Cum definim mediile „extreme” și pe locuitorii lor?
Din perspectiva noastră, mediile habitabile caracterizate de valori ale parametrilor fizici și chimici care depășesc cu mult pe cele considerate „optime” pentru viața omului pot fi definite drept „extreme”, iar organismele care le populează – „extremofile”. Mai jos vă oferim câteva exemple menite să susțină definițiile enunțate.
| Parametrii | Exemple de ecosisteme extreme | Tipuri de extremofile |
| Temperature (oC) <10
>50 |
Calote glaciare, permafrost;
Izvoare termale |
Criofile (psihrofile)
Termofile |
| Presiune (hidrostatică (atm) >100 | Zonele marine abisale | Barofile (piezofile) |
| pH<4
pH>9 |
Izvoare acide, ape de mină;
Lacuri şi soluri alcaline |
Acidofile
Alcalifile |
| Salinitate (%) >3 (30 g sare /l) | Lacuri şi soluri sărate | Halofile |
| Altele: Activitatea apei foarte scăzută (aw) <0,900;
radiații ionizante (Gy) > 1000; concentrații mari de metale grele, solvenți organici, gaze reducătoare (CH4, H2S) sau altele (CO/CO2);
Medii oligotrofe |
Suprafețe expuse iradiației solare intense (deșerturi,suprafețe artificiale);
Habitate puternic poluate; Habitate cu manifestări geotermale și emisii/acumulări de gaze geo- /biogenice; Habitate endolitice/din adâncimea scoarței terestre |
Xerofile
Radiorezistente Metalorezistente Tolerante la solvenți
Extrem-oligotrofe |
| Condiții extreme multiple | Izvoare termale si acide, lacuri termale, sărate și alcaline; habitate reci și uscate; habitate abisale cu manifestări geotermale; habitate saline poluate cu metale grele etc. | Poliextremofile |
How we define the ‘extreme’ environments’ and their inhabitants?
In our view, the habitable milieus characterized by physical and chemical parameters with values largely exceeding those considered ‘optimal’ for human life are defined as ‘extreme’ and their inhabitants, as ‘extremophiles’. Examples supporting this definition are given below.
| Parameters | Examples of ’extreme ecosystems’ | Extremophile subtype |
| Temperature (oC) <10
>50 |
Glaciers, permafrost;
Hot springs |
Cryophiles (psychrophiles)
Thermophiles |
| Pressure (hydrostatic, atm) >100 | Deep=sea zones | Barophiles (piezophiles) |
| pH<4
pH>9 |
Acid springs, acidic mine drainages;
Alkaline waters and soils |
Acidophiles
Alkaliphiles |
| Salinity (%) >3 (30 g salts /l) | Brines and saline soils | Halophiles |
| Others:
Low water activity (aw): <0.900; High ionizing radiation (Gy): >1000;
High heavy metal, organic solvents, reducing gasses (CH4, H2S) or CO/CO2 concentrations;
Extremely low nutrient concentration |
Dessicated (arid) and/ or UV/ cosmic rays-exposed natural/ artificial surfaces;
Highly polluted systems; Geothermal environments; geo-/biogenic gas-rich systems; Endolithic/ deep subsurface habitats |
Xerophiles
Radioresistants
Metaloresistant Solvent tolerants
Extreme oligotrophs |
| Multiple extreme conditions | Hot acidic springs; hot saline-alkaline waters; cold and dry high latitude deserts; deep-sea active volcanic areas; highly polluted saline systems, etc. | Polyextremophiles |
Some relevant references for those who are interested in extreme ecosystems, their dwellers and relevance for pure and applied life sciences.
Adams, M. W., Perler, F. B., & Kelly, R. M. (1995). Extremozymes: expanding the limits of biocatalysis. Bio/technology, 13(7), 662-668.
Andrei, A. Ş., Banciu, H. L., & Oren, A. (2012). Living with salt: metabolic and phylogenetic diversity of archaea inhabiting saline ecosystems. FEMS microbiology letters, 330(1), 1-9.
Cavicchioli, R. (2002). Extremophiles and the search for extraterrestrial life. Astrobiology, 2(3), 281-292.
Dance, A. (2020). Studying life at the extremes. Nature, 587(7832), 165-166.
Hough, D. W., & Danson, M. J. (1999). Extremozymes. Current opinion in chemical Biology, 3(1), 39-46.
Jørgensen, B. B., & Boetius, A. (2007). Feast and famine—microbial life in the deep-sea bed. Nature Reviews Microbiology, 5(10), 770-781.
Madigan, M. T., & Oren, A. (1999). Thermophilic and halophilic extremophiles. Current opinion in microbiology, 2(3), 265-269.
Merino, N., Aronson, H. S., Bojanova, D. P., Feyhl-Buska, J., Wong, M. L., Zhang, S., & Giovannelli, D. (2019). Living at the Extremes: Extremophiles and the Limits of Life in a Planetary Context. Frontiers in microbiology, 10, 780.
Pikuta, E. V., Hoover, R. B., & Tang, J. (2007). Microbial extremophiles at the limits of life. Critical reviews in microbiology, 33(3), 183-209.
Rothschild, L. J., & Mancinelli, R. L. (2001). Life in extreme environments. Nature, 409(6823), 1092-1101.
Seckbach, J., Oren, A., & Stan-Lotter, H. (2013). Polyextremophiles. Dordrecht: Springer. doi, 10, 978-94.
Stetter, K. O. (2006). Hyperthermophiles in the history of life. Philosophical Transactions of the Royal Society B: Biological Sciences, 361(1474), 1837-1843.
Van Den Burg, B. (2003). Extremophiles as a source for novel enzymes. Current opinion in microbiology, 6(3), 213-218.