scholarly journals Physicochemical Parameters Limiting Growth of Debaryomyces hansenii in Solutions of Hygroscopic Compounds and Their Effects on the Habitability of Martian Brines

Life ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1194
Author(s):  
Jacob Heinz ◽  
Vita Rambags ◽  
Dirk Schulze-Makuch
Keyword(s):  
Liquid Water ◽  
Freezing Point ◽  
Debaryomyces Hansenii ◽  
Solute Concentration ◽  
Stress Factors ◽  
Additional Stress ◽  
Dry Valleys ◽  
Halotolerant Yeast ◽  
Rich Media ◽  
Colony Forming Units

The availability of liquid water is a prerequisite for all lifeforms on Earth. In hyperarid subzero environments like the Dry Valleys in Antarctica or the near-subsurface of Mars liquid water might be provided temporarily by hygroscopic substances that absorb water from the atmosphere and lower the freezing point of water. To evaluate the potential of hygroscopic compounds to serve as a habitat, it is necessary to explore the microbial tolerances towards these substances and their life-limiting properties. Here we present a study investigating the tolerances of the halotolerant yeast Debaryomyces hansenii to various solutes. Growth experiments were conducted via counting colony forming units (CFUs) after inoculation of a liquid growth medium containing a specific solute concentration. The lowest water activities (aw) enabling growth were determined to be ~0.83 in glycerol and fructose-rich media. For all other solutes the growth-enabling aw was higher, due to additional stress factors such as chaotropicity and ionic strength. Additionally, we found that the solute tolerances of D. hansenii correlate with both the eutectic freezing point depressions and the deliquescence relative humidities of the respective solutes. Our findings strongly impact our understanding of the habitability of solute-rich low aw environments on Earth and beyond.

scholarly journals A New Record for Microbial Perchlorate Tolerance: Fungal Growth in NaClO4 Brines and its Implications for Putative Life on Mars

Life ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 53 ◽  
Author(s):  
Jacob Heinz ◽  
Tim Krahn ◽  
Dirk Schulze-Makuch
Keyword(s):  
Liquid Water ◽  
Sodium Perchlorate ◽  
Debaryomyces Hansenii ◽  
Fungal Growth ◽  
Natural Environments ◽  
Microbial Life ◽  
Purpureocillium Lilacinum ◽  
Halotolerant Yeast ◽  
Colony Forming Units ◽  
Microbial Habitat

The habitability of Mars is strongly dependent on the availability of liquid water, which is essential for life as we know it. One of the few places where liquid water might be found on Mars is in liquid perchlorate brines that could form via deliquescence. As these concentrated perchlorate salt solutions do not occur on Earth as natural environments, it is necessary to investigate in lab experiments the potential of these brines to serve as a microbial habitat. Here, we report on the sodium perchlorate (NaClO4) tolerances for the halotolerant yeast Debaryomyces hansenii and the filamentous fungus Purpureocillium lilacinum. Microbial growth was determined visually, microscopically and via counting colony forming units (CFU). With the observed growth of D. hansenii in liquid growth medium containing 2.4 M NaClO4, we found by far the highest microbial perchlorate tolerance reported to date, more than twice as high as the record reported prior (for the bacterium Planococcus halocryophilus). It is plausible to assume that putative Martian microbes could adapt to even higher perchlorate concentrations due to their long exposure to these environments occurring naturally on Mars, which also increases the likelihood of microbial life thriving in the Martian brines.

scholarly journals Detection of ammonia on Pluto’s surface in a region of geologically recent tectonism

2019 ◽  
Vol 5 (5) ◽  
pp. eaav5731 ◽  
Author(s):  
C. M. Dalle Ore ◽  
D. P. Cruikshank ◽  
S. Protopapa ◽  
F. Scipioni ◽  
W. B. McKinnon ◽  
...  
Keyword(s):  
Liquid Water ◽  
Freezing Point ◽  
Charged Particles ◽  
Tectonic Activity ◽  
Absorption Bands ◽  
Geological Process ◽  
New Horizons ◽  
Extensional Tectonic ◽  
Ultraviolet Photons ◽  
Recent Deposition

We report the detection of ammonia (NH3) on Pluto’s surface in spectral images obtained with the New Horizons spacecraft that show absorption bands at 1.65 and 2.2 μm. The ammonia signature is spatially coincident with a region of past extensional tectonic activity (Virgil Fossae) where the presence of H2O ice is prominent. Ammonia in liquid water profoundly depresses the freezing point of the mixture. Ammoniated ices are believed to be geologically short lived when irradiated with ultraviolet photons or charged particles. Thus, the presence of NH3 on a planetary surface is indicative of a relatively recent deposition or possibly through exposure by some geological process. In the present case, the areal distribution is more suggestive of cryovolcanic emplacement, however, adding to the evidence for ongoing geological activity on Pluto and the possible presence of liquid water at depth today.

scholarly journals Helicopter-borne transient electromagnetics in high-latitude environments: An application in the McMurdo Dry Valleys, Antarctica

Geophysics ◽  
2016 ◽  
Vol 81 (1) ◽  
pp. WA87-WA99 ◽  
Author(s):  
Neil Foley ◽  
Slawek Tulaczyk ◽  
Esben Auken ◽  
Cyril Schamper ◽  
Hilary Dugan ◽  
...  
Keyword(s):  
Liquid Water ◽  
Ross Sea ◽  
Mcmurdo Dry Valleys ◽  
Subsurface Water ◽  
Dry Valleys ◽  
Depth Of Penetration ◽  
Temporary Streams ◽  
Low Resistivity ◽  
Subsurface Environments ◽  
Ideal Tool

The McMurdo Dry Valleys are a polar desert in coastal Antarctica, where glaciers, permafrost, ice-covered lakes, and ephemeral summer streams coexist. Liquid water is found at the surface only in lakes and in the temporary streams that feed them. Past geophysical exploration has yielded ambiguous results regarding the presence of subsurface water. In 2011, we used a helicopter-borne, time-domain electromagnetic (TDEM) sensor to map resistivity in the subsurface across the Dry Valleys. The airborne electromagnetic (AEM) method excels at finding subsurface liquid water in polar deserts, where water remains liquid under cold conditions if it is sufficiently saline, and therefore electrically conductive. Over the course of 26 h of helicopter time, we covered large portions of the Dry Valleys and vastly increased our geophysical understanding of the subsurface, particularly with respect to water. Our data show extensive subsurface low-resistivity layers approximately 150–250 m below the surface and beneath higher resistivity layers. We interpret the low-resistivity layers as geologic materials containing freeze-concentrated or “cryoconcentrated” hyper saline brines lying beneath glaciers and frozen permafrost. These brines appeared to be contiguous with surface lakes, subglacial regions, and the Ross Sea, which could indicate a regional-hydrogeologic system, wherein solutes might be transported between surface reservoirs by ionic diffusion and subsurface flow. The presence of such brines underneath glaciers might have implications for glacier movement. Systems such as this, where brines exist beneath glacial ice and frozen permafrost, may exist elsewhere in coastal Antarctica; AEM resistivity is an ideal tool to find and survey them. Our application of TDEM demonstrates that in polar subsurface environments containing conductive brines, such a diffusive electromagnetic method is superior to radar surveying in terms of depth of penetration and ability to differentiate hydrogeologic conditions.

scholarly journals Ice composition evidence for the formation of basal ice from lake water beneath a cold-based Antarctic glacier

1999 ◽  
Vol 28 ◽  
pp. 277-281 ◽  
Author(s):  
R. D. Lorrain ◽  
S. J. Fitzsimons ◽  
M. J. Vandergoes ◽  
M. Stiévenard
Keyword(s):  
Lake Water ◽  
Freezing Point ◽  
Isotope Composition ◽  
Gas Content ◽  
Dry Valleys ◽  
Basal Ice ◽  
Lake Bottom ◽  
Ice Flows ◽  
Classical Models ◽  
Glacier Ice

AbstractEntrainment of debris by cold-based glaciers having basal temperatures as low as — 17°C can be observed in the Dry Valleys of south Victoria Land, Antarctica. The classical models developed to explain debris incorporation at the glacier base are inappropriate in such cases, since the basal temperature is well below the freezing point. An alternative model, based on the presence of ice-marginal lakes, has recently been proposed by one of the authors (S. F.). In this model, transient wet-base conditions can occur as ice flows onto the unfrozen sediments of the lake bottom, creating conditions favorable to the entrainment of sediments and to ice accretion by water freezing.Here we describe a situation where this model is consistent with an ice-composition study of the basal part of Suess Glacier, Taylor Valley. The stable isotope composition indicates that water freezing, most probably lake water, plays a major role in the formation of the basal ice layers. Total gas content of this basal ice is considerably depleted when compared to meteoric glacier ice, in accordance with a rejection mechanism during freezing. Its gas composition, strongly enriched in CO2, is also indicative of the presence of a former liquid phase.

scholarly journals Saccharomyces cerevisiae adapted to grow in the presence of low-dose rapamycin exhibit altered amino acid metabolism

2018 ◽  
Author(s):  
Duygu Dikicioglu ◽  
Elif Dereli Eke ◽  
Serpil Eraslan ◽  
Stephen G Oliver ◽  
Betul Kirdar
Keyword(s):  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Low Dose ◽  
Acid Metabolism ◽  
Immunosuppressive Drug ◽  
Stress Factors ◽  
Additional Stress ◽  
Key Factor ◽  
Cell Densities ◽  
Growth And Aging

ABSTRACTRapamycin is a potent inhibitor of the highly conserved TOR kinase, the nutrient-sensitive controller of growth and aging. It has been utilised as a chemotherapeutic agent due to its anti-proliferative properties and as an immunosuppressive drug, and is also known to extend lifespan in a range of eukaryotes from yeast to mammals. However, the mechanisms through which eukaryotic cells adapt to sustained exposure to rapamycin have not yet been thoroughly investigated. Here, S. cerevisiae response to long-term rapamycin exposure was investigated by identifying the physiological, transcriptomic and metabolic differences observed for yeast populations inoculated into low-dose rapamycin-containing environment. The effect of oxygen availability and acidity of extracellular environment on this response was further deliberated by controlling or monitoring the dissolved oxygen level and pH of the culture. Yeast populations grown in the presence of rapamycin reached higher cell densities complemented by an increase in their chronological lifespan, and these physiological adaptations were associated with a rewiring of the amino acid metabolism, particularly that of arginine. The ability to synthesise amino acids emerges as the key factor leading to the major mechanistic differences between mammalian and microbial TOR signalling pathways in relation to nutrient recognition. Furthermore, oxygen levels and extracellular acidity of the culture were observed to conjointly affect yeast populations, virtually acting as coupled physiological effectors; cells were best adapted when maximal oxygenation of the culture was maintained in slightly acidic pH, any deviation necessitated more extensive readjustment to additional stress factors.

scholarly journals Transport and Utilization of Hexoses and Pentoses in the Halotolerant Yeast Debaryomyces hansenii

1999 ◽  
Vol 65 (8) ◽  
pp. 3594-3598 ◽  
Author(s):  
Alexandra Nobre ◽  
Cândida Lucas ◽  
Cecília Leão
Keyword(s):  
Growth Parameters ◽  
Carbon Sources ◽  
Debaryomyces Hansenii ◽  
Transport Systems ◽  
Facilitated Diffusion ◽  
Xylose Transport ◽  
Halotolerant Yeast ◽  
Consumption Rates ◽  
Biomass Yields ◽  
Proton Uptake

ABSTRACT Debaryomyces hansenii is a yeast species that is known for its halotolerance. This organism has seldom been mentioned as a pentose consumer. In the present work, a strain of this species was investigated with respect to the utilization of pentoses and hexoses in mixtures and as single carbon sources. Growth parameters were calculated for batch aerobic cultures containing pentoses, hexoses, and mixtures of both types of sugars. Growth on pentoses was slower than growth on hexoses, but the values obtained for biomass yields were very similar with the two types of sugars. Furthermore, when mixtures of two sugars were used, a preference for one carbon source did not inhibit consumption of the other. Glucose and xylose were transported by cells grown on glucose via a specific low-affinity facilitated diffusion system. Cells derepressed by growth on xylose had two distinct high-affinity transport systems for glucose and xylose. The sensitivity of labeled glucose and xylose transport to dissipation of the transmembrane proton gradient by the protonophore carbonyl cyanidem-chlorophenylhydrazone allowed us to consider these transport systems as proton symports, although the cells displayed sugar-associated proton uptake exclusively in the presence of NaCl or KCl. When the V max values of transport systems for glucose and xylose were compared with glucose- and xylose-specific consumption rates during growth on either sugar, it appeared that transport did not limit the growth rate.

scholarly journals Formation of thrust-block moraines at the margins of dry-based glaciers, south Victoria Land, Antarctica

1996 ◽  
Vol 22 ◽  
pp. 68-74 ◽  
Author(s):  
Sean J. Fitzsimons
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Freezing Point ◽  
Water Pressure ◽  
Lacustrine Sediment ◽  
Dry Valleys ◽  
Bed Deformation ◽  
Sedimentary Structures ◽  
Victoria Land ◽  
Subglacial Meltwater

Several dry-based alpine glaciers in the Dry Valleys of south Victoria Land, Antarctica, have prominent end moraines. Examination of their morphology, structure and sedimentology shows they consist of blocks of sand, gravel and organic silt within which sedimentary structures unrelated to entrainment and transportation by ice are well preserved. The nature and preservation of sedimentary structures, together with the presence of algae mats in the sediment, suggest formation by proglacial entrainment, transportation and deposition of frozen blocks of lacustrine sediment. Previous explanations of the formation of thrust-block moraines, including those that stress the importance of elevated pore-water pressure and Weertman’s ice-debris accretion hypothesis, depend on the presence of subglacial meltwater or the 0° C isotherm being situated close to the glacier bed. These models appear inappropriate for cold, dry-based glaciers because their basal temperatures are well below freezing point and they rest on deep permafrost. Three alternative models for the formation of thrust-block moraines at the margins of dry-based glaciers are examined in this paper: block entrainment of sediment associated with frozen-bed deformation; entrainment by overriding and accretion of marginal-ice and debris aprons; and transient wet-based conditions associated with glaciers flowing into ice-marginal lakes.

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