bluuebunny/crossref_metadata_2025_split huggingface dataset:
GENETIC CHARACTERIZATION OF STRAINS OF CYANOBACTERIA USING PCR‐RFLP OF THE cpcBA INTERGENIC SPACER AND FLANKING REGIONS1
Authors: Bolch Christopher J. S. , Blackburn Susan I. , Neilan Brett A. , Grewe Peter M. 
Published: October 2004

ABSTRACTOligonucleotide primers, specific for conserved regions of the genes encoding the β‐ and α‐phycocyanin subunits of phycobilisomes (cpcB and cpcA) of cyanobacteria, were used to amplify a DNA fragment containing the intervening intergenic spacer region (cpcBA‐IGS) of 19 strains of three morphospecies of cyanobacteria. Six Australian strains were identified as Anabaena circinalis Rabenhorst, six strains were identified as Microcystis aeruginosa Kützing, and seven strains were identified as Nodularia spumigena Mertens. Restriction enzyme digestion of the amplification products from the strains revealed restriction fragment length polymorphism (RFLP) within all three morphospecies. Strains corresponding to M. aeruginosa were highly polymorphic: 11 of the 14 restriction enzymes used displayed RFLPs. The A. circinalis and N. spumigena strains were less variable: three of 14 enzymes and seven of 14 enzymes, respectively, showed RFLPs. The presence of genetic variation between strains within these three divergent morphospecies, which span two orders of cyanobacteria (Chroococcales Wettstein and Nostocales (Borzi) Geitler), show that the cpcBA‐ IGS fragment has broad application as a molecular marker for intrageneric studies of cyanobacteria systematics and genetics.
UTILITY OF THE MITOCHONDRIAL nad4L GENE FOR ALGAL AND PROTISTAN PHYLOGENETIC ANALYSIS1
Authors: Chesnick Joby M. , Tuxbury Kathyrn , Coleman Annette , Burger Gertraud , Lang B. Franz 
Published: October 2004

ABSTRACTMitochondrial gene sequences, in contrast to their plastid counterparts, have been rarely exploited for use in determining algal phylogenetic relationships. Their utilization would prove advantageous particularly for the assessment of evolutionary relationships among protistan lineages that include photo synthetic species and their colorless heterotrophic dependents that contain only a reduced plastid genome as well as ancestral nonphotosynthetic relatives. Recent studies that have examined mitochondrial protein (coxl, cox2, cob, and nad5) rather than ribosomal RNA genes confirm that these algal sequences are sufficiently conserved to be used routinely in algal systematics. In this investigation, we sequenced the mitochondrial nad4L gene, encoding a small (ca. 99‐amino acid) polypeptide subunit of the NADH dehydrogenase complex, from two chromophytic algae and an oomycete to determine its suitability for use in determining algal and protistan evolutionary relationships. Our analysis demonstrated that nad4L could clearly resolve these three organisms as a distinct clade, the stramenopiles, to the exclusion of terrestrial plants/chlorophytes and eufungi. However, the position of deeply rooted species within the stramenopiles proved tenuous and would best be examined in conjunction with the analysis of longer mitochondrial protein gene sequences.
TWO DISTINCT COLONIAL MORPHOTYPES OF AMPHORA COFFEAEFORMIS (BACILLARIOPHYCEAE) CULTURED ON SOLID MEDIA1
Authors: Garduño Rafael A. , Hall Beverley D. , Brown Leslie , Robinson Maurice G. 
Published: October 2004

ABSTRACTWhen cultured on different types of solid media, the marine‐fouling diatom Amphora coffeaeformis (Ag.) Kütz. consistently formed two distinct colonial morphotypes named tight and fuzzy. Tight colonies were comprised mainly of small, morphologically distorted, nonmotile cells, whereas morphologically normal and highly motile cells formed the fuzzy colonies. Cells from tight colonies were less adherent to glass, grew more slowly in liquid media, and had a slightly decreased viability on plates with copper than cells from fuzzy colonies. Whereas the protein profiles of the two types of cells were nearly identical in polyacrylamide gels stained with Coomassie blue, cells from tight colonies produced a significantly lower amount of a protease‐resistant, low Mr polysaccharide or glycoconjugate as detected in silver‐stained gels. The frequency of appearance of the fuzzy and tight morphotypes was not influenced by the mode of nutrition or the type of substratum to which the algal cells adhered. However, certain formulations of solid medium and the presence of growth‐inhibitory concentrations of copper in agar plates favored the formation of tight colonies. Due to their frequencies and patterns of appearance, it was clear that the two naturally formed morphotypes were not the consequence of spontaneous mutations, genetic rearrangement, or selection of stable natural variants, and we have hypothesized that they were linked to a normal physiological behavior. The tight colonial morphotype was used as a valuable marker to screen for true motility/adhesion mutants within an ultraviolet‐mutagenized population of A. coffeaeformis. Seven mutants were isolated that were non‐motile on agar plates, poorly adherent to glass, and distinguished from naturally formed cells from tight colonies by their inability to form fuzzy colonies upon subculture on solid media.
TEMPERATURE REQUIREMENTS FOR GROWTH AND SURVIVAL OF ANTARCTIC RHODOPHYTA1
Authors: Bischoff‐Bäsmann Bettina , Wiencke Christian 
Published: October 2004

ABSTRACTThe temperature requirement for growth and the upper survival temperatures (USTs) of 15 Antarctic red algal species collected on King George Island (South Shetland Islands) and Signy Island (South Orkney Islands) were determined. Two groups with different temperature requirements were identified. 1) A “eurythermal” group includes Rhodymenia subantarctica, Phyllophora ahnfeltioides, Gymnogongrus antarcticus, and Rhodochorton purpureum, growing between 0° and 10°C with optimum values at (0°) 5°(l0°)C. The USTs of these species and of Porphyra endiviifolium, Delesseria lancifolia, and Bangia atropurpurea were between 22° and 16°C. These species survived temperatures in a similar range as most endemic Arctic or Arctic/cold‐temperate species but exhibited a lower temperature demand for growth, suggesting an earlier contact with low temperatures than Arctic species. 2) A stenothermal group includes Pantoneura plocamioides, Myriogramme mangini, Ballia callitricha, Phyllophora antarctica, Gigartina skottsbergii, Georgiella confluens, and Plocamium cartilagineum growing at 0° or ≤5°C with optimum values at 0° or 5°C. The USTs of these species and of Phycodrys austrogeorgica were between 14° and 7°C. The species of this group must have had an even earlier contact with the Antarctic cold‐water environment than species of the “eurythermal” group. Gigartina skottsbergii, Georgiella confluens, Plocamium cartilagineum, and Pantoneura plocamioides were probably exposed longer to low temperatures than the other species of this group or Antarctic green and brown algae because they show the lowest temperature requirements so far determined in seaweeds. The results are discussed in the context of present local temperature regimes at the localities where the isolates were collected. Moreover, an attempt was made to explain the geographic distribution of individual species by the temperature requirements determined in this study. Only a few of the distribution limits are determined by temperature growth and/or survival characteristics. In many species (Rhodymenia subantarctica, Ballia callitricha, Gigartina skottsbergii, Bangia atropurpurea, Rhodochorton purpureum, and Plocamium cartilagineum), the development of temperature ecotypes is evident.
CELL‐ASSOCIATED PROTEOLYTIC ENZYMES FROM MARINE PHYTOPLANKTON1
Authors: Berges John A. , Falkowski Paul G. 
Published: October 2004

ABSTRACTDespite their central importance in cell metabolism, little is known about proteases in marine phytoplankton. We surveyed caseinolytic and leucine aminopeptidase (LAP) activities in log‐phase cultures of the chlorophyte Dunaliella tertiolecta Butcher, the diatom Thalassiosira weissflogii (Gru.) Fryxell et Hasle, the chrysophyte Isochrysis galbana Parke, the coccolithophorid Emiliania huxleyi (Lohm.) Hay et Mohler, and the cyanobacterium Synechococcus sp. (WH 5701). LAP activity was very low at pH < 6 and peaked between pH 7.5 and 8.5 in all species, whereas caseinolytic activity in most species showed only minor peaks in the pH 4–5 range and broad maxima above pH 8. Thus, acidic vacuolar proteases apparently represented only a small fraction of total protease activity. Attempts to classify proteases using selective inhibitors were inconclusive. Neither the serine/cysteine protease inhibitor leupeptin nor the aspartic protease inhibitor pepstatin. A inhibited caseinolytic or LAP activity in any species. The metalloprotease inhibitor EDTA was only effective against LAP activity in some species, causing average decreases of 30–50%, whereas the cysteine/serine protease inhibitor phenyl methyl sulfonylfluoride achieved at best a 30–60% decrease in caseinolytic activity. Caseinolytic activities were remarkably stable. At pH 7.5 and 25°C, extracts of D. tertiolecta, E. huxleyi, and Synechococcus showed no changes in activity after 24 h, whereas activity declined by less than 50% in the other species. Incubation of cell extracts for 1 h at 25°C in pH 7.5 buffer did not alter patterns of cell proteins, suggesting that endogenous proteases did not effectively degrade endogenous proteins. Casein zymograms were used to identify >200‐and <20‐kDa proteases in homogenates of log‐phase T. weissflogii; only the smaller protease was found in D. tertiolecta. Antibodies to the ATPase subunit (C) of the conserved, chloroplastic Clp protease from Pisum cross‐reacted with proteins in Synechococcus, D. tertiolecta, and I. galbana, but no cross‐reactions were found for any species with antibodies against the ClpP subunit from either E. coli or Nicotiana. Our results show that phytoplankton contain a diverse complement of proteases with novel characteristics.
CHANGES IN PHOTOSYNTHETIC YIELD, AMINO ACIDS, AND ORGANIC ACIDS ARE INDUCED BY AMMONIUM ADDITION TO CELLS OF PHORMIDIUM LAMINOSUM (CYANOPHYCEAE)1
Authors: Ochoa de Alda Jesús A. G. , Tapia María I. , Llama María J. , Serra Juan L. 
Published: October 2004

ABSTRACTThe effect of NH4+ addition to NO3−‐growing cells of the non‐N2‐fixing cyanobacterium Phormidium laminosum (Agardh) Gomont (strain OH‐1‐pCl1) on photo‐synthetic and respiratory electron transport as well as on the intracellular levels of amino acids and some organic acids was studied. Addition of ammonium to nitrate‐growing cells resulted in substantial increases in the pool size of most amino acids and a transient decrease in the pool size of organic acids. The high demand for organic acids was partially overcome by degradation of stored carbohydrates, more than by newly fixed carbon, as indicated by the large stimulation of the respiration rate upon ammonium addition. Following ammonium addition, the photosynthetic yield of the in vivo noncyclic electron transport decreased, and the sensitivity of photosystem II to photodamage increased. Results indicate that cells balance their photosynthetic and respiratory activities depending on nitrogen availability and point to an important involvement of respiration in providing energy for ammonium assimilation until adaptation of bioenergetic processes to the new nitrogen source is complete.
PHOTOSYNTHETIC RESPONSE OF THE GIANT KELP MACROCYSTIS PYRIFERA (PHAEOPHYCEAE) TO ULTRAVIOLET RADIATION1
Authors: Clendennen Stephanie K. , Zimmerman Richard C. , Powers Dennis A. , Alberte Randall S. 
Published: October 2004

ABSTRACTSolar ultraviolet radiation (UVA + UVB) impairs photosynthesis in marine algae. Canopy blades of the giant kelp Macrocystis pyrifera (L.) C. Agardh are exposed to high levels of solar UV in the field. To determine the effects of UV radiation on photosynthesis in the giant kelp and to identify sites of UV damage, O2 evolution, reaction center organization, light harvesting, and energy transfer efficiency were measured in canopy blades that had been exposed to elevated levels of UV in the laboratory. UV treatment reduced both the light‐saturated rate and the light‐limited rate of photosynthesis by 50% but produced no significant change in the rate of dark respiration. A significant impairment of photosystem II (PSII) reaction center function was observed, suggesting that PSII is a major site of damage in chromophytes. Reduced quantum efficiency of photosynthesis and loss of energy transfer from light‐harvesting pigments (fucoxanthin, chlorophyll a, and chlorophyll c) to PSII indicate that the major light‐harvesting complex of M. pyrifera, the fucoxanthin‐chlorophyll protein complex (FCPC), was another site of UV damage. These measures provide the first evidence of a direct effect of UV radiation on specific sites in the photosynthetic apparatus of chromophytes and indicate that in situ fluorescence excitation analysis may be a simple means to detect UV stress in algae.
EFFECT OF IRRADIANCE ON GROWTH AND REPRODUCTIVE PROCESSES DURING THE CELL CYCLE IN SCENEDESMUS ARMATUS (CHLOROPHYTA)1
Authors: Tukaj Zbigniew , Kubínová Anna , Zachleder Vilém 
Published: October 2004

ABSTRACTSynchronized populations of the chlorococcal alga Scenedesmus armatus (Chod.) Chod. were grown under five irradiance levels. During the cell cycles of these populations, reproductive processes such as DNA replication, nuclear division, protoplast fission, and daughter cell release and growth processes such as RNA and protein accumulation were followed. The amount of RNA and proteins increased stepwise with a short time interval between individual steps during which the rate of RNA and protein accumulation decreased. At each of the steps, the amount of RNA and protein approximately doubled and the number of steps increased with irradiance. At the end of each of the growth steps, a commitment to trigger the sequence of reproductive events (DNA replication, nuclear division, protoplast fission) was attained. After attaining the commitment point, the cells were able to trigger and terminate the whole reproductive sequence without any further growth, that is, even in the dark when the external supply of energy was cut off. With increasing irradiance, the number of commitment points attained during one cell cycle increased from one to four. Consequently, one to four sequences of the reproductive steps were triggered, and each of them ended by doubling the reproductive structures, which resulted in the formation of 2, 4, 8, or 16 daughter cells. The length of the precommitment periods shortened with increasing irradiance as the result of an increasing rate in growth. The length of postcommitment periods showed light independence and remained constant at the range of irradiances at which the number of growth steps and, consequently, the number of sequences of reproductive events did not change. At higher irradiances, the number of sequences of reproductive events increased, which caused a prolongation of postcommitment periods. The length of the cell cycle varied as a result of this distinct effect of irradiance on pre‐ and postcommitment periods.
CYANOBACTERIAL EVOLUTION AND PROCHLOROPHYTE DIVERSITY AS SEEN IN DNA‐DEPENDENT RNA POLYMERASE GENE SEQUENCES1
Authors: Palenik Brian , Swift Hewson 
Published: October 2004

ABSTRACTNucleotide sequence data from DNA‐dependent RNA polymerase (rpoC) genes were used to examine the phylogenetic relationships among the phycobiliprotein‐ and three known chlorophyll b‐containing (prochlorophyte) cyanobacteria. The phylogenetic trees obtained confirm the polyphyletic nature of the prochlorophytes. Data from Prochloron cells obtained from six different tunicate host species suggest that at least two closely related groups of Prochloron exist in the same area in Palau, West Caroline Islands. Overall, however, the genetic diversity within the analyzed samples was much smaller than within the nonsymbiotic Prochlorococcus.
ECOPHYSIOLOGY OF TROPICAL RHODOPHYTES. I. MICROSCALE ACCLIMATION IN PIGMENTATION1,2
Authors: Beach Kevin S. , Smith Celia M. 
Published: October 2004

ABSTRACTMicroscale pigment adjustments to a tropical photosynthetically active radiation and ultraviolet (UV) environment by the intertidal turf algae Ahnfeltiopsis concinna (J. Ag.) Silva et DeCew and Laurencia mcdermidiae (J. Ag) Abbott were promoted by thalli densities that self‐shade the under story portions of the same diminutive axes. Tissues of A. concinna from canopy microsites had significantly reduced levels of phycoerythrin, phycocyanin, and allophycocyanin compared to tissues from understory microsites of the same axes. Tissues of L. mcdermidiae from canopy microsites had reduced levels of only phycoerythrin compared to tissues from understory microsites. These alterations coupled with enhanced levels of carotenoid and UV‐absorbing compounds in tissues from canopy compared to tissues from understory microsites indicated a pattern of remarkably sensitive photoacclimation over the ≤10‐cm axes of these turf‐forming rhodophytes.Microscale variation in the in vivo UV absorbance capabilities for turfs of A. concinna and L. mcdermidiae was directly related to the amount of extractable UV‐absorbing compounds. An in vivo absorbance signature at ∼345 nm appears to provide a method to quickly and accurately gauge the potential UV‐shielding capacity of primary producers even at remarkably fine ecological scales. The capacity for highly responsive biochemical adjustments that result in marked canopy–understory distinctions coupled with a turf morphology may be crucial for macroalgal tolerance of physiological stresses associated with tropical intertidal zones. This responsive capacity allows for enhanced photoprotective mechanisms in tissues from canopy microsites while optimizing irradiance capture in deeply shaded tissues from understory microsites < 10 cm away.
ECOPHYSIOLOGY OF TROPICAL RHODOPHYTES. II. MICROSCALE ACCLIMATION IN PHOTOSYNTHESIS1
Authors: Beach Kevin S. , Smith Celia M. 
Published: October 2004

ABSTRACTParameters of photosynthesis vs. irradiance curves varied markedly between tissues from microsites along the < 10‐cm axes of the tropical intertidal red algae Ahnfeltiopsis concinna (J. Ag.) Silva et DeCew and Laurencia mcdermidiae (J. Ag.) Abbott. Differences in photosynthetic performance between tissues from canopy and understory microsites indicates that L. mcdermidiae exhibited an expected sun‐to‐shade acclimation but over the space of < 10 cm. Respiration, Ic, Ik, and Pmax values were significantly lower in tissues from the understory relative to tissues from the canopy of L. mcdermidiae, while photosystem I (PS I) sizes (PSU I) were significantly higher in tissues from understory microsites. Quantum efficiency was unchanged. Ahnfeltiopsis concinna, in contrast, exhibited higher α in tissues from understory rather than canopy microsites. The values of Pmax for tissues from the canopy of A. concinna were not higher than the understory, while PSU O2(PS II size) of tissues from canopy microsites were unusually higher than those of understory microsites. These characteristics suggest a high degree of irradiance stress in tissues from the canopy of A. concinna, the highest tidal alga in Hawaiian coastal zones. Acclimation to high photosynthetically active radiation and ultraviolet irradiance levels especially in tropical regions appears to be an essential mechanism(s) for stress resistance and persistence of intertidal algae. Algal turfs acclimate at microscales in part fostered by their dense stands that create sharp irradiance gradients as well as adjust physiologically to canopy irradiance levels as mechanisms for optimal photosynthetic performance and stress tolerance.
PURIFICATION AND CHARACTERIZATION OF GLYCOLATE OXIDASE FROM THE BROWN ALGA SPATOGLOSSUM PACIFICISM (PHAEOPHYTA)1
Authors: Iwamoto Koji , Suzuki Kensaku , Ikawa Tomoyoshi 
Published: October 2004

ABSTRACTGlycolate oxidase was purified to apparent homogeneity from the brown alga Spatoglossum pacificum Yendo. The 1326‐fold purified glycolate oxidase enzyme exhibited a specific activity of 22. 4 micromoles glyoxylate formed ·min−1·mg protein−1. The molecular weight of the native enzyme was estimated to be 230,000 by gel filtration. The subunit molecular weight of the enzyme was determined to be 49,000 by sodium dodecyl sulfate–polyacrylamide gel electrophoresis, suggesting that the native enzyme is a tetramer. There were two absorption peaks at 345 and 445 nm, indicating that glycolate oxidase is a flavoprotein. This enzyme had a high isoelectric point (pI 9.6) and a high pH optimum (pH 8.3). The Km values for glycolate and l‐lactate were 0.49 and 5.5 mM, respectively. This enzyme also had a broad specificity for other straight‐chain α‐hydroxy acids but not for β‐hydroxyacids. Cyanide, azide, N‐ethylmaleimide, and p‐chloromercuribenzoic acid did not affect the enzyme, whereas 2‐pyridylhydroxymethanesulfonic acid strongly inhibited it. These properties of glycolate oxidase from the brown alga S. pacificum are similar to the properties of the glycolate oxidasesfrom higher plants. Polyclonal antibodies raised against the polypeptide fragment of Spatoglossum glycolate oxidase could recognize glycolate oxidase from Spinacia oleracea L., although the cross‐reactivity was weak. The N‐terminal sequence of two internal polypeptide fragments of the enzyme from S. pacificum showed a high degree of similarity to that of glycolate oxidase from higher plants. These results suggest that glycolate oxidase from higher plants and brown algae share the same ancestral protein.
INORGANIC CARBON TRANSPORT IN RELATION TO CULTURE AGE AND INORGANIC CARBON CONCENTRATION IN A HIGH‐CALCIFYING STRAIN OF EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE)1
Authors: Nimer Nabil A. , Merrett Michael J. , Brownlee Colin 
Published: October 2004

ABSTRACTThe relationships among inorganic carbon transport, bicarbonate availability, intracellular pH, and culture age were investigated in high‐calcifying cultures of Emiliania huxleyi (Lohmann) Hay & Mohler. Measurement of inorganic carbon transport by the silicone‐oil centrifugation technique demonstrated that gadolinium, a potential Ca2+ channel inhibitor, blocked intracellular inorganic carbon uptake and photosynthetic 14CO2+ fixation in exponential‐phase cells. In stationary‐phase cells, the intracellular inorganic carbon concentration was unaffected by gadolinium. Gadolinium was also used to investigate the link between bicarbonate and Ca2+ transport in high‐calcifying cells of E. huxleyi. Bicarbonate availability had significant and rapid effects on pHi in exponential‐ but not in stationary‐phase cells. 4′, 4′‐Diisothiocyanostilbene‐2,2′‐disulfonic acid did not block bicarbonate uptake from the external medium by exponential‐phase cells. Inorganic carbon utilization by exponential‐ and stationary‐phase cells of Emiliania huxleyi was investigated using a pH drift technique in a closed system. Light‐dependent alkalization of the medium by stationary‐phase cells resulted in a final pH of 10.1 and was inhibited by dextran‐bound sulphonamide, an inhibitor of external carbonic anhydrase. Exponential‐phase cells did not generate a pH drift. Overall, the results suggest that for high‐calcifying cultures of E. huxleyi the predominant pathway of inorganic carbon utilization differs in exponential and stationary phase cells of the same culture.