Modification of the data-processing method for the turbidimetric bioassay of nisin

The data processing method of the turbidimetric bioassay of nisin was modified to facilitate its industrial application. The influence of the initial indicator concentration was minimized by a redefined specific dose of the bacteriocin as the quotient between the titer of the added bacteriocin and the initial population density of the indicator in the suspension. It was found that d _c = 0.125 μg ml⁻¹ was the critical dose of nisin that can cause a complete inhibition of the indicator, Pediococcus acidilactici UL5, with an initial OD of 0.135. To eliminate the interference of the cell debris, an equation, , exploiting d _c, was formulated to obtain the intrinsic survival proportion. The use of the specific dose of the bacteriocin and the intrinsic survival proportion as parameters of the dose/response curve greatly enhanced its repeatability and feasibility. A dual-dosage approach was developed to further simplify the conventional standard dose/response curve method.     

Energetics of the growth of Methanobacterium thermoautotrophicum and Methanococcus thermolithotrophicus on ammonium chloride and dinitrogen

Methanobacterium thermoautotrophicum was grown in continuous culture in a fermenter gassed with H₂ and CO₂ as sole carbon and energy sources, and in a medium which contained either NH₄Cl or gaseous N₂ as nitrogen source. Growth was possible with N₂. Steady states were obtained at various gas flow rates with NH₄Cl and with and the maintenance coefficient varied with the gas input and with the nitrogen source. Growth of Methanococcus thermolithotrophicus in continuous culture in a fermenter gassed with H₂, CO₂ as nitrogen, carbon and energy sources was also examined.Abbreviations molecular growth yield (g dry weight of cells per mol of CH₄ evolved) - growth rate (h^-1) - D dilution rate (h^-1) - rate (h_-1); relation of Neijssel and Tempest and of Stouthamer and Bettenhaussen - energy     

Complexation of oxoanions and cationic metals by the biscatecholate siderophore azotochelin

Azotochelin is a biscatecholate siderophore produced by the nitrogen-fixing soil bacterium Azotobacter vinelandii. The complexation properties of azotochelin with a series of oxoanions [Mo(VI), W(VI) and V(V)] and divalent cations [Cu(II), Zn(II), Co(II) and Mn(II)] were investigated by potentiometry, UV–vis and X-ray spectroscopy. Azotochelin forms a strong 1:1 complex with molybdate (log K = 7.6 ± 0.4) and with tungstate and vanadate; the stability of the complexes increases in the order Mo < V < W (log K _app^Mo = 7.3 ± 0.4; log K _app^V = 8.8 ± 0.4 and log K _app^W = 9.0 ± 0.4 at pH 6.6). The Mo atom in the 1:1 Mo–azotochelin complex is bound to two oxo groups in a cis position and to the two catecholate groups of azotochelin, resulting in a slightly distorted octahedral configuration. Below pH 5, azotochelin appears to form polynuclear complexes with Mo in addition to the 1:1 complex. Azotochelin also forms strong complexes with divalent metals. Of the metals studied, Cu(II) binds most strongly to azotochelin , followed by Zn(II) , Mn(II) and Co(II) . Since very few organic ligands are known to bind strongly to oxoanions (and particularly molybdate) at circumneutral pH, the unusual properties of azotochelin may be used for the separation and concentration of oxoanions in the laboratory and in the field. In addition, azotochelin may prove useful for the investigation of the biogeochemistry of Mo, W and V in aquatic and terrestrial systems. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Bioaccumulation of Heavy Metals by Green Algae

The biosorption of metal ions (Cr⁺³, , Cu⁺², and Ni⁺²) on two algal blooms (designated HD-103 and HD-104) collected locally was investigated as a function of the initial metal ion concentration. The main constituent of HD-103 is Cladophora sp., while Spirulina sp. is present significantly in the bloom HD-104. Algal biomass HD-103 exhibited the highest Cu⁺² uptake capacity (819 mg/g). This bloom adsorbed Ni⁺² (504 mg/g), Cr⁺³ (347 mg/g), and (168 mg/g). Maximum of Ni⁺² (1108 mg/g) is taken by HD-104. This species takes up 306, 202, and 576 mg/g Cr⁺³, , and Cu⁺², respectively. Equilibrium data fit very well to both the Langmuir and the Freundlich isotherm models. The sorption process followed the Freundlich model better. Pseudo-first-order kinetic model could describe the kinetic data. Infrared (IR) spectroscopic data were employed to identify the site(s) of bonding. It was found that phosphate and peptide moieties participate in the metal uptake by bloom HD-103. In the case of bloom HD-104, carboxylate and phosphate are responsible for the metal uptake. The role of protein in metal uptake by HD-103 was investigated using polyacrylamide gel electrophoresis.     

Suitability of the shaking flask for oxygen supply to microbiological cultures

Due of its simplicity the shaking flask is used in serial studies, e.g. in the screening for secondary metabolites or in the optimization of fermentation processes. Experimental investigations in these small bioreactors are often the first step in developing a large-scale fermentation process.Movement of the flask should produce sufficient mixing, supply of oxygen, and removal of carbon dioxide. In the case of fluids with low or moderate viscosity, gas transport is the most important aspect. This publication summarizes data necessary to calculate the gas transport. These data are derived from the consideration of the gas diffusions through the cotton plug as well as from the substance transport between the gas and liquid phases. As a result suitable fermentation conditions can be selected. Finally, the performance limits of the shaking flask are illustrated using the example of the oxygen supply in a Streptomyces tendae fermentation.List of Symbols A _s Cross section of plug - A Surface area of liquid in flask - a A/V _F specific phase interface area - c Concentration - c ^* Saturation concentration - c Plug diffusion term - D Widest diameter of flask - Diffusion coefficients in multicomponent gas mix tures - Diffusion coefficients in binary gas mixtures - Diffusion coefficient of oxygen in the liquid - d Diameter of neck of flask - e Eccentricity - G Volume-based mass flow - G _m Maximum volume-based mass flow - g Acceleration due to gravity - h Height coordinate - ¯H Mean height of plug - Hy p _i/c ^*, Henry constant - K Consistency index - k D _xy/D _xz, Ratio of diffusion coefficients in binary gas mixtures - k _M Monod constant - k _L a Mass transport coefficient: gas/liquid - M Molecular weight - m Flow exponent - n Speed of shaking - p Pressure - p _i Partial pressure of gas component i - q Area-based flow of volume - R , respiration ratio - Sc , Schmidt number - T Absolute temperature - V Flask volume - V _F Volume of liquid in flask - w Velocity of the Stefan flow - x, y, z Ratios of the partial pressures of the gases O₂, CO₂, N₂ - Rate of shear - Dynamic viscosity of the liquid - Kinematic viscosity of the liquid - Density of the liquid - _x, Density of O₂ gas - Surface tension Indices 0 State in gas volume of shaking flask - 1 State in outside air - G Gas volume - x, y, z O₂, CO₂, N₂     

Cell-to-cell pathway dominates xylem-epidermis hydraulic connection in<Emphasis Type="Italic"> Tradescantia fluminensis</Emphasis> (Vell. Conc.) leaves

A steady supply of water is indispensable for leaves to fulfil their photosynthetic function. Understanding water movement in leaves, especially factors that regulate the movement of water flux from xylem to epidermis, requires that the nature of the transport pathway be elucidated. To determine the hydraulic linkage between xylem and epidermis, epidermal cell turgor pressure (P _t) in leaves of Tradescantia fluminensis was monitored using a cell pressure probe in response to a 0.2 MPa step change in xylem pressure applied at the leaf petiole. Halftime of P _t changes were 10–30 times greater than that of water exchange across an individual cell membrane suggesting that cell-to-cell water transport constitutes a significant part of the leaf hydraulic path from xylem to epidermis. Furthermore, perfusion of H₂O₂ resulted in increases of both and by a factor of 2.5, indicating that aquaporins may play a role in the xylem to epidermis hydraulic link. The halftime for water exchange did not differ significantly between cells located at the leaf base (2.5 s), middle (2.6 s) and tip (2.5 s), indicating that epidermal cell hydraulic properties are similar along the length of the leaf. Following the pressure application to the xylem (0.2 MPa), P _t changed by 0.12, 0.06 and 0.04 MPa for epidermal cells at the base, middle and the tip of the leaf, respectively. This suggests that pressure dissipation between xylem and epidermis is significant, and that the pressure drop along the vein may be due to its structural similarities to a porous pipe, an idea which was further supported by measurements of xylem hydraulic resistance using a perfusion technique.     

Nitrogen sink strength of ectomycorrhizal morphotypes of <Emphasis Type="Italic">Quercus douglasii</Emphasis>, <Emphasis Type="Italic">Q. garryana</Emphasis>, and <Emphasis Type="Italic">Q. agrifolia</Emphasis> seedlings grown in a northern California oak woodland

Little information is known on what the magnitude of nitrogen (N) processed by ectomycorrhizal (ECM) fungal species in the field. In a common garden experiment performed in a northern California oak woodland, we investigated transfer of nitrogen applied as ¹⁵NH₄ or ¹⁵NO₃ from leaves to ectomycorrhizal roots of three oak species, Quercus agrifolia, Q. douglasii, and Q. garryana. Oak seedlings formed five common ectomycorrhizal morphotypes on root tips. Mycorrhizal tips were more enriched in ¹⁵N than fine roots. N transfer was greater to the less common morphotypes than to the more common types. ¹⁵N transfer from leaves to roots was greater when , not , was supplied. ¹⁵N transfer to roots was greater in seedlings of Q. agrifolia than in Q. douglasii and Q. garryana. Differential N transfer to ectomycorrhizal root tips suggests that ectomycorrhizal morphotypes can influence flows of N from leaves to roots and that mycorrhizal diversity may influence the total N requirement of plants.     

A molecular dynamics study on opioid activities of biphalin molecule

Molecular dynamics simulations of the biphalin molecule, (Tyr-D-Ala-Gly-Phe-NH)₂, and the active tetrapeptide hydrazide, Tyr-D-Ala-Gly-Phe-NH-NH₂ were performed to investigate the cause of the increased μ and δ receptor binding affinities of the former over the latter. The simulation results demonstrate that the acylation of the two equal tetrapeptide fragments of biphalin produces the constrained hydrazide bridges C₄^a - C₄￠- N₉ - N₁₀ {\hbox{C}}_4^{\alpha } - {{\hbox{C}}_4}\prime - {{\hbox{N}}_9} - {{\hbox{N}}_{{10}}} and N₉ - N₁₀ - C₅￠- C₅^a {{\hbox{N}}_9} - {{\hbox{N}}_{{10}}} - {{\hbox{C}}_5}\prime - {\hbox{C}}_5^{\alpha } , which in turn increase the opportunity of conformations for binding to μ or δ receptors. Meanwhile, the connection of the two active tetrapeptide fragments of biphalin also results in the constrained side chain torsion angle χ² at one of the two residues Phe. This constrained side chain torsion angle not only significantly increases the δ receptor binding affinity but also makes most of the δ receptor binding conformations of biphalin bind to the δ receptor through the fragment containing the mentioned residue Phe.     

The effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis)

To investigate the effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis), we measured the following: (1) the resting oxygen consumption rate $ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{rest}}}} } \right) $ , critical swimming speed (U _crit) and active oxygen consumption rate $ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} } \right) $ of fish at acclimation temperatures of 10, 15, 20, 25 and 30 °C and (2) the $ \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $ , U _crit and $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ of both exercise-trained (exhaustive chasing training for 14 days) and control fish at both low and high acclimation temperatures (15 and 25 °C). The relationship between U _crit and temperature (T) approximately followed a bell-shaped curve as temperature increased: U _crit = 8.21/{1 + [(T ? 27.2)/17.0]²} (R ² = 0.915, P < 0.001, N = 40). The optimal temperature for maximal U _crit (8.21 BL s^?1) in juvenile qingbo was 27.2 °C. Both the $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ and the metabolic scope (MS, $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} - \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $ ) of qingbo increased with temperature from 10 to 25 °C (P < 0.05), but there were no significant differences between fish acclimated to 25 and 30 °C. The relationships between $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ or MS and temperature were described as $ {\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} = 1,214.29/\left\{ {1 + \left[ {\left( {T - 28.8} \right)/10.6} \right]^{2} } \right\}\;\left( {R^{2} = 0.911,\;P < 0.001,\;N = 40} \right) $ and MS = 972.67/{1 + [(T ? 28.0)/9.34]²} (R ² = 0.878, P < 0.001, N = 40). The optimal temperatures for $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ and MS in juvenile qingbo were 28.8 and 28.0 °C, respectively. Exercise training resulted in significant increases in both U _crit and $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ at a low temperature (P < 0.05), but training exhibited no significant effect on either U _crit or $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ at a high temperature. These results suggest that exercise training had different effects on swimming performance at different temperatures. These differences may be related to changes in aerobic metabolic capability, arterial oxygen delivery, available dissolved oxygen, imbalances in ion fluxes and stimuli to remodel tissues with changes in temperature.     

The effect of temperature on post-feeding ammonia excretion and oxygen consumption in the southern catfish

The post-prandial rates of ammonia excretion (TAN) and oxygen consumption in the southern catfish (Silurus meridionalis) were assessed at 2 h intervals post-feeding until the rates returned to those of the fasting rates, at 17.5, 22.5, 27.5, and 32.5°C, respectively. Both fasting TAN and increased with temperature, and were lower than those previously reported for many fish species. The relationship between fasting TAN (mmol NH₃–N kg⁻¹ h⁻¹) and temperature (T, °C) was described as: fasting TAN = 0.144e ^0.0266T (r = 0.526, n = 27, P < 0.05). The magnitude of ammonia excretion and its ratio to total N intake during the specific dynamic action (SDA) tended to increase initially, and then decrease with increasing temperature. The ammonia quotient (AQ), calculated as mol NH₃–N/mol O₂, following feeding decreased as temperature increased. The relationship between AQ during SDA and temperature was described as: AQ_{during SDA} = 0.303e ^−0.0143T (r = 0.739, n = 21, P < 0.05). Our results suggest that ammonia excretion and oxygen consumption post-feeding are operating independently of each other. Furthermore, it appears that the importance of protein as a metabolic substrate in postprandial fish decreases with temperature.     

Theoretical study of AlH(2+)n (n=1-7) dications

The structures and stability of 1–7 dications were calculated at the ab initio MP2/aug-cc-pVTZ level of theory. The dications AlH²⁺ 1 and 2 were characterized to be unstable thermodynamically. However, these and the stable dications, 3–7 have considerable kinetic barriers for deprotonation. Each of the structures 3–7 contains one or more two-electron three-center (2e–3c) bonds. Aluminum atoms of these dications carry most of the positive charges, as indicated by NBO charge calculations.Dedicated to Professor Dr. Paul von Ragué Schleyer on the occasion of his 75th birthday     

The effects of fermentation conditions on yeast cell debris particle size distribution during high pressure homogenisation

Experiments were performed to characterize the particle size distribution of bakers' yeast cells during high pressure homogenisation. Results were obtained for mechanically agitated batch and continuously grown cultures under a range of operating conditions. It was found that the dependency of cell debris size distribution on the number of passes through the homogeniser and the homogeniser pressure was independent of the cell properties and culture conditions, but for a fixed pressure and number of passes the extent of disruption was strongly affected by the operating conditions in the fermenter. The entire cell debris size distributions were successfully simulated using the mean and variance of the distributions and a previously published model equation which related these parameters to the operating pressure and number of passes through the homogeniser.List of Symbols k breakage coefficient in Eq. 1 - d cell diameter - d ₅₀ median diameter of homogenate size distribution - d ₅₀ dimensionless d ₅₀ defined as - D dilution rate - F(d _NP) cumulative undersize distribution (volume basis) - N number of passes - P total pressure - P _threshold threshold pressure - P (P-P _threshold) - w Boltzmann parameter, Eq. 4 - w dimensionless standard deviation defined as Greek Letters exponent in Eq. 1 - exponent in Eq. 1 UCL is the Biotechnology and Biological Sciences Research Council's Interdisciplinary Research Centre for Biochemical Engineering and the Council's support to the participating UCL departments is gratefully acknowledged. The provision of continuous fermentation material from Dr. M. Gregory, Process System Engineering IRC, is gratefully acknowledged.     

Stress fermentation strategies for the production of hyperthermostable superoxide dismutase from Thermus thermophilus HB27: effects of ions

In this study, we explored how ammonium and metal ion stresses affected the production of recombinant hyperthermostable manganese superoxide dismutase (Mn-SOD). To improve Mn-SOD production, fed-batch culture in shake flasks and bioreactor fermentation were undertaken to examine the effects of $ {\text{NH}}_{ 4}^{{^{ + } }} $ and Mn²⁺ feeding. Under the optimized feeding time and concentrations of $ {\text{NH}}_{ 4}^{{^{ + } }} $ and Mn²⁺, the maximal SOD activity obtained from bioreactor fermentation reached some 480 U/ml, over 4 times higher than that in batch cultivation (113 U/ml), indicating a major enhancement of the concentration of Mn-SOD in the scale-up of hyperthermostable Mn-SOD production. In contrast, when the fed-batch culture with appropriate $ {\text{NH}}_{ 4}^{{^{ + } }} $ and Mn²⁺ feeding was carried out in the same 5-L stirred tank bioreactor, a maximal SOD concentration of some 450 U/ml was obtained, again indicating substantial increase in SOD activity as a result of $ {\text{NH}}_{ 4}^{{^{ + } }} $ and Mn²⁺ feeding. The isoelectric point (pI) of the sample was found to be 6.2. It was highly stable at 90 °C and circular dichroism measurements indicated a high α-helical content of 70 % as well, consistent with known SOD properties. This study indicates that $ {\text{NH}}_{ 4}^{{^{ + } }} $ and Mn²⁺ play important roles in Mn-SOD expression. Stress fermentation strategies established in this study are useful for large-scale efficient production of hyperthermostable Mn-SOD and may also be valuable for the scale-up of other extremozymes.     

Hyperfine interactions and electron distribution in FeIIFeI and FeIFeI models for the active site of the [FeFe] hydrogenases: Mössbauer spectroscopy studies of low-spin FeI

Mössbauer studies of [{μ-S(CH₂C(CH₃)₂CH₂S}(μ-CO)Fe^IIFe^I(PMe₃)₂(CO)₃]PF₆ (1 _OX ), a model complex for the oxidized state of the [FeFe] hydrogenases, and the parent Fe^IFe^I derivative are reported. The paramagnetic 1 _OX is part of a series featuring a dimethylpropanedithiolate bridge, introducing steric hindrance with profound impact on the electronic structure of the diiron complex. Well-resolved spectra of 1 _OX allow determination of the magnetic hyperfine couplings for the low-spin distal Fe^I ( $ {\text{Fe}}^{\text{I}} _{\text{ D}} $ Fe D I ) site, A _x,y,z  = [?24 (6), ?12 (2), 20 (2)] MHz, and the detection of significant internal fields (approximately 2.3 T) at the low-spin ferrous site, confirmed by density functional theory (DFT) calculations. Mössbauer spectra of 1 _OX show nonequivalent sites and no evidence of delocalization up to 200 K. Insight from the experimental hyperfine tensors of the Fe^I site is used in correlation with DFT to reveal the spatial distribution of metal orbitals. The Fe–Fe bond in [Fe₂{μ-S(CH₂C(CH₃)₂CH₂S}(PMe₃)₂(CO)₄] (1) involving two $ d_{{z^{2} }} $ d z 2 -type orbitals is crucial in keeping the structure intact in the presence of strain. On oxidation, the distal iron site is not restricted by the Fe–Fe bond, and thus the more stable isomer results from inversion of the square pyramid, rotating the $ d_{{z^{2} }} $ d z 2 orbital of $ {\text{Fe}}^{\text{I}} _{\text{ D}} $ Fe D I . DFT calculations imply that the Mössbauer properties can be traced to this $ d_{{z^{2} }} $ d z 2 orbital. The structure of the magnetic hyperfine coupling tensor, A, of the low-spin Fe^I in 1 _OX is discussed in the context of the known A tensors for the oxidized states of the [FeFe] hydrogenases.     

Toxicity assessment of common organic solvents using a biosensor based on algal photosynthetic activity measurement

The acute toxicities of common organic solvents (e.g., methanol, ethanol, isopropanol, acetone, acetonitrile, and dimethylformamide) were evaluated using a biosensor based on microalgal photosynthesis measurement. The biosensor was air-tight, with no headspace, preventing volatile organic toxicants from escaping into the environment as well as partitioning from the aqueous phase into the headspace until equilibrium was reached. Both the incubating and exposure times were set at 10 min. It was observed that only 2 h was needed to obtain complete dose-related inhibition of photosynthetic activity. The results showed that all the tested organic solvents inhibited algal photosynthesis with EC₅₀ ranging between 589 and 2,570 mM. The inhibition of these solvents was in the order: isopropanol > acetone > acetonitrile > ethanol > dimethylformamide > methanol. The quantitative structure-activity relationship (QSAR) between toxicity data and partition coefficient of the examined compounds could be modeled as follows: ${\text{log}}_{{10}} {\text{EC}}_{{50}} \;{\left( {\mu {\text{M}}} \right)} = - 0.6428\;{\text{log}}\;P + 5.76\;{\left( {{\text{R}}^{2} \approx 0.88} \right)}The acute toxicities of common organic solvents (e.g., methanol, ethanol, isopropanol, acetone, acetonitrile, and dimethylformamide) were evaluated using a biosensor based on microalgal photosynthesis measurement. The biosensor was air-tight, with no headspace, preventing volatile organic toxicants from escaping into the environment as well as partitioning from the aqueous phase into the headspace until equilibrium was reached. Both the incubating and exposure times were set at 10 min. It was observed that only 2 h was needed to obtain complete dose-related inhibition of photosynthetic activity. The results showed that all the tested organic solvents inhibited algal photosynthesis with EC₅₀ ranging between 589 and 2,570 mM. The inhibition of these solvents was in the order: isopropanol > acetone > acetonitrile > ethanol > dimethylformamide > methanol. The quantitative structure-activity relationship (QSAR) between toxicity data and partition coefficient of the examined compounds could be modeled as follows: \textlog₁₀ \textEC₅₀   ( m\textM ) = - 0.6428  \textlog  P + 5.76  ( \textR² ? 0.88 ){\text{log}}_{{10}} {\text{EC}}_{{50}} \;{\left( {\mu {\text{M}}} \right)} = - 0.6428\;{\text{log}}\;P + 5.76\;{\left( {{\text{R}}^{2} \approx 0.88} \right)}. This indicates that the photosynthetic activity of the microalga Pseudokirchneriella subcapitata is highly dependent on the hydrophobicity of these commonly used organic solvents.     

A Novel Approach for Bioremediation of a Coastal Marine Wastewater Effluent Based on Artificial Microbial Mats

A novel alternative for wastewater effluent bioremediation was developed using constructed microbial mats on low-density polyester. This biotechnology showed high removal efficiencies for nitrogen and phosphorous in a short retention time (48 h): 94% for orthophosphate (7.78 g m³ d⁻¹), 79% for ammonium (11.30 g m⁻³ d⁻¹), 78% for nitrite (7.46 g m⁻³ d⁻¹), and 83% for nitrate (8.55 g m⁻³ d⁻¹). The microbial mats were dominated by Cyanobacteria genera such as Chroococcus sp., Lyngbya sp., and bacteria of the subclass Proteobacteria representative of the Eubacteria Domain. Nitzschia sp. was the dominant Eukaryote Domain. Various N and P substrates in the wastewater permit the growth of self-forming and self-sustaining bacterial, microalgal, and cyanobacterial communities on a polyester support. The result is the continuous, self-sufficient growth of microbial mats. This is an innovative, economical, and environmentally safe alternative for the treatment of wastewater effluents in coastal marine environments.     

Environment and feeding change the ability of heart rate to predict metabolism in resting Steller sea lions (<Emphasis Type="Italic">Eumetopias jubatus</Emphasis>)

The ability to use heart rate (fh) to predict oxygen consumption rates ( [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} ) in Steller sea lions and other pinnipeds has been investigated in fasting animals. However, it is unknown whether established fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationships hold under more complex physiological situations, such as when animals are feeding or digesting. We assessed whether fh could accurately predict [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} in trained Steller sea lions while fasting and after being fed. Using linear mixed-effects models, we derived unique equations to describe the fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship for fasted sea lions resting on land and in water. Feeding did not significantly change the fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship on land. However, Steller sea lions in water displayed a different fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship after consuming a 4-kg meal compared with the fasting condition. Incorporating comparable published fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} data from Steller sea lions showed a distinct effect of feeding after a 6-kg meal. Ultimately, our study illustrated that both feeding and physical environment are statistically relevant when deriving [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} from telemetered fh, but that only environment affects the practical ability to predict metabolism from fh. Updating current bioenergetic models with data gathered using these predictive fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} equations will yield more accurate estimates of metabolic rates of free-ranging Steller sea lions under a variety of physiological, behavioral, and environmental states.     

Deletion of a 236 kb region around S 4-RNase in a stylar-part mutant S 4 sm -haplotype of Japanese pear

Japanese pear (Pyrus pyrifolia Nakai) has a gametophytic self-incompatibility (GSI) mechanism controlled by a single S-locus with multiple S-haplotypes, each of which contains separate genes that determine the allelic identity of pistil and pollen. The pistil S gene is the S-ribonuclease (S-RNase) gene, whereas good candidates for the pollen S gene are the F-box protein genes. A self-compatible (SC) cultivar, ‘Osa-Nijisseiki’, which is a bud mutant of ‘Nijisseiki’ (S ₂ S ₄), has a stylar-part mutant -haplotype, which lacks the S ₄-RNase gene but retains the pollen S gene. To delineate the deletion breakpoint in the -haplotype, we constructed a bacterial artificial chromosome (BAC) library from an S ₄-homozygote, and assembled a BAC contig of 570 kb around the S ₄-RNase. Genomic PCR of DNA from S ₄- and -homozygotes and the DNA sequence of the BAC contig allowed the identification of a deletion of 236 kb spanning from 48 kb upstream to 188 kb downstream of S ₄-RNase. The -haplotype lacks 34 predicted open reading frames (ORFs) including the S ₄-RNase and a pollen-specific F-box protein gene (termed as S ₄ F-box0). Genomic PCR with a primer pair designed from the deletion junctions yielded a product specific for the -haplotype. The product could be useful as a maker for early selection of SC cultivars harboring the -haplotype. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Nitrate and phosphate removal by<Emphasis Type="Italic"> Spirulina platensis</Emphasis>

The cyanobacterium Spirulina platensis was used to verify the possibility of employing microalgal biomass to reduce the contents of nitrate and phosphate in wastewaters. Batch tests were carried out in 0.5 dm³ Erlenmeyer flasks under conditions of light limitation (40 mol quanta m^–2 s^–1) at a starting biomass level of 0.50 g/dm³ and varying temperature in the range 23–40°C. In this way, the best temperature for the growth of this microalga (30°C) was determined and the related thermodynamic parameters were estimated. All removed nitrate was used for biomass growth (biotic removal), whereas phosphate appeared to be removed mainly by chemical precipitation (abiotic removal). The best results in terms of specific and volumetric growth rates ( =0.044 day^–1, Q _x =33.2 mg dm^–3 day^–1) as well as volumetric rate and final yield of nitrogen removal ( =3.26 mg dm^–3 day^–1, =0.739) were obtained at 30°C, whereas phosphorus was more effectively removed at a lower temperature. In order to simulate full-scale studies, batch tests of nitrate and phosphate removal were also performed in 5.0 dm³ vessels (mini-ponds) at the optimum temperature (30°C) but increasing the photon fluence rate to 80 mol quanta m^–2 s^–1 and varying the initial biomass concentration from 0.25 to 0.86 g/dm³. These additional tests demonstrated that an increase in the inoculum level up to 0.75 g/dm³ enhanced both NO₃ ^– and PO₄ ^3– removal, confirming a strict dependence of these processes on biomass activity. In addition, the larger surface area of the ponds and the higher light intensity improved removal yields and kinetics compared to the flasks, particularly concerning phosphorus removal ( =0.032–0.050 day^–1, Q _x =34.7–42.4 mg dm^–3 day^–1, =3.24–4.06 mg dm^–3 day^–1, =0.750–0.879, =0.312–0.623 mg dm^–3 day^–1, and =0.224–0.440).