Identification and characterization of genes conferring salt tolerance to Escherichia coli from pond water metagenome

Metagenomics provides culture-independent access to gene pool of the whole microbial communities. To identify genes responsible for salt tolerance in unculturable bacteria, Escherichia coli clones were enriched with an ability to grow at inhibitory NaCl concentrations (750 mM) from a pond water metagenomic library. From two unique clones, genes encoding for proteins with similarity to a putative general stress protein (GspM) harbouring GsiB domain and a putative enoyl-CoA hydratase (EchM) were identified to be responsible for salt tolerance. The gspM was expressed by its native promoter whereas the echM was expressed from the lacZ promoter of the plasmid. EchM was overexpressed with a hexahistidyl tag. Purified EchM showed crotonyl-CoA hydratase activity. These genes have potential application in generating salt tolerant recombinant bacteria or transgenic plants.

Sequence analysis of a salt tolerant metagenomic clone

Metagenome represent an unlimited resource for discovery of novel genes. Here we report, sequence analysis of a salt tolerant metagenomic clone (6B4) from a pond water metagenomic library. Clone 6B4 had an insert of 2254 bp with G+C composition of 64.06%. DNA sequence from 6B4 showed homology to DNA sequences from proteobacteria indicating origin of 6B4 metagenomic insert from a yet uncharacterized proteobacteria. Two encoded proteins from clone 6B4 showed match with ATP-dependent Clp protease adaptor protein (ClpS) and phasin, while two truncated encoded proteins showed match with poly-3-hydroxybutyrate synthase and permease. Clp complex is known to play a role in stress tolerance. Expression of ClpS from metagenomic clone is proposed to be responsible for salt tolerance of the metagenomic clone 6B4.

The resurrection plant Sporobolus stapfianus: An unlikely model for engineering enhanced plant biomass?

The resurrection grass Sporobolus stapfianus Gandoger can rapidly recover from extended periods of time in the desiccated state (water potential equilibrated to 2% relative humidity) (Gaff and Ellis, Bothalia 11:305–308 1974; Gaff and Loveys, Transactions of the Malaysian Society of Plant Physiology 3:286–287 1993). Physiological studies have been conducted in S. stapfianus to investigate the responses utilised by these desiccation-tolerant plants to cope with severe water-deficit. In a number of instances, more recent gene expression analyses in S. stapfianus have shed light on the molecular and cellular mechanisms mediating these responses. S. stapfianus is a versatile research tool for investigating desiccation-tolerance in vegetative grass tissue, with several useful characteristics for differentiating desiccation-tolerance adaptive genes from the many dehydration-responsive genes present in plants. A number of genes orthologous to those isolated from dehydrating S. stapfianus have been successfully used to enhance drought and salt tolerance in model plants as well as important crop species. In addition to the ability to desiccate and rehydrate successfully, the survival of resurrection plants in regions experiencing short sporadic rainfall events may depend substantially on the ability to tightly down-regulate cell division and cell wall loosening activities with decreasing water availability and then grow rapidly after rainfall while water is plentiful. Hence, an analysis of gene transcripts present in the desiccated tissue of resurrection plants may reveal important growth-related genes. Recent findings support the proposition that, as well as being a versatile model for devising strategies for protecting plants from water-loss, resurrection plants may be a very useful tool for pinpointing genes to target for enhancing growth rate and biomass production.

Sporobolus stapfianus, a model desiccation-tolerant grass

Sporobolus stapfianus Gandoger, one of ~40 known ‘anabiotic’grass species (i.e. ‘able to regain vital activity from a state of latent life’), is the most versatile tool for research into desiccation tolerance in vegetative grass tissue. Current knowledge on this species is presented, including the features that suit it for investigations into the plant’s ability to survive dehydration of its leaf protoplasm. The main contributors to desiccation tolerance in S. stapfianus leaves appear to be: accumulation during dehydration of protectants of membranes and proteins; mechanisms limiting oxidative damage; a retention of protein synthetic activity in late stages of drying that is linked with changes in gene expression and in the proteomic array; and an ability to retain net synthesis of ATP during drying. S. stapfianus exemplifies an advanced stage of an evolutionary trend in desiccation tolerant plants towards increased importance of the dehydration phase (for induction of tolerance, for synthesis of protectants and for proteomic changes).

Water-soluble acrylamide sulfonate copolymer for inhibiting shale hydration

Here we report a water-soluble acrylamide sulfonate copolymer for inhibiting shale hydrate formation. The copolymer, denoted as PANAA, was synthesized via copolymerization of acrylamide (AM), N,N-diallylbenzylamine (NAPA), acrylic acid (AA), and 2-(acrylamide)-2-methylpropane-1-sulfonic acid (AMPS). The performance of this new water-soluble copolymer for inhibiting shale hydration was investigated for the first time. The retention ratio of apparent viscosity of 2 wt % PANAA solution can reach 61.6% at 130 C and further up to 72.2% with 12 000 mg/L NaCl brine. The X-ray diffraction studies show that the addition of copolymer PANAA (5000 mg/L), in combination with a low loading of KCl (3 wt %), remarkably reduces the interlayer spacing of sodium montmorillonite (Na-MMT) in water from 19.04 to 15.65 Å. It has also found that these copolymer solutions, blending with KCl, can improve the retention of indentation hardness from 22% to 74% and increase the antiswelling ratio up to 84%. All results have demonstrated that the PANAA copolymer not only has excellent temperature-resistance and salt-tolerance but also exhibits a significant effect on inhibiting the hydration of clays and shale. © 2014 American Chemical Society.

A water-soluble antimicrobial acrylamide copolymer containing sulfitobetaine for enhanced oil recovery

Herein, we report a novel acrylamide copolymer with antimicrobial property as an enhanced oil recovery chemical. The copolymer was synthesized from acrylamide (AM), acrylic acid (AA) and 2-((2-(acryloyloxy)ethyl)dimethylammonio)ethyl sulfite (ADMES) using oxidation-reduction initiation system. Subsequently, the copolymer AM/AA/ADMES was evaluated and characterized on several aspects such as IR, ¹H NMR, intrinsic viscosity, and dissolubility. The AM/AA/ADMES solution exerted remarkable thickening ability, salt tolerance ability and viscoelasticity. In addition, the rheological properties, temperature resistance ability and long-term stability of AM/AA/ADMES were investigated systematically in the presence of sulfate-reducing bacteria and relatively low viscosity loss could be obtained compared to partially hydrolyzed polyacrylamide. On the basis of core flooding experiments, AM/AA/ADMES was found to be a valuable prospect with 10.5 resistance factor, 4.6 residual resistance factor and up to 11.0% enhanced oil recovery.

A novel water-soluble hydrophobically associating polyacrylamide based on oleic imidazoline and sulfonate for enhanced oil recovery

3-(2-(2-Heptadec-8-enyl-4,5-dihydro-imidazol-1-yl)ethylcarbamoyl)acrylic acid (NIMA), 3-(diallyl-amino)-2-hydroxypropyl sulfonate (NDS), acrylamide (AM) and acrylic acid (AA) were successfully utilized to prepare novel acrylamide-based copolymers (named AM/AA/NIMA and AM/AA/NDS/NIMA) which were functionalized by a combination of imidazoline derivative and/or sulfonate via redox free-radical polymerization. The two copolymers were characterized by infrared (IR) spectroscopy, 1H nuclear magnetic resonance (1H NMR), viscosimetry, pyrene fluorescence probe, thermogravimetry (TG) and differential thermogravimetry (DTG). As expected, the polymers exhibited excellent thickening property, shear stability (viscosity retention rate 5.02% and 7.65% at 1000 s-1) and salt-tolerance (10:000 mg L-1 NaCl: viscosity retention rate up to 17.1% and 10.2%) in comparison with similar concentration partially hydrolyzed polyacrylamide (HPAM). The temperature resistance of the AM/AA/NDS/NIMA solution was also remarkably improved and the viscosity retention rate reached 54.8% under 110 °C. According to the core flooding tests, oil recovery could be enhanced by up to 15.46% by 2000 mg L-1 of the AM/AA/NDS/NIMA brine solution at 80 °C.

Selection and characterization of probiotic culture of Streptococcus thermophilus from dahi

For the isolation of probiotic cultures of Streptococcus thermophilus from dahi, we collected 120 samples from the southern regions of Punjab, Pakistan. Eleven isolates were obtained, and six were scrutinized for antibacterial activities against food-borne pathogens. The carbohydrate fermentation profile of these six strains was determined by the API50 CHL system. Additionally, these strains were amplified for their 16S rRNA regions to confirm their genotypic relationship. Furthermore, phenotypic characteristics among these strains were established by S-layer protein analysis of their cell walls by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and by plasmid profiling. The outer cell wall layers of these strains have 6-14 different sizes of protein bands of 27, 34, 37, 40, 45 and 60 kDa molecular weight. Similarly, except S02FT, all strains have a single prominent plasmid of 23 kbp, whereas S02FT has an additional plasmid of 9 kbp. On the basis of this unique feature and a wide spectrum of killing patterns against pathogenic bacteria, S. thermophilus S02FT was further characterized. This culture showed an optimum antibacterial activity of 800 AU/ml at pH 5.0-5.5 and a temperature of 30-37°C. It grows well in in vitro acidic conditions and tolerates bile salt up to 2% concentration. It was resistant to nalidixic acid, ciprofloxacin, gentamicin and sulphamethoxazol, but showed intermediate behaviour to vancomycin and erythromycin.

A novel α-aminophosphonic acid-modified acrylamide-based hydrophobic associating copolymer with superb water solubility for enhanced oil recovery

As a non-renewable resource, the rational exploitation of oil has attracted a large amount of attention. Among many methods for enhanced oil recovery, polymer flooding is the most suitable method of chemical flooding for non-marine reservoirs and therefore various modified acrylamide-based copolymers have been studied. In this study, a novel α-aminophosphonic acid-modified hydrophobic associating copolymer was successfully synthesized by copolymerization of acrylamide, acrylic acid, N-allyldodecanamide and 1-(dimethylamino)allylphosphonic acid. The copolymer was characterized by FT-IR, 1H NMR and thermogravimetry and exhibited superior water solubility and thickening capability. Subsequently, the shear resistance, temperature resistance and salt tolerance of the copolymer solution were investigated. The value of apparent viscosity retention of a 2000 mg L-1 copolymer solution was as high as 58.55 mPa s at a shear rate of 170 s-1 and remained at 40.20 mPa s at 120 °C. The values of apparent viscosity retention of 55.41 mPa s, 59.95 mPa s and 52.97 mPa s were observed in solutions of 10000 mg L-1 NaCl, 1200 mg L-1 MgCl2, and 1200 mg L-1 CaCl2, respectively. These were better than those of partially hydrolyzed polyacrylamide under the same conditions. In addition, an increase of up to 14.52% in the oil recovery rate compared with that for water flooding could be achieved in a core flooding test using a 2000 mg L-1 copolymer solution at 65 °C.

Recruitment of a keystone tree species must concurrently manage flooding and browsing

Multiple pressures (land-use change, water extraction and climate change) interact to influence biodiversity and ecosystem processes, but direct evidence for interactions among multiple pressures is limited. Floodplain forests are an acute example of how interacting pressures (river regulation, water extraction, decreasing rainfall and mammal browsing) interact to degrade native ecosystems. We conducted a 2-year field experiment to determine how flooding, browsing and sediment salinity interacted to determine in situ seedling survival and growth of the keystone floodplain tree species (Eucalyptus camaldulensis Dehnh.). On semi-arid floodplains of southern Australia, 1-year-old seedlings were planted on the banks of six ephemeral creeks, three of which were flooded with management flows before planting while the others remained dry. Four plots were established at each creek, two open to browsing and two fenced to exclude mammal herbivores. Flooding had a strong positive effect on seedling survival and height, but browsing had strong negative effects. Sediment salinity (a covariate rather than a designed effect) had a weak negative effect on seedling survival and height. The positive effects of flooding were largely offset by the negative interaction with browsing and, to a lesser extent, sediment salinity. Although flooding has been restored to some degraded floodplain forests subjected to river regulation and a drying climate, the long-term success of such actions is likely to be undermined by persistent browsing. Synthesis and applications. Management actions that focus on single pressures (e.g. infrequent flooding) and processes (e.g. mature tree survival) while ignoring other pressures are unlikely to sustain populations of keystone species, suggesting that complementary strategies (managed flooding with herbivore control) are necessary to sustain recruitment and, therefore, ensure the future health of these essential ecosystems.

Increased Biomass, Seed Yield and Stress Tolerance Is Conferred in Arabidopsis by a Novel Enzyme from the Resurrection Grass Sporobolus stapfianus That Glycosylates the Strigolactone Analogue GR24

Isolation of gene transcripts from desiccated leaf tissues of the resurrection grass, Sporobolus stapfianus, resulted in the identification of a gene, SDG8i, encoding a Group 1 glycosyltransferase (UGT). Here, we examine the effects of introducing this gene, under control of the CaMV35S promoter, into the model plant Arabidopsis thaliana. Results show that Arabidopsis plants constitutively over-expressing SDG8i exhibit enhanced growth, reduced senescence, cold tolerance and a substantial improvement in protoplasmic drought tolerance. We hypothesise that expression of SDG8i in Arabidopsis negatively affects the bioactivity of metabolite/s that mediate/s environmentally-induced repression of cell division and expansion, both during normal development and in response to stress. The phenotype of transgenic plants over-expressing SDG8i suggests modulation in activities of both growth- and stress-related hormones. Plants overexpressing the UGT show evidence of elevated auxin levels, with the enzyme acting downstream of ABA to reduce drought-induced senescence. Analysis of the in vitro activity of the UGT recombinant protein product demonstrates that SDG8i can glycosylate the synthetic strigolactone analogue GR24, evoking a link with strigolactone-related processes in vivo. The large improvements observed in survival of transgenic Arabidopsis plants under cold-, salt- and drought-stress, as well as the substantial increases in growth rate and seed yield under non-stress conditions, indicates that overexpression of SDG8i in crop plants may provide a novel means of increasing plant productivity.

Salt and drought stresses in safflower : a review

Safflower is one of the oldest cultivated crops, usually grown at a small scale. Safflower is grown for flowers used for coloring, flavoring foods, dyes, medicinal properties, and livestock feed. Safflower is underutilized but gaining attention due to oil yield potential and the ability to grow under high temperatures, drought, and salinity. Salinity and drought have negative effects by disrupting the ionic and osmotic equilibrium of the plant cells. The stress signal is perceived by membranes then transduced in the cell to switch on the stress responsive genes. This review discusses on stress tolerance mechanisms in safflower. Strategies are proposed for enhancing drought and salt resistance in safflower.

Laboratory model studies of flushing of trapped salt water from a blocked tidal estuary

Results are presented from a series of laboratory model studies of the flushing of saline water from a partially- or fully-closed estuary. Experiments have been carried out to determine quantitatively the response of the trapped saline volume to fresh water flushing discharges Q for different values of the estuary bed slope α and the density difference (∆ρ)_o between the saline and fresh water. The trapped saline water forms a wedge within the estuary and for maintained steady discharges, flow visualisation and density profile data confirm that its response to the imposition of the freshwater purging flow occurs in two stages, namely (i) an initial phase characterised by intense shear-induced mixing at the nose of the wedge and (ii) a relatively quiescent second phase where the mixing is significantly reduced and the wedge is forced relatively slowly down and along the bed slope. Scalings based upon simple energy balance considerations are shown to be successful in (i) describing the time-dependent wedge behaviour and (ii) quantifying the proportion of input kinetic energy converted into increasing the potential energy of the wedge/river system. Measurements show that the asymptotic value of the energy conversion factor increases with increasing value of the river Froude number Fr_o at small values of Fr_o, thereafter reaching a maximum value and a gradual decrease at the highest values of Fr_o. Dimensional analysis considerations indicate that the normalised, time-dependent wedge position (x_w)³(g')o/q² can be represented empirically by a power-law relationship of the form (x_w)[(g')_o/q²]^1/3 =C [(t)[(g')_o²/q]^1/3]"where the proportionality coefficient C is a function of both Fr_o and the slope angle α and the exponent n has a value of 0.24. Successful attempts are made to relate the model data to existing field observations from a microtidal estuary.

Experiments with multiple, intermittent periodic flushing flows confirm the importance of the starting phase of each flushing event for the time dependent behaviour of the saline wedge after reaching equilibrium in the intervals between such events. For the parameter ranges investigated and for otherwise-identical external conditions, no significant differences are found in the position of the wedge between cases of sequential multiple flushing flows and steady single discharges of the same total duration.

Observation of inter- and intramolecular C---H...F hydrogen bonding in Gingras' salt: [n-Bu4N]+[Ph3SnF2]-

The crystal and molecular structure of Gingras' salt [n-Bu₄N]^₊ [Ph₃SnF₂]⁻ is reported, which reveals a variety of inter- and intramolecular C---H...F hydrogen bonding interactions. A ¹¹⁹Sn MAS-NMR spectrum was recorded and a tensor analysis has been performed according to the method of Herzfeld and Berger. The results are discussed in terms of the molecular structure and are compared with the parent compound Ph₃SnF as well as with Mes₃SnF (Mes=mesityl).