scholarly journals Adaptation and Acclimation of Photosynthetic Microorganisms to Permanently Cold Environments

2006 ◽  
Vol 70 (1) ◽  
pp. 222-252 ◽  
Author(s):  
Rachael M. Morgan-Kiss ◽  
John C. Priscu ◽  
Tessa Pocock ◽  
Loreta Gudynaite-Savitch ◽  
Norman P. A. Huner
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Extreme Environments ◽  
Energy Sources ◽  
Temperature Dependent ◽  
Low Light ◽  
Cold Environments ◽  
Phototrophic Microorganisms ◽  
Energy Products ◽  
Dependent Processes

SUMMARY Persistently cold environments constitute one of our world's largest ecosystems, and microorganisms dominate the biomass and metabolic activity in these extreme environments. The stress of low temperatures on life is exacerbated in organisms that rely on photoautrophic production of organic carbon and energy sources. Phototrophic organisms must coordinate temperature-independent reactions of light absorption and photochemistry with temperature-dependent processes of electron transport and utilization of energy sources through growth and metabolism. Despite this conundrum, phototrophic microorganisms thrive in all cold ecosystems described and (together with chemoautrophs) provide the base of autotrophic production in low-temperature food webs. Psychrophilic (organisms with a requirement for low growth temperatures) and psychrotolerant (organisms tolerant of low growth temperatures) photoautotrophs rely on low-temperature acclimative and adaptive strategies that have been described for other low-temperature-adapted heterotrophic organisms, such as cold-active proteins and maintenance of membrane fluidity. In addition, photoautrophic organisms possess other strategies to balance the absorption of light and the transduction of light energy to stored chemical energy products (NADPH and ATP) with downstream consumption of photosynthetically derived energy products at low temperatures. Lastly, differential adaptive and acclimative mechanisms exist in phototrophic microorganisms residing in low-temperature environments that are exposed to constant low-light environments versus high-light- and high-UV-exposed phototrophic assemblages.

The cooler side of mycorrhizas: their occurrence and functioning at low temperatures

2007 ◽  
Vol 85 (1) ◽  
pp. 51-62 ◽  
Author(s):  
Mark Tibbett ◽  
John W.G. Cairney
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Mycorrhizal Fungi ◽  
Nutrient Acquisition ◽  
Significant Part ◽  
Freezing Resistance ◽  
Ecological Consequences ◽  
Cold Environments ◽  
Edaphic Conditions ◽  
Mycorrhizal Associations

Mycorrhizal associations occur in a range of habitats in which soils are subject to low temperature (≤15 °C) for a significant part of the year. Despite this, most of our understanding of mycorrhizal fungi and their interactions with their plant hosts is based on physiological investigations conducted in the range 20–37 °C using fungi of temperate origin. Comparatively little consideration has been given to the cold edaphic conditions in which many mycorrhizas survive and prosper, and the physiological and ecological consequences of their low temperature environments. In this review, we consider the distribution and persistence of arbuscular and ectomycorrhizal mycorrhizal associations in cold environments and highlight progress in understanding adaptations to freezing resistance and nutrient acquisition at low temperature in mycorrhizal fungi.

scholarly journals Psychrobacter arcticus 273-4 Uses Resource Efficiency and Molecular Motion Adaptations for Subzero Temperature Growth

2009 ◽  
Vol 191 (7) ◽  
pp. 2340-2352 ◽  
Author(s):  
Peter W. Bergholz ◽  
Corien Bakermans ◽  
James M. Tiedje
Keyword(s):  
Gene Expression ◽  
Energy Metabolism ◽  
Low Temperature ◽  
Low Temperatures ◽  
Extreme Environments ◽  
Resource Efficiency ◽  
Subzero Temperature ◽  
Rna Helicases ◽  
Temperature Growth ◽  
Peptidyl Prolyl Isomerases

ABSTRACT Permafrost soils are extreme environments that exert low-temperature, desiccation, and starvation stress on bacteria over thousands to millions of years. To understand how Psychrobacter arcticus 273-4 survived for >20,000 years in permafrost, transcriptome analysis was performed during growth at 22°C, 17°C, 0°C, and −6°C using a mixed-effects analysis of variance model. Genes for transcription, translation, energy production, and most biosynthetic pathways were downregulated at low temperatures. Evidence of isozyme exchange was detected over temperature for d-alanyl-d-alanine carboxypeptidases (dac1 and dac2), DEAD-box RNA helicases (csdA and Psyc_0943), and energy-efficient substrate incorporation pathways for ammonium and acetate. Specific functions were compensated by upregulation of genes at low temperature, including genes for the biosynthesis of proline, tryptophan, and methionine. RNases and peptidases were generally upregulated at low temperatures. Changes in energy metabolism, amino acid metabolism, and RNase gene expression were consistent with induction of a resource efficiency response. In contrast to results observed for other psychrophiles and mesophiles, only clpB and hsp33 were upregulated at low temperature, and there was no upregulation of other chaperones and peptidyl-prolyl isomerases. relA, csdA, and dac2 knockout mutants grew more slowly at low temperature, but a dac1 mutant grew more slowly at 17°C. The combined data suggest that the basal biological machinery, including translation, transcription, and energy metabolism, is well adapted to function across the growth range of P. arcticus from −6°C to 22°C, and temperature compensation by gene expression was employed to address specific challenges to low-temperature growth.

SPIN FLUCTUATIONS IN TCo2 STUDIED BY RESISTIVITY AND THERMOPOWER EXPERIMENTS (T = Y, Lu, Sc, Hf, Zr, Ce)

1993 ◽  
Vol 07 (01n03) ◽  
pp. 370-373 ◽  
Author(s):  
N. BARANOV ◽  
E. BAUER ◽  
E. GRATZ ◽  
R. HAUSER ◽  
A. MARKOSYAN ◽  
...  
Keyword(s):  
Low Temperature ◽  
Specific Heat ◽  
Temperature Dependence ◽  
Temperature Region ◽  
Low Temperatures ◽  
Spin Fluctuations ◽  
General Tendency ◽  
Electronic Specific Heat ◽  
Temperature Dependent

The temperature dependence of the resistivity and the thermopower in the region from 4.2K up to 1000K for the six isostructural paramagnetic compounds TCo 2 (T=Y, Lu, Sc, Hf, Zr, Ce) is studied. The resistivity ρ (T) follows a T 2 dependence at low temperatures in all these compounds. Plotting the A values into an A vs. γ2 diagram shows that YCo 2, LuCo 2, and ScCo 2 are spinfluctuation systems (A and γ denote the coefficients in ρ (T) = ρ0 + AT 2 and that of the electronic specific heat, respectively) HfCo 2 and ZrCo 2 do not fit into this general tendency in the ( A , γ2)-diagram. The temperature dependent thermopower S(T) in YCo 2, LuCo 2 and ScCo 2 exhibits a pronounced minimum in the low temperature region. These minima are obviously connected with the existence of spin fluctuations (paramagnon-drag). Spin fluctuations in HfCo 2 and ZrCo 2 are less important. This we conclude also from the ten times smaller A-values and the missing minimum in the thermopower at low temperatures.

Weak Localization Effects in Fluorineintercalated Graphite Fibers

1990 ◽  
Vol 209 ◽  
Author(s):  
S.L. Di Vittorio ◽  
M.S. Dresselhaus ◽  
V. Bayot ◽  
L. Piraux ◽  
J-P. Issi ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Low Temperatures ◽  
Weak Localization ◽  
Temperature Dependent ◽  
Weak Magnetic Fields ◽  
Graphite Fibers ◽  
Temperature Dependent Resistivity ◽  
High Fields ◽  
Hole Interaction

ABSTRACTThe intercalation of fluorine into graphite introduces defects into the highly crystalline pristine fibers. These defectsare studied using temperature-dependent resistivity and magnetoresistance measurements. A logarithmic increase in resistivity at low temperature is observed, whereas the high temperature behavior is metallic. At weak magnetic fields and low temperatures, a negative magnetoresistance is observed, which becomes positive at high fields. These effects are explainedusing the two theories of weak localization and hole-hole interaction. In the light of TEM pictures of the microstructure of the fluorinated fibers, the origin of the defects in the intercalated fibers is discussed.

scholarly journals Low-Temperature Biosurfactants from Polar Microbes

2020 ◽  
Vol 8 (8) ◽  
pp. 1183
Author(s):  
Benjamin Trudgeon ◽  
Markus Dieser ◽  
Narayanaganesh Balasubramanian ◽  
Mitch Messmer ◽  
Christine M. Foreman
Keyword(s):  
Low Temperature ◽  
Petroleum Hydrocarbons ◽  
Sodium Dodecyl ◽  
Extreme Environments ◽  
Industrial Applications ◽  
Index Test ◽  
Biotechnological Potential ◽  
Cold Environments ◽  
Wide Range ◽  
Harsh Conditions

Surfactants, both synthetic and natural, are used in a wide range of industrial applications, including the degradation of petroleum hydrocarbons. Organisms from extreme environments are well-adapted to the harsh conditions and represent an exciting avenue of discovery of naturally occurring biosurfactants, yet microorganisms from cold environments have been largely overlooked for their biotechnological potential as biosurfactant producers. In this study, four cold-adapted bacterial isolates from Antarctica are investigated for their ability to produce biosurfactants. Here we report on the physical properties and chemical structure of biosurfactants from the genera Janthinobacterium, Psychrobacter, and Serratia. These organisms were able to grow on diesel, motor oil, and crude oil at 4 °C. Putative identification showed the presence of sophorolipids and rhamnolipids. Emulsion index test (E24) activity ranged from 36.4–66.7%. Oil displacement tests were comparable to 0.1–1.0% sodium dodecyl sulfate (SDS) solutions. Data presented herein are the first report of organisms of the genus Janthinobacterium to produce biosurfactants and their metabolic capabilities to degrade diverse petroleum hydrocarbons. The organisms’ ability to produce biosurfactants and grow on different hydrocarbons as their sole carbon and energy source at low temperatures (4 °C) makes them suitable candidates for the exploration of hydrocarbon bioremediation in low-temperature environments.

Mechanical Properties

1983 ◽  
pp. 237-267
Author(s):  
D. T. Read
Keyword(s):  
Mechanical Properties ◽  
Low Temperature ◽  
Mechanical Behavior ◽  
Low Temperatures ◽  
Metals And Alloys ◽  
Cryogenic Temperatures ◽  
Temperature Dependent ◽  
Test Procedures

Abstract The mechanical properties of a material describe the relations between the stresses acting on the material and its resulting deformations. Stresses capable of producing permanent deformations, which remain after the stresses are removed, are considered in this chapter. The effects of cryogenic temperatures on the mechanical properties of metals and alloys are reviewed in this chapter; the effects on polymers and glasses are discussed briefly. The fundamental mechanisms controlling temperature-dependent mechanical behavior, phenomena encountered in low-temperature testing, and the mechanical properties of some representative engineering metals and alloys are described. Modifications of test procedures for low temperatures and sources of data are also included.

scholarly journals Terrestrial Permafrost as a Model Environment for Bioastronomy

2004 ◽  
Vol 213 ◽  
pp. 359-362
Author(s):  
A. Tsapin ◽  
G. D. McDonald
Keyword(s):  
Low Temperatures ◽  
Extreme Environments ◽  
Bacterial Cells ◽  
Amino Acid Racemization ◽  
Cold Environments ◽  
Viable Bacteria ◽  
The Relationship ◽  
Siberian Permafrost ◽  
Model Environment ◽  
Key Questions

The extent to which organisms can survive extended periods of metabolic inactivity in cold environments such as permafrost is one of the key questions in the study of life in extreme environments and for astrobiology. Viable bacteria have been cultured from million year-old Siberian permafrost samples, but the relationship between the age of the bacteria and the age of the sediments remains controversial. In this study we analyze the level of racemization of amino acids in permafrost samples collected from several sites in Northern Siberia. We have shown that even during long exposures to low temperatures (−10°C to −15°C), the bacterial cells in permafrost are not completely dormant, but continue to metabolize and at least partially control the extent of amino acid racemization.

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

INVAR M93

Alloy Digest ◽  
2008 ◽  
Vol 57 (1) ◽  
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Low Temperatures ◽  
Bend Strength ◽  
Temperature Performance ◽  
Ni Content ◽  
Precision Alloys ◽  
Ni Alloy

Abstract Invar is an Fe-Ni alloy with 36% Ni content that exhibits the lowest expansion of known metals from very low temperatures up to approximately 230 deg C (445 deg F). Invar M93 is a cryogenic Invar with improved weldability. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear and bend strength as well as fracture toughness and fatigue. It also includes information on low temperature performance as well as forming and joining. Filing Code: FE-143. Producer or source: Metalimphy Precision Alloys.

scholarly journals The Candidate Genes Underlying a Stably Expressed QTL for Low Temperature Germinability in Rice (Oryza sativa L.)

Rice ◽  
2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Tifeng Yang ◽  
Lian Zhou ◽  
Junliang Zhao ◽  
Jingfang Dong ◽  
Qing Liu ◽  
...  
Keyword(s):  
Low Temperature ◽  
Differential Expression ◽  
Candidate Genes ◽  
Complex Traits ◽  
Molecular Breeding ◽  
Genome Wide Association Study ◽  
Oryza Sativa L ◽  
Sequence Comparisons ◽  
Cold Environments ◽  
Promising Source

Abstract Background Direct seeding is an efficient cultivation technique in rice. However, poor low temperature germinability (LTG) of modern rice cultivars limits its application. Identifying the genes associated with LTG and performing molecular breeding is the fundamental way to address this issue. However, few LTG QTLs have been fine mapped and cloned so far. Results In the present study, the LTG evaluation of 375 rice accessions selected from the Rice Diversity Panel 2 showed that there were large LTG variations within the population, and the LTG of Indica group was significantly higher than that of Japonica and Aus groups (p < 0.01). In total, eleven QTLs for LTG were identified through genome-wide association study (GWAS). Among them, qLTG_sRDP2–3/qLTG_JAP-3, qLTG_AUS-3 and qLTG_sRDP2–12 are first reported in the present study. The QTL on chromosome 10, qLTG_sRDP2–10a had the largest contribution to LTG variations in 375 rice accessions, and was further validated using single segment substitution line (SSSL). The presence of qLTG_sRDP2–10a could result in 59.8% increase in LTG under 15 °C low temperature. The expression analysis of the genes within qLTG_sRDP2–10a region indicated that LOC_Os10g22520 and LOC_Os10g22484 exhibited differential expression between the high and low LTG lines. Further sequence comparisons revealed that there were insertion and deletion sequence differences in the promoter and intron region of LOC_Os10g22520, and an about 6 kb variation at the 3′ end of LOC_Os10g22484 between the high and low LTG lines, suggesting that the sequence variations of the two genes could be the cause for their differential expression in high and low LTG lines. Conclusion Among the 11 QTLs identified in this study, qLTG_sRDP2–10a could also be detected in other three studies using different germplasm under different cold environments. Its large effect and stable expression make qLTG_sRDP2–10a particularly valuable in rice breeding. The two genes, LOC_Os10g22484 and LOC_Os10g22520, were considered as the candidate genes underlying qLTG_sRDP2–10a. Our results suggest that integrating GWAS and SSSL can facilitate identification of QTL for complex traits in rice. The identification of qLTG_sRDP2–10a and its candidate genes provide a promising source for gene cloning of LTG and molecular breeding for LTG in rice.

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