrobacter sp. 273-4, which grow at subzero temperatures, were used to study cold-acclimated physiology. Changes in membrane composition and exopolysaccharides were defined as a function of growth at 24, 4 and −2.5 °C in the presence and absence of 5% NaCl. As expected, there was a decrease in fatty acid saturation and chain length at the colder temperatures and a further decrease in the degree of saturation at higher osmolarity. A shift in carbon source utilization and antibiotic resistance occurred at 4 versus 24 °C growth, perhaps due to changes in the membrane transport. Some carbon substrates were used uniquely at 4 °C and, in general, increased antibiotic sensitivity was observed at 4 °C. All the permafrost strains tested were resistant to long-term freezing (1 year) and were not particularly unique in their UVC tolerance. Most of the tested isolates had moderate ice nucleation activity, and particularly interesting was the fact that the Gram-positive Exiguobacterium showed some soluble ice nucleation activity. In general the features measured suggest that the Siberian organisms have adapted to the conditions of long-term freezing at least for the temperatures of the Kolyma region which are −10 to −12 °C where intracellular water is likely not frozen.”
Citation: Monica A. Ponder, Sarah J. Gilmour, Peter W. Bergholz, Carol A. Mindock, Rawle Hollingsworth, Michael F. Thomashow, James M. Tiedje, FEMS Microbiology Ecology, Volume 53, Issue 1, Pp. 103 – 115, DOI:

Long-term persistence of bacterial DNA (Willerslev et al. 2004) [FULL TEXT]
Abstract: “The persistence of bacterial DNA over geological timespans remains a contentious issue. In direct contrast to in vitro based predictions, bacterial DNA and even culturable cells have been reported from various ancient specimens many million years (Ma) old. As both ancient DNA studies and the revival of microorganisms are known to be susceptible to contamination, it is concerning that these results have not been independently replicated to confirm their authenticity. Furthermore, they show no obvious relationship between sample age, and either bacterial composition or DNA persistence, although bacteria are known to differ markedly in hardiness and resistance to DNA degradation. We present the first study of DNA durability and degradation of a broad variety of bacteria preserved under optimal frozen conditions, using rigorous ancient DNA methods. The results demonstrate that non-spore-forming gram-positive (GP) Actinobacteria are by far the most durable, out-surviving endospore-formers such as Bacillaceae and Clostridiaceae. The observed DNA degradation rates are close to theoretical calculations, indicating a limit of ca. 400 thousand years (kyr) beyond which PCR amplifications are prevented by the formation of DNA interstrand crosslinks (ICLs).”
Citation: Eske Willerslev, Anders J. Hansen, Regin Rønn, Tina B. Brand, Ian Barnes, Carsten Wiuf, David Gilichinsky, David Mitchell, Alan Cooper, Current Biology, Volume 14, Issue 1, 6 January 2004, Pages R9–R10,

Reproduction and metabolism at − 10°C of bacteria isolated from Siberian permafrost (Bakermans et al. 2003) [FULL TEXT]
Abstract: “We report the isolation and properties of several species of bacteria from Siberian permafrost. Half of the isolates were spore-forming bacteria unable to grow or metabolize at subzero temperatures. Other Gram-positive isolates metabolized, but never exhibited any growth at − 10°C. One Gram-negative isolate metabolized and grew at − 10°C, with a measured doubling time of 39 days. Metabolic studies of several isolates suggested that as temperature decreased below + 4°C, the partitioning of energy changes with much more energy being used for cell maintenance as the temperature decreases. In addition, cells grown at − 10°C exhibited major morphological changes at the ultrastructural level.”
Citation: Bakermans, C., Tsapin, A. I., Souza-Egipsy, V., Gilichinsky, D. A. and Nealson, K. H. (2003), Reproduction and metabolism at − 10°C of bacteria isolated from Siberian permafrost. Environmental Microbiology, 5: 321–326. doi:10.1046/j.1462-2920.2003.00419.x.

Low-temperature recovery strategies for the isolation of bacteria from ancient permafrost sediments (Vishnivetskaya et al. 2000) [FULL TEXT]
Abstract: “Permafrost represents a unique ecosystem that has allowed the prolonged survival of certain bacterial lineages at subzero temperatures. To better understand the permafrost microbial community, it is important to identify isolation protocols that optimize the recovery of genetically diverse bacterial lineages. We have investigated the impact of different low-temperature isolation protocols on recovery of aerobic bacteria from northeast Siberian permafrost of variable geologic origin and frozen for 5000 to 3 million years. Low-nutrient media enhanced the quantitative recovery of bacteria, whereas the isolation of diverse morphotypes was maximized on rich media. Cold enrichments done directly in natural, undisturbed permafrost led not only to recovery of increased numbers of bacteria but also to isolation of genotypes not recovered by means of liquid low-temperature enrichments. On the other hand, direct plating and growth at 4°C also led to recovery of diverse genotypes, some of which were not recovered following enrichment. Strains recovered from different permafrost samples were predominantly oligotrophic and non-spore-forming but were otherwise variable from each other in terms of a number of bacteriological characteristics. Our data suggest that a combination of isolation protocols from different permafrost samples should be used to establish a culture-based survey of the different bacterial lineages in permafrost.”
Citation: Vishnivetskaya, T., Kathariou, S., McGrath, J. et al. Extremophiles (2000) 4: 165. doi:10.1007/s007920070031.

Metabolic Activity of Permafrost Bacteria below the Freezing Point (Rivkina et al. 2000) [FULL TEXT]
Abstract: “Metabolic activity was measured in the laboratory at temperatures between 5 and −20°C on the basis of incorporation of14C-labeled acetate into lipids by samples of a natural population of bacteria from Siberian permafrost (permanently frozen soil). Incorporation followed a sigmoidal pattern similar to growth curves. At all temperatures, the log phase was followed, within 200 to 350 days, by a stationary phase, which was monitored until the 550th day of activity. The minimum doubling times ranged from 1 day (5°C) to 20 days (−10°C) to ca. 160 days (−20°C). The curves reached the stationary phase at different levels, depending on the incubation temperature. We suggest that the stationary phase, which is generally considered to be reached when the availability of nutrients becomes limiting, was brought on under our conditions by the formation of diffusion barriers in the thin layers of unfrozen water known to be present in permafrost soils, the thickness of which depends on temperature.”
Citation: E. M. Rivkina, E. I. Friedmann, C. P. McKay, D. A. Gilichinsky, Appl. Environ. Microbiol. August 2000 vol. 66 no. 8 3230-3233, doi: 10.1128/AEM.66.8.3230-3233.2000.

Hygienic problems in using permafrost soils for organic waste disposal (Bölter & Höller, 1999) [FULL TEXT]
Abstract: “This paper reviews the risks on hygienic problems in the northern environments by reindeer slaughter and related waste disposals. Such risks are evident from anticipated possible changes in the socio-economic structure in this region and changes in land use and animal keeping. There are several problems going along with different pathogens and their infection ways. Precautions have to be taken especially for those organisms which can live for long times under dormant stages or which form spores.”
Citation: Manfred Bölter, Christiane Höller, Polarforschung 66 (1/2),61 – 65,1996 (erschienen 1999).

Characterization of Viable Bacteria from Siberian Permafrost by 16S rDNA Sequencing (Shi et al. 1997) [FULL TEXT]
Abstract: “Viable bacteria were found in permafrost core samples from the Kolyma-Indigirka lowland of northeast Siberia. The samples were obtained at different depths; the deepest was about 3 million years old. The average temperature of the permafrost is −10°C. Twenty-nine bacterial isolates were characterized by 16S rDNA sequencing and phylogenetic analysis, cell morphology, Gram staining, endospore formation, and growth at 30°C. The majority of the bacterial isolates were rod shaped and grew well at 30°C; but two of them did not grow at or above 28°C, and had optimum growth temperatures around 20°C. Thirty percent of the isolates could form endospores. Phylogenetic analysis revealed that the isolates fell into four categories: high-GC Gram-positive bacteria, β-proteobacteria, γ-proteobacteria, and low-GC Gram-positive bacteria. Most high-GC Gram-positive bacteria and β-proteobacteria, and all γ-proteobacteria, came from samples with an estimated age of 1.8–3.0 million years (Olyor suite). Most low-GC Gram-positive bacteria came from samples with an estimated age of 5,000–8,000 years (Alas suite).”
Citation: Shi, T., Reeves, R., Gilichinsky, D. et al. Microb Ecol (1997) 33: 169. doi:10.1007/s002489900019.

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