Shift In Temperature Optimum Research Articles

Some peculiarities in vertical distribution of metazoan microzooplankton in the Black Sea in spring

Based on material, received in the 84th and 93rd cruises of the RV “Professor Vodyanitsky”, vertical distribution of microplankton fraction of metazooplankton (MM) in the Black Sea in spring was analyzed. A total of 27 stations were examined both in the coastal zone and in the deep sea. The 10-L bottles of the CTD probes “Mark-III Neil Brown” and “Sea Bird 911” were used to collect 4–6 L of water from 4–11 horizons of the water column. The samples obtained were concentrated by the reverse filtration through the plankton net with the mesh size of 10 µm. Quantitative and systematic analysis of all samples was carried out totally in the Bogorov chamber using an MBS-9 stereo microscope. The main factors determining nature of the distribution are MM species composition, physical structure of the water column, and hydrodynamic processes affecting its stability/instability. Nauplii of Black Sea Copepoda and veligers of Bivalvia were the most numerous systematic groups in “spring” MM. Mollusc veligers determined abundance maxima in the lower layers of shallow water habitats, while copepods prevailed over large depths and determined total abundance peaks in the upper and middle water layers. Daily time series experiment showed that advective hydrodynamic processes can significantly affect MM vertical distribution, changing physical structure of the water column. For some species, in most cases, a correlation of their distribution with vertical profiles of temperature and salinity was revealed, which rarely manifested at total MM abundance level. A comparison of two spring seasons (2016 and 2017) showed the relationship between vertical distribution of MM abundance and temperature to be more pronounced in cases of low temperature. A change in the sign of correlation with temperature was detected during spring season for Oithona similis: an initially cold-loving species of Black Sea copepods. This revealed in a more superficial distribution of the maxima abundance of this species at lower seasonal temperatures, which could reflect a shift in temperature optimum for the species population and play the role of an adaptive reaction in conditions of seasonal changes in sea thermal characteristics.

Enhancement of the thermostability of Streptomyces kathirae SC-1 tyrosinase by rational design and empirical mutation

This study aimed to improve the thermostability of a newly cloned tyrosinase from Streptomyces kathirae SC-1. The POPMuSiC algorithm was applied to predict the folding free energy change (ΔDG) of amino acid substitution. Site-directed mutagenesis was used to construct mutants (Q7K, G234P, and Q7K/G234P), and the mutant, and wild-type enzymes were expressed in Escherichia coli (DE3). Compared to the wild-type tyrosinase, all three mutant enzymes showed improved thermal properties. The mutant with combined substitution (Q7K/G234P) showed the most pronounced shifts in temperature optima, about 10°C upward, and the half-life for thermal inactivation at 60°C, and melting temperatures were increased by 3 times and approximately 10°C, respectively. Finally, the mechanisms responsible for the increased thermostability were analyzed through comparative analysis of structure models. The structure-based rational design strategies in this study may also provide further insight into the thermostability of other industrial enzymes and suggest further potential industrial applications.

Thermostability Improvement of a Streptomyces Xylanase by Introducing Proline and Glutamic Acid Residues

Protein engineering is commonly used to improve the robustness of enzymes for activity and stability at high temperatures. In this study, we identified four residues expected to affect the thermostability of Streptomyces sp. strain S9 xylanase XynAS9 through multiple-sequence analysis (MSA) and molecular dynamic simulations (MDS). Site-directed mutagenesis was employed to construct five mutants by replacing these residues with proline or glutamic acid (V81P, G82E, V81P/G82E, D185P/S186E, and V81P/G82E/D185P/S186E), and the mutant and wild-type enzymes were expressed in Pichia pastoris. Compared to the wild-type XynAS9, all five mutant enzymes showed improved thermal properties. The activity and stability assays, including circular dichroism and differential scanning calorimetry, showed that the mutations at positions 81 and 82 increased the thermal performance more than the mutations at positions 185 and 186. The mutants with combined substitutions (V81P/G82E and V81P/G82E/D185P/S186E) showed the most pronounced shifts in temperature optima, about 17°C upward, and their half-lives for thermal inactivation at 70°C and melting temperatures were increased by >9 times and approximately 7.0°C, respectively. The mutation combination of V81P and G82E in adjacent positions more than doubled the effect of single mutations. Both mutation regions were at the end of long secondary-structure elements and probably rigidified the local structure. MDS indicated that a long loop region after positions 81 and 82 located at the end of the inner β-barrel was prone to unfold. The rigidified main chain and filling of a groove by the mutations on the bottom of the active site canyon may stabilize the mutants and thus improve their thermostability.

Which are the most important parameters for modelling carbon assimilation in boreal Norway spruce under elevated [CO2] and temperature conditions?

Photosynthesis is highly responsive to environmental and physiological variables, including phenology, foliage nitrogen (N) content, atmospheric CO2 concentration ([CO2]), irradiation (Q), air temperature (T) and vapour pressure deficit (D). Each of these responses is likely to be modified by long-term changes in climatic conditions such as rising air temperature and [CO2]. When modelling photosynthesis under climatic changes, which parameters are then most important to calibrate for future conditions? To assess this, we used measurements of shoot carbon assimilation rates and microclimate conditions collected at Flakaliden, northern Sweden. Twelve 40-year-old Norway spruce trees were enclosed in whole-tree chambers and exposed to elevated [CO2] and elevated air temperature, separately and in combination. The treatments imposed were elevated temperature, +2.8 °C in July/August and +5.6 °C in December above ambient, and [CO2] (ambient CO2 ∼370 μ mol mol(-1), elevated CO2 ∼700 μ mol mol(-1)). The relative importance of parameterization of Q, T and D responses for effects on the photosynthetic rate, expressed on a projected needle area, and the annual shoot carbon uptake was quantified using an empirical shoot photosynthesis model, which was developed and fitted to the measurements. The functional form of the response curves was established using an artificial neural network. The [CO2] treatment increased annual shoot carbon (C) uptake by 50%. Most important was effects on the light response curve, with a 67% increase in light-saturated photosynthetic rate, and a 52% increase in the initial slope of the light response curve. An interactive effect of light saturated photosynthetic rate was found with foliage N status, but no interactive effect for high temperature and high CO2. The air temperature treatment increased the annual shoot C uptake by 44%. The most important parameter was the seasonality, with an elongation of the growing season by almost 4 weeks. The temperature response curve was almost flat over much of the temperature range. A shift in temperature optimum had thus an insignificant effect on modelled annual shoot C uptake. The combined temperature and [CO2] treatment resulted in a 74% increase in annual shoot C uptake compared with ambient conditions, with no clear interactive effects on parameter values.

Effect of water temperature on the development and energetics of early, mid and late-stage phyllosoma larvae of spiny lobster Sagmariasus verreauxi

The effect of water temperature on the survival, growth, respiration, apparent feed intake and activity of Sagmariasus verreauxi phyllosoma during early, mid and late larval development through metamorphosis was examined. Early-stage phyllosoma were cultured from hatch to instar 4 at temperatures 17, 20, 23, 26 and 29°C for between 18 and 44days. Survival and rate of development were greatest at 26°C, while all animals died at 29°C. The optimum temperature for larval growth in weight was 23°C. Optimum metabolic feeding efficiency measured as the maximum convection requirement index, (CRI, quotient of feed intake and oxygen consumption) was from 23 to 26°C. Reduced growth at 26 compared to 23°C was likely due to accelerated development, resulting in a disequilibrium between moult increment and energy storage rates, whereas, lower metabolic feeding efficiency at 17–20°C may be attributed to increased energetic expenditure associated with activity. Mid-stage phyllosoma were cultured from instar 8 to instars 10–11 over 69days at 19, 21, 23, 25, and 27°C. Survival was reduced at 27°C. The optimum temperature for growth, development and CRI was 23°C. Late-stage phyllosoma were cultured from instar 13 over 112days, or until metamorphosis, at 21, 23 and 25°C. There was no significant difference in survival among temperatures. The rate of development was fastest at 23°C with 36% of phyllosoma metamorphosing to puerulus, compared to 20% at 21°C and 28% at 25°C. Mass of final instar phyllosoma and puerulus were greatest at 21°C, demonstrating a downward shift in the optimum temperature for late-stage phyllosoma. The shift in temperature optimum for late-stage larvae involves changes in feeding and energy metabolism. The study demonstrates that the physiological energetics of S. verreauxi changes with larval ontogenetic development, which is an important consideration for optimizing spiny lobster propagation success.

Performance of Aspergillus niger B 03 β-xylosidase immobilized on polyamide membrane support

The dynamics of β-xylosidase biosynthesis from Aspergillus niger B 03 was investigated in laboratory bioreactor. Maximum xylosidase activity 5.5 U/ml was achieved after 80 h fermentation at medium pH 4.0. The isolated β-xylosidase was immobilized on polyamide membrane support and the basic characteristics of the immobilized enzyme were determined. Maximum immobilization and activity yield obtained was 30.0 and 6.8%, respectively. A shift in temperature optimum and pH optimum was observed for immobilized β-xylosidase compared to the free enzyme. Immobilized enzyme exhibited maximum activity at 45 °C and pH 4.5 while its free counterpart at 70 °C and pH 3.5, respectively. Thermal stability at 40 and 50 °C and storage stability of immobilized β-xylosidase were investigated at pH 5.0. Kinetic parameters K m, V max and K i were determined for both enzyme forms. Free and immobilized β-xylosidase were tested for xylose production from birchwood xylan. The substrate was preliminarily depolymerized with xylanase to xylooligosaccharides and the amount of xylose obtained after their hydrolysis with free and immobilized β-xylosidase was determined by HPLC analysis. Continuous enzyme hydrolysis of birchwood xylan was performed with xylanase and free or immobilized β-xylosidase. The maximum extent of hydrolysis was 25 and 30% with free and immobilized enzyme, respectively. Immobilized preparation was also examined for reusability in 20 consecutive cycles at 40 °C.

Modelling Optimal Temperature Acclimation of the Photosynthetic Apparatus in C3Plants with Respect to Nitrogen Use

Abstract A new hypothesis for temperature acclimation by the photosynthetic apparatus is presented. An optimization model is developed to examined effects of changes in the organization of photosynthetic components on leaf photosynthesis under various growth temperatures where the photosynthetic apparatus is not damaged. In this model, photosynthetic rate is limited either by the capacity of ribulose bisphosphate carboxylase (RuBPCase) to consume ribulose bisphosphate (RuBP), or by the capacity of RuBP regeneration. For temperature dependence of the RuBPCase activity, data fromSpinacia oleraceaL., which have a temperature optimum of 30 °C, are used. For temperature dependence of the capacity of RuBP regeneration, two contrasting curves that have temperature optima of 30 °C (Eucalyptus paucifloraSieb. ex Spreng) and 40 °C (Larrea divaricataCav.) are applied. The temperature dependence of each process is fixed for respective species, but the rate of each process varies with changes in the amounts of components. The cost of proteins, in terms of nitrogen, required to carry out each process is calculated when nitrogen is partitioned differently among photosynthetic components. The optimal nitrogen partitioning that maximizes daily photosynthesis at a given temperature is obtained. The predicted temperature optimum of the photosynthetic rate inLarrea divaricataexhibits large shifts with changes in target temperature, while shifts are negligible inEucalyptus pauciflora. It is suggested that the shift in temperature optimum of photosynthetic rate is large when the temperature dependences of the capacities of RuBPCase and RuBP regeneration differ from each other.

Gas exchange characteristics and temperature relations of two desert annuals: A comparison of a winter-active and a summer-active species.

The gas exchange characteristics of two C3 desert annuals with contrasting phenologies, Geraea canescens T. & G. (winter-active) and Dicoria canescens T. & G. (summer-active), both Asteraceae, were determined for plants grown under a moderate (25°/15° C, day/night temperature) and a high (40°/27° C) growth temperature regime. Both species had high photosynthetic capacities; maximum net photosynthetic rates were 38 and 48 μmol CO2 m-2 s-1 for Geraea and Dicoria, respectively, and were not influenced by growth temperature regime. However, the temperature optima of net photosynthesis shifted from 26° C for Geraea and from 28° C for Dicoria when grown under the moderate temperature regime to 31° C for both species when grown under the high temperature regime. Although the shifts in temperature optima were smaller than those observed for many desert perennials, both species showed substantial increases in photosynthetic rates at high temperatures when grown at 40°/27° C. In general, the gas exchange characteristics of Geraea and Dicoria were very similar to each other and to those reported for other C3 desert annuals. Geraea and Dicoria experienced different seasonal patterns of change in several environmental variables. For Geraea, maximum daily air temperature (T a) increased from 24° to 41° C over its growing season while Dicoria experienced maximum T a at midseason (45° C). At points during their respective growing seasons when midday T a ranged between 35° and 40° C, leaf temperatures (T 1) of both species were below T a and, therefore, were closer to the photosynthetic temperature optima measured in the laboratory. Leaf conductances to water vapor (g 1) and water potentials (ψ) were high at these times, but later in their growing seasons Dicoria maintained high g 1 and ψ while Geraea showed large decreases in these quantities. The ability of Dicoria to successfully growth through the hot, dry summers of the California deserts may be related to its ability to acquire the available water in locally mesic habitats.

Effect of Water Stress on the Temperature Optima of Net CO2 Exchange for Two Desert Species

AbstractThe temperature dependence of net CO2 exchange was determined at various soil water potentials for two sympatric desert species. Notholaena parryi D. C. Eat. (Pteridaceae) and Encelia farinosa Gray (Compositae). As water stress increased, the temperature optimum of apparent (net) photosynthesis shifted 7 to 10°C downward and the maximum rate decreased for both species. The downward shift in temperature optimum with water stress was the result of a greater fractional stomatal closure with increasing temperature and a lowering of the temperature where maximal CO2 residual conductance of the mesophyll cells occurred. This lowering of the temperature for maximal CO2 residual conductance appears to reflect (1) a greater effect of water stress on gross photosynthesis than on respiration plus photorespiration and (2) the higher temperature optimum for respiration plus photorespiration than for gross photosynthesis. The downward shift in the temperature optimum of apparent photosynthesis can have a significant effect on the predicted carbon balance of plants as the soil water potential decreases.