A total of four Martian samples, one surface and one subsurface sample at each of the two Viking landing sites, Chryse Planitia and Utopia Planitia, have been analyzed for organic compounds by a gas chromatograph-mass spectrometer. In none of these experiments could organic material of Martian origin be detected at detection limits generally of the order of parts per billion and for a few substances closer to parts per million. The evolution of water and carbon dioxide, but not of other inorganic gases, was observed upon heating the sample to temperatures of up to 500 C. The absence of organic compounds seems to preclude their production on the planet at rates that exceed the rate of their destruction. It also makes it unlikely that living systems that behave in a manner similar to terrestrial biota exist, at least at the two Viking landing sites.

The search for organic substances and inorganic volatile compounds in the surface of Mars

For many years, the extreme environment of the Antarctic Dry Valleys was thought to play host to just a few viable microorganisms. However, as Cary and colleagues explain, recent work has led to the identification of a complex community structure that is able to survive in one of the coldest and driest places on Earth. The arid soils of the Antarctic Dry Valleys constitute some of the oldest, coldest, driest and most oligotrophic soils on Earth. Early studies suggested that the Dry Valley soils contained, at best, very low levels of viable microbiota. However, recent applications of molecular methods have revealed a dramatically contrasting picture — a very wide diversity of microbial taxa, many of which are uncultured and taxonomically unique, and a community that seems to be structured solely by abiotic processes. Here we review our understanding of these extreme Antarctic terrestrial microbial communities, with particular emphasis on the factors that are involved in their development, distribution and maintenance in these cold desert environments.

On the rocks: the microbiology of Antarctic Dry Valley soils.

Two surface samples collected from the Chryse Planitia region of Mars were heated to temperatures up to 500 degrees C, and the volatiles that they evolved were analyzed with a gas chromatograph-mass spectrometer. Only water and carbon dioxide were detected. This implies that organic compounds have not accumulated to the extent that individual components could be detected at levels of a few parts in 10(9) by weight in our samples. Proposed mechanisms for the accumulation and destruction of organic compounds are discussed in the light of this limit.

Search for organic and volatile inorganic compounds in two surface samples from the chryse planitia region of Mars.

Recent applications of molecular genetics to edaphic microbial communities of the McMurdo Dry Valleys and elsewhere have rejected a long-held belief that Antarctic soils contain extremely limited microbial diversity. The Inter-Valley Soil Comparative Survey aims to elucidate the factors shaping these unique microbial communities and their biogeography by integrating molecular genetic approaches with biogeochemical analyses. Although the microbial communities of Dry Valley soils may be complex, there is little doubt that the ecosystem's food web is relatively simple, and evidence suggests that physicochemical conditions may have the dominant role in shaping microbial communities. To examine this hypothesis, bacterial communities from representative soil samples collected in four geographically disparate Dry Valleys were analyzed using molecular genetic tools, including pyrosequencing of 16S rRNA gene PCR amplicons. Results show that the four communities are structurally and phylogenetically distinct, and possess significantly different levels of diversity. Strikingly, only 2 of 214 phylotypes were found in all four valleys, challenging a widespread assumption that the microbiota of the Dry Valleys is composed of a few cosmopolitan species. Analysis of soil geochemical properties indicated that salt content, alongside altitude and Cu2+, was significantly correlated with differences in microbial communities. Our results indicate that the microbial ecology of Dry Valley soils is highly localized and that physicochemical factors potentially have major roles in shaping the microbiology of ice-free areas of Antarctica. These findings hint at links between Dry Valley glacial geomorphology and microbial ecology, and raise previously unrecognized issues related to environmental management of this unique ecosystem.

/pdf/the-inter-valley-soil-comparative-survey-the-ecology-of-dry-afjvvdfll1.pdf

The Inter-Valley Soil Comparative Survey: the ecology of Dry Valley edaphic microbial communities.

Algae occur in nearly all terrestrial environments on earth and are invariably encountered both on and beneath soil surfaces. The algal flora of the soil includes members of the Cyanochloronta, Chlorophycophyta, Euglenophycophyta, Chrysophycophyta, and Rhodophycophyta. Thirty-eight genera of prokaryotic and 147 genera of eukaryotic algae include terrestrial species, the majority of which are edaphic. Whereas systematic nomenclature of blue-green algae adheres to traditional classification based upon morphological features, proper taxonomic treatment of eukaryotic soil algae is predicated on standard methods of culture and interpretation of physiological attributes, plant mass characteristics, and morphological properties of axenic clones. While knowledge of the physiological ecology of soil algae is primarily based on laboratory evidence, it is well established that solar radiation, water, and temperature are the most important abiotic factors governing their distribution, metabolism, and life history strategies. Biotic interactions are often as important, whereas ionic factors (including pH), oxidation-reduction potential, and soil texture are less important, if only because their influences are less well understood. Algae play an important role in primary and secondary plant community succession by acting as an integral part of the colonial synusium. The principal functional attributes of algal communities in soil include primary production, dinitrogen fixation, and stabilization of aggregates. Although as many as 108 algae per gram have been documented, soils commonly support between 103 and 104 per gram. As an avenue for the incorporation of carbon and nitrogen and for minimizing erosion through stabilization of aggregates, algae are valuable in agriculture. Although manipulation of edaphic algal populations in temperate countries is of novel occurence, their successful use in India as a means for reclaiming saline soils and as a source of fertilizer nitrogen is well documented. Soil algae are affected by synthetic pesticides and pollutants. In general, most herbicides, fungicides, and soil fumigants are detrimental to soil algae while most insecticides are not. Algae have been utilized as biological assay organisms for anticipating crop response to both fertilizers and pesticides because of their biochemical similarity to higher plants and their quick generation time. As future research with soil algae leads to a greater awareness of their importance in soil, it might be anticipated that manipulation of populations in agricultural systems of temperate regions will become more widespread with consideration of the potential benefits of soil algae made by scientists in other disciplines.

The systematics and ecology of soil algae

Microbiology, ecology and microclimatology of soil sites in Dry Valleys of southern Victoria land, Antarctica

Soil microbial ecology of Wheeler Valley, Antarctica.

Soil microbial and ecological studies in southern Victoria land

1 T h i s paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract no. NAS 7-100, sponsored by the National Aeronautics and Space Adminis­ tration. Logistic support and facilities for the portion of the study performed in Antarctica were arranged by the Office of Antarctic Programs, National Science Foundation. of 1967-1968 have been examined at the Jet Propul­ sion Laboratory to determine their toxicity. During a traverse made with Prof. Robert E. Benoit of the Virginia Polytechnic Institute, 18 soil samples were collected at depths up to four inches near the head of the Matterhorn Glacier in the Asgard Range (Fig. 2 ) , on a ridge east of Rhone Glacier at 1,867 m, and in an intersecting east-west valley that extends from the Matterhorn to Lake Bonney in Taylor Valley at an elevation of 107 m. Two additional samples, nos. 632 and 639, were obtained on the northern side of the Asgard Range, above Wright Valley.

https://epub.ub.uni-muenchen.de/3441/1/3441.pdf

Roy E. Cameron

Papers

Microbiology, ecology and microclimatology of soil sites in Dry Valleys of southern Victoria land, Antarctica

Soil microbial ecology of Wheeler Valley, Antarctica.

Soil microbial and ecological studies in southern Victoria land

Soil toxicity in Antarctic Dry Valleys