The stromatolites at Shark Bay, Western Australia, are analogues of some of the oldest evidence of life on Earth. The aim of this study was to identify and spatially characterize the specific microbial communities associated with Shark Bay intertidal columnar stromatolites. Conventional culturing methods and construction of 16S rDNA clone libraries from community genomic DNA with both universal and specific PCR primers were employed. The estimated coverage, richness and diversity of stromatolite microbial populations were compared with earlier studies on these ecosystems. The estimated coverage for all clone libraries indicated that population coverage was comprehensive. Phylogenetic analyses of stromatolite and surrounding seawater sequences were performed in ARB with the Greengenes database of full-length non-chimaeric 16S rRNA genes. The communities identified exhibited extensive diversity. The most abundant sequences from the stromatolites were a-and c-proteobacteria (58%), whereas the cyanobacterial community was characterized by sequences related to the genera Euhalothece, Gloeocapsa, Gloeothece, Chroococcidiopsis, Dermocarpella, Acaryochloris, Geitlerinema and Schizothrix. All clones from the archaeal-specific clone libraries were related to the halophilic archaea; however, no archaeal sequence was identified from the surrounding seawater. Fluorescence in situ hybridization also revealed stromatolite surfaces to be dominated by unicellular cyanobacteria, in contrast to the sub-surface archaea and sulphate-reducing bacteria. This study is the first to compare the microbial composition of morphologically similar stromatolites over time and examine the spatial distribution of specific microorganismic groups in these intertidal structures and the surrounding seawater at Shark Bay. The results provide a platform for identifying the key microbial physiology groups and their potential roles in modern stromatolite morphogenesis and ecology.

Recently, halite and sulfate evaporate rocks have been discovered on Mars by the NASA rovers, Spirit and Opportunity. It is reasonable to propose that halophilic microorganisms could have potentially flourished in these settings. If so, biomolecules found in microorganisms adapted to high salinity and basic pH environments on Earth may be reliable biomarkers for detecting life on Mars. Therefore, we investigated the potential of Resonance Raman (RR) spectroscopy to detect biomarkers derived from microorganisms adapted to hypersaline environments. RR spectra were acquired using 488.0 and 514.5 nm excitation from a variety of halophilic archaea, including Halobacterium salinarum NRC-1, Halococcus morrhuae, and Natrinema pallidum. It was clearly demonstrated that RR spectra enhance the chromophore carotenoid molecules in the cell membrane with respect to the various protein and lipid cellular components. RR spectra acquired from all halophilic archaea investigated contained major features at approximately 1000, 1152, and 1505 cm ؊1 . The bands at 1505 cm ؊1 and 1152 cm ؊1 are due to in-phase C¨C ( 1 ) and C-C stretching ( 2 ) vibrations of the polyene chain in carotenoids. Additionally, in-plane rocking modes of CH 3 groups attached to the polyene chain coupled with C-C bonds occur in the 1000 cm ؊1 region. We also investigated the RR spectral differences between bacterioruberin and bacteriorhodopsin as another potential biomarker for hypersaline environments. By comparison, the RR spectrum acquired from bacteriorhodopsin is much more complex and contains modes that can be divided into four groups: the C¨C stretches (1600-1500 cm ؊1 ), the CCH in-plane rocks (1400-1250 cm ؊1 ), the C-C stretches (1250-1100 cm ؊1 ), and the hydrogen out-of-plane wags (1000-700 cm ؊1 ). RR spectroscopy was shown to be a useful tool for the analysis and remote in situ detection of carotenoids from halophilic archaea without the need for large sample sizes and complicated extractions, which are required by analytical techniques such as high performance liquid chromatography and mass spectrometry.

Tardigrades inhabiting terrestrial environments exhibit extraordinary resistance to ionizing radiation and UV radiation although little is known about the mechanisms underlying the resistance. We found that the terrestrial tardigrade Ramazzottius varieornatus is able to tolerate massive doses of UVC irradiation by both being protected from forming UVC-induced thymine dimers in DNA in a desiccated, anhydrobiotic state as well as repairing the dimers that do form in the hydrated animals. In R. varieornatus accumulation of thymine dimers in DNA induced by irradiation with 2.5 kJ/m2 of UVC radiation disappeared 18 h after the exposure when the animals were exposed to fluorescent light but not in the dark. Much higher UV radiation tolerance was observed in desiccated anhydrobiotic R. varieornatus compared to hydrated specimens of this species. On the other hand, the freshwater tardigrade species Hypsibius dujardini that was used as control, showed much weaker tolerance to UVC radiation than R. varieornatus, and it did not contain a putative phrA gene sequence. The anhydrobiotes of R. varieornatus accumulated much less UVC-induced thymine dimers in DNA than hydrated one. It suggests that anhydrobiosis efficiently avoids DNA damage accumulation in R. varieornatus and confers better UV radiation tolerance on this species. Thus we propose that UV radiation tolerance in tardigrades is due to the both high capacities of DNA damage repair and DNA protection, a two-pronged survival strategy.

Extremophilic archaea were stained with the LIVE/DEAD BacLight kit under conditions of high ionic strength and over a pH range of 2.0 to 9.3. The reliability of the kit was tested with haloarchaea following permeabilization of the cells. Microorganisms in hypersaline environmental samples were detectable with the kit, which suggests its potential application to future extraterrestrial halites.Numerous archaea (archaebacteria) thrive in hostile conditions such as salt brines, hot springs, and acidic or alkaline environments (20). Their membrane lipids differ from those of (eu)bacteria and other organisms because they contain ether linkages instead of ester linkages, are composed of regularly branched phytanyl and biphytanyl chains instead of fatty acyl chains, and possess glycerol ethers, which are sn-2,3 substituted rather than sn-1,2 substituted (13). These properties are thought to contribute to the greater chemical stability of archaeal lipids (13,22) and the generally low permeability of archaeal membranes (5,14). The LIVE/DEAD BacLight bacterial viability kit (henceforth referred to as the LIVE/DEAD kit) from Molecular Probes is widely used for the enumeration of bacteria (2,8,12) and provides an indication of the fraction of active cells. The kit consists of two nucleic acid stains: SYTO 9, which penetrates most membranes freely, and propidium iodide, which is highly charged and normally does not permeate cells but does penetrate damaged membranes. Simultaneous application of both dyes therefore results in green fluorescence of viable cells with an intact membrane, whereas dead cells, because of a compromised membrane, show intense red fluorescence (10). Archaea have not been treated with the LIVE/DEAD kit, except for one psychrophilic isolate (15); in view of the low permeability of their membranes and their existence in habitats that often border on the physicochemical limits of life, it was of interest to determine if the LIVE/DEAD kit would detect extremophilic archaea and provide reliable information about their viability.Archaeal strains were purchased from the DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany), except Halobacterium sp. strain NRC-1 ATCC 700922, which was obtained from LGC, London, United Kingdom. Haloarchaea were grown at 37°C in M2 medium (27), except Halococcus and haloalkaliphiles, which were grown in M2S medium (25) or Tindall's medium (26), respectively, and Halobacterium sp. strain NRC-1, which was grown in ATCC medium no. 2185 (http://www.lgcpromochem .com/atcc/). Acidianus brierleyi DSM 1651T (21) and Sulfolobus acidocaldarius DSM 639 T (31) were grown at 65 to 70°C in DSM medium no. 150 (http://www.dsmz.de/media/med150 .htm) and ATCC medium no. 1723 (http://www.atcc.org /SearchCatalogs/Search.cfm), respectively. The dyes of LIVE /DEAD BacLight kit L-7012 (Molecular Probes, Inc., Eugene, Oreg.) were freshly diluted with water and used as previously described (3, 10). Staining with 4Ј,6Ј-diamidino-2-phenylindole (DAPI) was done as described b...

BIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). The design of the multiuser facility supports—among others—the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs and terrestrial mineral mixtures were then exposed to space and to simulated Mars-like conditions by way of the EXPOSE-R2 facility. In this special issue, we present the first set of data obtained in reference to our investigation into the habitability of Mars and limits of life. This project was initiated and implemented by the BIOMEX group, an international and interdisciplinary consortium of 30 institutes in 12 countries on 3 continents. Preflight tests for sample selection, results from ground-based simulation experiments, and the space experiments themselves are presented and include a complete overview of the scientific processes required for this space experiment and postflight analysis. The presented BIOMEX concept could be scaled up to future exposure experiments on the Moon and will serve as a pretest in low Earth orbit.