海洋浮游藻类无机碳利用机理的研究

为了认识海洋浮游藻类在碳充足和碳受限条件下对水体中溶解无机碳 (DIC)的利用方式与可能机理 ,对 13种海洋浮游藻类在不同pH和CO2 浓度及不同DIC条件下细胞外碳酸酐酶 (CA)的活性进行了分析测定。结果显示 :13种藻中 ,只有Amphidiniumcarterae和Prorocentrumminimum在碳充足条件下具细胞外CA活性。Melosirasp .、Phaeodactylumtricornutum、Skeletonemacostatum、Thalassiosirarotula、Emilianiahuxleyi和Pleurochrysiscarterae则在碳受限条件下才具细胞外CA活性。Chaetoceroscompressus、Glenodiniumfoliaceum、Coccolithuspelagicus、Gephrocapsaoceanica和Heterosigmaakashiwo即使在碳受限条件下也未检测到细胞外CA活性。应用封闭系统中pH漂移技术和阴离子交换抑制剂 4′4′ diisothiocyanatostilbene_2 ,2_disulfonicacid (DIDS)等的研究表明 ,Coc.pelagicus和G .oceanica可通过阴离子交换机制进行HCO-3 的直接利用。H .akashiwo没有潜在的HCO-3 直接利用或细胞外CA催化的HCO-3 利用     

海洋浮游藻类无机碳利用机理的研究

为了认识海洋浮游藻类在碳充足和碳受限条件下对水体中溶解无机碳(DIC)的利用方式与可能机理,对13种海洋浮游藻类在不同pH和CO2浓度及不同DIC条件下细胞外碳酸酐酶(CA)的活性进行了分析测定.结果显示:13种藻中,只有Amphidinium carterae和Prorocentrum minimum在碳充足条件下具细胞外CA活性.Melosira sp.、Phaeodactylum tricornutum、Skeletonema costatum、Thalassiosira rotula、Emiliania huxleyi和Pleurochrysis carterae则在碳受限条件下才具细胞外CA活性.Chaetoceros compressus、Glenodinium foliaceum、Coccolithus pelagicus、 Gephrocapsa oceanica和Heterosigma akashiwo即使在碳受限条件下也未检测到细胞外CA活性.应用封闭系统中pH漂移技术和阴离子交换抑制剂4′4′-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS)等的研究表明,Coc. pelagicus和G. oceanica可通过阴离子交换机制进行HCO-3的直接利用.H. akashiwo没有潜在的HCO-3直接利用或细胞外CA催化的HCO-3利用.     

Bicarbonate Utilization in Anabaena

Blue-green algal growth frequently occurs in water with relatively high pH and high levels of organic carbon which are related by the pH-dependent ionization of inorganic carbon. This relationship, which may regulate natural populations, was examined using a factorial experimental design in which the metabolic response of Anabaena flos-aquae was measured as a function of pH and total inorganic carbon. The concentration of the products of ionization were calculated. Algal responses were determined manometrically as rates of photosynthesis and respiration. The overriding factor regulating the growth of Anabaena was pH, and no obvious relationship was found to exist between oxygen evolution or uptake and the concentration of any form of inorganic carbon.     

Light Harvesting and Utilization by Phytoplankton

In this study we use a model based on target theory to analyzesteady-state photosynthesis-irradiance relationships in continuouslight. From the average turnover time () of photosynthetic units(PSU_O2), numerical analyses of the model coefficients, and measurementsof the light field and cell absorptivity, apparent absorptioncrosssections of photosystem II (PSII) were determined for three species of marine unicellular algaegrown at different irradiance levels. These cross-sections generally,but not always, increased with decreased growth irradiance.Additionally, the ratios of photosystem I/photosystem II reactioncenters were calculated from measurements of oxygen flash yieldsand chlorophyll/P₇₀₀ ratios. From the ratios of the reactioncenters, cell absorptivity and the apparent absorption cross-sectionof photosystem II, the apparent absorption cross-sections ofphotosystem I (PSI) were also calculated. Finally, on the basis of our calculated absorptioncross-sections, we estimated the minimum quantum requirementsfor O₂ evolution. Our results suggest that the absorption cross-sectionsof PS I and PS II vary independently and the minimum quantumrequirements for O₂ vary by more than twofold, increasing from9.1 to 20.6 quanta/O₂, as growth irradiance increases. The increasein quantum requirement corresponds to larger apparent cross-sectionsfor photosystem I and higher carotenoid/chlorophyll ratios. (Received October 15, 1985; Accepted July 17, 1986)     

Amine Oxidases of Marine Phytoplankton

Some phytoplankton utilized a novel mechanism for obtaining nitrogen from primary amines. They oxidized the primary amines to produce extracellular hydrogen peroxide and aldehydes and used the third reaction product, ammonium, as a nitrogen source. The specificity, regulation, inhibition by bromoethylamine, and potential dependence on copper of this process are described.     

Methanol Production by a Broad Phylogenetic Array of Marine Phytoplankton

Methanol is a major volatile organic compound on Earth and serves as an important carbon and energy substrate for abundant methylotrophic microbes. Previous geochemical surveys coupled with predictive models suggest that the marine contributions are exceedingly large, rivaling terrestrial sources. Although well studied in terrestrial ecosystems, methanol sources are poorly understood in the marine environment and warrant further investigation. To this end, we adapted a Purge and Trap Gas Chromatography/Mass Spectrometry (P&T-GC/MS) method which allowed reliable measurements of methanol in seawater and marine phytoplankton cultures with a method detection limit of 120 nanomolar. All phytoplankton tested (cyanobacteria: Synechococcus spp. 8102 and 8103, Trichodesmium erythraeum, and Prochlorococcus marinus), and Eukarya (heterokont diatom: Phaeodactylum tricornutum, coccolithophore: Emiliania huxleyi, cryptophyte: Rhodomonas salina, and non-diatom heterokont: Nannochloropsis oculata) produced methanol, ranging from 0.8–13.7 micromolar in culture and methanol per total cellular carbon were measured in the ranges of 0.09–0.3%. Phytoplankton culture time-course measurements displayed a punctuated production pattern with maxima near early stationary phase. Stabile isotope labeled bicarbonate incorporation experiments confirmed that methanol was produced from phytoplankton biomass. Overall, our findings suggest that phytoplankton are a major source of methanol in the upper water column of the world’s oceans.     

Biogeography of Photosynthetic Light-Harvesting Genes in Marine Phytoplankton

Background

Photosynthetic light-harvesting proteins are the mechanism by which energy enters the marine ecosystem. The dominant prokaryotic photoautotrophs are the cyanobacterial genera Prochlorococcus and Synechococcus that are defined by two distinct light-harvesting systems, chlorophyll-bound protein complexes or phycobilin-bound protein complexes, respectively. Here, we use the Global Ocean Sampling (GOS) Project as a unique and powerful tool to analyze the environmental diversity of photosynthetic light-harvesting genes in relation to available metadata including geographical location and physical and chemical environmental parameters.

Methods

All light-harvesting gene fragments and their metadata were obtained from the GOS database, aligned using ClustalX and classified phylogenetically. Each sequence has a name indicative of its geographic location; subsequent biogeographical analysis was performed by correlating light-harvesting gene budgets for each GOS station with surface chlorophyll concentration.

Conclusion/Significance

Using the GOS data, we have mapped the biogeography of light-harvesting genes in marine cyanobacteria on ocean-basin scales and show that an environmental gradient exists in which chlorophyll concentration is correlated to diversity of light-harvesting systems. Three functionally distinct types of light-harvesting genes are defined: (1) the phycobilisome (PBS) genes of Synechococcus; (2) the pcb genes of Prochlorococcus; and (3) the iron-stress-induced (isiA) genes present in some marine Synechococcus. At low chlorophyll concentrations, where nutrients are limited, the Pcb-type light-harvesting system shows greater genetic diversity; whereas at high chlorophyll concentrations, where nutrients are abundant, the PBS-type light-harvesting system shows higher genetic diversity. We interpret this as an environmental selection of specific photosynthetic strategy. Importantly, the unique light-harvesting system isiA is found in the iron-limited, high-nutrient low-chlorophyll region of the equatorial Pacific. This observation demonstrates the ecological importance of isiA genes in enabling marine Synechococcus to acclimate to iron limitation and suggests that the presence of this gene can be a natural biomarker for iron limitation in oceanic environments.     

Differential Growth Responses of Marine Phytoplankton to Herbicide Glyphosate

Glyphosate is a globally popular herbicide to kill weeds and its wide applications may lead to accumulation in coastal oceans as a source of phosphorus (P) nutrient or growth inhibitor of phytoplankton. We studied the physiological effects of glyphosate on fourteen species representing five major coastal phytoplankton phyla (haptophyta, bacillariophyta, dinoflagellata, raphidophyta, and chlorophyta). Based on growth responses to different concentrations of glyphosate under contrasting dissolved inorganic phosphorus (DIP) conditions, we found that phytoplankton species could be classified into five groups. Group I (Emiliania huxleyi, Skeletonema costatum, Phaeodactylum tricornutum) could utilize glyphosate as sole P-source to support growth in axenic culture, but in the presence of DIP, they were inhibited by both 36-μM and 360-μM glyphosate. Group II (Karenia mikimotoi, Prorocentrum minimum, Dunaliella tertiolecta, Symbiodinium sp., Heterosigma akashiwo and Alexandrium catenella) could not utilize glyphosate as sole P-source to support growth, and in the presence of DIP growth was not affected by 36-μM but inhibited by 360-μM glyphosate. Glyphosate consistently enhanced growth of Group III (Isochrysis galbana) and inhibited Group IV (Thalassiosira weissflogii, Thalassiosira pseudonana and Chattonella marina) regardless of DIP condition. Group V (Amphidinium carterae) exhibited no measurable response to glyphosate regardless of DIP condition. This grouping is not congruent with the phylogenetic relationships of the phytoplankton species suggesting functional differentiation driven by environmental pressure. We conclude that glyphosate could be used as P-source by some species while is toxic to some other species and yet has no effects on others. The observed differential effects suggest that the continued use of glyphosate and increasing concentration of this herbicide in the coastal waters will likely exert significant impact on coastal marine phytoplankton community structure.     

一氧化氮(NO)对海洋浮游植物的作用

该文介绍海洋浮游植物内源一氧化氮(NO)的产生,NO对海洋浮游植物生长的作用,以及有关NO在海洋浮游植物环境胁迫响应中生理作用的研究现状,并对与这些问题相关的研究趋势作了分析和讨论。     

一氧化氦（NO）对海洋浮游植物的作用

该文介绍海洋浮游植物内源一氧化氮（NO）的产生,NO对海洋浮游植物生长的作用,以及有关NO在海洋浮游植物环境胁迫响应中生理作用的研究现状,并对与这些问题相关的研究趋势作了分析和讨论。     

Evidence for Bicarbonate Transport in Species of Red and Brown Macrophytic Marine Algae

Cook, C. M., Lanaras, T. and Colman, B. 1986. Evidence for bicarbonatetransport in species of red and brown macrophytic marine algae.—J.exp. Bot. 37: 977–984. The capacity of 17 species of marine macrophytes to take up has been examined by comparing the rate of photosynthetic O₂-evolution with the photosyntheticrate which could be supported solely by CO₂ arising from theuncatalysed dehydration of . No external carbonic anhydrase was detected by potentiometricassay in any of the species used. At pH 8?0, the rates of photosyntheticO₂-evalution exceeded the CO₂ supply rate 6 to 24-fold in 15species of red algae, and 7 to 11-fold in 2 species of brownalgae. The ratio of photosynthetic O₂-evalution to the CO₂ supplyrate was even higher (19 to 101: 1) at pH 9?0. It is evidentfrom this data that the rate of CO₂ supply from the spontaneousbreakdown of cannot support the observed rates of photosynthesis in these algae. Thus, thedata provide substantive evidence that is taken up by these marine macrophytes as a sourceof substrate for photosynthesis. Key words: Macrophytic marine algae, bicarbonate transport     

Characterization of a Nitrogen-Regulated Protein Identified by Cell Surface Biotinylation of a Marine Phytoplankton

The biotinylating reagent succinimidyl 6-(biotinamido)hexanoate was used to label the cell surfaces of the cosmopolitan, marine, eukaryotic microorganism Emiliania huxleyi under different growth conditions. Proteins characteristic of different nutrient conditions could be identified. In particular, a nitrogen-regulated protein, nrp1, has an 82-kDa subunit that is present under nitrogen limitation and during growth on urea. It is absent under phosphate limitation or during exponential growth on nitrate or ammonia. nrp1 is the major membrane or wall protein in nitrogen-limited cells and is found in several strains of E. huxleyi. It may be a useful biomarker for examining the physiological state of E. huxleyi cells in their environment.     

Growth Rates of Marine Phytoplankton: Correlation with Light Absorption by Cell Chlorophyll a

To better predict plant production in the sea, it would be desirable to be able to calculate, from easily obtainable measurements at one sampling, the growth rate of the prevailing stock of phytoplankton. To this end growth rates, pigment composition, cell volume and cell surface area data were collected for several species of marine phytoplankton in logarithmic growth at 20–21°C and 0.07 cal/cm². min light intensity. Similar data for one species, Dunaliella tertiolecta, are given for several combinations of light intensity and temperature, and for another species, Ditylum brightwellii, grown in nitrogen deficiency. The problem of estimating growth rates of phytoplankton was divided into three parts: 1) variation of growth rate among diverse species and its relationship to light absorption by cell chlorophyll a: 2) variation in growth rate with light intensity; 3) variation in growth rate with temperature. An equation has been formulated for calculating growth rate which provides a more precise fit of the data than do equations for growth rate based upon cell surface/volume ratios or cell volume. The formulation is based upon light absorption by chlorophyll a. It allows for variations in the efficiency of utilization of light absorbed by chlorophyll a and the changes in chlorophyll a content resulting from light intensity and temperature differences. We do not attempt to predict variations in growth rate with photoperiod or spectral distribution, nor do we allow for light effects upon growth rate not mediated by photosynthesis, so the model is, at best, a rough approximation of reality.     

Organic Carbon Utilization by Resting Cells of Thiosulfate-Oxidizing Marine Heterotrophs

Two thiosulfate-oxidizing marine heterotrophs, strains 12W and 16B, were tested for utilization of [¹⁴C]glucose and [¹⁴C]acetate, respectively, in the presence or absence of thiosulfate. Thiosulfate oxidation caused an increase in organic carbon incorporation and a corresponding decrease in respiration at pH 6.5, near the optimum pH for thiosulfate oxidation and thiosulfate-stimulated growth in these bacteria. The amount of glucose or acetate metabolized remained virtually unaffected by thiosulfate oxidation. The metabolic shift in carbon utilization was diminished by increasing the initial pH to 8.0. The results indicate that marine heterotrophs 12W and 16B exhibit a type of mixotrophic metabolism which differs from that observed in the thiobacilli.     

Growth of Pure Cultures of Marine Phytoplankton in the Presence of Toxicants

The effects of 17 toxicants on the growth of five species of algae in pure culture were studied. The two species displaying the greatest sensitivity to the action of each of the compounds tested were Monochrysis lutheri and Phaeodactylum tricornutum, and the most resistant species was Protococcus. Of eight different classes of toxicants tested, substituted urea compounds and a mercuric compound were most effective in inhibiting growth of all algal species at the lowest concentrations.     

Taxonomic Variability in the Electron Requirement for Carbon Fixation Across Marine Phytoplankton

Fast Repetition Rate fluorometry (FRRf) has been increasingly used to measure marine primary productivity by oceanographers to understand how carbon (C) uptake patterns vary over space and time in the global ocean. As FRRf measures electron transport rates through photosystem II (ETR_PSII), a critical, but difficult to predict conversion factor termed the “electron requirement for carbon fixation” (Φ_e,C) is needed to scale ETR_PSII to C‐fixation rates. Recent studies have generally focused on understanding environmental regulation of Φ_e,C, while taxonomic control has been explored by only a handful of laboratory studies encompassing a limited diversity of phytoplankton species. We therefore assessed Φ_e,C for a wide range of marine phytoplankton (n = 17 strains) spanning multiple taxonomic and size classes. Data mined from previous studies were further considered to determine whether Φ_e,C variability could be explained by taxonomy versus other phenotypic traits influencing growth and physiological performance (e.g., cell size). We found that Φ_e,C exhibited considerable variability (~4–10 mol e^‐ · [mol C]^?1) and was negatively correlated with growth rate (R² = 0.7, P < 0.01). Diatoms exhibited a lower Φ_e,C compared to chlorophytes during steady‐state, nutrient‐replete growth. Inclusion of meta‐analysis data did not find significant relationships between Φ_e,C and class, or growth rate, although confounding factors inherent to methodological inconsistencies between studies likely contributed to this. Knowledge of empirical relationships between Φ_e,C and growth rate coupled with recent improvements in quantifying phytoplankton growth rates in situ, facilitate up‐scaling of FRRf campaigns to routinely derive Φ_e,C needed to assess ocean C‐cycling.     

Links between Phytoplankton and Bacterial Community Dynamics in a Coastal Marine Environment

Bacteria and phytoplankton dynamics are thought to be closely linked in coastal marine environments, with correlations frequently observed between bacterial and phytoplankton biomass. In contrast, little is known about how these communities interact with each other at the species composition level. The purpose of the current study was to analyze bacterial community dynamics in a productive, coastal ecosystem and to determine whether they were related to phytoplankton community dynamics. Near-surface seawater samples were collected in February, May, July, and September 2000 from several stations in the Bay of Fundy. Savin et al. (M.C. Savin et al., Microb Ecol 48: 51-65) analyzed the phytoplankton community in simultaneously collected samples. The attached and free-living bacterial communities were collected by successive filtration onto 5 m and 0.22 m pore-size filters, respectively. DNA was extracted from filters and bacterial 16S rRNA gene fragments were amplified and analyzed by denaturing gradient gel electrophoresis (DGGE). DGGE revealed that diversity and temporal variability were lower in the free-living than the attached bacterial community. Both attached and free-living communities were dominated by members of the Roseobacter and Cytophaga groups. Correspondence analysis (CA) ordination diagrams showed similar patterns for the phytoplankton and attached bacterial communities, indicating that shifts in the species composition of these communities were linked. Similarly, canonical CA revealed that the diversity, abundance, and percentage of diatoms in the phytoplankton community accounted for a significant amount of the variability in the attached bacterial community composition. In contrast, ordination analyses did not reveal an association between free-living bacteria and phytoplankton. These results suggest that there are specific interactions between phytoplankton and the bacteria attached to them, and that these interactions influence the composition of both communities.