High Salt Medium Research Articles

Resins that reversibly bind algae for harvesting and concentration

Algae have great potential to address a number of important needs such as water remediation and as a feedstock for biofuel and biochemicals. At present, harvesting or removing algae is expensive, especially in terms of the cost of making biofuel. The expense of harvesting algae arises from the cost of pumping and processing large amounts of water. In an effort to explore less expensive methods for harvesting, a series of weak anion exchange resins incorporating various weak bases with different pKa values were developed to bind and release algae as a function of pH. The best of these resins bind about 10% of their weight in algae, show 100% reversibility and reusability, and the ability to concentrate algae from dilute suspension to 30 g L−1. Furthermore, they have the potential for desalting algae grown in high salt media. These resins provide a low cost method for harvesting algae without pumping water or introducing large amounts of chemicals into the feedwater, harvested algae, or the environment. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 1143–1149, 2013

Adjusting membrane lipids under salt stress: the case of the moderate halophilic organism Halobacillus halophilus

The lipid composition of Halobacillus halophilus was investigated by combined thin-layer chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analyses of the total lipid extract. Main polar lipids were found to be sulfoquinovosyldiacylglycerol and phosphatidylglycerol, while cardiolipin was a minor lipid together with phosphatidic acid, alanyl-phosphatidylglycerol and two not yet fully identified lipid components. In addition the analyses of residual lipids, associated with denatured proteins after the lipid extraction, revealed the presence of significant amounts of cardiolipin, indicating that it is a not readily extractable phospholipid. Post decay source mass spectrometry analyses allowed the determination of acyl chains of main lipid components. On increasing the culture medium salinity, an increase in the shorter chains and the presence of chain unsaturations were observed. These changes in the lipid core structures might compensate for the increase in packing and rigidity of phospholipid and sulfoglycolipid polar heads in high-salt medium, therefore contributing to the homeostasis of membrane fluidity and permeability in salt stress conditions.

Enzymatic characterization of transglutaminase from Streptomyces mobaraensis DSM 40587 in high salt and effect of enzymatic cross-linking of yak milk proteins on functional properties of stirred yogurt

Streptomyces transglutaminase (TGase) purified from high-salt medium was characterized and applied into yak yogurts. The purified enzyme presented a Michaelis constant of 40.47mmol and a maximum velocity of 44.44U/mg of protein for N-carboxybenzoyl-l-glutaminyl-glycine in the hydroxamate procedure. The purified TGase exhibited optimum activity at 55°C and pH 6.0. The enzyme was not stable above 50°C and was stable within a pH range of 5.0 to 10.0 at 4°C for 12h and pH 5.0 to 9.0 at 37°C for 30min. The TGase activity was not affected by Ca2+, K+, Ba2+, or Na+, but slightly inhibited by Fe2+, Mg2+, and Mn2+, and strongly by Cu2+ and Zn2+. To explore yak milk products, it was used to produce yogurt and TGase was used. It was found that TGase-catalyzed cross-linking was effective in improving functional properties of stirred yak yogurt. Treated yogurt produced a strong acid gel, higher consistency, cohesiveness, index of viscosity, and creamier mouth feel than the untreated product. Furthermore, yak yogurt treated with TGase presented lower wet yak hair or sweat odor, or both. Therefore, TGase can be used to pave the way for exploration of novel yak products to overcome the issues of peculiar wet yak hair or sweat odor, or both.

Glycosphingolipid synthesis is essential for MDCK cell differentiation

Glycosphingolipids (GSLs), which are highly concentrated at the apical membrane of polarized epithelial cells, are key components of cell membranes and are involved in a large number of processes. Here, we investigated the ability of hypertonicity (high salt medium) to induce Madin–Darby Canine Kidney (MDCK) cell differentiation and found an increase in GSL synthesis under hypertonic conditions. Then, we investigated the role of GSLs in MDCK cell differentiation induced by hypertonicity by using two approaches. First, cultured cells were depleted of GSLs by exposure to D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP). Second, cells were transfected with an siRNA specific to glucosylceramide synthase, the key enzyme in GSL synthesis. Exposure of cells to both treatments resulted in the impairment of the development of the apical membrane domain and the formation of the primary cilium. Enzymatic inhibitions of the de novo and the salvage pathway of GSL synthesis were used to determine the source of ceramide responsible of the GSL increase involved in the development of the apical membrane domain induced by hypertonicity. The results from this study show that extracellular hypertonicity induces the development of a differentiated apical membrane in MDCK cells by performing a sphingolipid metabolic program that includes the formation of a specific pool of GSLs. The results suggest as precursor a specific pool of ceramides formed by activation of a Fumonisin B1-resistant ceramide synthase as a component of the salvage pathway.

Effects of Fat on Relationship between Particle Size and Physical Properties of Cross-Linking Yogurt by Purified Transglutaminase from <i>Streptomyces mobaraensis</i> DSM 40587

The purified TGase produced by Streptomyces mobaraensis DSM 40587 from high salt medium was applied to whole and skim milk yogurt. During yogurt fermentation, no negative effect of TGase on fermentation time was found. Protein cross-linking by TGase was enhanced at varying concentrations from 0 to 5 U/g protein, resulting in a increase of apparent viscosity and decrease of syneresis. Furthermore, texture parameters were improved. However, extensive cross-linking resulted in too big size of the aggregates. The formation of these polymers resulted in a coarse texture of yogurt. Fat had no impact on the apparent viscosity and texture parameters, but significant changes in cross-linking of protein, syneresis and the sizes of the aggregates. From the range of TGase concentrations examined for properties of yogurt, the optimal level of TGase for skim milk yogurt was 1 U/g protein; however, for whole milk yogurt was 3 U/g protein.

Metabolic Pathways for Photobiological Hydrogen Production by Nitrogenase- and Hydrogenase-containing Unicellular Cyanobacteria Cyanothece

Current biotechnological interest in nitrogen-fixing cyanobacteria stems from their robust respiration and capacity to produce hydrogen. Here we quantify both dark- and light-induced H(2) effluxes by Cyanothece sp. Miami BG 043511 and establish their respective origins. Dark, anoxic H(2) production occurs via hydrogenase utilizing reductant from glycolytic catabolism of carbohydrates (autofermentation). Photo-H(2) is shown to occur via nitrogenase and requires illumination of PSI, whereas production of O(2) by co-illumination of PSII is inhibitory to nitrogenase above a threshold pO(2). Carbohydrate also serves as the major source of reductant for the PSI pathway mediated via nonphotochemical reduction of the plastoquinone pool by NADH dehydrogenases type-1 and type-2 (NDH-1 and NDH-2). Redirection of this reductant flux exclusively through the proton-coupled NDH-1 by inhibition of NDH-2 with flavone increases the photo-H(2) production rate by 2-fold (at the expense of the dark-H(2) rate), due to production of additional ATP (via the proton gradient). Comparison of photobiological hydrogen rates, yields, and energy conversion efficiencies reveals opportunities for improvement.

Factors associated with the occurrence of MRSA CC398 in herds of fattening pigs in Germany

BackgroundThe purpose of this study was to investigate the prevalence of MRSA in herds of fattening pigs in different regions of Germany, and to determine factors associated with the occurrence of this pathogen. For this purpose pooled dust samples were collected, and a questionnaire covered information regarding herd characteristics and management practices. Samples were pre-enriched in high-salt medium followed by selective enrichment containing cefoxitin/aztreonam, and culturing. Presumptive colonies were confirmed by multiplex-PCR targeting nuc-, mecA- and 16S rRNA-genes. Isolates were spa- and SCCmec-, and in selected cases, multilocus sequence-typed. Susceptibilities to 13 antimicrobials were determined by broth microdilution. Statistical analysis was carried out using backward stepwise logistic regression to calculate odds ratios with the MRSA test result as the outcome and herd characteristics as categorical covariates.ResultsOverall, 152 of 290 (52%) fattening pig farms tested positive for MRSA. The prevalence in the east, north- and south-west of Germany ranged from 39 to 59%.t011 (66%) and t034 (23%) were the most commonly identified spa-types, and 85% of isolates carried SCCmec Type V. Identified spa-types were all associated with clonal complex CC398. Susceptibility testing revealed that all isolates were resistant to tetracycline. High resistance rates were also found for sulfamethoxazole/trimethoprim (40%), and quinupristin/dalfopristin (32%). In addition, 83% of strains displayed multidrug resistant (> 3 substance classes) phenotypes.Logistic regression revealed herd size (large farms OR: 5.4; CI: 2.7-11.2; p < 0.05), and production type (wean-to-finish OR: 4.0; CI: 1.6-10.4; p < 0.05) as risk factors associated with a positive MRSA finding in fattening pig operations.ConclusionsMRSA CC398 is widely distributed among herds of fattening pigs in Germany. Farm management plays a crucial role in the dissemination of MRSA with herd size, and production type representing potential major indicators.

Protein glycosylation as an adaptive response in Archaea: growth at different salt concentrations leads to alterations in Haloferax volcanii S‐layer glycoprotein N‐glycosylation

To cope with life in hypersaline environments, halophilic archaeal proteins are enriched in acidic amino acids. This strategy does not, however, offer a response to transient changes in salinity, as would post-translational modifications. To test this hypothesis, N-glycosylation of the Haloferax volcanii S-layer glycoprotein was compared in cells grown in high (3.4 M NaCl) and low (1.75 M NaCl) salt, as was the glycan bound to dolichol phosphate, the lipid upon which the N-linked glycan is assembled. In high salt, S-layer glycoprotein Asn-13 and Asn-83 are modified by a pentasaccharide, while dolichol phosphate is modified by a tetrasaccharide comprising the first four pentasaccharide residues. When the same targets were considered from cells grown in low salt, substantially less pentasaccharide was detected. At the same time, cells grown at low salinity contain dolichol phosphate modified by a distinct tetrasaccharide absent in cells grown at high salinity. The same tetrasaccharide modified S-layer glycoprotein Asn-498 in cells grown in low salt, whereas no glycan decorated this residue in cells grown in the high-salt medium. Thus, in response to changes in environmental salinity, Hfx. volcanii not only modulates the N-linked glycans decorating the S-layer glycoprotein but also the sites of such post-translational modification.

Three new compounds from Aspergillus terreus PT06-2 grown in a high salt medium.

To investigate the structurally novel and bioactive natural compounds from marine-derived microorganisms under high salinity, the fungus Aspergillus terreus PT06-2 was isolated from the sediment of the Putian Sea Saltern, Fujian, China. Three new compounds, terremides A (1) and B (2) and terrelactone A (3), along with twelve known compounds (4–15) were isolated and identified from the fermentation broth of A. terreus PT06-2 at 10% salinity. Among these metabolites, compounds 4 and 15 only produced in the 10% salinity culture, were identified as methyl 3,4,5-trimethoxy-2-(2-(nicotinamido) benzamido) benzoate, and (+)-terrein, respectively. The new compounds 1 and 2 exhibited antibacterial activity against Pseudomonas aeruginosa and Enterobacter aerogenes with MIC values of 63.9 and 33.5 μM, respectively. Compounds 5 showed moderate anti-H1N1 activity and lower cytotoxicity with IC50 and CC50 values of and 143.1 and 976.4 μM, respectively.

Emergence of a Globally Dominant IncHI1 Plasmid Type Associated with Multiple Drug Resistant Typhoid

Typhoid fever, caused by Salmonella enterica serovar Typhi (S. Typhi), remains a serious global health concern. Since their emergence in the mid-1970s multi-drug resistant (MDR) S. Typhi now dominate drug sensitive equivalents in many regions. MDR in S. Typhi is almost exclusively conferred by self-transmissible IncHI1 plasmids carrying a suite of antimicrobial resistance genes. We identified over 300 single nucleotide polymorphisms (SNPs) within conserved regions of the IncHI1 plasmid, and genotyped both plasmid and chromosomal SNPs in over 450 S. Typhi dating back to 1958. Prior to 1995, a variety of IncHI1 plasmid types were detected in distinct S. Typhi haplotypes. Highly similar plasmids were detected in co-circulating S. Typhi haplotypes, indicative of plasmid transfer. In contrast, from 1995 onwards, 98% of MDR S. Typhi were plasmid sequence type 6 (PST6) and S. Typhi haplotype H58, indicating recent global spread of a dominant MDR clone. To investigate whether PST6 conferred a selective advantage compared to other IncHI1 plasmids, we used a phenotyping array to compare the impact of IncHI1 PST6 and PST1 plasmids in a common S. Typhi host. The PST6 plasmid conferred the ability to grow in high salt medium (4.7% NaCl), which we demonstrate is due to the presence in PST6 of the Tn6062 transposon encoding BetU.

Comparison Between a Tetraploid Turnip and Its Diploid Progenitor ( Brassica rapa L.): The Adaptation to Salinity Stress

Abstract Polyploidy is pursued in plant breeding programs due mainly to its ability to yield larger vegetative or reproductive organs. In controlled growth chamber experiments, a tetraploid turnip ( cv. Aijiaohuang, 4n) and its diploid progenitor ( cv. Aijiaohuang, 2n) were evaluated for their tolerance to salinity stress via investigations on a group of physiological parameters. The results indicate that the tetraploid turnip exhibit better adaptation to a high concentration salt medium (200 mmol L −1), as evidenced by a less-affected germination rate and a healthier morphological appearance at the seedling stage. Furthermore, an extension of salinity stress up to a certain period of time at the 5-7-leaf stage shows differences between the tetraploid turnip and its diploid progenitor. The former had a higher K +/Na + ratio in the roots, higher glutathione concentration and antioxidant activities in the leaves, and smaller reductions in photosynthetic capacity in terms of leaf chlorophyll content. Studies on the differences between an autopolyploid and its respective relative, from which the autopolyploid originated, in terms of their tolerance to salinity and/or other abiotic stresses, have remained rather limited. The comparison is interesting due to a homogenous genetic background.

Enhanced Level of Anthocyanin Leads to Increased Salt Tolerance in Arabidopsis PAP1-D Plants upon Sucrose Treatment

Many lines of evidence indicate that the increased activity of enzymes involved in phenolic compound biosynthesis and the subsequent accumulation of these compounds correlate with plant resistance to abiotic and biotic stresses. The production of anthocyanin pigment gene (PAP1) was previously identified using an activation tagging approach in Arabidopsis thaliana. A. thaliana PAP1-Dominant (pap1-D) mutant was generated by activation tagging. Throughout development, the pap1-D plant exhibited massive and widespread activation of genes encoding enzymes involved in phenylpropanoid natural product biosynthesis. Due to increased anthocyanin levels, pap1-D showed enhanced tolerance to salt, an important abiotic stress imposed on plants. In pap1-D plants, PAP1 transcript accumulation increased significantly in response to salt stress and abscisic acid. Enhanced anthocyanin levels induced by sucrose treatment increased the chance of survival of pap1-D and wild-type plants exposed to a high salt medium. Taken together, results of the present study indicate that genetic engineering of the flavonoid biosynthetic pathway can be used for successful improvement of plant survival in arid areas.

Drosophila melanogaster SAP18 protein is required for environmental stress responses

SAP18, a highly evolutionarily conserved protein, has been proposed to be involved in multiple cellular processes, from gene regulation to mRNA processing. To gain further insight into the role of SAP18, we performed genome-wide expression profiling of dsap18 mutant Drosophila melanogaster embryos and we found that dSAP18 is required for the expression of immune and stress related genes. We show that dSAP18 colocalizes with histone H3 phosphorylation, which has been implicated in the regulation of genes in response to signaling stimuli. dsap18 mutant larvae develop melanotic tumors after heat shock and the viability of dsap18 mutant flies is reduced after fungal infection or in high-salt medium. Altogether, our results indicate that dSAP18 is a key player in transcriptional responses to stress. Structured summarydSAP18 and H3colocalize: shown by fluorescence microscopy (view interaction)

Bend, Spin, Swim

Engineering Nanostructures that undergo directional propulsion (“nanoswimmers”) have recently been powered by catalytic chemical reactions (such as hydrogen peroxide disproportionation) or electric fields. Gao et al. now show that flexible nanowires powered by external magnetic fields can swim in a manner analogous to bacterial flagella. After sequential electrodeposition of gold-silver-nickel nanowires (6 µm long and 200 nm in diameter), the silver section was thinned via hydrogen peroxide oxidation to create a flexible linker. In solution, the nanowires respond to a rotating magnetic field, but the nickel head rotates through a greater solid angle than does the gold tail. This broken symmetry, along with tailoring of the segment lengths and magnetic field modulation, allows the structure to swim at speeds of up to 6 µm/s, even in high-salt media. J. Am. Chem. Soc. 132 , 10.1021/ja1072349 (2010).

Magnetically Powered Flexible Metal Nanowire Motors

Fuel-free magnetically driven propulsion of flexible Au/Ag/Ni nanowires, with a gold 'head' and nickel 'tail', linked by a partially dissolved and weakened silver bridge, is described. The flexible bridge facilitates the cyclic mechanical deformations under an external rotating magnetic field. Under such a field the nickel segment starts to rotate, facilitating the rotation of the gold segment at a different amplitude, hence breaking the system symmetry and inducing the movement. Forward ('pushing') and backward ('pulling') magnetically powered locomotion and a precise On/Off motion control are achieved by tailoring the length of the nickel and gold segments and modulating the magnetic field, respectively. Efficient locomotion in urine samples and in high-salt media is illustrated. The new magnetic nanowire swimmers can be prepared in large scale using a simple template electrodeposition protocol and offer considerable promise for diverse practical applications.

New method for electroporation of Lactobacillus species grown in high salt

We here describe a new method for electroporation of Lactobacillus species, obligately homofermentative and facultatively heterofermentative, based on the cell-wall weakening resulting from growth in high-salt media. For L. casei, optimum transformation efficiency of up to 10 5 transformants per microgram of plasmid DNA was achieved following growth in the presence of 0.9 M NaCl. Plasmids of different sizes and replication origins were also similarly transformed. These competent cells could be used either directly or stored frozen, up to 1 month, for future use, with similar efficiency. This protocol was assayed with different Lactobacillus species: L. delbrueckii subsp. lactis, L. paracasei, L. plantarum and L. acidophilus, and it was found that they were transformed with similar efficiency.

Production of Trametes gallica lignocellulases for wheat straw degradation

Trametes gallica (T. gallica) is a high producer of lignin-degrading enzymes including laccases, lignin peroxidases (LiPs), manganese-dependent peroxidases (MnPs), and hemicellulases (Hcels). The enzyme activities could peak at an early stage of fermentation. The activities of laccases and LiPs were high in high-nitrogen, low–carbon, and high inorganic salt media, while the activities of MnPs, and Hcels were the high in low-nitrogen, high–carbon, and high inorganic salt medium. It was found that T. gallica caused 34.4% mass losses after 20 days, 46.7% after 30 days, and 70.1% after 60 days, and at the same time T. gallica was able to degrade lignin at an early stage of solid fermentation. Based on these results, T. gallica may be a strain candidate for biopulping in the paper industry.

Mitochondrial Function Is an Inducible Determinant of Osmotic Stress Adaptation in Yeast

Hyperosmotic stress triggers a great variety of adaptive responses in eukaryotic cells that affect many different physiological functions. Here we investigate the role of the mitochondria during osmostress adaptation in budding yeast. Mitochondrial function is generally required for proper salt and osmotic stress adaptation because mutants with defects in many different mitochondrial components show hypersensitivity to increased NaCl and KCl concentrations. Mitochondrial protein abundance rapidly increases upon osmoshock in a selective manner, because it affects Calvin cycle enzymes (Sdh2 and Cit1) and components of the electron transport chain (Cox6) but not the ATP synthase complex (Atp5). Transcription of the SDH2, CIT1, and COX6 genes is severalfold induced within the first minutes of osmotic shock, dependent to various degree on the Hog1 and Snf1 protein kinases. Mitochondrial succinate dehydrogenase enzyme activity is stimulated upon osmostress in a Snf1-dependent manner. The osmosensitivity of mitochondrial mutants is not caused by impaired stress-activated transcription or by a general depletion of the cellular ATP pool during osmostress. We finally show that the growth defect of mitochondrial mutants in high salt medium can be partially rescued by supplementation of glutathione. Additionally, mitochondrial defects cause the hyperaccumulation of reactive oxygen species during salt stress. Our results indicate that the antioxidant function of the mitochondria might play an important role in adaptation to hyperosmotic stress.

Characterization of the PMT Gene Family in Cryptococcus neoformans

BackgroundProtein-O-mannosyltransferases (Pmt's) catalyze the initial step of protein-O-glycosylation, the addition of mannose residues to serine or threonine residues of target proteins.Methodology/Principal FindingsBased on protein similarities, this highly conserved protein family can be divided into three subfamilies: the Pmt1 sub-family, the Pmt2 sub-family and the Pmt4 sub-family. In contrast to Saccharomyces cerevisiae and Candida albicans, but similar to filamentous fungi, three putative PMT genes (PMT1, PMT2, and PMT4) were identified in the genome of the human fungal pathogen Cryptococcus neoformans. Similar to Schizosaccharomyces pombe and C. albicans, C. neoformans PMT2 is an essential gene. In contrast, the pmt1 and pmt4 single mutants are viable; however, the pmt1/pmt4 deletions are synthetically lethal. Mutation of PMT1 and PMT4 resulted in distinct defects in cell morphology and cell integrity. The pmt1 mutant was more susceptible to SDS medium than wild-type strains and the mutant cells were enlarged. The pmt4 mutant grew poorly on high salt medium and demonstrated abnormal septum formation and defects in cell separation. Interestingly, the pmt1 and pmt4 mutants demonstrated variety-specific differences in the levels of susceptibility to osmotic and cell wall stress. Delayed melanin production in the pmt4 mutant was the only alteration of classical virulence-associated phenotypes. However, the pmt1 and pmt4 mutants showed attenuated virulence in a murine inhalation model of cryptococcosis.Conclusion/SignificanceThese findings suggest that C. neoformans protein-O-mannosyltransferases play a crucial role in maintaining cell morphology, and that reduced protein-O-glycosylation leads to alterations in stress resistance, cell wall composition, cell integrity, and survival within the host.

Salt Stress Induces Production of Melanin Related Metabolites in the Phytopathogenic Fungus Leptosphaeria Maculans

A search for stress metabolites produced by the plant pathogenic fungus Leptosphaeria maculans (asexual stage Phoma lingam) cultured in high salt medium led to the isolation and structure elucidation of two metabolites associated with melanin biosynthesis and cell melanization, a self-protection mechanism against salt stress. The chemical structures of the metabolites were deduced by detailed analysis of 1D and 2D NMR spectroscopic data and chemical transformations.