Carnobacterium pleistocenium

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Classification

Higher order taxa

Domain: Bacteria Phylum: Bacillota Class: Bacilli Order: Lactobacillales Family: Carnobacteriaceae Genus: Carnobacterium Species: Carnobacterium pleistocenium

Species

NCBI: [1]

Carnobacterium Pleistocenium

2. Description and significance

Carnobacterium pleistocenium is a facultative anaerobe, psychrophilic bacterium that was isolated from permafrost in Alaska dating back to approximately 32,000 years ago [1]. It is part of the genus Carnobacterium, which currently includes eight species that all have capabilities of growing in low temperatures [2]. C. pleistocenium is Gram-positive, motile, rod-shaped, and non- spore forming [2]. The unique characteristics of the genus make it an educational organism for scientific research relating to biotechnology, climate change, bio-preservatives and space exploration [3][4]. C. pleistocenium is capable of "springing to life" after prolonged dormancy, sensitive to certain antibiotics, and can grow under low-pressure and anoxic conditions, making it promising for biotechnological applications like cold-active enzyme production and bioremediation [2][5][6][7].

3. Genome structure

The whole genome of C. pleistocenium is 2.7 Mb containing 2,507 protein coding genes with a G+C content of 35% 8 . The melting temperature of the total genomic strain is 62ºC 2 . C. pleistocenium contains unique genes coding for cold shock proteins (CSPs) and flagellar assembly proteins 2 . Knowledge of genes and DNA sequences of the Carnobacterium genus is limited, and the identification of genes associated with certain carnobacterial metabolic traits is primarily derived from specific strains, implying a potential strain-specific nature for these genes 4 . 16S rRNA gene sequence analysis found that the FTR1 isolated strain of C. pleistocenium shared 99.8 % similarity with Carnobacterium alterfunditum, but the DNA hybridization only showed 39% relatedness, as well as the genome size and G+C content being different between the two 2 .

4. Cell structure

C. pleistocenium is a Gram-positive, motile bacteria with small rod-shaped (bacilli) morphology approximately 0·7–0·8 μm wide and 1·0–1·5 μm long 2 . It is non-spore forming 2 . On growth mediums, C. pleistocenium occur solely, in pairs or irregular curved chains 2 . Cold shock proteins (CSPs) help C. pleistocenium survive and quickly adapt to harsh environments 9 . The cell wall of C. Pleistocenium is gram-positive, which is thick and continuous, composed of mostly peptidoglycans 2 .

5. Metabolism & Life Cycle

C. pleistocenium has undergone metabolic adaptations that allow it to survive in low temperature environments. C. Pleistocenium is a facultative anaerobic that utilizes oxygen when available, but can thrive in anoxic CO2 rich environments2. C. pleistocenium exhibits chemoorganoheterotroph metabolism that uses sugars, as well as some products of proteolysis for metabolism2, producing acetate, ethanol, and CO22. C. pleistocenium has the metabolic ability to ferment sugars to produce lactic acid, however this pathway is not found in all strains. Permafrost contains large amounts of organic carbon, which are metabolized by C. pleistocenium when thawed, facilitating its growth2.

C. Pleistocenium grows in pH range 6.5–9.5 and has optimum growth at pH 7.3–7.5. The temperature range for growth is 0–28 °C, with optimal growth at 24 °C2. C. Pleistocenium grows best on d-trehalose, which is of the disaccharide class produced by fungi, yeasts, and similar organisms2. C. Pleistocenium contains specific enzymes and proteins that allow it to ‘come to life’ when permafrost layers are thawed because it can readily metabolize the organic products produced as the layers thaw2,5.

6. Ecology

C. pleistocenium receives its name from the location and geological age of the sample isolated from permafrost in Alaska from the Pleistocene era and is considered a biological indicator of permafrost biogeochemistry and genesis2. Isolated solely from the ice core permafrost, it is unknown where else C. pleistocenium may be found, as other species of the genus have been discovered in vacuum-packed meat and are capable of growing in refrigerated food10. C. pleistocenium can be classified as an indicator species because of its rare characteristics which help to determine the conditions of the environment it is found, such as its ability to metabolize thawed organic carbon. As a facultative anaerobe, C. pleistocenium utilizes available oxygen when present, which reduces oxygen levels, causing the development of ideal conditions for obligate anaerobes to grow2.

Global warming-induced forest fires and permafrost melting are reshaping the microbial communities, specifically altering nutrient cycling of carbon and nitrogen, potentially fostering conditions for C. pleistocenium to adapt to the changing environment11.

7. Pathology

C. pleistocenium is sensitive to ampicillin, kanamycin, gentamicin, tetracycline and rifampicin and chloramphenicol2. C. pleistocenium has not yet shown pathogenic traits or natural transmission mechanisms, but other species of the genus carry such traits, specifically in fish. Carnobacterium piscicola has pathogenic features in rainbow trout and salminoids 3,10. These findings call for reevaluation of Gram-positive bacilli belonging to Lactobacillus-Carnobacterium as they may have potential to be pathogenic and highly virulent3. However, other species such as Carnobacterium inhibens, found in salmon, inhibit growth of fish pathogens acting as a probiotic 10,12. Thus, it is difficult to conclude the potential pathogenic or probiotic features of C. pleistocenium.

8. Current Research

Current research is being done to understand the potential for cold-tolerant organisms to exist on planets like Mars. Under low oxygen, low pressure, and low temperature conditions, C. pleistocenium enters a state of dormancy and returns back to normal activity when introduced to more mild conditions6. This has led scientists to speculate if ancient microbes on Mars could return to life after being in a state of latency in the ice in Mars, as C. pleistocenium was able to tolerate permanently-frozen conditions for thousands of years5. It is not yet known how C. Pleistocenium may react with other extraterrestrial factors, such as increased solar UV radiation and low organic matter levels in soil. Continued research into psychro-tolerant bacteria like C. pleistocenium suggest the possibility for extraterrestrial microbes to be found in the frozen permafrost and glaciers on other planets and moons in the Milky Way and beyond5. C. pleistocenium is also being used to study how microbial communities in permafrost conditions are affected by global warming and rapid heating caused by forest fires. Microbes such as C. pleistocenium are crucial for carbon recycling, and understanding their responses to these changes is critical for potential strategies for the conservation of carbon biomass going forward11. C. pleistocenium is able to metabolize the products of permafrost thaw, aiding in current understanding of how microbial communities thrive or fail to thrive in major environmental changes.

9. References

[1] Wikipedia contributors. (2022, November 10). Carnobacterium pleistocenium. In Wikipedia, The Free Encyclopedia. 15:54, September 25, 2023, from https://en.wikipedia.org/w/index.php?title=Carnobacterium_pleistocenium&oldid=11211 54928

[2] Pikuta, E. V., Marsic, D., Bej, A., Tang, J., Krader, P., & Hoover, R. B. (2005). Carnobacterium pleistocenium sp. nov., a novel psychrotolerant, facultative anaerobe isolated from permafrost of the Fox Tunnel in Alaska. International journal of systematic and evolutionary microbiology 55:473–478.

[3] Toranzo, A., Romalde, J., Nunez, S., Figueras, A., & Barja, J. (1993). An epizootic in farmed, market-sized rainbow trout in Spain caused by a strain of carnobacterium piscicola of unusual virulence. Diseases of Aquatic Organisms 17:87–99.

[4] Leisner, J. J., Laursen, B. G., Prévost, H., Drider, D., & Dalgaard, P. (2007). Carnobacterium: positive and negative effects in the environment and in foods. FEMS microbiology reviews 31:592–613.

[5] NASA/Marshall Space Flight Center. (2005, March 3). NASA Astrobiologist Identifies New 'Extreme' Life Form. ScienceDaily. September 22, 2023 from www.sciencedaily.com/releases/2005/02/050224093714.htm

[6] Nicholson, W. L., Krivushin, K., Gilichinsky, D., & Schuerger, A. C. (2013). Growth of Carnobacterium spp. from permafrost under low pressure, temperature, and anoxic atmosphere has implications for Earth microbes on Mars. Proceedings of the National Academy of Sciences of the United States of America 110:666–671.

[7] OpenAI. (2023). ChatGPT [Large language model].

[8] DOE Joint Genome Institute. (2014). Carnobacterium Pleistocenium FTR1 Genome Assembly Asm74428v1 - NCBI - NLM. National Center for Biotechnology Information, U.S. National Library of Medicine. October 27, 2023 from www.ncbi.nlm.nih.gov/datasets/genome/GCF_000744285.1/.

[9] Bae W, Xia B, Inouye M, Severinov K. (2000.) Escherichia coli CspA-family RNA chaperones are transcription antiterminators. Proc Natl Acad Sci USA 97:7784–7789.

[10] Kim, M. S., Roh, S. W., Nam, Y. D., Yoon, J. H., & Bae, J. W. (2009). Carnobacterium jeotgali sp. nov., isolated from a Korean traditional fermented food. International journal of systematic and evolutionary microbiology, 59(Pt 12), 3168–3171.

[11] Taş, N., Prestat, E., McFarland, J. et al. (2014). Impact of fire on active layer and permafrost microbial communities and metagenomes in an upland Alaskan boreal forest.

[12] Nicholson, W.L., Davis, C.L., Shapiro, N. et al. (2016). An improved high-quality draft genome sequence of Carnobacterium inhibens subsp. inhibens strain K1T. Stand in Genomic Sci 11: 65.

[13] Rakitin, A., Beletsky, A., Mardanov, A. et al. (2020) Prokaryotic community in Pleistocene ice wedges of Mammoth Mountain. Extremophiles 24:93-105.

[14] Ivancic, T., Jamnik, P. & Stopar, D. Cold shock CspA and CspB protein production during periodic temperature cycling in Escherichia coli. BMC Res Notes 6, 248 (2013). https://doi.org/10.1186/1756-0500-6-248

10. Authorship Statement

R.K. and I.P. contributed to classification, descriptions, and significance. I.P. drafted genome structure I.P and M.T drafted cell structure. Z.H. and M.T. drafted metabolism and life cycle. I.P. and R.K. edited and revised. Z.H. and I.P. drafted ecology content. Additionally edited and revised with assistance of M.T. I.P. drafted pathology notes. D.R. and R.K. edited and revised. D.R. formulated current research. R.K. and I.P. worked with ChatGPT to provide revisions to the draft.

Edited by [Isabella Puljic, Rena Khoury, Marc Tjin, Zaydra Harper, and Demi Ring], students of [mailto:jmbhat@bu.edu Jennifer Bhatnagar] for [http://www.bu.edu/academics/cas/courses/cas-bi-311/ BI 311 General Microbiology], 2023, Boston University. [[Category:Pages edited by students of Jennifer Bhatnagar at Boston University]]