Hypersaline Condition Research Articles

The modulation of leaf metabolism plays a role in salt tolerance of Cymodocea nodosa exposed to hypersaline stress in mesocosms.

Applying proteomics, we tested the physiological responses of the euryhaline seagrass Cymodocea nodosa to deliberate manipulation of salinity in a mesocosm system. Plants were subjected to a chronic hypersaline condition (43 psu) to compare protein expression and plant photochemistry responses after 15 and 30 days of exposure with those of plants cultured under normal/ambient saline conditions (37 psu). Results showed a general decline in the expression level of leaf proteins in hypersaline stressed plants, with more intense reductions after long-lasting exposure. Specifically, the carbon-fixing enzyme RuBisCo displayed a lower accumulation level in stressed plants relative to controls. In contrast, the key enzymes involved in the regulation of glycolysis, cytosolic glyceraldehyde-3-phosphate dehydrogenase, enolase 2 and triose-phosphate isomerase, showed significantly higher accumulation levels. These responses suggested a shift in carbon metabolism in stressed plants. Hypersaline stress also induced a significant alteration of the photosynthetic physiology of C. nodosa by means of a down-regulation in structural proteins and enzymes of both PSII and PSI. However we found an over-expression of the cytochrome b559 alpha subunit of the PSII initial complex, which is a receptor for the PSII core proteins involved in biogenesis or repair processes and therefore potentially involved in the absence of effects at the photochemical level of stressed plants. As expected hypersalinity also affects vacuolar metabolism by increasing the leaf cell turgor pressure and enhancing the up-take of Na+ by over-accumulating the tonoplast specific intrinsic protein pyrophosphate-energized inorganic pyrophosphatase (H(+)-PPase) coupled to the Na+/H+-antiporter. The modulation of carbon metabolism and the enhancement of vacuole capacity in Na+ sequestration and osmolarity changes are discussed in relation to salt tolerance of C. nodosa.

DNA damage induced by hydroquinone can be prevented by fungal detoxification

Hydroquinone is a benzene metabolite with a wide range of industrial applications, which has potential for widespread human exposure; however, the toxicity of hydroquinone on human cells remains unclear. The aims of this study are to investigate the cytotoxicity and genotoxicity of hydroquinone in human primary fibroblasts and human colon cancer cells (HCT116). Low doses of hydroquinone (227-454 μM) reduce the viability of fibroblasts and HCT116 cells, determined by resazurin conversion, and induce genotoxic damage (DNA strand breaks), as assessed by alkaline comet assays. Bioremediation may provide an excellent alternative to promote the degradation of hydroquinone, however few microorganisms are known that efficiently degrade it. Here we also investigate the capacity of a halotolerant fungus, Penicillium chrysogenum var. halophenolicum, to remove hydroquinone toxicity under hypersaline condition. The fungus is able to tolerate high concentrations of hydroquinone and can reverse these noxious effects via degradation of hydroquinone to completion, even when the initial concentration of this compound is as high as 7265 μM. Our findings reveal that P. chrysogenum var. halophenolicum efficiently degrade hydroquinone under hypersaline conditions, placing this fungus among the best candidates for the detoxification of habitats contaminated with this aromatic compound.

Salinity-induced oxidative stress and regulation of antioxidant defense system in the marine macroalga Ulva prolifera

The physiological and biochemical responses to salinity stresses in Ulva prolifera were investigated, including growth rate, level of oxidative stress and regulation of antioxidant defense system. A six-day exposure to hyposaline (10‰) and hypersaline (60‰) conditions resulted in a significant decrease in growth rate and maximum photosynthetic quantum efficiency (Fv/Fm) compared with the control (30‰). Increases in H 2O 2 contents correlated to the level of lipid peroxidation, which suggested that oxidative damage occurred in salinity stress and was more severe at 60‰ than at 10‰. The amount of total soluble protein (TSP) significantly increased in a hypersaline condition. The fluctuations of four antioxidant substrates and four antioxidant enzymes were determined after the long-term salinity stress. Compared to growth at 30‰, low salinities led to a major increase in activities of catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR), coupled with an increase in contents of ascorbate, glutathione and β-carotenoid. Thalli exposed to hypersaline conditions rapidly accumulated glutathione and did not affect the content of ascorbate, α-tocopherol and β-carotenoid. The activities of CAT, SOD, ascorbate peroxidase (APX) and GR increased in hypersaline conditions, suggesting that reactive oxygen scavenging enzymes played an important role in U. prolifera for adapting to the hypersaline condition. The alterations in antioxidant enzymes and substrates are not consistent between hyposaline and hypersaline stresses in U. prolifera, but the regulation of antioxidant defense system was a vital tolerance mechanism involved in the oxidative stress.

Shallow marine ecosystem feedback to the Permian/Triassic mass extinction

Late Permian reefs developed widely on shallow marine carbonate platforms in South China but disappeared far below the main mass extinction level of the latest Permian. The collapse of reef ecosystem may be related to the enhanced volcanism at the end of Late Permian. Notably, some colony corals and reef-building sponges were found to occur near the mass extinction boundary, inferring the eclipse of reef ecosystem is ahead of the disappearance of reef-building organisms, and the triggers would be present long before the main mass extinction. As the primary producers, the calcareous algae are rich in platform limestones of Late Permian and played a very important role in maintaining the shallow benthic ecosystems. The calcareous algae were found to disappear synchronously with the great reduction of foraminifers, which were ecologically associated with these algae. The extinction of Late Permian calcareous algae greatly reduced the biodiversity of primary producers in the shallow marine environment and destroyed in part the structure and the base of the shallow marine ecosystems, which in turn cause the extinction of ecologically associated metazoan. Microbialites developed on carbonate platforms immediately after the end-Permian mass extinction, representing a simple and unique microbial ecosystem. Widespread occurrence of microbialites symbolized the deterioration of marine environmental conditions and the dramatic revolution of marine ecosystems. As the new primary producers instead of the extinguished calcareous algae, cyanobacteria in the microbialites were an important base of this peculiar ecosystem and contributed greatly to the survival of the remnant faunas after the mass extinction. Widespread occurrence of microbialites in shallow marine environment is suggested to be related to the elevated level of volcanism-induced greenhouse gases and enhanced evaporation and hypersaline condition in addition to the decrease of metazoan grazing pressure. The change from calcareous algae and reef ecosystem to the cyanobacteria-dominated microbial ecosystem documented in the shallow marine sequences in South china is the ecological feedback to the deterioration of the marine environmental conditions probably induced by volcanism.

Early Hydrocarbon Generation of Algae and Influences of Inorganic Environments during Low Temperature Simulation

Algae were simulated for 5 years at low temperature (80°C) in order to study their early hydrocarbon generation processes. The samples were analyzed by gas chromatography-mass spectrometry. The results show that the range of carbon numbers and relative concentrations of alkanes are different under different simulated conditions. Hypersaline condition favors the formation and maturity of saturates. Iron ion probably delays the evolutionary pathways from phytol to phytene to phyane, while may catalyse the release of high concentrations of squalene and bicyclic terpanes. Meanwhile, common aromatic compounds have been formed during this low temperature simulation, and high abundant methyldibenzothiophenes were found in the hypersaline sample. The formation pathways of methylnaphthalenes in the early evolution of algae were proposed tentatively. By mathematical cluster and factor analyses on some classical thermal maturity parameters, the converted relations between phenanthrene and methylphenanthrenes and their inorganic environmental effects were discussed.

Geochemical signatures of Late Holocene paleo-hydrological changes from Phulera and Pokharan saline playas near the eastern and western margins of the Thar Desert, India

Stratigraphical, mineralogical, geochemical and optical dating methods were used to reconstruct paleo-hydrological changes in two playas (Phulera, 500 mm/a and Pokharan, 200 mm/a) in near extremum climatic regions of the Thar Desert. Sediment successions in shallow profiles from Phulera and Pokharan contain three and four stratigraphic units, respectively, each with characteristic geochemical properties. These units reflect changes in chemical weathering, detrital input, salinity and provide a measure of the changes in precipitation (i.e. monsoon) through time. Sediments from Pokharan suggest short rainfall events during ca. 6.6–4 ka, relatively stable fresh water (higher and persistent rainfall) regime during 4–2.3 ka, and a hyper saline (low rainfall) condition during 2.3–1.1 ka. Sediments at Phulera, record hyper saline (low rainfall) lacustrine conditions during <2.3 ka to >1.4 ka. Higher abundance of gypsum in Pokharan (2.3–1.1 ka) and proto-dolomite in Phulera (2.3–1.4 ka) are nearly synchronous and reflect enhancement of salinity. Selenite crystals in Pokharan and large desiccation cracks in buried horizons at Phulera reflect desiccation of playas at ca. 2 ka. Both playas progressively became less saline after 1.4 ka. Given the regional nature of this record, these changes are attributed to fluctuation of the monsoon over the Indian sub continent.

Response of the Asian Sea Bass Lates calcarifer Fingerlings to Different Feeding Rates and Feeding Frequencies Reared in Hyper Saline Condition

Response of the Asian Sea Bass Lates calcarifer Fingerlings to Different Feeding Rates and Feeding Frequencies Reared in Hyper Saline Condition

Analysis of Protein Expression Profiles of Halobacillus dabanensis D-8T Under Optimal and High Salinity Conditions

Two-dimensional (2-D) gel electrophoresis was employed to display the expression profiles of proteins of Halobacillus dabanensis D-8(T) under 1%, 10%, and 20% salinities. Approximately 700 protein spots could be detected in the 2-D gels by Imagemastertrade mark 2D Platinum software. The molecular masses of the majority of intracellular proteins were distributed in the range of 17.5 kDa-66 kDa and isoelectric points of 4.0-5.9. In total 133 protein spots were observed with a changed expression level under different salinity conditions. Sixty-two protein spots showed upregulation and 26 new protein spots were found under high salinity conditions, while 25 protein spots were downregulated and 20 spots disappeared. Twenty-seven proteins with a markedly changed expression in hypersaline environments were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF/MS) and MASCOT. A changed expression pattern was observed for proteins related to energy-producing pathways, stress regulators, and proteins involved in the survival of strain D-8(T) under high salt challenges. Many proteins play necessary roles in the adaptation to high salt or as a general stress protein, and some proteins are salt-stressed specific proteins that improve the capability of salt-tolerance of strain D-8(T) growth under extremely hypersaline condition.

Production of polyhydroxyalkanoates from inexpensive extruded rice bran and starch by Haloferax mediterranei

Low-cost raw materials can be used to reduce significantly the production cost of polyhydroxyalkanoates (PHA). In this study, extruded rice bran (ERB) and extruded cornstarch (ECS) were used as carbon sources to produce PHA by an archaea, Haloferax mediterranei, which cannot use native rice bran or cornstarch as a carbon source. By employing pH-stat control strategy to maintain pH at 6.9-7.1 in a 5-liter jar fermentor using ERB:ECS (1:8 g/g) as the major carbon source, we obtained a cell concentration of 140 g/L, PHA concentration of 77.8 g/L and PHA content of 55.6 wt.% in a repeated fed-batch fermentation. In contrast, when ECS was used as the major carbon source, we obtained 62.6 g/L cell concentration, 24.2 g/L PHA concentration and 38.7 wt.% PHA content. Under a hyper-saline condition and with no nitrogen-limitation restriction, the repeated fed-batch process can be sustained a long time for the mass production of PHA.

Primary habitats of the St Lucia Estuarine System, South Africa, and their responses to mouth management

Four primary habitats have been identified in the St Lucia estuarine system, each having a suite of characteristic vegetation types. These can be described as follows: (1) open water; (2) intertidal shoreline; (3) 'dry' shoreline and island (i.e. those habitats without any freshwater source other than rainfall); and (4) groundwater-dependent shoreline. The responses of these habitats to changes in water level, salinity and other determinants have been described. An understanding of these responses facilitates the management of the estuary mouth. Past records indicate that the mouth closed naturally at the start of a drought, but the management policy was to keep it open by dredging the berm which developed at the mouth. While the mouth was open, seawater replaced estuary water lost to evaporation and the system eventually became hypersaline. An assessment of the range of physical conditions that occur in St Lucia Estuary and the response in each habitat indicated that the open mouth hypersaline condition is the most detrimental, resulting in die-back of shoreline vegetation. This understanding supported the management decision that resulted in the mouth being kept closed since 2002. Since then, the estuary has been characterised by high salinity but low water levels, and therefore large-scale die-back of shoreline vegetation has not occurred.