bluuebunny/crossref_metadata_2025_split huggingface dataset:
ANTIOXIDATIVE PROTECTION OF PERIDINIUM GATUNENSE IN LAKE KINNERET: SEASONAL AND DAILY VARIATION1
Authors: Butow Barbara J. , Wynne David , Tel‐Or Elisha 
Published: October 2004

ABSTRACTA comprehensive antioxidative mechanism was found in the freshwater dinoflagellate Peridinium gatunense Lemm. during the spring bloom in Lake Kinneret. Ascorbate was present throughout the bloom period and was responsible, together with catalase, for the elimination of photosynthetically produced H2O2. As glutathione concentrations and ascorbate regenerative enzymes were negligible during mid‐spring, ascorbate was presumably biosynthesized during the photosynthetically active period. Antioxidative activity increased overall at the end of the spring in conjunction with elevated ambient stress conditions, for example high light. Under such circumstances, ascorbate was regenerated. Ascorbate levels doubled when cells were exposed to an increase in irradiance from 60 to 600 μmol photons·m−2·s−1, and on addition of H2O2, concentrations increased a further 20‐fold. Significant antioxidative activity was also noted in the dark, although this was dependent on the presence of H2O2. Diurnal changes in antioxidants and their regenerative enzymes were observed. The activities of mono‐dehydroascorbate reductase, glutathione reductase, and ascorbate concentrations showed ultraradian periodicity and were completely in phase throughout the day/night period. Dehydroascorbate reductase activity and glutathione concentrations were also in phase but showed aperiodic variation, as did ascorbate peroxidase activity. Superoxide dismutase and catalase activities were generally out of phase during the 24‐h period but did show ultraradian periodicity. Lake samples entrained under constant light revealed an inate 12‐h rhythm for catalase activity, during at least 36 h.
SUPEROXIDE DISMUTASE ACTIVITY IN PERIDINIUM GATUNENSE IN LAKE KINNERET: EFFECT OF LIGHT REGIME AND CARBON DIOXIDE CONCENTRATION1
Authors: Butow Barbara J. , Wynne David , Tel‐Or Elisha 
Published: October 2004

ABSTRACTThe activity of superoxide dismutase (EC 1.15.1.1, superoxide: superoxide oxidoreductase) (SOD) was determined in Peridinium gatunense Lemm. under natural and controlled conditions. SOD activity increased toward the end of the spring algal bloom in Lake Kinneret simultaneously with maximal photosynthetic activity and conditions of elevated ambient stress such as high irradiance. Activity staining of native polyacrylamide gel electrophoresis gels of bloom samples showed a similar pattern to the spectrophotometrically measured SOD. Both Mn SOD and CuZn SOD were present, however no Fe SOD was found in Peridinium. One of three isoenzymes of Mn SOD showed marked differential regulation of activity under stress. An increase in the quantity of the 32‐kDa Mn SOD polypeptide during the bloom was found to be unrelated to senescence; it was assumed that this polypeptide was induced by stress. Thus, SOD in Peridinium undergoes physiological and molecular acclimation to seasonal environmental changes. When Peridinium was exposed to various O2 and CO2 concentrations in culture, CuZn SOD significantly increased under high C02 concentrations and normoxic conditions (20% O2). However, at high irradiances, Peridinium cultures exposed to low and high CO2 concentrations also had similar CuZn SOD activity. It was concluded that stressful irradiance is the overriding cause of increased SOD activity in both lake samples and in cultures of Peridinium.
INTERACTION OF NITROGEN FIXATION AND PHOSPHORUS LIMITATION IN APHANIZOMENON FLOS‐AQUAE (CYANOPHYCEAE)1
Authors: De Nobel W. T. (Pim) , Snoep Jacky L. , Westerhoff Hans V. , Mur Luuc R. 
Published: October 2004

ABSTRACTThe effect of simultaneous nitrogen fixation and phosphorus limitation on the physiological adaptation and growth performance of Aphanizomenon flos‐aquae (L.) Ralfs PCC 7905 was studied in continuous culture. In the absence of ammonia, N2 fixation occurred and the maximum growth rate (as determined in diluted batch cultures) was lower. However, no distinction could be made between the steady‐state N uptake rates (based on cellular N contents) of N2‐fixing cells and cells grown with ammonia. At the higher dilution rates, the residual P concentration increased with increasing dilution rate, more so under N2‐fixing conditions, compared to the cultures grown in the presence of ammonia. More generally, the yield of biomass per consumed P, as the biomass concentration itself, decreased with increasing dilution rate, and both were lower under N2‐fixing conditions. The restricted biomass production under N2‐fixing conditions suggests that reduction of N loading may benefit lake restoration projects. The influence of N2‐fixation on the severity of P limitation is discussed in terms of metabolic control analysis. From the increase of the residual P concentration on switching from ammonium to N2‐fixing conditions, it is deduced that under N2‐fixing and P‐limited conditions, control of growth is shared by N and P metabolism.
ACCLIMATION OF SYNECHOCOCCUS STRAIN WH7803 TO AMBIENT CO2 CONCENTRATION AND TO ELEVATED LIGHT INTENSITY1
Authors: Hassidim Miriam , Keren Nir , Ohad Itzhak , Reinhold Leonora , Kaplan Aaron 
Published: October 2004

ABSTRACTA CO2 concentrating mechanism has been identified in the phycoerythrin‐possessing Synechococcus sp. WH7803 and has been observed to be severely inhibited by short exposure to elevated light intensities. A light treatment of 300–2000 μmol quanta·m−2·s−1 resulted in a considerable decay in the variable fluorescence of PSII with time, suggesting decreased efficiency of energy transfer from the phycobilisomes, direct damage to the reaction center II, or both. Measurements of the activity of PSII and changes in fluorescence emission spectra during a light treatment of 1000 μmol quanta·m−2·s−1 indicated considerable reduction in the energy flow from the phycocyanin to the phycobilisome terminal acceptor and chlorophyll a. Consequently, whereas the maximal photosynthetic rate, at saturating light and Co2 concentration, was hardly affected by a light treatment of 1000 μmol quanta·m−2·s−1 for 2 h, the light intensity required to reach that maximum increased with the duration of the light treatment.
GROWTH, DARK RESPIRATION AND PHOTOSYNTHETIC PARAMETERS OF THE COCCOLITHOPHORID EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE) ACCLIMATED TO DIFFERENT DAY LENGTH‐IRRADIANCE COMBINATIONS1
Authors: Nielsen Marianne V. 
Published: October 2004

ABSTRACTGrowth, dark respiration rate, photosynthetic parameters, and chemical composition were determined for Emiliania huxleyi (Lohmann) Hay et Mohler acclimated to different combinations of day length (12, 18, 24 h) and irradiance (30, 100, 200, 800 μmol·m−2·s−1). Specific growth rate (μ, day−1) and carbon‐specific dark respiration rate (rCd, day−1) were independent of day length, but increased significantly with increasing irradiance. The photosynthetic parameters depended on the initial acclimation day length and irradiance: Chlorophyll a‐specific maximum photosynthetic rate (PmB) increased up to threefold with decreasing day length and twofold with increasing irradiance. The maximum light utilization coefficient (αB) and maximum quantum yield (φm) increased up to threefold with decreasing day length. αB increased almost four‐fold with decreasing irradiance, whereas φm was independent of irradiance. Literature data for phytoplankton indicate that PmB consistently increases with increasing irradiance, and day length‐irradiance responses of αB and φm are species specific. Results from the present experiment and other studies indicate that if day length‐irradiance variability in the photosynthetic parameters are neglected, this may cause an over‐ or underestimation up to a factor of two in the photosynthetic rate estimation based on these parameters.
IMMUNOLOCALIZATION OF CENTRIN DURING FERTILIZATION AND THE FIRST CELL CYCLE IN FUCUS DISTICHUS AND PELVETIA COMPRESSA (FUCALES, PHAEOPHYCEAE)1
Authors: Bisgrove Sherryl R. , Nagasato Chikako , Motomura Taizo , Kropf Darryl L. 
Published: October 2004

ABSTRACTAntibodies that recognize the centrosome‐associated protein centrin were used to characterize centrosomal origin and positioning during fertilization and the first cell cycle in Fucus distichus subsp. evanescens (C. Agardh) Powell and Pelvetia compressa (J. Agardh) De Toni. Centrin was identified in sperm, eggs, and zygotes on protein blots, indicating the protein is present in both gametes. Using immunofluorescence microscopy, centrin was found in discrete foci in sperm. In contrast, eggs lack centrosomes and centrin was not detectable by immunofluorescence, indicating that centrin was probably dispersed in the cytoplasm. Two foci of centrin were present on the nuclear envelope of zygotes, but microtubules remained dispersed over the zygotic nucleus. Centrin foci separated over the nuclear envelope as the first cell cycle progressed. Microtubules became concentrated at the centrin foci to form centrosomes that gave rise to the spindle poles at mitosis.
PASSAGE OF A MARINE BROWN ALGAL DNA VIRUS FROM ECTOCARPUS FASCICULATUS (ECTOCARPALES, PHAEOPHYCEAE) TO MYRIOTRICHIA CLAVAEFORMIS (DICTYOSIPHONALES, PHAEOPHYCEAE): INFECTION SYMPTOMS AND RECOVERY1
Authors: Maier Ingo , Rometsch Elke , Wolf Susanne , Kapp Markus , Müller Dieter G. , Kawai Hiroshi 
Published: October 2004

ABSTRACTA dsDNA virus (EfasV‐1) isolated from Ectocarpus fasciculatus Harvey infected Myriotrichia clavaeformis Harvey, a species belonging to a different brown algal order. The virus did not complete its infection cycle in the foreign host but caused infertility due to malformed reproductive structures. After some time in culture, the host's reproductive capacity was sometimes restored with concomitant loss of at least part of the viral genome. This incidence of interordinal virus transfer is discussed in relation to possibilities for virus‐mediated horizontal gene transfer in brown algae.
CARBONIC ANHYDRASE IN THE MARINE DIATOM THALASSIOSIRA WEISSFLOGII (BACILLARIOPHYCEAE)1
Authors: Roberts Samantha B. , Lane Todd W. , Morel François M. M. 
Published: October 2004

ABSTRACTThe zinc metalloenzyme carbonic anhydrase plays a critical role in inorganic carbon acquisition in marine diatoms, thus conferring on zinc a key role in oceanic carbon cycling. As a first step in determining the location and function of carbonic anhydrase (CA) in Bacillariophyceae, we purified and partially sequenced CA from T. weissflogii (Gru) Fryxell et Hasle (TWCA1) and cloned the corresponding cDNA (twca1). The twca1 sequence is different from other known algal carbonic anhydrase genes, and encodes a protein of roughly 34 kDa. The amino terminal amino acids sequenced from purified TWCA1 are 72 residues downstream of the putative starting methionine predicted by twca1. This difference may be due to the presence of a short‐lived signal sequence designed to guide the enzyme to the correct cellular location. The absence of any homology between TWCA1 and previously sequenced CAs from Chlorophyceae may indicate either convergent evolution or that carbon acquisition represents a fundamental physiological difference among algal phyla.
PHYLOGENETIC ANALYSIS OF MORPHOLOGICAL SPECIES OF CARTERIA (VOLVOCALES, CHLOROPHYTA) BASED ON rbcL GENE SEQUENCES1
Authors: Nozaki Hisayoshi , Ito Motomi , Watanabe Makoto M. , Takano Hiroyoshi , Kuroiwa Tsuneyoshi 
Published: October 2004

ABSTRACTFour related species in the unicellular volvocalean genus Carteria [C. crucifera Pascher, C. eugametos Mitra, C. inversa (Korshikov) Bourrelly and C. cerasiformis Nozaki et al.] were delineated on the basis of recent comparative light and electron microscopy of a large number of culture strains. However, the species thus delineated may not represent natural or monophyletic entities. In the present study, 1128 base pairs of the chloroplast protein‐coding gene (large subunit of ribulose‐1,5‐bisphosphate carboxylase/oxygenase gene) from 12 Carteria strains representing the four species as well as from related volvocalean species were analyzed to elucidate the phylogenetic status of the taxonomic or morphologic species of Carteria. The sequence data showed that the 12 Carteria strains exhibit four robust monophyletic groups which are strictly consistent with the four taxonomic species. These results are discussed in relation to contrasting results found in other microalgal genera. It is concluded that phylogenetic analysis, based on DMA sequence data and comparative morphologic characterization of species and using a large number of culture strains, is essential to a natural system of microalgal species taxonomy.
SINGLE LOCUS MICROSATELLITES IN GRACILARIALES (RHODOPHYTA): HIGH LEVEL OF GENETIC VARIABILITY WITHIN GRACILARIA GRACILIS AND CONSERVATION IN RELATED SPECIES1
Authors: Wattier Rémi , Dallas John F. , Destombe Christophe , Saumitou‐Laprade Pierre , Valero Myriam 
Published: October 2004

ABSTRACTFour single locus microsatellites identified in the red alga Gracilaria gracilis (Stackhouse) Steentoft, Irvine, et Farnham (Rhodophyta) were examined for allelic diversity at different spatial and taxonomic levels. First, because simple morphological diagnostic characters are often missing within the Gracilariaceae, we developed a simple and rapid method based on rDNA ITS size variation in order to verify the taxonomic status of the samples used in this study. All European (including Mediterranean samples), Argentinian, and Namibian samples used in our study were confirmed to be a homogenous G. gracilis group. By contrast, our results on rDNA ITS sizes showed that Gracilaria from Japan, initially identified as G. gracilis, was different from the rest of the G. gracilis group. Secondly, microsatellite polymorphism and conservation at the species level was tested on the worldwide collection of G. gracilis and within a single population. The loci Gv1AAG and Gv1AAC showed no allelic variation, whereas two others, Gv1CT and Gv2CT, were highly polymorphic. All microsatellite loci were conserved within G. gracilis, except in the sample from Japan. The taxonomic status of G. gracilis from Japan is thus questionable. This study revealed a high level of within‐population polymorphism (52 alleles for Gv1CT and 12 for Gv2CT). Moreover, the combination of these two loci was shown to be very powerful for identifying individuals within a population, that is, 93% of the individuals were characterized by a unique genotype. Finally, conservation of the four loci was tested in taxonomically related species of Gracilaria (G. chilensis, G. pacifica, and G. tikvahiae) and two Gracilariopsis species (Gs. sp. and Gs. longissima). The results suggest that the polymorphic locus Gv2CT may provide a valuable genetic marker within the different species of the Gracilariaceae.
PORGUENIA PERUVIANA GEN. ET SP. NOV., A MARINE CENTRIC DIATOM WITH AN UNUSUAL OCELLUS1
Authors: Sullivan Michael J. 
Published: October 2004

ABSTRACTA new diatom genus and species, Porguenia peruviana Sullivan, is described from an Eocene marine deposit from the Paracas Peninsula, Peru. The valve outline is circular and the areolation is best described as pseudoloculate; spines of any type are lacking. A ring of elongated, densely packed rimoportulae is situated on the secondary marginal ridge. Externally, each rimoportula consists of a long, flattened, fluted upper portion supported by a shorter cylindrical stalk. The processes are winged and exhibit various degrees of curvature of the major axis. Typically, six reniform ocelli of unusual structure are situated centrifugally to the ring of rimoportulae and interrupt the true marginal ridge. Because the perforation plate differs from that of all other ocellus‐bearing diatoms, a new term has been introduced for this structure, the diaphoron. The placement and structure of this newly discovered “perforation plate” do not allow Porguenia to be placed in any circumscribed family, although the Triceratiaceae would appear at present to be the most closely related family.
GENETIC DIVERSITY WITHIN BALTIC SEA POPULATIONS OF NODULARIA (CYANOBACTERIA)1
Authors: Hayes Paul K. , Barker Gary L. A. 
Published: October 2004

ABSTRACTThe determination of the genetic structure of microbial populations has, until recently, required the establishment of many independent clonal cultures for genotypic analysis. In such studies it has been necessary to assume that isolates able to grow in laboratory culture are representative of the full range of diversity within the natural population. In order to test this assumption we used the polymerase chain reaction (PCR) to amplify the intergenic spacer region of the Phycocyanin operon (PC‐IGS) from filaments of Nodularia taken both from clonal cultures and from natural populations in the Baltic Sea. Analysis of the nucleotide sequences revealed more variation among 16 cultured isolates than within 23 single filaments sampled from a natural population. As a means of rapidly determining population genetic structure we designed and used mixtures of allele‐specific amplification primers in diagnostic PCRs to identify which PC‐IGS allele was present in single filaments from natural cyanobacterial assemblages. Using this method, we determined the PC‐IGS genotype of 156 filaments from 9 sampling stations throughout the central basin of the Baltic Sea in July 1996. Our results show that two distinct genotypes of Nodularia are present in the population at all stations. Although the two types were present in approximately equal numbers, they were not distributed uniformly.
PRIMARY ADHESION OF ENTEROMORPHA (CHLOROPHYTA, ULVALES) PROPAGULES: QUANTITATIVE SETTLEMENT STUDIES AND VIDEO MICROSCOPY1
Authors: Callow Maureen E. , Callow James A. , Pickett‐Heaps Jeremy D. , Wetherbee Richard 
Published: October 2004

ABSTRACTQuantitative methods and associated kinetic analyses have been used for the first time to study detailed aspects of the settlement and adhesion of various types of Enteromorpha popagule. Time course experiments showed that quadri and biflagellate zoospores and zygotes adhered rapidly, but a proportion within any one population appeared to be incompetent at adhering to the substratum. Kinetic (Scatchard) analysis of adhesion experiments performed at a range of zoospore concentrations revealed density‐dependent effects not previously reported, with positive cooperativity at low spore densities and negative cooperativity at high spore densities. High‐resolution video microscopy was used for the first time to reveal details of the various stages in the settlement and adhesion of zoospores and zygotes. Novel observations were made of an initial, temporary phase of attachment via the apical papilla, followed by a permanent phase of commitment, characterized by discharge of adhesive‐containing cytoplasmic vesicles, as the cell contracted against the surface, and adsorption of flagella. The phase of commitment was followed by exploitation of the surface through amoeboid‐like movements at the interface. Gregarious settlement behavior was frequently observed leading to the formation of rafts of cells. The possible mechanisms and significance of density‐dependent spore adhesion are discussed.
EFFECTS OF ULTRAVIOLET RADIATION ON PHOTOSYNTHESIS IN THE SUBTROPICAL MARINE DIATOM, CHAETOCEROS GRACILIS (BACILLARIOPHYCEAE)1
Authors: Hazard Christina , Lesser Michael P. , Kinzie Robert A. 
Published: October 2004

ARSTRACTAcclimation to ambient ultraviolet radiation (UVR) was examined in a subtropical marine diatom, Chaetoceros gracilis Schutt. Short‐term exposure to UVR (<24 h) reduced the efficiency of photosynthetic energy conversion, carbon fixation, activity of 1,5‐bisphosphate carboxylase‐loxygenase (RUBISCO), and the rapid turnover of the putative Dl reaction center (32 kda) protein, whereas longer‐term exposure to ambient UVR (24–48 h) revealed a steady‐state acclimation, defined as recovery of carbon fixation and RUBISCO activity to rates equivalent to treatments without exposure to UVR. The turnover of D1 and chlorophyll a (Chl a) remained high during exposure to UVR. Efficiency of energy conversion by photosystem II, measured with double flash (pump and probe) fluorometry, increased by 24% in cells acclimated to UVR. Acclimation to UVR had no detectable effect on the functional absorption cross‐section or cellular concentrations of Chl a, Chl c, or total carotenoids. However, the maximum rate of carbon fixation was reduced by UVR on a Chl a basis but remained unaffected on a per‐cell basis. Response to UVR exposure in this subtropical diatom has two components: a short‐term inhibitory response and a longer‐term acclimation process that ameliorates the inhibition of carbon fixation.
THE EFFECT OF GROWTH TEMPERATURE AND CULTURE DENSITY ON THE MOLECULAR SPECIES COMPOSITION OF THE GALACTOLIPIDS IN THE RED MICROALGA PORPHYHDIUM CRUENTUM (RHODOPHYTA)1
Authors: Adlerstein Daniel , Bigogno Chiara , Khozin Inna , Cohen Zvi 
Published: October 2004

ABSTRACTThe effects of biomass concentration and growth temperature on the molecular species composition of the major galactolipids of the red microalga Porphyridium cruentum Nag. were detmined. At lower biomass concentrations, the Δ17 desaturation of arachidonic acid to eicosapentaenoic acid (20:5) was enhanced in both prokaryotic‐type and eukalyotic‐type molecular species of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol. We suggest that chloroplastic Δ17 desaturation is correlated with the availability of light. A reduction in the growth temperature led to an increase in the proportion of the eukalyotic molecular species of MGDG, especially for 20:5/ 20:5 MGDG, These results suggest that this molecular species, and perhaps eukaryotic molecular species in general, may play a role in the adaptation of cells to low growth temperatures.
AUTOLYSIS KINETICS OF THE MARINE DIATOM DITYLUM BRIGHTWELLII (BACILLARIOPHYCEAE) UNDER NITROGEN AND PHOSPHORUS LIMITATION AND STARVATION1
Authors: Brussaard Corina P. D. , Noordeloos Anna A. M. , Riegman Roel 
Published: October 2004

ABSTRACTAutolysis kinetics in axenic cultures of the diatom Ditylum brightwellii (West) Grunow were studied under nutrient limitation in continuous cultures and under nutrient starvation in batch‐mode cultures obtained by switching off nutrient supply in the continuous cultures. Under N limitation, the specific algal autolysis rates (δ, day−1) were found constant at 0.014 ± 0.002 day−1over a broad range of specific dilution rates (D, day−1) (0.09–0.56 day−1), implying an intrinsic death factor independent of the physiologzc state of the algal cells. Under P limitation, 8 was inversely related to D and ranged between 0.067 and 0.005 day−1 at D = 0.17–0.44 day−1. Under conditions of nutrient stamation, the degree of algal nutrient deficiency prior to stamation affected autolysis rates (δb, day−1) and subsequently survival of the algal cultures. Nitrogen‐starved D. brightwellii showed highest δb (maximum, 0.10 day−1) when precultured at the higher growth rates. Phosphorus stamation led to highest δb (maximum, 0.21 day−1) in the cultures preconditioned at the lower steady state growth rates. The lower death rates for D. brightwellii under limitation and starvation of N compared to P suggest that D. brightwellii was better equipped to handle N than P deficiency. The present results showed that cell lysis induced by nutrient stress was a significant cause of mortality in D. brightwellii and provided more insight into the field distribution of this neritic diatom.