E. Imre Friedmann

Endolithic blue-green algae in the dry valleys: primary producers in the antarctic desert ecosystem.

Endolithic unicellular blue-green algae occur under the surface of orthoquartzite rocks in the dry valleys of southern Victoria Land, Antarctica. This report of primary producers in the Antarctic desert ecosystem suggests that, in future efforts to detect life in extraterrestrial (for example, martian) environments, scientists should consider the possible existence of endolithic life forms.

Temperature and Moisture Conditions for Life in the Extreme Arid Region of the Atacama Desert: Four Years of Observations Including the El Niño of 1997–1998

The Atacama along the Pacific Coast of Chile and Peru is one of the driest and possibly oldest deserts in the world. It represents an extreme habitat for life on Earth and is an analog for life in dry conditions on Mars. We report on four years (September 1994-October 1998) of climate and moisture data from the extreme arid region of the Atacama. Our data are focused on understanding moisture sources and their role in creating suitable environments for photosynthetic microorganisms in the desert surface. The average air temperature was 16.5 degrees C and 16.6 degrees C in 1995 and 1996, respectively. The maximum air temperature recorded was 37.9 degrees C, and the minimum was -5.7 degrees C. Annual average sunlight was 336 and 335 W m(-2) in 1995 and 1996, respectively. Winds averaged a few meters per second, with strong föhn winds coming from the west exceeding 12 m s(-1). During our 4 years of observation there was only one significant rain event of 2.3 mm, which occurred near midnight local time. We suggest that this event was a rainout of a heavy fog. It is of interest that the strong El Niño of 1997-1998 brought heavy rainfall to the deserts of Peru, but did not bring significant rain to the central Atacama in Chile. Dew occurred at our station frequently following high nighttime relative humidity, but is not a significant source of moisture in the soil or under stones. Groundwater also does not contribute to surface moisture. Only the one rain event of 2.3 mm resulted in liquid water in the soil and beneath stones for a total of only 65-85 h over 4 years. The paucity of liquid water under stones is consistent with the apparent absence of hypolithic (under-stone) cyanobacteria, the only known primary producers in such extreme deserts.

Effects of water stress on cryptoendolithic cyanobacteria from hot desert rocks

Four strains of Chroococcidiopsis and one Chroococcus, all isolated from extreme arid desert rocks, and one marine Chroococcus, were subjected to water stress using both matric and osmotic control methods. For all Chroococcidiopsis strains, photosynthetic rates decreased with decreasing water potential. After 24h preincubation the decrease was linear but after 72h there was a sharp drop below-3400 kPa (aw≏0.976). In contrast, the two Chroococcus strains showed optimum photosynthesis between-3000 and-4000 KPa. It appears, therefore, that Chroococcidiopsis in deserts may have a different survival strategy in response to aridity than Chroococcus (rare in deserts).Absolute rates of 14CO2 uptake were higher in matric than in osmotic control systems. It is suggested that, in a matric experimental system, the water status is more representative of the natural conditions in arid environments.The consistent differences between different strains in their response to water stress suggest that this character in Cyanobacteria may be of taxonomic significance.

Nitrogen economy of endolithic microbial communities in hot and cold deserts.

The source of combined nitrogen in endolithic microbial communities was studied in samples from desert localities in North and South America, the Middle East, South Africa, and Antarctica. Nitrogen fixation (acetylene reduction) seems to occur only exceptionally. Evidence suggests that, in general, the nitrogen source for endolithic microorganisms in deserts is abiotically fixed nitrogen produced by atmospheric electric discharges (lightning or aurorae), conveyed to the rock by atmospheric precipitation. Nitrogen is apparently not a limiting factor in these low-productivity communities. An incomplete nitrogen cycle seems to be present which includes the following pathways: supply of nitrates and ammonia from the atmosphere; decomposition of organic matter to ammonia; reassimilation of ammonia; ammonia volatilization; loss of organic matter through weathering (only in certain Antarctic rocks); biological nitrogen fixation (exceptional).

A primitive cyanobacterium as pioneer microorganism for terraforming Mars

The primitive characteristics of the cyanobacterium Chroococcidiopsis suggest that it represents a very ancient type of the group. Its morphology is simple but shows a wide range of variability, and it resembles certain Proterozoic microfossils. Chroococcidiopsis is probably the most desiccation-resistant cyanobacterium, the sole photosynthetic organism in extreme arid habitats. It is also present in a wide range of other extreme environments, from Antarctic rocks to thermal springs and hypersaline habitats, but it is unable to compete with more specialized organisms. Genetic evidence suggests that all forms belong to a single species. Its remarkable tolerance of environmental extremes makes Chroococcidiopsis a prime candidate for use as a pioneer photosynthetic microorganism for terraforming of Mars. The hypolithic microbial growth form (which lives under stones of a desert pavement) could be used as a model for development of technologies for large-scale Martian farming.

Life on Mars - How it disappeared (if it was ever there)

The cryptoendolithic microbial community in the Ross Desert (McMurdo Dry Valleys) of Antarctica exists at temperatures significantly below the temperature optima of the primary producers. Surviving near the limit of their physiological adaptability, the organisms are under severe environmental stress, so further deterioration in the environment results in cell damage and death. The sequence of events leading to extinction is considered to be a terrestrial analog for disappearance of possible life on early Mars. Progressive stages of cell damage and death in the Ross Desert material are documented with transmission electron microscopy.

Gene Transfer to the Desiccation-Tolerant Cyanobacterium Chroococcidiopsis

The coccoid cyanobacterium Chroococcidiopsis dominates microbial communities in the most extreme arid hot and cold deserts. These communities withstand constraints that result from multiple cycles of drying and wetting and/or prolonged desiccation, through mechanisms which remain poorly understood. Here we describe the first system for genetic manipulation of Chroococcidiopsis. Plasmids pDUCA7 and pRL489, based on the pDU1 replicon of Nostoc sp. strain PCC 7524, were transferred to different isolates of Chroococcidiopsis via conjugation and electroporation. This report provides the first evidence that pDU1 replicons can be maintained in cyanobacteria other than Nostoc and Anabaena. Following conjugation, both plasmids replicated in Chroococcidiopsis sp. strains 029, 057, and 123 but not in strains 171 and 584. Both plasmids were electroporated into strains 029 and 123 but not into strains 057, 171, and 584. Expression of P(psbA)-luxAB on pRL489 was visualized through in vivo luminescence. Efficiencies of conjugative transfer for pDUCA7 and pRL489 into Chroococcidiopsis sp. strain 029 were approximately 10(-2) and 10(-4) transconjugants per recipient cell, respectively. Conjugative transfer occurred with a lower efficiency into strains 057 and 123. Electrotransformation efficiencies of about 10(-4) electrotransformants per recipient cell were achieved with strains 029 and 123, using either pDUCA7 or pRL489. Extracellular deoxyribonucleases were associated with each of the five strains. Phylogenetic analysis, based upon the V6 to V8 variable regions of 16S rRNA, suggests that desert strains 057, 123, 171, and 029 are distinct from the type species strain Chroococcidiopsis thermalis PCC 7203. The high efficiency of conjugative transfer of Chroococcidiopsis sp. strain 029, from the Negev Desert, Israel, makes this a suitable experimental strain for genetic studies on desiccation tolerance.

FINE STRUCTURE OF CAPITULAR FILAMENTS IN THE COENOCYTIC GREEN ALGA PENICILLUS1,2,3

Capitular filaments of Penicillus capitatus contain a large central vacuole. The parietal cytoplasm is densely packed, devoid of chloroplasts in the growing tip, and becomes convoluted and sponge‐like as extensions of the vacuole penetrate the cytoplasm in mature portions of the filament. Structure of organelles and their distribution in the filament are described. The vacuole contains a variety of inclusions, such as membranous configurations, spherical bodies, electron dense bodies, and calcium oxalate monohydrate crystals, each of the latter surrounded by a chamber associated with microtubules. Endophytic bacteria are present throughout the vacuole and occasionally in the tip cytoplasm. Some vacuolar components of P. pyriformis are described for comparison.

Calcium oxalate crystals in the aragonite-producing green alga penicillus and related genera.

Calcium oxalate crystals occur in the marine green algae Penicillus, Rhipocephalus, and Udotea, known as producers of sedimentary aragonite needles. In contrast to the externally deposited aragonite crystals which are generally < 15 micrometers long, the oxalate crystals are larger (up to 150 micrometers) and are located in the vacuolar system of the plant. No calcium oxalate was found in the related but noncalcifying genera Avrainvillea and Cladocephalus.

Ecology and biology of microfungi from Antarctic rocks and soils

Abstract Cryptoendolithic microbial communities, living in porous sandstone rocks in the McMurdo Dry Valleys (Ross Desert) of Southern Victoria Land, Antarctica, were found within weathered pegmatite rocks in Northern Victoria Land, and the first endemic Antarctic fungal genus Friedmanniomyces endolithicus anam.‐gen. and sp. nov. was isolated from this community. Selected microfungi from these communities and from soil were examined for the production of extracellular enzymes and antibiotic substances. The cryptoendolithic strain CCFEE 5001 was particularly remarkable for consistent glycosidase activity, coupled with barely detectable growth. Chitinase activity was highest in the soil mi‐crofungus Verticillium cfr. lecanii (CCFEE 5003). This strain and its purified chitinase were active on Mucor plumbeus, Cladospori‐um cladosporioides, Aspergillus versicolor, and Penicillium verrucosum, producing mycelial damage and cell lysis. The strain CCFEE 5020, isolated from rocks, showed antibiotic activity against Pseudomonas putida, Sarcina sp., Bacillus subtilis, and Escherichia coli, under the test conditions. Good antibiotic activity was produced in the temperature range of 5° to 25° C, pH 4.0, agitation at 700 rpm, and areation at 1.0 vvm, in media containing 0.5% substrate sugar, though this supported only minimal growth. The investigation of soil microfungi in contrasting sites at the BIOTAS area at Edmonson Point indicated that both the presence of bird colonies and changes in temperature and UV exposure obtained by using plastic cloches influenced species composition and density. A ‘Culture Collection of Fungi from Extreme Environments’ (CCFEE) has been established at the University of Tuscia, housing fungal strains from Antarctica.