Dynamic Light Scattering Studies on Hydrodynamic Properties of Fibrinogen-Fibronectin Complex

Abstract

A high molecular weight ‘cryogel’ was obtained as insoluble complexes by cold incubation at near-freezing temperatures from heparinized plasma of patients with rheumatoid arthritis. After the cryogel was solubilized at 37°C, 1:1 complex of fibrinogen and fibronectin was purified at room temperature by affinity chromatography on a gelatin-Sepharose 4B. Hydrodynamic properties of the complex were investigated as a function of temperature and NaCl concentration using a dynamic light scattering. The diffusion coefficients of the complex at 20°C decreased with increasing of NaCl concentration as free fibronectin. The complex appears to be a more compact form at low ionic concentration, which is associated with conformational changes of fibronectin. The diffusion coefficient of the complex at 20°C in 0.05 M Tris- HCl(pH7.4) containing 0.5 M NaCl was estimated as 8.5× 10^?8 cm²s^?1. The complex did not dissociate over the temperature range from 20 to 37°C. The diffusion coefficients of the complex decreased significantly at 12°C and 40°C. The thermal denaturation of fibrinogen molecule in the complex was observed at 40°C. The CONTIN analysis of the light scattering data showed that the complex associated to form higher aggregates at 15°C, but not at near- freezing temperature. The equilibrium between the complex and higher aggregates appeared reversible.     

Quasielastic light-scattering studies on human fibrinogen and fibrin. II. Fibrin polymerization

The shape of fibrin intermediate polymers as well as the rate of fibrinogen polymerization was studied using diffusion measured by quasielastic light scattering. After their length distribution was narrowed by gel filtration, the polymers yielded translational and rotational diffusion coefficients of 0.37 ± 0.05 × 10^?7 cm² sec^?1 and 142 ± 32 sec^?1, respectively. Theoretical considerations indicated the polymers to be rigid rods. The rate of polymerization of fibrinogen monitored by diffusion paralleled that provided by simulataneous intensity measurements. Both monitors indicated polymerization occurs most rapidly at 30°C.     

Comparative NMR studies of diffusional water permeability of red blood cells from different species: XVIII platypus (Ornithorhynchus anatinus) and saltwater crocodile (Crocodylus porosus)

As part of a programme of comparative measurements of P _d (diffusional water permeability) the RBCs (red blood cells) from an aquatic monotreme, platypus (Ornithorhynchus anatinus), and an aquatic reptile, saltwater crocodile (Crocodylus porosus) were studied. The mean diameter of platypus RBCs was estimated by light microscopy and found to be ～6.3 μm. P _d was measured by using an Mn²⁺‐doping 1H NMR (nuclear magnetic resonance) technique. The P _d (cm/s) values were relatively low: ～2.1×10^?3 at 25°C, 2.5×10^?3 at 30°C, 3.4×10^?3 at 37°C and 4.5 at 42°C for the platypus RBCs and ～2.8×10^?3 at 25°C, 3.2×10^?3 at 30°C, 4.5×10^?3 at 37°C and 5.7×10^?3 at 42°C for the crocodile RBCs. In parallel with the low water permeability, the E _a,d (activation energy of water diffusion) was relatively high, ～35 kJ/mol. These results suggest that “conventional” WCPs (water channel proteins), or AQPs (aquaporins), are probably absent from the plasma membranes of RBCs from both the platypus and the saltwater crocodile.     

Oxygen Diffusion from the Roots of Rice Grown under Non-waterlogged Conditions

Three rice varieties, cv. Norin 36, cv. Norin 37 and cv. Yubae, were grown in a loam with a 20 cm water-table which gave aerobic conditions to a depth of not less than 15 to 17 cm. Under these conditions Norin 36 grew more vigorously and tillered more frequently than the other two varieties. The rates of oxygen diffusion at 23°C from roots up to 11 cm in length were however appreciably lower for Norin 36 (4.3 × 10^?8g · cm^?2 of root surface · min^?1) than for Norin 37 or Yubae (c. 7.8 × 10^?8g). A considerable increase (up to 200 %) in the oxygen diffusion rate (ODR) from the roots occurred if they were cooled to 3°C, and at this temperature differences in ODR between the varieties were not significant. For a purely physical system, because of the decrease in the diffusion coefficient of oxygen in water, and, the increase in oxygen solubility, a drop of c. 20 % in ODR should accompany the above 20°C drop in temperature. A 16 % drop was recorded for artificial ‘roots’ under these conditions. It was concluded that respiratory activity at the higher temperature must have been responsible for the low readings and intervarietal differences observed at 23°C. By increasing the 3°C values by 25 % a mean value of 14.2 × 10^?8g · cm^?2 of root surface · min^?1 was recorded for the three varieties, being the probable ODR at 23°C in the absence of a respiratory factor. Calculations show that respiratory activity removed enough oxygen to reduce the ODR for Norin 36 by more than 9 × 10^?8g, and for Norin 37 and Yubae by c. 6.7 × 10^?8g · cm^?2 of root surface · min^?1. Anatomical investigations showed that cortical breakdown was always extensive at 4 to 4.5 cm from the apex of the roots. In some cases however breakdown had not occurred in the basal segment of the root. No opinion could be formed as to whether differences in the amount of cortical breakdown between the varieties might have occasioned the respiratory differences observed. An interesting feature of the root anatomy was the failure of breakdown in those regions of the roots through which lateral roots emerged.     

Inelastic light scattering studies of solutions of the chloroplast coupling factor (CF1) at high and low ionic strength

The translational diffusion coefficient of CF₁ at low and high protein concentration as well as at different ionic strength (0.05 – 1.65 M) wsa determined by means of quasi-elastic light scattering experiments. The diffusion coefficient changes from D_20,w^o = 3.12 × 10^?7 cm² · sec^?1 at 0.05 M, pH 7.8, 20°C, to D_20,w^o = 3.52 × 10^?7 cm² · sec^?1 at 1.6 M, pH 7.8, 20°C. At high enzyme concentration (20 mg/ml) and under crystallization conditions (Paradies, BBRC 91: 685, 1979) CF₁ behaves as a solution of “true” hard spheres, whereas at low salt concentration the ionic atmosphere has a larger spatial extent, resulting in a higher effective hydrodynamic radius (R_H = 65 Å).     

Growth of Salvinia molesta as affected by water temperature and nutrition I. Effects of nitrogen level and nitrogen compounds

The growth of Salvinia molesta D.S. Mitchell was studied in a greenhouse using controlled-temperature water-baths at 16, 19 and 22°C and 4 different nitrogen compounds (NO₃^?, NH₄⁺, NH₄NO₃ and urea) at levels up to 60 mg N l^?1. Little growth occurred at 16°C even if 20 mg N l^?1 was supplied together with other nutrients including phosphorus (2 mg H₂PO₄-P l^?1). The highest relative growth rate and total dry matter production occurred at 22°C when plants were supplied with 20 mg NH₄-N l^?1. At this temperature, the NH₄⁺ ion was superior to the NO₃^? ion or urea as a nitrogen source (almost doubling the biomass), but was not significantly better than NH₄NO₃. Over a period of 19 days for plants receiving 0.02 mg NH₄-N l^?, biomass increased 4-fold at 16°C, 9-fold at 19°C and 10-fold at 22°C. In contrast, for plants receiving 20 mg NH₄-N l^?1, biomass increased 4-fold at 16°C, 18-fold at 19°C and 38-fold at 22°C.     

NMR study of rapid water diffusion across lipid bilayers in dipalmitoyl lecithin vesicles

A method for measurement of rapid diffusional exchange between external and internal water in lecithin vesicles is described. Paramagnetic ions were inserted inside DPL vesicles and the NMR relaxation times for water protons were measured as a function of temperature. It was found that water diffusion rate is described by a single activation energy of 15±1 kcal/mole in the temperature range 16 – 35°C and exhibits a maximum at 44°C. The permeability of DPL vesicles to water was calculated to 16–18 × 10^?4 cm/s at 44°C and 1.7 × 10^?4 cm/s at 20°C.     

The two-cross immunodiffusion technique: diffusion coefficients and precipitating titers of IgG in human serum and rabbit serum antibodies.

The two-cross technique, a new two-dimensional double-diffusion technique in gelplates, has been applied for simultaneous determination of precipitating titers and diffusion coeffients of antigen and antibody in body fluids. The advantage of this technique is that it works without using any standard solution and ensures conditions of “time-invariant sink”. The theory of the technique has been verified by experimental results on the precipitating system human serum-rabbit anti-human IgG in phosphate-buffered saline solution at pH 7.4. The results obtained using several modes of calculations from experimental parameters have been compared and found satisfactory. The accuracy and reproducibility of the results have been confirmed. It has been found that at 20°C the diffusion coefficient of human IgG in 10-times-diluted serum is (4.4 ± 0.2) × 10^?7 cm² s^?1, while the diffusion coefficient of rabbit anti-human IgG in a purified preparation is (2.9 ± 0.2) × 10^?7 cm² s^?1. The critical precipitating concentration of human IgG against rabbit anti-human IgG is invariable to concentration and amounts to 0.174 ± 0.03 mg/100 ml at pH 7.4.     

Growth of Salvinia molesta as affected by water temperature and nutrition II. Effects of phosphorus level

The growth of Salvinia molesta D.S. Mitchell, as affected by phosphorus supply and water temperature, was studied in a greenhouse using controlled water temperature baths at 16, 19 and 22°C. For significant responses to the phosphorus treatments to be obtained it was found necessary to use P-deficient plant propagules (containing <0.01% P on a dry matter basis). For these plants the highest relative growth rate and dry matter production occurred at 22°C when they received 10.01 mg PO₄P l^?1, but this was not significantly different from that of plants receiving 1.01 mg PO₄-P l^?1. Over a period of 21 days for plants receiving 0.02 mg PO₄ l^?1 the biomass increased 4-fold at 19°C and 6-fold at 22°C. In contrast, for plants receiving 10.01 mg PO₄-P l^?1 biomass was increased 20-fold at 19°C and 32-fold at 22°C. At the latter temperature, when receiving 60.01 mg PO₄-P l^?1, plants concentrated up to 1.3% of phosphorus on a dry matter basis, suggesting a possible use as a biological filter and purifier of contaminated waters.     

Esteroproteolytic enzymes from the submaxillary gland. Kinetics and other physicochemical properties.

Two esteroproteolytic enzymes (A and D) have been isolated from the mouse submaxillary gland and shown to be pure by ultracentrifugation, immunoelectrophoresis, acrylamide-gel electrophoresis, and amino acid analyses. The enzymes have molecular weights of approximately 30,000 and are structurally and antigenically related. Narrow pH optima between 7.5 and 8.0 are exhibited by both enzymes. The “pK₁'s” are between 6.0 and 6.5 and the “pK₂'s” are near 9.0. A marked preference for arginine-containing esters is shown by both enzymes. The maximum specific activity of enzyme A on p-tosylarginine methyl ester (TAME) at pH 8 was 2500–3000 μm min^?1 mg^?1 and for enzyme D, 400–600 μm min^?1 mg^?1. With TAME as substrate, the K_m for enzyme A was 8 × 10^?4m at 25 °C and 6 × 10^?4m at 37 °C. For D, K_m was 3 × 10^?4 at 25 °C and 2 × 10^?4m at 37 °C.An apparent activation of enzyme D by tosylarginine (TA), a product of TAME hydrolysis, and all α-amino acids examined was due to removal of an inhibitor by chelation. This effect could be duplicated by 8-hydroxyquinoline and diethyldithiocarbamate but not by EDTA. Enzyme A was not affected by these substances to any remarkable extent. Several divalent ions proved to be potent inhibitors of enzyme D. Both enzymes are inactivated by the active site reagents diisopropyl phosphofluoridate and tosyllysine chloromethylketone but much less rapidly than is trypsin. Nitrophenyl-4-guanidionobenzoate reacts with a burst of nitrophenol liberation but with a rapid continuing hydrolysis. One active site per molecule is indicated. Enzyme D is inactivated by urea, reversibly at 10 m and with maximal permanent losses at 6 m. Autolysis of the unfolded form by the native enzyme when they coexist at intermediate urea concentrations appears to occur.Identity of enzyme D and the epithelial growth factor binding protein is demonstrated.     

Translational and rotational diffusion of tobacco mosaic virus from polarized and depolarized light scattering

The translational and rotational dynamics of tobacco mosaic virus in sodium phosphate buffer (pH =7.5) solutions has been investigated by polarized and depolarized light scattering Rayleigh linewidth studies. For concentrations ranging from 1.75 × 10^?4 g ml^?1 to 0.25 × 10^?4 g ml^?1 the translational diffusion coefficient (D_T) has been found to be slightly concentration dependent and extrapolation to zero concentration gives D₀^20°C = 0.34 ± 0.01 × 10^?7 cm²S^?1. A full analysis of the polarized spectra obtained at high and low scattering angles and the depolarized spectra at near zero scattering angles has enabled these techniques to be compared and the rotational diffusion constant D_R to be determined. At a solution concentration of 1.75 × 10^?4 g ml^?1 a mean value is found to be D_R^20°C = 350 ± 30s^?1. These values of D_T and D_R are in approximate agreement with calculations based on models of the tobacco mosaic virus molecule as a cylindrical rod.     

Growth,biochemical and enzymatic responses of thermal cyanobacterium Gloeocapsa sp. (Cyanophyceae) to temperature and irradiance

The present study describes a strain of Gloeocapsa sp. designated as Gacheva 2007/R‐06/1, originally isolated from a geothermal flow located in Rupite, Bulgaria. To evaluate whether this cyanobacterium is locally adapted to hot environment or has the ability to tolerate lower temperatures, its growth, biochemical composition, enzyme isoforms and activity of the main antioxidant enzymes and proteases were characterized under various temperatures and two irradiance levels. The strain was able to grow over the whole temperature range (15–40°C) under two different photon fluence densities – 132 μmol photons m^?2 s^?1 (unilateral, low light, LL) and 2 × 132 μmol photons m^?2 s^?1 (bilateral, high light, HL). The best growth occurred at either 34°C and LL or at 36°C and HL, but significant growth inhibition was noted at 15°C and 40°C. Low temperature treatment (15°C) resulted in higher levels of total protein and an increased activity of manganese superoxide dismutase (MnSOD) and glutathione reductase, as compared to optimum growth temperatures. After simultaneous exposure to 15°C and HL, increases in lipid content and activity of iron superoxide dismutase and catalase (CAT) were also observed. Cultivation of cells at 40°C enhanced MnSOD, CAT and peroxidase activities, regardless of irradiance level. Increased total protein content and protease activity at 40°C was only associated with the HL treatment. Overall, these results indicate that Gloeocapsa sp. strain Gacheva 2007/R‐06/1 used different strategies to enable cells to efficiently acclimate and withstand adverse low or high temperatures. This strain obviously tolerates a wide range of temperatures below its natural habitat temperature, and does not seem to be locally adapted to its original thermal regime. It behaved as a thermotolerant rather than a thermophilic cyanobacterium, which suggests its wider distribution in nature.     

A photobleaching recovery study of glucocorticoid effects on lateral mobilities of a lipid analog in S3G HeLa cell membranes

Treatment of the S3G strain of HeLa cells with dexamethasone inhibits cholesterol synthesis and thus results in decreased plasma membrane cholesterol-to-protein ratios. Incubation of HeLa cells with dexamethasone for 24 h lowers the steady-state fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) in intact cell plasma membranes and isolated plasma membranes (Johnston, D. and Melnykovych, G. (1980) Biochim. Biophys. Acta 596, 320–324). We have examined the effect of dexamethasone treatment of S3G HeLa cells on the lateral diffusion of the fluorescent lipid analogue 3,3′-dioctadecylindocarbocyanine iodide (DiI) by the fluorescence photobleaching recovery technique. The lateral diffusion of DiI was measured in cells 0, 2, 6, 12, and 24 h following treatment with dexamethasone and in cells identically handled without dexamethasone at 37°C. The diffusion constants of DiI in the treated and untreated cell membranes at zero time were (4.52±0.30) · 10^?9 cm²/s and (4.56±0.24) · 10^?9 cm²/s, respectively. There was no significant change in the lateral diffusion of DiI in the untreated cells over the 24 h period. The lateral diffusion of the lipid probe in the dexamethasone-treated cells began to increase 6 h following treatment and reached (6.43±0.27) · 10^?9 cm²/s at 24 h. The lateral diffusion of DiI was also measured at 25, 17, 10 and 4°C following 24 h incubation with and without dexamethasone. The effect of dexamethasone treatment on the lipid probe lateral diffusion observed at 37°C is decreased at 25°C and reversed in direction at 10 and 4°C. These results agree with those obtained in artificial systems containing varying amounts of cholesterol and support the suggestion that cholesterol acts to suppress phospholipid phase changes in animal cells. The lateral diffusion of DiI localized as a monolayer at a mineral oil-water interface was measured by fluorescence photobleaching recovery. The resulting data and the viscosity of the mineral oil were used to calculate the microviscosities of the plasma membranes of untreated and dexamethasone-treated cells at 25°C. Membrane microviscosities were also calculated from the fluorescence polarization studies cited above. In both cases the dexamethasone treatment reduced the apparent microviscosity by approximately 25%. However, the absolute microviscosity values obtained by the two techniques differ by a factor of 3.     

Lateral and transversal diffusion and phase transitions in erythrocyte membranes. An excimer fluorescence study

The lateral diffusion of the excimer-forming probe pyrene decanoic acid has been determined in erythrocyte membranes and in vesicles of the lipid extracts. The random walk of the probe molecules is characterized by their jump frequency, v_j, within the lipid matrix. At T = 35°C a value of v_j = 1.6 · 10³ s^?1 is found in erythrocyte membranes. A somewhat slower mobility is determined in vesicles prepared from lipid extracts of the erythrocyte membrane. Depending on structure and charge of the lipids we obtain jump frequencies between 0.8 · 10⁸ s^?1 and 1.5 · 10⁸ s^?1 at T = 35°C. The results are compared with jump frequencies yielded in model membranes.The mobility of molecules perpendicular to the membrane surface (transversal diffusion) is investigated. Erythrocyte ghosts doped with pyrene phosphatidylcholine were mixed with undoped ghosts in order to study the exchange kinetics of the probe molecule. A fast transfer between the outer layers of the ghost cells ($\text{τ}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 1.6}\text{min at}\text{T = 37°}\text{C}$) is found. The exchange process between the inner and the outer layer of one erythrocyte ghost (flip-flop process) following this fast transfer occurs with a half-life time value of $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 100}\text{min at}\text{T = 37°}\text{C}$.The application of excimer-forming probes presumes a fluid state of the membrane. Therefore we investigated the phase transition behaviour using the excimer technique. Beside a thermotropic phase transition at T = 23°C and T = 33°C we observed an additional fluidity change at T = 38°C in erythrocyte ghosts. This transition is attached to a separation of the boundary lipid layer from the intrinsic proteins. No lipid phase transition is observed in liposomes from isolated extracts of the erythrocyte membrane with our methods.     

Photosynthetic performance and resistance to photoinhibition of Zea mays L. leaves grown at sub-optimal temperature

The performance of the photosynthetic apparatus was examined in the third leaves of Zea mays L. seedlings grown at near-optimal (25 °C) or at suboptimal (15 °C) temperature by measuring chlorophyll (ChI) a fluorescence parameters and oxygen evolution in different temperature and light conditions. In leaf tissue grown at 25 and 15 °C, the quantum yield of PSII electron transport (ψ_PSII) and the rate of O₂ evolution decreased with decreasing temperature (from 25 to 4 °C) at a photon flux density of 125 μmol m^?2 s^?1. In leaves grown at 25 °C, the decrease of ψ_PSII correlated with a decrease of photochemical ChI fluorescence quenching (q_p), whereas in leaves crown at 15 °C q_p was largely insensitive to the temperature decrease. Compared with leaves grown at 25 °C, leaves grown at 15 °C were also able to maintain a higher fraction of oxidized to reduced Q_A (greater q_p) at high photon flux densities (up to 2000 μmol m^?2 s^?1), particularly when the measurements were performed at high temperature (25 °C). With decreasing temperature and/or increasing light intensity, leaves grown at 15 °C exhibited a substantial quenching of the dark level of fluorescence F₀ (q₀) whereas this type of quenching was virtually absent in leaves grown at 25 °C. Furthermore, leaves grown at 15 °C were able to recover faster from photo inhibition of photosynthesis after a photoinhibitory treatment (1200 μmol m^?2 s^?1 at 25, 15 or 6 °C for 8 h) than leaves grown at 25 °C. The results suggest that, in spite of having a low photosynthetic capacity, Z. mays leaves grown at sub optimal temperature possess efficient mechanisms of energy dissipation which enable them to cope better with photoinhibition than leaves grown at near-optimal temperature. It is suggested that the resistance of Z. mays leaves grown at 15 °C to photoinhibition is related to the higher content of carotenoids of the xanthophyll cycle (violaxanthin + antheraxanthin + zeaxanthin) measured in these leaves than in leaves grown at 25 °C.     

OLISTHODISCUS LUTEUS (CHRYSOPHYCEAE) I. EFFECTS OF SALINITY AND TEMPERATURE ON GROWTH. MOTILITY AND SURVIVALS1, 2

The effect of salinity and temperature on Olisthodiscus luteus Carter has been examined to across the relative importance of these factory on dynamics of natural population. A salinity range 2–50% was observed with increased tolerance to low salinity (<5%.) at higher temperature (20–30°C). Slinities at 4–5%. Had densities of 10³ cells/ml^?1, and growth >0.5 division day^?1 at temperature of 15–30°C higher salinities (5–50%.) variable but distinct optima for density, growth and motility were observed 5, 10 and 30°C. Density and motility showed no clear optima from 10–10%.15–25°C where maximum growth rates >1.0 division/day^?1 were common. Temperature increased from (0.5–1.9 division. Day^?1) and increases of three orders of magnitude (10^2?10³) for maximum densities. Temperature optima 20°C for growth 5–35%. And 25°C for >40%. were observed. The implications of these findings to natural populations of O. luleus are discussed.     

The Effect of Leaf Water Potential, Leaf Temperature and Light Intensity on Leaf Diffusion Resistance and the Transpiration of Leaves of Malus sylvestris

The relationship between leaf resistance to water vapour diffusion and each of the factors leaf water potential, light intensity and leaf temperature was determined for leaves on seedling apple trees (Malus sylvestris Mill. cv. Granny Smith) in the laboratory. Leaf cuticular resistance was also determined and transpiration was measured on attached leaves for a range of conditions. Leaf resistance was shown to be independent of water potential until potential fell below — 19 bars after which leaf resistance increased rapidly. Exposure of leaves to CO₂-free air extended the range for which resistance was independent of water potential to — 30 bars. The light requirement for minimum leaf resistance was 10 to 20 W m^?2 and at light intensities exceeding these, leaf resistance was unaffected by light intensity. Optimum leaf temperature for minimum diffusion resistance was 23 ± 2°C. The rate of change measured in leaf resistance in leaves given a sudden change in leaf temperature increased as the magnitude of the temperature change increased. For a sudden change of 1°C in leaf temperature, diffusion resistance changed at a rate of 0.01 s cm^?1 min^?1 whilst for a 9°C leaf temperature change, diffusion resistance changed at a rate of 0.1 s cm^?1 min^?1. Cuticular resistance of these leaves was 125 s cm^?1 which is very high compared with resistances for open stomata of 1.5 to 4 s cm^?1 and 30 to 35 s cm^?1 for stomata closed in the dark. Transpiration was measured in attached apple leaves enclosed in a leaf chamber and exposed to a range of conditions of leaf temperature and ambient water vapour density. Peak transpiration of approximately 5 × 10^?6 g cm^?2 s^?1 occurred at a vapour density gradient from the leaf to the air of 12 to 14 g m^?3 after which transpiration declined due presumably to increased stomatal resistance. Leaves in CO₂-free air attained a peak transpiration of 11 × 10^?6 g cm^?2 s^?1 due to lower values of leaf resistance in CO₂ free air. Transpiration then declined in these leaves due to development of an internal leaf resistance (of up to 2 s cm^?1). The internal resistance was masked in leaves at normal CO₂ concentrations by the increase in stomatal resistance.     

Effects of light,temperature and salinity on the growth rate of harmful marine diatoms,Chaetoceros convolutus and C. concavicornis that kill netpen salmon

Chaetoceros convolutus and C. concavicornis have been implicated in the death of salmon in netpens in the Pacific Northwest by damaging the salmon's gills. To better understand how environmental factors affect the distribution of these two species, the interacting effects of light, temperature and salinity on growth rate were examined by growing these species under a range of temperatures (4–18 °C), light (10–175 μmol photon m⁻² s⁻¹) and salinities (10–30‰). For C. convolutus, the growth rate showed a hyperbolic relationship with irradiance at 8, 14 and 18 °C and light saturation occurred at 9, 14 and 20 μmol photon m^t s⁻¹ respectively. At 4 °C for C. convolutus and 8 °C for C. concavicornis, cells grew at μ_max, even at the lowest irradiances tested (10 μmol photon m⁻² s⁻¹). For C. convolutus, the amount of light required to saturate growth rate increased with temperature in an approximately linear fashion. The Q₁₀ was 1.88, calculated by averaging over both species. C. concavicornis was the more euryhaline species growing at salinities as low as 17.5‰, while C. convolutus grew only at 25‰ and above.     

Biomass and terpenoids produced by mutant strains of <Emphasis Type="Italic">Arthrospira</Emphasis> under low temperature and light conditions

The filamentous Cyanobacterium Arthrospira is commercially produced and is a functional, high-value, health food. We identified 5 low temperature and low light intensity tolerant strains of Arthrospira sp. (GMPA1, GMPA7, GMPB1, GMPC1, and GMPC3) using ethyl methanesulfonate mutagenesis and low temperature screening. The 5 Arthrospira strains grew rapidly below 14?°C, 43.75 μmol photons m^?2 s^?1 and performed breed conservation at 2.5?°C, 8.75 μmol photons m^?2 s^?1. We used morphological identification and molecular genetic analysis to identify GMPA1, GMPA7, GMPB1 and GMPC1 as Arthrospira platensis, while GMPC3 was identified as Arthrospira maxima. Growth at different culture temperatures was determined at regular intervals using dry biomass. At 16?°C and 43.75 μmol photons m^?2 s^?1, the maximum dry biomass production and the mean dry biomass productivity of GMPA1, GMPB1, and GMPC1 were 2057?±?80 mg l^?1, 68.7?±?2.5 mg l^?1 day^?1, 1839?±?44 mg l^?1, 60.6?±?1.8 mg l^?1 day^?1, and 2113?±?64 mg l^?1, 77.7?±?2.5 mg l^?1 day^?1 respectively. GMPB1 was chosen for additional low temperature tolerance studies and growth temperature preference. In winter, GMPB1 grew well at mean temperatures <10?°C, achieving 3258 mg dry biomass from a starting 68 mg. In summer, GMPB1 grew rapidly at mean temperatures more than 28?°C, achieving 1140 mg l^?1 dry biomass from a starting 240 mg. Phytonutrient analysis of GMPB1 showed high levels of C-phycocyanin and carotenoids. Arthrospira metabolism relates to terpenoids, and the methyl-d-erythritol 4-phosphate pathway is the only terpenoid biosynthetic pathway in Cyanobacteria. The 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR) gene from GMPB1 was cloned and phylogenetic analysis showed that GMPB1 is closest to the Cyanobacterium Oscillatoria nigro-viridis PCC711. Low temperature tolerant Arthrospira strains could broaden the areas suitable for cultivation, extend the seasonal cultivation time, and lower production costs.     

Effect of irradiance and temperature on the photosynthesis of a cultivated red alga,Pyropia tenera (= Porphyra tenera), at the southern limit of distribution in Japan

The effect of irradiance and temperature on the photosynthesis of the red alga, Pyropia tenera, was determined for maricultured gametophytes and sporophytes collected from a region that is known as one of the southern limits of its distribution in Japan. Macroscopic gametophytes were examined using both pulse‐amplitude modulated fluorometry and/or dissolved oxygen sensors. A model of the net photosynthesis–irradiance (P‐E) relationship of the gametophytes at 12°C revealed that the net photosynthetic rate quickly increased at irradiances below the estimated saturation irradiance of 46 μmol photons m^?2 s^?1, and the compensation irradiance was 9 μmol photons m^?2 s^?1. Gross photosynthesis and dark respiration for the gametophytes were also determined over a range of temperatures (8–34°C), revealing that the gross photosynthetic rates of 46.3 μmol O₂ mg_chl‐a^?1 min^?1 was highest at 9.3 (95% Bayesian credible interval (BCI): 2.3–14.5)°C, and the dark respiration rate increased at a rate of 0.93 μmol O₂ mg_chl‐a^?1 min^?1°C^?1. The measured dark respiration rates ranged from ?0.06 μmol O₂ mg_chl‐a^?1 min^?1 at 6°C to ?25.2 μmol O₂ mg_chl‐a^?1 min^?1 at 34°C. The highest value of the maximum quantum yield (Fv/Fm) for the gametophytes occurred at 22.4 (BCI: 21.5–23.3) °C and was 0.48 (BCI: 0.475–0.486), although those of the sporophyte occurred at 12.9 (BCI: 7.4–15.1) °C and was 0.52 (BCI: 0.506–0.544). This species may be considered well‐adapted to the current range of seawater temperatures in this region. However, since the gametophytes have such a low temperature requirement, they are most likely close to their tolerable temperatures in the natural environment.