Halophilic Archaea: Life with Desiccation, Radiation and Oligotrophy over Geological Times.

Halophilic archaebacteria (Haloarchaea) can survive extreme desiccation, starvation and radiation, sometimes apparently for millions of years. Several of the strategies that are involved appear specific for Haloarchaea (for example, the formation of halomucin, survival in fluid inclusions of halite), and some are known from other prokaryotes (dwarfing of cells, reduction of ATP). Several newly-discovered haloarchaeal strategies that were inferred to possibly promote long-term survival-halomucin, polyploidy, usage of DNA as a phosphate storage polymer, production of spherical dormant stages-remain to be characterized in detail.

Thaumarchaeal ammonium oxidation and evidence for a nitrogen cycle in a subsurface radioactive thermal spring in the Austrian Central Alps.

Previous studies had suggested the presence of ammonium oxidizing Thaumarchaeota as well as nitrite oxidizing Bacteria in the subsurface spring called Franz Josef Quelle (FJQ), a slightly radioactive thermal mineral spring with a temperature of 43.6-47°C near the alpine village of Bad Gastein, Austria. The microbiological consortium of the FJQ was investigated for its utilization of nitrogen compounds and the putative presence of a subsurface nitrogen cycle.

Properties of Halococcus salifodinae, an Isolate from Permian Rock Salt Deposits, Compared with Halococci from Surface Waters.

Halococcus salifodinae BIpT DSM 8989T, an extremely halophilic archaeal isolate from an Austrian salt deposit (Bad Ischl), whose origin was dated to the Permian period, was described in 1994. Subsequently, several strains of the species have been isolated, some from similar but geographically separated salt deposits. Hcc.

Survival of spores of the UV-resistant Bacillus subtilis strain MW01 after exposure to low-earth orbit and simulated martian conditions: data from the space experiment ADAPT on EXPOSE-E.

In the space experiment "Molecular adaptation strategies of microorganisms to different space and planetary UV climate conditions" (ADAPT), bacterial endospores of the highly UV-resistant Bacillus subtilis strain MW01 were exposed to low-Earth orbit (LEO) and simulated martian surface conditions for 559 days on board the European Space Agency's exposure facility EXPOSE-E, mounted outside the International Space Station. The survival of B. subtilis MW01 spores from both assays (LEO and simulated martian conditions) was determined by a colony-formation assay after retrieval.

Responses of haloarchaea to simulated microgravity.

Various effects of microgravity on prokaryotes have been recognized in recent years, with the focus on studies of pathogenic bacteria. No archaea have been investigated yet with respect to their responses to microgravity. For exposure experiments on spacecrafts or on the International Space Station, halophilic archaea (haloarchaea) are usually embedded in halite, where they accumulate in fluid inclusions.

UV photoreactions of the extremely haloalkaliphilic euryarchaeon Natronomonas pharaonis.

The objective of this study was to investigate the photobiological responses of the haloalkaliphilic euryarchaeon Natronomonas pharaonis to environmentally relevant polychromatic UV radiation, simulating either the present UV radiation climate (lambda>290 nm) or that of the early Earth (lambda>220 nm), and to monochromatic UVC radiation (lambda=254 nm) for comparison with the literature data. UV-induced bipyrimidine DNA photoproducts were determined using a sensitive and accurate HPLC tandem mass spectrometry assay, allowing to identify and quantify each type of photoproducts formed in the DNA of a UV-irradiated halophilic archaeon. The thymine cytosine (TC) pyrimidine (6-4) pyrimidone photoproduct and the TC cyclobutane pyrimidine dimer accounted for almost 80% of the total induced DNA photolesions, regardless of the wavelength range tested.

Identification of polyhydroxyalkanoates in Halococcus and other haloarchaeal species.

Polyhydroxyalkanoates (PHAs) are accumulated in many prokaryotes. Several members of the Halobacteriaceae produce poly-3-hydroxybutyrate (PHB), but it is not known if this is a general property of the family. We evaluated identification methods for PHAs with 20 haloarchaeal species, three of them isolates from Permian salt.

Raman spectroscopy as a potentialmethod for the detection of extremely halophilic archaea embedded in halite in terrestrial and possibly extraterrestrial samples.

Evidence for the widespread occurrence of extraterrestrial halite, particularly on Mars, has led to speculations on the possibility of halophilic microbial forms of life; these ideas have been strengthened by reports of viable haloarchaea from sediments of geological age (millions of years). Raman spectroscopy, being a sensitive detection method for future astrobiological investigations onsite, has been used in the current study for the detection of nine different extremely halophilic archaeal strains which had been embedded in laboratory-made halite crystals in order to simulate evaporitic conditions. The cells accumulated preferentially in tiny fluid inclusions, in simulation of the precipitation of salt in natural brines.

Halorubrum chaoviator sp. nov., a haloarchaeon isolated from sea salt in Baja California, Mexico, Western Australia and Naxos, Greece.

Three halophilic isolates, strains Halo-G*T, AUS-1 and Naxos II, were compared. Halo-G* was isolated from an evaporitic salt crystal from Baja California, Mexico, whereas AUS-1 and Naxos II were isolated from salt pools in Western Australia and the Greek island of Naxos, respectively. Halo-G*T had been exposed previously to conditions of outer space and survived 2 weeks on the Biopan facility.

Investigating the effects of simulated martian ultraviolet radiation on Halococcus dombrowskii and other extremely halophilic archaebacteria.

The isolation of viable extremely halophilic archaea from 250-million-year-old rock salt suggests the possibility of their long-term survival under desiccation. Since halite has been found on Mars and in meteorites, haloarchaeal survival of martian surface conditions is being explored. Halococcus dombrowskii H4 DSM 14522(T) was exposed to UV doses over a wavelength range of 200-400 nm to simulate martian UV flux.

Crenarchaeota and their role in the nitrogen cycle in a subsurface radioactive thermal spring in the Austrian Central Alps.

Previous results from a 16S rRNA gene library analysis showed high diversity within the prokaryotic community of a subterranean radioactive thermal spring, the "Franz-Josef-Quelle" (FJQ) in Bad Gastein, Austria, as well as evidence for ammonia oxidation by crenarchaeota. This study reports further characterization of the community by denaturing gradient gel electrophoresis (DGGE) analysis, fluorescence in situ hybridization (FISH), and semiquantitative nitrification measurements. DGGE bands from three types of samples (filtered water, biofilms on glass slides, and naturally grown biofilms), including samples collected at two distinct times (January 2005 and July 2006), were analyzed.

Biodegradation of fuel oil hydrocarbons by a mixed bacterial consortium in sandy and loamy soils.

The aerobic degradation of light fuel oil in sandy and loamy soils by an environmental bacterial consortium was investigated. Soils were spiked with 1 or 0.1% of oil per dry weight of soil.

Searching for life on Mars: selection of molecular targets for ESA's aurora ExoMars mission.

The European Space Agency's ExoMars mission will seek evidence of organic compounds of biological and non-biological origin at the martian surface. One of the instruments in the Pasteur payload may be a Life Marker Chip that utilizes an immunoassay approach to detect specific organic molecules or classes of molecules. Therefore, it is necessary to define and prioritize specific molecular targets for antibody development.

Halococcus qingdaonensis sp. nov., a halophilic archaeon isolated from a crude sea-salt sample.

A Gram-negative, extremely halophilic, coccoid archaeal strain, CM5(T), was isolated from a crude sea-salt sample collected near Qingdao, China. The organism grew optimally at 35-40 degrees C and pH 6.0 in the presence of 20 % (w/v) NaCl.

Communities of archaea and bacteria in a subsurface radioactive thermal spring in the Austrian Central Alps, and evidence of ammonia-oxidizing Crenarchaeota.

Scanning electron microscopy revealed great morphological diversity in biofilms from several largely unexplored subterranean thermal Alpine springs, which contain radium 226 and radon 222. A culture-independent molecular analysis of microbial communities on rocks and in the water of one spring, the "Franz-Josef-Quelle" in Bad Gastein, Austria, was performed. Four hundred fifteen clones were analyzed.

Reclassification of Pseudomonas beijerinckii Hof 1935 as Chromohalobacter beijerinckii comb. nov., and emended description of the species.

Pseudomonas beijerinckii (type strain DSM 7218(T)=ATCC 19372(T)=NCIMB 9041(T)) was isolated from salted beans and was first described by Hof in 1935. 16S rRNA gene sequence comparisons demonstrated its close relatedness (>97-99 %) to species of the genus Chromohalobacter. A recent isolate from salted herrings originating from the Baltic Sea, strain 3b, also clustered phylogenetically within this genus.

Extremely halophilic archaea and the issue of long-term microbial survival.

Halophilic archaebacteria (haloarchaea) thrive in environments with salt concentrations approaching saturation, such as natural brines, the Dead Sea, alkaline salt lakes and marine solar salterns; they have also been isolated from rock salt of great geological age (195-250 million years). An overview of their taxonomy, including novel isolates from rock salt, is presented here; in addition, some of their unique characteristics and physiological adaptations to environments of low water activity are reviewed. The issue of extreme long-term microbial survival is considered and its implications for the search for extraterrestrial life.

Evaluation of the LIVE/DEAD BacLight kit for detection of extremophilic archaea and visualization of microorganisms in environmental hypersaline samples.

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.

Halobacterium noricense sp. nov., an archaeal isolate from a bore core of an alpine Permian salt deposit, classification of Halobacterium sp. NRC-1 as a strain of H. salinarum and emended description of H. salinarum.

Two rod-shaped haloarchaeal strains, A1 and A2, were isolated from a bore core from a salt mine in Austria. The deposition of the salt is thought to have occurred during the Permian period (225-280 million years ago). The 16S rDNA sequences of the strains were 97.

Halococcus dombrowskii sp. nov., an archaeal isolate from a Permian alpine salt deposit.

Several extremely halophilic coccoid archaeal strains were isolated from pieces of dry rock salt that were obtained three days after blasting operations in an Austrian salt mine. The deposition of the salt is thought to have occurred during the Permian period (225-280 million years ago). On the basis of their polar-lipid composition, 16S rRNA gene sequences, cell shape and growth characteristics, the isolates were assigned to the genus Halococcus.

Very similar strains of Halococcus salifodinae are found in geographically separated permo-triassic salt deposits.

The authors have previously isolated a novel extremely halophilic archaeon, Halococcus salifodinae Blp, from Austrian rock salt deposited about 250 million years ago. In this study they compared strain Blp with two other halococci isolated independently from geographically distant salt deposits of similar age, and with two recent isolates (N1 and H2) from the same site as strain Blp. Strain BG2/2 was from a salt mine in Germany and strain Br3 from a halite deposit in England; both resembled Hc.