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PubMedDate not supplied

Changes in the vestibular function during space flight.

An analysis of observations and investigations carried out in space flight has shown that some cosmonauts and astronauts have experienced vestibular disorders during the transition to weightlessness. Vestibular-sensory disorders include: Spatial illusions (the feelings of falling down, being in an upside-down position, the sensations of rotation of the craft or the body) and vertigo occurring during the onset of the orbital flight and head movements; Feelings, similar to those experienced in response to Coriolis accelerations on the Earth, which occasionally develop in weightlessness during the spacecraft rotation upon abrupt head and body movements and restrained feet; Feelings "of the load on the vestibular analyser which is unlike any Earth-bound effects" upon abrupt head movements during the first hours of an orbital flight and "a prolonged movement" during the switch-off of thrusters in weightlessness. Vestibular-vegetative disorders comprise a complex of symptoms similar to those of motion sickness: loss of appetite, stomach awareness (12%), hypersalination, nausea (9.6%) and vomiting (4.8%). Soviet studies suggest that the vestibular tolerance to the flight effects depends on the natural stability and training to the cumulative effect of adequate vestibular stimuli. This has been used in the development of the system of vestibular selection. Changes in the vestibular function seem to play the major role in the development of motion sickness in weightlessness, extra-labyrinthine factors being contributory. The current hypotheses have not yet been adequately confirmed in experiments. A detailed physiological analysis allows the conclusion that the decisive factor in the development of motion sickness may be the disturbance of the function of analysers responsible for spatial orientation which take the form of sensory conflicts as well as an altered reactivity of the organism due to the hemodynamic rearrangement.

Aerospace Medicine↗

PubMed1995

Nucleotide sequence of the ATPase A- and B-subunits of the halophilic archaebacterium Haloferax volcanii and characterization of the enzyme.

Using PCR with degenerate oligonucleotides, we amplified two conserved regions of the plasma membrane ATPase A (alpha)- and B (beta)-subunit-encoding genes from Haloferax volcanii, a halophilic archaeon. The amplified fragments were cloned and sequenced, and then used as homologous probes to clone genomic restriction fragments, one of which contained the nearly complete atpA- and atpB-gene. To complete the latter one, we sequenced a region of an overlapping fragment using synthetic oligonucleotides as primers. The deduced amino-acid sequence showed a high degree of similarity with the A and B sequences of Halobacterium halobium-ATPase, and a relatively high degree with Daucus carota V-ATPase, but less similarity to F-ATPase alpha- and beta-subunits. Like in V-ATPases, the A-subunit is more related to the catalytic F-ATPase beta-subunit, whereas B corresponds to alpha. Cross-reaction of antibodies against CF1-alpha (synthetic peptide) with B and CF1-beta with A of Haloferax volcanii confirmed this finding. The ATPase of Haloferax volcanii is a halophilic enzyme, the amino-acid sequences contain about 20% negatively charged residues. This is discussed in terms of adaption to hypersaline conditions. The enzyme is specific for ATP, we determined KM values for ATP in presence of Mn2+ and Mg2+, respectively. Other nucleotides, including GTP and ADP are competitive inhibitors of ATP hydrolysis. Despite of the high degree of similarity to the Halobacterium enzyme, the ATPase showed no sensitivity to most of the tested inhibitors of ATP hydrolysis. NEM, a specific inhibitor for V-ATPases inhibited the enzyme only slightly. Bafilomycin, NBD-Cl and nitrate showed no effect. These results will be discussed in context with some specific differences in the primary structure of the Haloferax A-subunit.

Amino Acid Sequence↗

PubMed1994

Elevated CO2: impact on diurnal patterns of photosynthesis in natural microbial ecosystems.

Algae, including blue-green algae (cyanobacteria), are the major source of fixed carbon in many aquatic ecosystems. Previous work has shown that photosynthetic carbon fixation is often enhanced in the presence of additional carbon dioxide (CO2). This study was undertaken to determine if this CO2 fertilization effect extended to microbial mats, and, if so, at what times during the day might the addition of CO2 affect carbon fixation. Four microbial mats from diverse environments were selected, including mats from a hypersaline pond (area 5, Exportadora de Sal, Mexico), the marine intertidal (Lyngbya, Laguna Ojo de Liebre, Mexico), an acidic hotspring (Cyanidium, Nymph Creek, Yellowstone National Park), and an acidic stream at ambient temperature (Zygogonium, Yellowstone National Park). Carbon fixation in the absence of additional CO2 essentially followed the rising and falling sunlight levels, except that during the middle of the day there was a short dip in carbon fixation rates. The addition of CO2 profoundly enhanced carbon fixation rates during the daylight hours, including during the midday dip. Therefore, it is unlikely that the midday dip was due to photoinhibition. Surprisingly, enhancement of carbon fixation was often greatest in the early morning or late afternoon, times when carbon fixation would be most likely to be light limited.

Animals↗

PubMed1991

Method for determining stable isotope ratios of dissolved organic carbon in interstitial and other natural marine waters.

A procedure is described for the analysis of the stable carbon isotopic composition of dissolved organic carbon (DOC) in natural waters from marine and higher-salinity environments. Rapid (less than 5 min) and complete oxidation of DOC is achieved using a modification of previous photochemical oxidation techniques. The CO2 evolved from DOC oxidation can be collected in less than 10 min for isotopic analysis. The procedure is at present suitable for oxidation and collection of 1-5 micromoles of carbon and has an associated blank of 0.1-0.2 micromole of carbon. Complete photochemical oxidation of DOC standards was demonstrated by quantitative recovery of CO2 as measured manometrically. Isotopic analyses of standards by photochemical and high-temperature sealed-tube combustion methods agreed to within 0.3%. Photochemical oxidation of DOC in a representative sediment pore-water sample was also quantitative, as shown by the excellent agreement between the photochemical and sealed-tube methods. The delta 13C values obtained for pore-water DOC using the two methods of oxidation were identical, suggesting that the modified photochemical method is adequate for the isotopically non-fractionated oxidation of pore-water DOC. The procedure was evaluated through an analysis of DOC in pond and pore waters from a hypersaline microbial mat environment. Concentrations of DOC in the water column over the mat displayed a diel pattern, but the isotopic composition of this DOC remained relatively constant (average delta 13C = -12.4%). Pore-water DOC exhibited a distinct concentration maximum in the mat surface layer, and delta 13C of pore-water DOC was nearly 8% lighter at 1.5-2.0-cm depth than in the mat surface layer (0-0.5-cm depth). These results demonstrate the effectiveness of the method in elucidating differences in DOC concentration and delta 13C over biogeochemically relevant spatial and temporal scales. Carbon isotopic analysis of DOC in natural waters, especially pore waters, should be a useful probe of biogeochemical processes in recent environments.

Carbon↗

PubMed1989

Relationships among Vibrio costicola strains assessed by DNA-DNA hybridization.

Deoxyribonucleic acid (DNA)-DNA hybridization was used to determine the relationships among 14 strains of Vibrio costicola isolated from cured meats or hypersaline waters. Our results indicate that the strains investigated should be considered members of the same genomic species, with homologies of 60% or higher with the V. costicola strains used as reference. Low DNA relatedness was found with other marine vibrios or moderately halophilic bacteria tested. The guanine-plus-cytosine base contents of DNAs from the 14 V. costicola strains were 47.6 to 51.1 mol%.

Base Composition↗

PubMed2006

Dehydration-induced expression of LEA proteins in an anhydrobiotic chironomid.

Late embryogenesis abundant (LEA) proteins are associated with desiccation tolerance in anhydrobiotic organisms. The larvae of an African chironomid, Polypedilum vanderplanki, are able to withstand almost complete desiccation during which they enter a state of suspended animation. Here, we developed an EST database from desiccating larvae and isolated three cDNAs encoding proteins (PvLEA1, PvLEA2, and PvLEA3) with highly significant matches to Group 3 LEA proteins. Both mRNA and protein levels of all three examples were increased by dehydration stress imposed by either desiccation or hypersalinity, and one protein, PvLEA2, is likely to be post-translationally processed into smaller molecules. This first description of LEA protein genes in arthropods suggests that this protein family is widespread throughout invertebrate phyla, and that animals, plants, and microorganisms possess similar mechanisms for combating dehydration stress.

Animals↗

PubMed2006

Avian cestodes affect the behaviour of their intermediate host Artemia parthenogenetica: an experimental study.

The brine shrimp Artemia parthenogenetica (Crustacea, Branchiopoda) is intermediate host for several cestode species whose final hosts are waterbirds. Previous field studies have shown that brine shrimps infected with cestodes have a bright red colour and are spatially segregated in the water column. However, the ethological mechanisms explaining such field observations are unknown. Changes in appearance and behaviour induced by trophically transmitted parasites have been shown to increase the risk of predation by the final host. In this experimental study, we compared the behaviour of uninfected Artemia and those infected by avian cestodes. We found that parasitised individuals behave differently from unparasitised ones in several ways. In contrast to uninfected individuals, infected brine shrimps were photophilous and showed increased surface-swimming behaviour. These observations suggest that the modified behaviour (in addition to the bright red colour of the majority of the infected individuals) results in infected brine shrimps becoming more vulnerable to avian final hosts, which facilitates parasite transmission. We discuss our results in terms of the adaptive nature of behavioural changes and their potential implications for the hypersaline ecosystem.

Animals↗

PubMed2005

Effects of salinity on beta-carotene production by Dunaliella tertiolecta DCCBC26 isolated from the Urmia salt lake, north of Iran.

This study examined the effect of different salt concentrations (0.05-3 M of NaCl) on the kinetics of growth, total carotenoids and beta-carotene (all-trans and 9-cis) accumulated in Dunaliella tertiolecta DCCBC26, a microalgae strain isolated from the Urmia hypersaline lake, northwest of Iran. Results indicated that the highest amount of carotenoids detected (11.73 mg/l) was in the salinity of 0.5 M NaCl during the stationary growth phase. The percentage of the all-trans and 9-cis-beta-carotene in the exponential phase were 92% and 32% in salinities of 3 M and 0.5 M, respectively. However, only 23% of the beta-carotene was detected in the stationary growth phase of the microalgae in 0.5 M salinity and was 9-cis isomer.

Cell Culture Techniques↗

PubMed2005

A microprobe analysis of inorganic elements in Halobacterium salinarum.

Halobacterium salinarum were grown on peptone agar containing 4.28 M NaCl, 0.036 M K and other salts. Stationary phase organisms were lifted onto carbon planchets, freeze-dried, carbon coated and examined in a scanning electron microscope equipped with an X-ray spectrometer. Intracellular element concentrations (mol/kg H(2)O) were determined using a bulk analysis program with appropriate standards. The cell K concentration was 110 times that of the medium. For Na this value was 0.3 and for Cl, 1.1. When Rb was present in the medium, its intracellular concentration was 77 times higher than the external value. The cation minus anion value suggests a high fixed negative charge, 0.72 equivalents. Intracellular apparent dielectric constants were calculated using cellular EMFs derived from the literature, and sodium concentration. The determined values ranged from 22-28 (vs 80 for normal water) suggesting phases of structured cell water. Ionic distributions in these extremophiles are treated according to the classical principles elucidated by Willard Gibbs and represents a heterogeneous system in thermodynamic equilibrium with the hypersaline environment. Factors to be considered are: (1) composition of Halobacterium and its immobile negative charge; (2) the physicochemical properties of the individual ions (charge, ionic radius, hydration energy, standard chemical potential); (3) the dielectric constant of the dispersion medium (water); and (4) the binding of ions, particularly potassium.

Chlorides↗

PubMed2025

A deep metagenomic atlas of Qinghai-Xizang Plateau lakes reveals their microbial diversity and salinity adaptation mechanisms.

The Qinghai-Xizang Plateau (QXP), harboring the planet's highest density of plateau lakes, offers an exceptional biogeographic environment for studying extremophilic microbial communities and their adaptation to salinity. Through deep metagenomic sequencing, we construct the Qinghai-Xizang Lake Sediment Genome (QXLSG) catalog, a high-resolution genomic catalog comprising 5,866 metagenome-assembled genomes (MAGs), 58.16 million non-redundant protein encoding genes, and 19,008 biosynthetic gene clusters. Notably, 80.78% of the 2,742 species-level MAGs represent undescribed taxa, significantly expanding the known microbial diversity. Salinity emerges as the primary environmental factor influencing microbial community. Functional annotation highlights that the "salt-out" strategy, particularly the uptake of glycine betaine, is the main mechanism for salinity tolerance. This strategy is prevalent in both hypersaline lake communities and the dominant microbial phyla. Overall, this study provides a crucial genetic resource for future bioprospecting and deepens our understanding of the fundamental mechanisms of microbial adaptation to extreme saline environments.

Lakes↗

PubMed2005

Deep sea mining for unique biocatalysts.

In this issue of Chemistry and Biology, Ferrer and coworkers describe the discovery of five esterases from a distinct deep sea hypersaline biotope. Interestingly, one enzyme has two unique features-it contains three active centers mediating distinct esterolytic activities, and its tertiary/quaternary structure can be modulated by environmental changes.

Bacterial Proteins↗

PubMed2005

Effects of widely used pharmaceuticals and a detergent on oxidative stress biomarkers of the crustacean Artemia parthenogenetica.

Pharmaceuticals are continuously dispersed into the environment as a result of human and veterinary use, posing relevant environmental concerns. The present paper reports the acute toxic effects of three therapeutic agents (diazepam, clofibrate and clofibric acid) and a detergent, sodium dodecylsulphate (SDS), to the hypersaline crustacean Artemia parthenogenetica. This study specially focused on oxidative stress parameters, namely (1) total and selenium-dependent glutathione-peroxidase (GPx), (2) glutathione reductase (GRed), (3) total superoxide dismutase (SOD), and (4) glutathione-S-transferases (GSTs). The effects of tested substances on lipid peroxidation (thiobarbituric acid reactive substances, TBARS), and soluble cholinesterases (ChE) were also investigated. Diazepam caused a significant inhibition of ChE (LOEC = 7.04 mg/l) and total GPx activities. SDS was responsible for a decrease in the activity of both ChE (LOEC = 8.46 mg/l) and GRed (LOEC = 4.08 mg/l). Both fibrates (clofibrate and clofibric acid) were responsible for significant decreases in Se-dependent GPx, with LOEC values of 176.34 and 3.09 mg/l, respectively. Clofibrate also caused a slight increase of TBARS content of A. parthenogenetica homogenates. These results indicate that the exposure to all the tested compounds induced alterations on the cellular redox status in A. parthenogenetica. In addition, diazepam was shown to have the capability of interfering with A. parthenogenetica neurotransmission, through the inhibition of ChE.

Animals↗

PubMed2005

Acute toxicity of widely used pharmaceuticals in aquatic species: Gambusia holbrooki, Artemia parthenogenetica and Tetraselmis chuii.

Pharmaceuticals are continuously dispersed into the environment as a result of human and veterinary use, posing relevant environmental concerns. This study evaluated the acute toxicity of three therapeutic agents (diazepam, clofibrate, and clofibric acid) and a detergent (sodium dodecyl sulfate; SDS) in three aquatic species, namely the euryhaline fish Gambusia holbrooki, the hypersaline crustacean Artemia parthenogenetica, and the marine algae Tetraselmis chuii. The ranking of 50% lethal concentrations (LC50) for the two animal species and 50% inhibitory concentration (IC50) for the algal species was, in decreasing order, clofibric acid > SDS > diazepam > clofibrate for G. holbrooki, clofibric acid > clofibrate > SDS > diazepam for A. parthenogenetica, and clofibric acid > clofibrate > SDS > diazepam for T. chuii. These differences show that the intrinsic nature of test organisms must be considered when evaluating the toxicity of these agents to aquatic ecosystems.

Animals↗

PubMed2006

Use of the genus Artemia in ecotoxicity testing.

Information related to varied uses of several species of the genus Artemia (commonly known as brine shrimp), is dispersed among literature from several scientific areas, such as Ecology, Physiology, Ecotoxicology, Aquaculture and Genetics. The present paper reviews information related to Artemia that may be considered relevant for ecotoxicity testing. Integration of different areas of scientific knowledge concerning biology, life cycle and environmental needs of Artemia is of crucial importance when considering the interpretation of results drawn from tests involving this genus. Furthermore, this paper provides suggestions to overcome problems related to toxicity assessment with the use of Artemia as test organism in bioassays, under the scope of estuarine, marine and hypersaline environments. Aspects related to variability in results, adoptable toxicity end-points, culture conditions, characteristics of species and strains, influence of geographical origins over physiological features and responses to exposure to chemical agents are considered.

Animals↗

PubMed2006

Prokaryotic life in a potash-polluted marsh with emphasis on N-metabolizing microorganisms.

Prokaryotic life along the salt gradient of the potash marsh resulting from mining waste at Schreyahn, Northern Germany, was screened for the distribution of total prokaryote (assessed by the 16S rRNA gene) and of N2-fixing (nifH gene), denitrifying (nosZ) and nitrifying (amoA) microorganisms. Information on prokaryotes was retrieved from the different soil sites (a) by culturing in conventional media, (b) by isolating the DNA, amplifying the target genes by PCR followed by sequencing, (c) by employing the recently developed computer program (TReFID [Rösch, C., Bothe, H., 2005. Improved assessment of denitrifying, N2-fixing, and total-community bacteria by terminal restriction fragment length polymorphism analysis using multiple restriction enzymes. Applied and Environmental Microbiology 71, 2026-2035]) based on tRFLP data. New sequences were obtained as well as ones that were almost identical to those found at far distant locations. Whereas the distribution of plants strictly follows the salt gradient, this is apparently not the case with prokaryotes. Bacteria of hypersaline areas coexist with salt-non-tolerant species. The recently developed TReFID program is successfully applied to characterize a prokaryote community structure.

Bacteria↗

PubMed2024

Multi-omics association study of hexadecane degradation in haloarchaeal strain Halogranum rubrum RO2-11.

Haloarchaea with the capacity to degrade alkanes is promising to deal with petroleum pollution in hypersaline environments. However, only a limited number of haloarchaeal species are investigated, and their pathway and mechanism for alkane degradation remain unclear. In this study, Halogranum rubrum RO2-11, a haloarchaeal strain, verified the ability to degrade kerosene and hexadecane in 184 g/L NaCl, with 53% and 52% degradation rates after 9 and 4 days, respectively. Genome sequencing and gene annotation indicated that strain RO2-11 possesses a complete potential alkane-degrading pathway, of which alkane hydroxylases may include CYP450, AlmA, and LadA. Transcriptome and metabolome analyses revealed that the upregulation of related genes in TCA cycle, lysine biosynthesis, and acetylation may help improve hexadecane degradation. Additionally, an alternative degrading pathway of hexadecane based on dual-terminal β-oxidation may occur in strain RO2-11. It is likely to be the first report of alkane degradation by the genus Halogranum, which may be helpful for applications of oil-pollution bioremediation under high-salt conditions.

Alkanes↗

PubMed2005

Diversity of halophilic archaea in the crystallizers of an Adriatic solar saltern.

Haloarchaeal diversity in the crystallizers of Adriatic Secovlje salterns was investigated using gene fragments encoding 16S rRNA and bacteriorhodopsin as molecular markers. Screening of 180 clones from five gene libraries constructed for each gene targeted revealed 15 different 16S rRNA and 10 different bacteriorhodopsin phylotypes, indicating higher haloarchaeal diversity than previously reported in such hypersaline environments. Furthermore, results of rarefaction analysis indicated that analysis of an increasing number of clones would have revealed additional diversity. Finally, most sequences from the crystallizers grouped within the Halorubrum branch, whereas square-shaped 'Haloquadratum' relatives, repeatedly reported to dominate crystallizer communities, were rare. Presence of such special and diverse haloarchaeal community could be attributed to the Secovlje salterns rare continuous short-cycling salt production mechanism.

Bacteriorhodopsins↗

PubMed2004

High survival and stability rates of Escherichia coli dried in hydroxyectoine.

The tetrahydropyramidine hydroxyectoine acts as an osmolyte in a range of bacterial species, but its use as a desiccation protectant is less well explored. Recently, it was demonstrated that hydroxyectoine provides effective stabilisation of the Gram-negative species Pseudomonas putida, which is only relatively poorly preserved by the better-characterised protectant, trehalose. It is now shown that hydroxyectoine also protects the paradigmatic bacterium, Escherichia coli: osmotically-preconditioned E. coli dried in hydroxyectoine exhibited a high degree of desiccation tolerance, similar to that achieved using trehalose in this species. Hydroxyectoine is apparently accumulated from hypersaline medium in preference to trehalose biosynthesis, but E. coli loaded with hydroxyectoine in this way showed reduced stability in the dry state. This suggests that, although both hydroxyectoine and trehalose perform equally well as extracellular protectants, trehalose is preferred for intracellular protection.

Amino Acids, Diamino↗