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Djctyocha perlaevis. Rate of I4CO2 incorporation into protein (o), polysaccharide (q), lipids ( A ) , and low-molecularweight metabolites ( 0 ) as a function of the number of isolated cells vial-'. Protein: Y =-32 + 66X (r = 0.998); polysaccharide: Y =-28 t 43X (r = 0.995); lipids. Y = 50 + 42X (r = 0.996); low-molecular-weight metabolltes: Y = 92 + 88X (r = 0.995)
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Ring opening of epoxides has been an area of interest for organic chemists, owing to their reactivity toward nucleophiles. Such reactions yield important products depending on the type of nucleophiles used. This review article covers the synthetic approaches (1991–2015) used for the ring opening of epoxides via carbon nucleophiles.
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... A differential extraction technique first employed by Morris et al. (1974) was used to partition the assimilated l4C0, between lipid, protein, polysaccharide, and small molecular weight intermediate compounds. T h e procedure was similar to that outlined in Taguchi and Laws (1985). T h e fractionation technique separated the cell material into chloroform-soluble compounds (lipid), trichloroacetic acid (TCA)-insoluble compounds (protein), TCAsoluble compounds (polysaccharide plus nucleic acids), and methanol-water soluble compounds (low molecular weight intermediates). ...
Lipid synthesis of three marine diatoms was studied with a 14CO2 incorporation technique in silicate limited batch cultures. Growth rates were independent of the silicate concentration but the cellular yields were proportional to the initial amount of silicate. At the beginning of the stationary growth phase, lipid synthesis rates per unit culture volume increased by 1.7 times for Chaetoceros gracilis, 3.1 times for Hantzschia sp., and 2.8 times for Cyclotella sp., respectively compared to those during the exponential growth phase. Lipid carbon accounted for as much as 57% of the carbon in C. gracilis, 71% in Hantzschia sp., and 65% in Cyclotella sp., respectively. Additional enrichment with silicate during stationary growth phase allowed the cultures to grow further. Lipid synthesis rates were reduced during the subsequent growth phase, and the growth rates themselves were dependent on the level of biomass achieved during the previous stationary phase. However, the cellular yields were similar and probably controlled by light.
... The experimental methods that have been developed rely upon both autecological and synecological approaches. The autecological approaches include single-cell isolation techniques and the direct measurement of nuclear division (22,(26)(27)(28). These methods yield average values for the growth rate (,u) of individual species of microorganisms within a mixed-species assemblage (20,21,25). ...
A method is presented for determining both the average turnover rate and the standard deviation of the average turnover rate of the adenine nucleotide (AN) pool within a population of microorganisms. The method requires the calculation of the initial slope and curvature of a plot of AN specific activity versus time following the introduction of [H]adenine. An analysis of noise-corrupted data indicated that the method is capable of detecting a lack of uniformity in the turnover rate when the coefficient of variation of the turnover rate exceeds 39%. An analysis of field data revealed a significant lack of uniformity in the turnover rates of microbial communities in a marine sediment sample and freshwater pond but no significant nonuniformity in the turnover rates of microbial communities in a seawater sample and in a second freshwater pond. Although the method has been applied only to the analysis of AN turnover rates, it is applicable to any intracellular pool for which a suitable radioactive precursor exists.
The kinetics of population growth and death were investigated in Anabaena flos-aquae (Lyngb.) Bréb grown at light intensities ranging from limitation to photoinhibition (5 W·m−2 to 160 W·m−2) in a nutrient-replete turbidostat. Steady-state growth rate (μ, or dilution rate, D) increased with light intensity from 0.44·day−1 at a light intensity of 5 W·m−2 to 0.99·day−1 at 20 W·m−2 and started to decrease above about 22 W·m−2, reaching 0.56·day−1 at 160 W·m−2. The Haldane function of enzyme inhibition fit the growth data poorly, largely because of the unusually narrow range of saturation intensity. However, it produced a good fit (P < 0.001) for growth under photoinhibition. Anabaena flos-aquae died at different specific death rates (γ) below and above the saturation intensity. When calculated as the slope of a vx−1 and D−1 plot, where vx and D are cell viability (or live cell fraction) and dilution rate, respectively; γ was 0.047·day−1 in the range of light limitation and 0.103·day−1 under photoinhibition. Live vegetative cells and heterocysts, either in numbers or as a percentage of the total cells, showed a peak at the saturation intensity and decreased at lower and higher intensities. The ratio of live heterocysts to live vegetative cells increased with intensity when light was limiting but decreased when light was supersaturating. In cells growing at the same growth rate, the ratio was significantly lower under light inhibition than under subsaturation and the cell N:C ratio was also lower under inhibition. The steady-state rate of dissolved organic carbon (DOC) production increased with light intensity. However, its production as a percentage of the total C fixation was lowest at the optimum intensity and increased as the irradiance decreased or increased. The rate and percentage was significantly higher under photoinhibition than limitation in cells growing at the same growth rate. About 22% of the total fixed carbon was released as DOC at the highest light intensity. No correlation was found between the number of dead cells and DOC.
The effect of light intensity on the release of dissolved organic carbon during photosynthesis on NaH14CO3 was investigated using the phytoplanktonic CyanobacteriumOscillatoria rubescens. The released products were fractionated by molecular size and chemical identifications attempted using combined thin-layer electrophoresis and chromatography, and high pressure liquid chromatography.
Within the range of irradiances tested (from 6 to 60 µmole m−2 sec−1), though the upper one inhibited photosynthesis ofO. rubescens, light had little effect on the quantity and composition of the excreted products. The released carbon was always lower than 3% of the incorporated carbon, and mainly composed (62 to 86%) by small molecular weight compounds. The prevailing identified compounds were amino acids which represented more than 20% of the excreted carbon. Among organic acids, glycolic acid accounted for less than 2% of the recovered radioactivity. Glucose was the only identified sugar.
The extent of enhanced post-illumination respiration (EPIR) has been investigated in a number of microalgae. Respiration rates, as determined by O-2 consumption, were enhanced (in all but one case) by 50-140% following pre-exposure to high photon flux compared to rates obtained for steady-state dark respiration. The extent of EPIR was dependent more on photon flux than on duration of exposure, although the latter did have some effect. In Isochrysis galbana and Chaetoceros calcitrens, EPIR effects were also demonstrated using [C-14]CO2 evolution. In I.galbana, release of CO2 from cells pre-exposed to a period of high photon flux was most rapid from carbohydrate and low-molecular-weight metabolites. Data obtained from Thalassiosira weisflogii indicate that cells grown at low photon flux are more susceptible to EPIR than those grown under high photon flux. These results are discussed in the context of various hypotheses that have been proposed regarding the mechanism of EPIR effects.
The time course of adaptation from a high to a low photon flux density was studied in the marine chlorophyte Dunaliella tertiolecta. A one-step transition from 700 to 70 micromole quanta per square meter per second resulted in a reduction of doubling rate from 1.1 to 0.4 per day within 24 hours, followed by a slower accumulation of photosynthetic pigments, light harvesting antenna complexes, Photosystem II reaction centers and structural lipids that constitute the thylakoid membranes. Photoregulated changes in the biochemical composition of the thylakoid proteins and lipids were functionally accompanied by decreases in the minimal photosynthetic quantum requirement and photosynthetic capacity, and an increase in the minimal turnover time for in vivo electron transport from water to CO(2). Analysis of de novo synthesis of thylakoid membranes and proteins indicates that a high light to low light transition leads to a transient in carbon metabolism away from lipid biosynthesis toward the synthesis of the light harvesting antenna protein complexes, accompanied by a slower restoration rate of reaction centers and thylakoid membranes. This pattern of sequential synthesis of light harvesting complexes followed by reaction centers and membranes, appears to optimize light harvesting capabilities as cells adapt to low photon flux densities.
