Salinity Adaptation Research Articles

Permanent draft genome of the malachite-green-tolerant bacterium Rhizobium sp. MGL06

Rhizobium sp. MGL06, the first Rhizobium isolate from a marine environment, is a malachite-green-tolerant bacterium with a broader salinity tolerance (range: 0.5% to 9%) than other rhizobia. This study sequences and annotates the draft genome sequence of this strain. Genome sequence information provides a basis for analyzing the malachite green tolerance, broad salinity adaptation, nitrogen fixation properties, and taxonomic classification of the isolate.

A transcriptomic analysis of striped catfish (Pangasianodon hypophthalmus) in response to salinity adaptation: De novo assembly, gene annotation and marker discovery

The striped catfish (Pangasianodon hypophthalmus) culture industry in the Mekong Delta in Vietnam has developed rapidly over the past decade. The culture industry now however, faces some significant challenges, especially related to climate change impacts notably from predicted extensive saltwater intrusion into many low topographical coastal provinces across the Mekong Delta. This problem highlights a need for development of culture stocks that can tolerate more saline culture environments as a response to expansion of saline water-intruded land. While a traditional artificial selection program can potentially address this need, understanding the genomic basis of salinity tolerance can assist development of more productive culture lines. The current study applied a transcriptomic approach using Ion PGM technology to generate expressed sequence tag (EST) resources from the intestine and swim bladder from striped catfish reared at a salinity level of 9ppt which showed best growth performance. Total sequence data generated was 467.8Mbp, consisting of 4,116,424 reads with an average length of 112bp. De novo assembly was employed that generated 51,188 contigs, and allowed identification of 16,116 putative genes based on the GenBank non-redundant database. GO annotation, KEGG pathway mapping, and functional annotation of the EST sequences recovered with a wide diversity of biological functions and processes. In addition, more than 11,600 simple sequence repeats were also detected. This is the first comprehensive analysis of a striped catfish transcriptome, and provides a valuable genomic resource for future selective breeding programs and functional or evolutionary studies of genes that influence salinity tolerance in this important culture species.

Transcriptome differences between two sister desert poplar species under salt stress.

BackgroundPopulus euphratica Oliv and P. pruinosa Schrenk (Salicaceae) both grow in dry desert areas with high summer temperatures. However, P. euphratica is distributed in dry deserts with deep underground water whereas P. pruinosa occurs in deserts in which there is underground water close to the surface. We therefore hypothesized that these two sister species may have evolved divergent regulatory and metabolic pathways during their interaction with different salt habitats and other stresses. To test this hypothesis, we compared transcriptomes from callus exposed to 24 h of salt stress and control callus samples from both species and identified differentially expressed genes (DEGs) and alternative splicing (AS) events that had occurred under salt stress.ResultsA total of 36,144 transcripts were identified and 1430 genes were found to be differentially expressed in at least one species in response to salt stress. Of these DEGs, 884 and 860 were identified in P. euphratica and P. pruinosa, respectively, while 314 DEGs were common to both species. On the basis of parametric analysis of gene set enrichment, GO enrichment in P. euphratica was found to be significantly different from that in P. pruinosa. Numerous genes involved in hormone biosynthesis, transporters and transcription factors showed clear differences between the two species in response to salt stress. We also identified 26,560 AS events which were mapped to 8380 poplar genomic loci from four libraries. GO enrichments for genes undergoing AS events in P. euphratica differed significantly from those in P. pruinosa.ConclusionsA number of salt-responsive genes in both P. euphratica and P. pruinosa were identified and candidate genes with potential roles in the salinity adaptation were proposed. Transcriptome comparisons of two sister desert poplar species under salt stress suggest that these two species may have developed different genetic pathways in order to adapt to different desert salt habitats. The DEGs that were found to be common to both species under salt stress may be especially important for future genetic improvement of cultivated poplars or other crops through transgenic approaches in order to increase tolerance of saline soil conditions.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-337) contains supplementary material, which is available to authorized users.

Nitrilase superfamily aryl acylamidase from the halotolerant mangrove Streptomyces sp. 211726

A novel nitrilase superfamily amidase gene, designated azl13, was cloned from Streptomyces sp. 211726. Bioinformatic and biochemical analysis indicated that Azl13 belongs to a new subfamily in branch 13 of the nitrilase superfamily. His6-Azl13 was expressed in Escherichia coli BL21(DE3) and had the expected molecular mass of 31 kDa, and the enzymatic activity was best at 40 °C, pH 8.0. His6-Azl13 had amidase, aryl acylamidase, and acyl transferase activities, and it displayed an unusually wide substrate spectrum. His6-Azl13 was most active on 4-guanidinobutyramide, which is probably its natural substrate, moderately active on short-chain aliphatic amides and weakly active hydrolyzing aromatic and heterocyclic amides. His6-Azl13 also catalyzed acyl transfer to hydroxylamine from acetamide or the herbicide propanil. The substrate spectrum differs from that of the Pseudomonas amidase RamA, probably reflecting high salinity adaptation. The broad substrate spectrum of Azl13 is potentially useful for chemical synthesis and biodegradation.

An evolutionarily conserved RNase-based mechanism for repression of transcriptional positive autoregulation.

It is known that environmental context influences the degree of regulation at the transcriptional and post-transcriptional levels. However, the principles governing the differential usage and interplay of regulation at these two levels are not clear. Here, we show that the integration of transcriptional and post-transcriptional regulatory mechanisms in a characteristic network motif drives efficient environment-dependent state transitions. Through phenotypic screening, systems analysis, and rigorous experimental validation, we discovered an RNase (VNG2099C) in Halobacterium salinarum that is transcriptionally co-regulated with genes of the aerobic physiologic state but acts on transcripts of the anaerobic state. Through modelling and experimentation we show that this arrangement generates an efficient state-transition switch, within which RNase-repression of a transcriptional positive autoregulation (RPAR) loop is critical for shutting down ATP-consuming active potassium uptake to conserve energy required for salinity adaptation under aerobic, high potassium, or dark conditions. Subsequently, we discovered that many Escherichia coli operons with energy-associated functions are also putatively controlled by RPAR indicating that this network motif may have evolved independently in phylogenetically distant organisms. Thus, our data suggest that interplay of transcriptional and post-transcriptional regulation in the RPAR motif is a generalized principle for efficient environment-dependent state transitions across prokaryotes.

Resveratrol and its combination with α-tocopherol mediate salt adaptation in citrus seedlings

Resveratrol, a phytoalexin found in red wine, has the potential to impact a variety of human diseases but its function in plants exposed to stressful conditions is still unknown. In the present study the effect of exogenous application of resveratrol (Res), α-tocopherol (α-Toc) and their combination (Res + α-Toc) in salt adaptation of citrus seedlings was investigated. It was found that Res, α-Toc or Res + α-Toc treatments reduced NaCl-derived membrane permeability (EL), lipid peroxidation (MDA) and pigments degradation, whereas companied Res and α-Toc application also reduced H2O2 accumulation in leaves and restored the reduction of photosynthesis induced by NaCl. Application of Res under salinity retained Cl− in roots while Res + α-Toc reduced the translocation of Na+ and Cl− to leaves. Carbohydrates and proline, phenols, total ascorbic acid and glutathione were remarkably affected by NaCl as well as by chemical treatments in leaves and roots of citrus. NaCl treatment increased the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD), glutathione reductase (GR), polyphenol oxidase (PPO) in leaves while SOD and POD activities were decreased in roots by this treatment. Also, Res, α-Toc or Res + α-Toc treatments displayed tissue specific activation or deactivation of the antioxidant enzymes. Overall, this work revealed a new functional role of Res in plants and provided evidence that the interplay of between Res and α-Toc is involved in salinity adaptation.

Variations in osmotic adjustment and water relations of Sphaerophysa kotschyana: Glycine betaine, proline and choline accumulation in response to salinity.

BackgroundSphaerophysa kotschyana Boiss. is naturally distributed in overly salty regions. The key to the completion of the life cycles of S. kotschyana in harsh saline soils may be hidden in changes of its osmo-protectants, but there is currently no information about the interaction between osmotic adjustment and water relations in adaptation to saline conditions. The aim of this article was to determine growth, relative growth rate (RGR), relative water content (RWC), osmotic potential (ΨΠ), photosynthetic efficiency (Fv/Fm), thiobarbituric acid-reactive substances (TBARS) and osmo-protectant contents [proline (Pro), choline (Cho) and glycine betaine (GB)] in S. kotschyana leaves and roots exposed to 0, 150 or 300 mM NaCl for 7 and 14 d (days).ResultsThe results clearly showed that the reductions in growth, RWC, Fv/Fm, RGR and ΨΠ were more pronounced at 300 mM, especially after 14 d. In the same group, the highest increase in TBARS was recorded in roots (126%) and leaves (31%). The induction at 150 mM was not as high. Therefore, roots appear to be the most vulnerable part of this plant. Moreover, S. kotschyana was able to withstand short-term low salinity.ConclusionsThe osmo-protectant accumulation in S. kotschyana as a salinity acclimation or adaptation was sufficient for toleration of low salt concentration (150 mM). In contrast, the plants exposed to the highest NaCl concentration (300 mM) were not able to maintain the ability to prevent water loss because of further decrease in root/shoot ratio of fresh weight (FW) and dry weight (DW), RWC and RGR.Electronic supplementary materialThe online version of this article (doi:10.1186/1999-3110-55-6) contains supplementary material, which is available to authorized users.

Proteome variance differences within populations of European whitefish (Coregonus lavaretus) originating from contrasting salinity environments

Variation in gene expression is an important component of the phenotypic differences observed in nature. Gene expression variance across biological groups and environmental conditions has been studied extensively and has revealed specific genes and molecular mechanisms of interest. However, little is known regarding the importance of within-population gene expression variation to environmental adaptation. To address this issue, we quantified the proteomes of individuals of European whitefish (Coregonus lavaretus) from populations that have previously been shown to have adapted during early development to freshwater and brackishwater salinity environments. Using MS-based label-free proteomics, we studied 955 proteins in eight hatch-stage fish embryos from each population that had been reared in either freshwater or brackishwater salinity conditions. By comparing the levels of within-population protein expression variance over individuals and per protein between populations, we found that fish embryos from the population less affected by salinity level had also markedly higher levels of expression variance. Gene Ontologies and molecular pathways associated with osmoregulation showed the most significant difference of within-population proteome variance between populations. Several new candidate genes for salinity adaptation were identified, emphasising the added value of combining assessments of within-population gene expression variation with standard gene expression analysis practices for better understanding the mechanisms of environmental adaptation. We demonstrate the benefits of studying within-population gene expression variance together with more typical methods of gene expression profiling. Proteome variance differences within European whitefish populations originating from different salinity environments allowed us to identify several new candidate genes for salinity adaptation in teleost fish and generate many further hypotheses to be tested. This article is part of a Special Issue entitled: Proteomics of non-model organisms.

The ecological genomic basis of salinity adaptation in Tunisian Medicago truncatula

BackgroundAs our world becomes warmer, agriculture is increasingly impacted by rising soil salinity and understanding plant adaptation to salt stress can help enable effective crop breeding. Salt tolerance is a complex plant phenotype and we know little about the pathways utilized by naturally tolerant plants. Legumes are important species in agricultural and natural ecosystems, since they engage in symbiotic nitrogen-fixation, but are especially vulnerable to salinity stress.ResultsOur studies of the model legume Medicago truncatula in field and greenhouse settings demonstrate that Tunisian populations are locally adapted to saline soils at the metapopulation level and that saline origin genotypes are less impacted by salt than non-saline origin genotypes; these populations thus likely contain adaptively diverged alleles. Whole genome resequencing of 39 wild accessions reveals ongoing migration and candidate genomic regions that assort non-randomly with soil salinity. Consistent with natural selection acting at these sites, saline alleles are typically rare in the range-wide species' gene pool and are also typically derived relative to the sister species M. littoralis. Candidate regions for adaptation contain genes that regulate physiological acclimation to salt stress, such as abscisic acid and jasmonic acid signaling, including a novel salt-tolerance candidate orthologous to the uncharacterized gene AtCIPK21. Unexpectedly, these regions also contain biotic stress genes and flowering time pathway genes. We show that flowering time is differentiated between saline and non-saline populations and may allow salt stress escape.ConclusionsThis work nominates multiple potential pathways of adaptation to naturally stressful environments in a model legume. These candidates point to the importance of both tolerance and avoidance in natural legume populations. We have uncovered several promising targets that could be used to breed for enhanced salt tolerance in crop legumes to enhance food security in an era of increasing soil salinization.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1160) contains supplementary material, which is available to authorized users.

Prokaryotic expression of the Portunus trituberculatus Ferritin gene during salinity stress

We evaluated the effect of ferritin on the ability of the swimming crab to adapt to salinity stress.We amplified the Ferritin gene from the sixth gill of the swimming crab and cloned it into the pET 28 a(+) expression vector.The vector was transformed into Escherichia coli DE3(BL21) and induced by IPTG.The Ferritin protein was successfully induced by IPTG,yielding a band that was consistent with the theoretical value(19.448 kD).The survival rate of recombinant plasmid transferred E.coli was higher than that of empty vector transferred cells.Furthermore,the recombinant plasmid significantly improved the tolerance of E.coli to salinity stress.Our results suggest that Ferritin improves the ability of E.coli to cope with salinity stress and so may also play a role in salinity adaptation in P.trituberculatus.

Identification and characterization of salt responsive miRNA-SSR markers in rice (Oryza sativa)

Salinity is an important abiotic stress that affects agricultural production and productivity. It is a complex trait that is regulated by different molecular mechanisms. miRNAs are non-coding RNAs which are highly conserved and regulate gene expression. Simple sequence repeats (SSRs) are robust molecular markers for studying genetic diversity. Although several SSR markers are available now, challenge remains to identify the trait-specific SSRs which can be used for marker assisted breeding. In order to understand the genetic diversity of salt responsive-miRNA genes in rice, SSR markers were mined from 130 members of salt-responsive miRNA genes of rice and validated among the contrasting panels of tolerant as well as susceptible rice genotypes, each with 12 genotypes. Although 12 miR-SSRs were found to be polymorphic, only miR172b-SSR was able to differentiate the tolerant and susceptible genotypes in 2 different groups. It had also been found that miRNA genes were more diverse in susceptible genotypes than the tolerant one (as indicated by polymorphic index content) which might interfere to form the stem-loop structure of premature miRNA and their subsequent synthesis in susceptible genotypes. Thus, we concluded that length variations of the repeats in salt responsive miRNA genes may be responsible for a possible sensitivity to salinity adaptation. This is the first report of characterization of trait specific miRNA derived SSRs in plants.

Transcriptome Analysis of Portunus trituberculatus in Response to Salinity Stress Provides Insights into the Molecular Basis of Osmoregulation

BackgroundThe swimming crab, Portunus trituberculatus, which is naturally distributed in the coastal waters of Asia-Pacific countries, is an important farmed species in China. Salinity is one of the most important abiotic factors that influence not only the distribution and abundance of crustaceans, it is also an important factor for artificial propagation of the crab. To better understand the interaction between salinity stress and osmoregulation, we performed a transcriptome analysis in the gills of Portunus trituberculatus challenged with salinity stress, using the Illumina Deep Sequencing technology.ResultsWe obtained 27,696,835, 28,268,353 and 33,901,271 qualified Illumina read pairs from low salinity challenged (LC), non-challenged (NC), and high salinity challenged (HC) Portunus trituberculatus cDNA libraries, respectively. The overall de novo assembly of cDNA sequence data generated 94,511 unigenes, with an average length of 644 bp. Comparative genomic analysis revealed that 1,705 genes differentially expressed in salinity stress compared to the controls, including 615 and 1,516 unigenes in NC vs LC and NC vs HC respectively. GO functional enrichment analysis results showed some differentially expressed genes were involved in crucial processes related to osmoregulation, such as ion transport processes, amino acid metabolism and synthesis processes, proteolysis process and chitin metabolic process.ConclusionThis work represents the first report of the utilization of the next generation sequencing techniques for transcriptome analysis in Portunus trituberculatus and provides valuable information on salinity adaptation mechanism. Results reveal a substantial number of genes modified by salinity stress and a few important salinity acclimation pathways, which will serve as an invaluable resource for revealing the molecular basis of osmoregulation in Portunus trituberculatus. In addition, the most comprehensive sequences of transcripts reported in this study provide a rich source for identification of novel genes in the crab.

Role of membrane lipid in osmoregulatory processes during salinity adaptation: a study with chloride cell of mud crab, Scylla serrata

A significant variation in membrane fluidity, lipid composition, fatty acids profile and intra–extracellular ion concentrations of chloride cells was observed in the estuarine mud crab, Scylla serrata, when they were acclimated to 1 and 35 psu. About 60% decrease in Km and Vmax of Na+/K+-ATPase, Mg2+ ATPase and Ca2+ ATPase enzymes and 85% increase in the same was observed when the crabs were acclimated to 1 and 35 psu saline water, respectively. The changed membrane lipid bilayer composition and fluidity of the plasma membrane of chloride cell help in modulating activity of Na+/K+-ATPase and thus regulate the ionic composition of the cell during salinity adaptation.

Investigation of soil and water salinity, its effect on crop production and adaptation strategy

Bangladesh is a deltaic country with total area of 147,570 km2. The major part (80%) of the country consists of alluvial sediments deposited by the river Ganges, Brahmaputra, Tista, Jamuna, Meghna and their tributaries. The coastal region covers almost 29,000 sq. km or about 20% of the country. Moreover, the coastal areas of Bangladesh cover more than 30% of the cultivable lands of the country. About 53% of the coastal areas are affected by salinity. Agricultural land use in these areas is very poor, which is much lower than a country’s average cropping intensity. Salinity causes unfavorable environment and hydrological situation that restrict the normal crop production throughout the year. The factors which contribute significantly to the development of saline soil are, tidal flooding during wet season (June to October), direct inundation by saline water, and upward or lateral movement of saline ground water during dry season (November to May). The severity of salinity problem in Bangladesh increases with the desiccation of the soil. It affects crops depending on degree of salinity at the critical stages of growth, which reduces yield and in severe cases total yield is lost. Therefore, it is very important to investigate the present scenario of soil and water affected by salinity on crop production of the study area. It is found from the study area named south-western zone of Bangladesh (selected eight sites of seven Upazila under greater Khulna district) that salinity level increased in April to May and decreased in October to November in every year. It has effect on crop yield in dry season due to increased salinity level. If Ganges water supply has increased in dry season, it reduces the salinity effect in crop production in Khulna. Rainfall also reduces the surfaces soil salinity. Key words: Salinity, coastal region, cultivable lands, cropping intensity, salinity adaptability.

Genome and Transcriptome Analyses Provide Insight into the Euryhaline Adaptation Mechanism of Crassostrea gigas

BackgroundThe Pacific oyster, Crassostrea gigas, has developed special mechanisms to regulate its osmotic balance to adapt to fluctuations of salinities in coastal zones. To understand the oyster’s euryhaline adaptation, we analyzed salt stress effectors metabolism pathways under different salinities (salt 5, 10, 15, 20, 25, 30 and 40 for 7 days) using transcriptome data, physiology experiment and quantitative real-time PCR.ResultsTranscriptome data uncovered 189, 480, 207 and 80 marker genes for monitoring physiology status of oysters and the environment conditions. Three known salt stress effectors (involving ion channels, aquaporins and free amino acids) were examined. The analysis of ion channels and aquaporins indicated that 7 days long-term salt stress inhibited voltage-gated Na+/K+ channel and aquaporin but increased calcium-activated K+ channel and Ca2+ channel. As the most important category of osmotic stress effector, we analyzed the oyster FAAs metabolism pathways (including taurine, glycine, alanine, beta-alanine, proline and arginine) and explained FAAs functional mechanism for oyster low salinity adaptation. FAAs metabolism key enzyme genes displayed expression differentiation in low salinity adapted individuals comparing with control which further indicated that FAAs played important roles for oyster salinity adaptation. A global metabolic pathway analysis (iPath) of oyster expanded genes displayed a co-expansion of FAAs metabolism in C. gigas compared with seven other species, suggesting oyster’s powerful ability regarding FAAs metabolism, allowing it to adapt to fluctuating salinities, which may be one important mechanism underlying euryhaline adaption in oyster. Additionally, using transcriptome data analysis, we uncovered salt stress transduction networks in C. gigas.ConclusionsOur results represented oyster salt stress effectors functional mechanisms under salt stress conditions and explained the expansion of FAAs metabolism pathways as the most important effectors for oyster euryhaline adaptation. This study was the first to explain oyster euryhaline adaptation at a genome-wide scale in C. gigas.

Effect of overexpression of proline dehydrogenase on high saline adaptation through proline utilization in Escherichia coli

The effect of the amount of proline dehydrogenase PutA expression on the mechanism of adaptation of Escherichia coli cells under high salinity was analyzed. The PutA gene derived from E. coli expression plasmid was introduced into E. coli cell, and PutA high expression strain BL21-PutA was developed. Transcription of the PutA was induced by the addition of gene expression inducer IPTG, and high transcription was observed under 1 M NaCl condition. Growth of E. coli BL21-PutA in a Davis minimal medium was inhibited under 1 M NaCl condition, but it was remarkably recovered by the addition of L-proline. On the other hand, the recovery of growth in the presence of L-proline was inhibited when IPTG was added. Under 1 M NaCl condition, L-proline was quickly accumulated in cells, regardless of the strains. On the other hand, intracellular concentration of L-proline in BL21-PutA cells cultured with IPTG was lower than BL21 cells. These data suggested that the amount of the expression of PutA affected the adaptation of high salinity with L-proline in E. coli cells. Key words: Escherichia coli, high salinity adaptation, proline dehydrogenase PutA, overexpression

Molecular cloning and characterization of acyl-CoA binding protein (ACBP) gene from shrimp Penaeus monodon exposed to salinity stress

Acyl-CoA binding protein (ACBP), a protein present ubiquitously in wide range of organisms play significant role in transport of acyl groups for macromolecular biosynthesis involved in various functional and regulatory processes. In crustaceans, ACBP has functional role in growth, reproduction and temperature tolerance. In the present study, two suppression subtractive hybridization (SSH) cDNA libraries were performed using gut tissues of shrimp Penaeus monodon exposed to low (3ppt) and high (55ppt) salinity stress conditions. SSH library resulted in identification of differentially expressed genes that belonged to various functional classes such as the nucleic acid regulation and replication, defence proteins, allergen protein, signal transduction pathways, apoptosis, energy and metabolism, cell cycle regulation and hypothetical proteins. ACBP was identified as one of the differentially expressed gene in both the SSH libraries of shrimp P. monodon subjected to low and high salinity stress. The full-length cDNA of P. monodon ACBP gene was isolated and the sequence revealed 273bp open reading frame encoding 90 amino acids with molecular mass of 10kDa and pI 6.8. The ORF showed presence of four phosphorylation sites, with absence of signal peptide sequence and glycosylation sites. The deduced amino acid sequence of ACBP exhibited high sequence identity (92%) with ACBP class of protein identified from Fenneropenaeus chinensis. Real time PCR analysis of shrimps subjected to 3ppt salinity conditions after 2weeks revealed an increase in expression of ACBP transcripts, in the gut (28.08-folds), gills (11.71-folds) and in the muscle tissues (1.70-folds). Whereas, shrimps exposed to 55ppt salinity conditions after 2weeks exhibited increased ACBP transcript levels in the gut (11.95-folds), gills (1.052-folds) and muscle tissues (7.35-folds). The significant increase in expression levels of ACBP in various tissues of shrimps suggests a functional role of this gene in salinity stress tolerance and adaptation.

Effects of salinity on serum osmolality,catalase and gill ion-regulatory enzyme activities in silver pomfret

The juvenile silver pomfret were cultured in water with salinity 14,25 and 36,respectively,for 96h. And their serum osmolality,catalase( CAT) and gill V-H+-ATPase( VHA),Ca2 +-ATPase,carbonic anhydrase( CA) activities w ere tested in different salinity over time in this experiment. In this study,the serum osmolality w hich fluctuated w as positively correlated to salinity,and its variation range is 271- 379mOsm / kg. The serum osmolality of different salinity w ould return to normal at 96 h. CAT activities of salinity 36 and 14 returned to normal after they rose significantly( P 0. 05); the highest point of them w as salinity 36 at 8 h. VHA activities rose,then recovered in salinity 14,kept stable in control salinity,fell dow n then recovered in salinity 36. Ca2 +-ATPase activities increased significantly w hen salinity changed( P 0. 05),and the variation trend in salinity 14 w as more identifiable than that in salinity 36. CA activities in salinity 14 and 36 both increased significantly( P 0. 05),and the highest point w as found in salinity 36 at24 h. Through analysis of the data,the serum osmolality w as significantly negatively correlated to gill VHA activity( P 0. 01),and it w as significantly negatively correlated to CA activity( P 0. 01) in low salinity adaptation( 14 and 25). It also illustrated a contrary trend betw een serum osmolality and Ca2 +-ATPase activity in salinity 14. This research proved that serum osmolality w hich changes w ith salinity,w ill activate CAT w hen silver pomfret adapts to different salinity. And VHA,Ca2 +-ATPase and CA are playing important roles in osmoregulation.

The start-up and saline adaptation of mesophilic anaerobic sequencing batch reactor treating sludge from recirculating aquaculture systems

Treatment of sludge from aquaculture is a matter of special importance and there is a need for salt-tolerant biological wastewater treatment to coincide with the development of brackish/marine aquaculture. The aims of the current study were to determine the ability of anaerobic sequencing batch reactor (ASBR) to anaerobically digest sludge from fresh-water recirculating aquaculture systems and the ability of adaptation to low saline conditions. The mesophilic ASBR were evaluated with loading rates between 0.12 and 0.41g chemical oxygen demand (COD)/day at a 20-day hydraulic retention time (HRT) for start-up and with organic loading rates (OLR) of 0.39–0.41gCOD/Lday at a 20-day HRT for saline adaptation. The average removal rate of total chemical oxygen demand (TCOD), total suspended solids (TSS) and volatile suspended solids (VSS) of the ASBR were above 97%, 96% and 91% during the stabilization period of the experimental reactors. The average daily gas production of ASBR was between 0.013 and 0.022L/g TCOD from day 118. A sludge-mass reduction of up to 94±2.3%, TCOD reduction of 44±13% and VSS/SS of 39–70% were demonstrated for the reactor performance during the gas production period. However, the process of gas production was obviously inhibited, presumably by salt, and unstable due to the dissolved COD (DCOD), total ammonium nitrogen (TAN) and alkalinity of the effluents of the experimental reactors and TSS and sludge volume index (SVI) observed within the reactors. The daily gas production was observed to decrease during the saline adaptation period and stopped when the salinity of the effluents was higher than 8.7ppt until the end of the experiment.

Ectonucleotidase and acetylcholinesterase activities in silver catfish (Rhamdia quelen) exposed to different salinities

Abstract The purpose of this study was to investigate whether salinity adaptation can alter the purinergic (ecto-nucleoside triphosphate diphosphohydrolase; NTPDase and, 5′-nucleotidase) and cholinergic (acetylcholinesterase; AChE) systems in whole brain and blood tissue of the silver catfish, Rhamdia quelen. Silver catfish were gradually adapted to salinities of 0, 4 or 8 ppt and maintained at the experimental salinity for 10 days before brain and blood samples were collected. Blood AChE activity decreased significantly at 8 ppt and significant decreases in AChE activity were observed in the brain with salinity increases. ATP hydrolysis did not change between the groups. In contrast, ADP and AMP hydrolysis in silver catfish maintained at salinities of 4 and 8 ppt were significantly higher than those kept at 0 ppt. In conclusion, this study showed that there is an enhancement in the NTPDase (ADP hydrolysis) and 5′-nucleotidase activities in the brains of silver catfish exposed to increased salinity. Therefore, the activities of these enzymes can act as markers of salinity changes.