Microbial ecology of absolute extreme environments, astrobiology, experimental and molecular taxonomy of cyanobacteria (blue-green algae). Many of these studies were carried out in collaboration with the late Dr. Roseli O. Friedmann.

Microbial ecology of absolute extreme environments. Organisms in extreme environments are adapted to the conditions of their surroundings, such as low or high temperatures and high salinity, but physiological adaptation has its limits, and in some environments on Earth, conditions are beyond these limits. Such "absolute extreme" environments are not lifeless but are inhabited by organisms living "on the edge" near the absolute limits of their physiological potential. Under these conditions, even a slight deterioration in the environment may result in death and extinction. The study of such environments yields information on the limits of life on Earth, as well as on the process of extinction. This research is directly relevant to astrobiology, the study of the possibility of extraterrestrial life. Specifically, extreme cold and dry environments, like the Antarctic desert, are the closest terrestrial analogs to conditions on early Mars. The study of absolute extreme environments yields important information for the reconstruction of events that may have led to the extinction of life on early Mars, as well as for design of life-detection methods for use on Mars.

Dr. Friedmann's research approach was based on the integration of field work and laboratory investigations. He conducted active field programsin polar (Arctic and Antarctic) deserts, in the Negev desert (Israel), Gobi (Mongolia), and the Atacama desert (Chile). The practical organization of field work was made possible through the Polar Desert Research Center. The Culture Collection of Microorganisms from Extreme Environments (CCMEE) maintains living cultures for research purposes. The CCMEE was located at Florida State University until Dr. Friedmann's retirement. It is now maintained at the University of Oregon (see http://cultures.uoregon.edu/default.htm). Laboratory work included ecophysiological measurements, diverse microbiological techniques, scanning and transmission electron microscopy, light microscopy, and other methods.

Antarctic and Arctic deserts. The Ross desert (McMurdo Dry Valleys) of Antarctica is an approximately 5000-km² ice-free area of high mountains and deep valleys. Temperatures are almost always below the freezing point, and low temperature is the most important ecological limiting factor. In the mountains, the rock surfaces are almost lifeless, but rich communities of microorganisms exist under the surface, colonizing the air spaces inside porous sandstone rocks. Dr. Friedmann studied this peculiar ecosystem for over 20 years. Many microbial inhabitants (algae, fungi, cyanobacteria, heterotrophic bacteria) of the Ross Desert were isolated in culture for use in experimental laboratory studies. The cultures are available from the CCMEE. The nanoclimate (the climate in the millimeter range, the environment of microorganisms) was continuously monitored for six years by automated satellite-mediated weather stations. One central goal in these studies was to measure the environmental parameters that limit life in the Antarctic desert. In the geological past, climate fluctuations resulted in extinctions, and fossilized communities bear witness of past periods of cooling in the general climate. Similar studies were also conducted on Ellesmere Island (Canada), an Arctic equivalent of the Antarctic Ross Desert.

Negev desert (Israel) and Gobi desert (Mongolia). Dr. Friedmann studied these two extremely arid deserts on a comparative basis, as the environmental limiting factor, lack of water, is similar in the two, whereas other climatic factors are very different.

Microorganisms, mostly drought-tolerant cyanobacteria, live either inside rocks (in the Negev) or under stones of the so-called desert pavement, small stones covering the desert floor (Gobi and Negev). They survive there because of their ability to tolerate long periods of desiccation.

Atacama desert (Chile). One of the most interesting deserts on Earth, the Atacama is so dry that in some parts no rain has ever been recorded. Dr. Friedmann's studies were intended to find out whether totally lifeless "absolute deserts" exist in such places. If so, these places constitute an absolute limit for life on Earth. A special feature of the Atacama is the presence of "fog oases," localized areas where fog accumulates even though there is no rain, and where succulent higher plants and specialized microorganisms use atmospheric humidity as their sole water source. The cytological mechanism by which this use is achieved is unclear, and Dr. Friedmann's research efforts were centered on the solution of this problem.

Bacteria in Arctic and Antarctic permafrost. The taxonomy and physiology of viable bacteria in Arctic and Antarctic permafrost (frozen soil) up to several million years old were studied in cooperation with Russian scientists. Metabolic activity in permafrost bacteria was quantified at temperatures as low as -20°C.

Research on cyanobacteria. The molecular taxonomy and ecophysiology of cyanobacteria living in absolute extreme environments were studied.

Astrobiology. Magnetite crystal chains (fossil traces of magnetotactic bacteria) in terrestrial fossil lakebeds and in the meteorite ALH84001.

McKay, C. P., E. I. Friedmann, R. A. Wharton, and W. L. Davis. 1992. History of water on Mars: a biological perspective. Advances in Space Research 12(4):231-238.

Friedmann, E. I., editor. 1993. Antarctic Microbiology. Wiley-Liss, New York. 634 pp.

Friedmann, E. I., L. Kappen, M. A. Meyer, and J. A. Nienow. 1993. Long-term productivity in the cryptoendolithic microbial community of the Ross Desert, Antarctica. Microbial Ecology 25:51-69.

Friedmann, E. I. 1994. Permafrost as microbial habitat. In: D. A. Gilichinsky (ed.): Viable Microorganisms in Permafrost. Russian Academy of Sciences, Pushchino, Russia, pp. 21-26.

Friedmann, E. I., and R. Ocampo-Friedmann. 1995. A primitive cyanobacterium as pioneer microorganism for terraforming Mars. Advances in Space Research 15(3):243-246.

Grilli-Caiola, M., D. Billi and E. I. Friedmann. 1996. Effect of desiccation on envelopes of the cyanobacterium Chroococcidiopsis sp. (Chroococcales). Eur. J. Phycol. 31:97-105.

Shi, T, R. H. Reeves, D. A. Gilichinsky, and E. I. Friedmann. 1997. Characterization of viable bacteria from Siberian permafrost by 16S rDNA sequencing. Microbial Ecology 33:169-179.

Wilson, G. S., P. Braddock, S. L. Foreman, E. I. Friedmann, E. M. Rivkina, J. P. Chanton, D. A. Gilichinsky, D. G. Fyodorov-Davidov, V. E. Ostroumov, V. Sorokovikov, and M. C. Wizevich. 1998. Coring for microbial records of Antarctic climate. Antarct. J. U.S. Rev. 1996 31(2):83-84).

McKay, C. P., M. R. Mellon, and E. I. Friedmann. 1998. Soil temperatures and stability of ice-cemented ground in the McMurdo Dry Valleys, Antarctica. Antarct. Science 10:31-38.

Sun, H. and E. I. Friedmann. (1998). Growth on geological time scales in the Antarctic cryptoendolithic microbial community. Geomicrobiol. J. 16:193-202.

Friedmann, E. I., Wierzchos, J., Ascaso, C., and Winklhofer, M. 2001. Chains of magnetite crystals in the meteorite ALH 84001: evidence of biogenous origin. Proc. Natl. Acad. Sci. US. 98:2176–2181.

Billi, D., Friedmann, E. I., Helm, R. F., and Potts, M. 2001. Gene transfer in the desiccation-tolerant cyanobacterium Chrooroccidiopsis sp. J. Bacteriol. 183:2298–2305.

Matsumoto, G. I., Nienow, J. A., Friedmann, E. I., Sekiya, E., and Ocampo–Friedmann, R. 2004. Biogeochemical features of lipids in endolithic microbial communities in the Ross Desert (McMurdo Dry Valleys), Antarctica. Cell. Mol. Biol. 50:591–604.

Friedmann, E. I., and Sun, H. J. 2005. Communities adjust their temperature optima by shifting producer-to-consumer ratio, shown in lichens as models I. Hypothesis. Microb. Ecol. 49:523–527.

Sun, H. J., and Friedmann, E. I. 2005. Communities adjust their temperature optima by shifting producer-to-consumer ratio, shown in lichens as models II. Experimental verification. Microb. Ecol. 49:528–535.

Selbmann, L., de Hoog, G. S., Mazzaiglia, A., Friedmann, E. I., and Onofri, S. 2005. Fungi at the end of life: cryptoendolithic black fungi from Antarctic deserts. Studies Mycol. 51:1–32.

Warren-Rhodes, K. A., Rhodes, K. L., Pointing, S. B., Ewing, S., Lacap, D. C., Gómez-Silva, B., Amundson, R., Friedmann, E. I., and McKay, C. P. In press. Hypolithic cyanobacteria, dry limit of photosynthesis and microbial ecology in the hyperarid Atacama Desert. Microb. Ecol.

Friedmann, E. I., and Thistle, A. B. (eds.). 1993. Antarctic Microbiology. Wiley Liss, New York. 634 pp. Taxonomic and geographic index to book.