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141.
142.
Inorganic carbon (Ci) uptake and efflux has been investigated in the marine microalga Nannochloropsis gaditana Lubian by monitoring CO2 fluxes in cell suspensions using mass spectrometry. Addition of H13CO3
− to cell suspensions in the dark caused a transient increase in the CO2 concentration in the medium far in excess of the equilibrium CO2 concentration. The magnitude of this release was dependent on the length of time the cells had been kept in the dark. Once
equilibrium between the Ci species had been achieved, a CO2 efflux was observed after saturating light intensity was applied to the cells. External carbonic anhydrase (CA) was not detected
nor does this species demonstrate a capacity to take up CO2 by active transport. Photosynthetic O2 evolution and the release CO2 in the dark depend on HCO3
− uptake since both were inhibited by the anion exchange inhibitor, 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS).
The bicarbonate uptake mechanism requires light but can also continue for short periods in the dark. Ethoxyzolamide, a CA
inhibitor, markedly inhibited CO2 efflux in the dark, indicating that CO2 efflux was dependent upon the intracellular dehydration of HCO3
−. These results indicate that Nannochloropsis possesses a bicarbonate uptake system which causes the accumulation of high intracellular Ci levels and an internal CA which
maintains the equilibrium between CO2 and HCO3
− and thus causes a subsequent release of CO2 to the external medium.
Received: 20 September 1999 / Accepted: 25 October 1999 相似文献
143.
144.
Martha Guerrero‐Olazarán Luis L. Escamilla‐Treviño Mauricio Castillo‐Galván Juan A. Gallegos‐López José M. Viader‐Salvadó 《Biotechnology progress》2009,25(5):1310-1316
Shrimp (Litopenaeus vannamei) trypsinogen has never been isolated from its natural source. To assess the production of L. vannamei trypsinogen, we engineered Pichia pastoris strains and evaluated two culture approaches with three induction culture media, to produce recombinant shrimp trypsinogen for the first time. The trypsinogen II cDNA was fused to the signal sequence of the Saccharomyces cerevisiae alpha mating factor, placed under the control of the P. pastoris AOX1 promoter, and integrated into the genome of P. pastoris host strain GS115. Using standard culture conditions for heterologous gene induction of a GS115 strain in shake flasks, recombinant shrimp trypsinogen was not detected by SDS‐PAGE and Western blot analysis. Growth kinetics revealed a toxicity of recombinant shrimp trypsinogen or its activated form over the cell host. Thus, a different culture approach was tested for the induction step, involving the use of high cell density cultures, a higher frequency of methanol feeding (every 12 h), and a buffered minimal methanol medium supplemented with sorbitol or alanine; alanine supplemented medium was found to be more efficient. After 96 h of induction with alanine supplemented medium, a 29‐kDa band from the cell‐free culture medium was clearly observed by SDS‐PAGE, and confirmed by Western blot to be shrimp trypsinogen, at a concentration of 14 μg/mL. Our results demonstrate that high density cell cultures with alanine in the induction medium allow the production of recombinant shrimp trypsinogen using the P. pastoris expression system, because of improved cell viability and greater stability of the recombinant trypsinogen. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 相似文献
145.
Water potentials for developing cladodes and fruits of a succulent plant, including xylem-versus-phloem implications for water movement 总被引:3,自引:1,他引:3
Nobel Park S.; Andrade Jose Luis; Wang Ning; North Gretchen B. 《Journal of experimental botany》1994,45(12):1801-1807
Developing cladodes had lower water potentials and developingfruits had higher water potentials than the underlying cladodesof the widely cultivated prickly pear cactus, Opuntia ficus-indica.The 0.06 MPa lower value in 4-week-old daughter cladodes indicateda typical water potential gradient from the underlying clad-odealong the xylem of 0.2 MPa m1; the 0.17 MPa highervalue in 4-week-old fruits, which decreased to 0.07 MPa by 10weeks, implicated the phloem as their supplier of water. Thephloem sap of the underlying cladodes had an osmotic pressureof only 0.90 to 0.98 MPa, so the phloem could supply a relativelydilute solution to the photosynthetically dependent fruits (daughtercladodes of O. ficus-indica are photosynthetically independentat 4 weeks). Although the water potentials were similar foradjacent tissues, the osmotic pressures were lower for the water-storagecompared with the photosynthetic tissue; the osmotic pressureswere higher for xylem sap from fruits, for which xylary flowapparently occurred toward the underlying cladodes, than fordaughter cladodes. The relative capacitance (change in relativewater content divided by change in tissue water potential) wasapproximately 0.71 MPa1 for the water-storage tissueand the photosynthetic tissue of both daughter cladodes andfruits at 4 weeks of age. When these organs approached maturityat 10 weeks, the relative capacitance increased about 40% fortheir water-storage tissue, but decreased 30% for their photosynthetictissue. As the plant water content decreases during drought,about twice as much water will thus be lost per unit volumeof the water-storage tissue compared with the photosynthetictissue of maturing fruits and cladodes. Key words: Opuntia ficus-indica, phloem, relative water content, water capacitance, water potential 相似文献
146.
Marta Rodríguez-Sáiz Juan Luis de la Fuente José Luis Barredo 《Applied microbiology and biotechnology》2010,88(3):645-658
Astaxanthin is a red xanthophyll (oxygenated carotenoid) with large importance in the aquaculture, pharmaceutical, and food
industries. The green alga Haematococcus pluvialis and the heterobasidiomycetous yeast Xanthophyllomyces dendrorhous are currently known as the main microorganisms useful for astaxanthin production at the industrial scale. The improvement
of astaxanthin titer by microbial fermentation is a requirement to be competitive with the synthetic manufacture by chemical
procedures, which at present is the major source in the market. In this review, we show how the isolation of new strains of
X. dendrorhous from the environment, the selection of mutants by the classical methods of random mutation and screening, and the rational
metabolic engineering, have provided improved strains with higher astaxanthin productivity. To reduce production costs and
enhance competitiveness from an industrial point of view, low-cost raw materials from industrial and agricultural origin have
been adopted to get the maximal astaxanthin productivity. Finally, fermentation parameters have been studied in depth, both
at flask and fermenter scales, to get maximal astaxanthin titers of 4.7 mg/g dry cell matter (420 mg/l) when X. dendrorhous was fermented under continuous white light. The industrial scale-up of this biotechnological process will provide a cost-effective
method, alternative to synthetic astaxanthin, for the commercial exploitation of the expensive astaxanthin (about $2,500 per
kilogram of pure astaxanthin). 相似文献
147.
Long term effects of manure, charcoal and mineral fertilization on crop production and fertility on a highly weathered Central Amazonian upland soil 总被引:58,自引:0,他引:58
Christoph Steiner Wenceslau G. Teixeira Johannes Lehmann Thomas Nehls Jeferson Luis Vasconcelos de Macêdo Winfried E. H. Blum Wolfgang Zech 《Plant and Soil》2007,291(1-2):275-290
Application of organic fertilizers and charcoal increase nutrient stocks in the rooting zone of crops, reduce nutrient leaching
and thus improve crop production on acid and highly weathered tropical soils. In a field trial near Manaus (Brazil) 15 different
amendment combinations based on equal amounts of carbon (C) applied through chicken manure (CM), compost, charcoal, and forest
litter were tested during four cropping cycles with rice (Oryza sativa L.) and sorghum (Sorghum bicolor L.) in five replicates. CM amendments resulted in the highest (P < 0.05) cumulative crop yield (12.4 Mg ha−1) over four seasons. Most importantly, surface soil pH, phosphorus (P), calcium (Ca), and magnesium (Mg) were significantly
enhanced by CM. A single compost application produced fourfold more grain yield (P < 0.05) than plots mineral fertilized in split applications. Charcoal significantly improved plant growth and doubled grain
production if fertilized with NPK in comparison to the NPK-fertilizer without charcoal (P < 0.05). The higher yields caused a significantly greater nutrient export in charcoal-amended fields, but available nutrients
did not decrease to the same extent as on just mineral fertilized plots. Exchangeable soil aluminum (Al) was further reduced
if mineral fertilizer was applied with charcoal (from 4.7 to 0 mg kg−1). The resilience of soil organic matter (SOM) in charcoal amended plots (8 and 4% soil C loss, mineral fertilized or not
fertilized, respectively) indicates the refractory nature of charcoal in comparison to SOM losses over 20 months in CM (27%),
compost amended (27%), and control plots (25% loss). 相似文献
148.
149.
David Monticelli Pedro M. Araújo James E. Hines Paulo Q. Tenreiro Luis P. Silva Jaime A. Ramos 《Journal of avian biology》2014,45(1):75-84
Adult survival, an important fitness component, is usually 1) lower in lighter individuals due to their reduced ability to survive winter conditions compared to heavier ones, especially in resident species at northern temperate latitudes and 2) lower in females compared with males due to higher reproductive costs incurred by females. In this paper, a capture–mark–recapture dataset of 649 cetti's warblers Cettia cetti ringed seasonally at two wetlands in central Portugal over an 11‐yr period (2000–2010) was modelled in a multi‐state framework to examine the influence of these individual covariates on apparent adult survival, while controlling for the presence of transient individuals in our study area. The probability of change in mass state (ψLight→Heavy, ψHeavy→Light) during the annual cycle was also estimated. Overall, birds survived better during spring–summer (breeding/moulting periods) compared with autumn–winter, but there was no effect of body mass on apparent adult survival probability. The modelling detected a significant interaction between sex and season, in which resident females survived better than resident males in spring–summer (?RF= 0.857 ± 0.117 and ?RM= 0.698 ± 0.181) while the opposite pattern was found in autumn–winter (?RM= 0.440 ± 0.086 and ?RF= 0.339 ± 0.084). In addition, cetti's warblers had a tendency to lose mass in spring–summer (ψHeavy → Light= 0.560 ± 0.063) and to regain mass in autumn–winter (ψLight→Heavy= 0.701 ± 0.069). This pattern of body mass change during the annual cycle may reflect energetic costs to reproduction and moulting, and/or a response to increased starvation risk during winter. High body mass, however, did not increase adult survival in this population presumably due to the relatively mild winter weather prevailing in central Portugal. Survival estimates are more likely to be explained by important ecological and behavioural differences between the two sexes in polygynous passerines. Our results highlight that studies aiming to identify the main factors shaping survival and individual fitness in polygynous species should be conducted during different phases of their annual cycle. 相似文献