bluuebunny/crossref_metadata_2025_split huggingface dataset:
MACROALGAL RESPONSES TO NITROGEN SOURCE AND AVAILABILITY: AMINO ACID METABOLIC PROFILING AS A BIOINDICATOR USING GRACILARIA EDULIS (RHODOPHYTA)1
Authors: Jones Adrian B. , Dennison William C. , Stewart George R. 
Published: October 2004

ABSTRACTThe use of macroalgae as biological indicators of dissolved nutrient source and availability in the water column was investigated. Total tissue nitrogen (N) content, pigments, and amino acids of the red alga Gracilaria edulis (Gmelin) Silva were compared to N source and availability in laboratory and field incubations to identify responses that would serve as bioindicators of N. Field‐collected algae were preincubated (6–8 wk) in low‐nutrient seawater to deplete their luxury reserves ofN. Incubations were then conducted for periods of 3 d in laboratory aquaria (N‐spiked seawater) and in the field using macroalgal incubation chambers. After incubation in different N sources (NH4+, NO3−, and urea) in laboratory aquaria, photosynthetic pigments (phycoerythrin and chlorophyll a) and total tissue N increased, in response to increasing [NH4+] but not to [NO3−] or [urea]. Incubation in two ranges of [NH4+], one from 0 to 80 μM and the other from 0 to 800 μM, in laboratory aquaria increased the total amino acid pool. Citrulline concentrations were the most responsive to [NH4+] (r2= 0. 84). NH4+ source treatments produced increases in citrulline, phenylalanine, serine, and free NH4+ and decreases in alanine; NO3− treatments produced increases in glutamic acid, citrulline, and alanine; and urea treatments produced increases in free NH4+ and decreases in phenylalanine and serine. The observed variations in amino acid content facilitated the development of an index for each N source based on relative concentrations of various amino acids (i. e. metabolic profiling). Gracilaria edulis was incubated along a field N gradient in the Brisbane River (three sites) and Moreton Bay (four sites), Queensland, Australia. Both phycoerythrin and tissue N appeared to respond equally to NH4+ and NO3− availability in the field. N source indices, based on amino acid concentration, were effective predictors of both [NH4+] and [NO3−] over a wide range of concentrations along the field gradient. Macroalgal physiological responses, particularly amino acid content, to changes in source and availability of N appear to be useful as sensitive bioindicators of N.
GROWTH PATTERN, REPRODUCTION, AND SELF‐THINNING IN SEAWEEDS1
Authors: Flores‐Moya Antonio , Fernández José A. , Niell F. Xavier 
Published: October 2004

ABSTRACTIn unispecific plant stands, the logarithm of mean individual weight (w) depends on the logarithm of density (d) by the ‐3/4 power law (a slope of ‐1.5 and an intercept ranging from 2.3 to 5.0). The analysis of the w and d relationships in whole cohorts of two seaweed species from the Strait of Gibraltar shows deviations from the canonical equation. The kelp Phyllariopsis purpurascens (C. Agardh) Henry et South (Phaeophyta) growing at a 30‐m depth has the lowest intercept value (0.6) recorded for any plant species and a slope not significantly different from ‐1.5. The slope value is in accordance with those found in species whose growth is not stopped by reproduction. Irradiance under a single layer of blades was lower than the photosynthetic light compensation point, and this could be due to overdispersion of the shoots and, in consequence, to the low intercept value of the self‐thinning equation. The w to d relationships in Asparagopsis armata Harvey (Rhodophyta) show two different components: no dependence between these two variables (slope not significantly different from 0) at densities < 500 shoots·m−2, and a slope more negative (‐2.1) than proposed by the ‐3/2 power law at densities > 500 shoots·m−2. The pattern at high densities could be due to intraspecific competition for light, whereas the slope ∼0 at low densities could be related to inhibition of growth by reproduction (cystocarp and carpospore production). Therefore, rather than being considered exceptional, we suggest that a gradient of variability could be expected in the dependence of w on d when specific growth patterns and reproduction are considered.
COLONIZATION AND REPRODUCTION OF THE EPIBIOTIC FLAGELLATE COLACIUM VESICULOSUM (EUGLENOPHYCEAE) ON DAPHNIA PULEX1
Authors: Al‐Dhaheri Rowaya S. , Willey Ruth L. 
Published: October 2004

ABSTRACTThe epibiotic flagellate Colacium vesiculosum Pringsheim attaches to planktonic species of Daphnia in freshwater habitats. Previous studies found that prevalence (percentage of substrate organisms carrying attached epibionts) and intensity (number of attached epibionts on a given substrate organism) are low early in the Daphnia intermolt period and are high late in the intermolt period. We tested the hypothesis that increases of Colacium cells attached to Daphnia occur both by rapid initial and continuous colonization and by cell reproduction. Epibiont prevalence and intensities were determined at successive intermolt stages of Daphnia pulex Leydig collected from freshwater ponds in Colorado. Colonization was continuous throughout the intermolt period and was most important to epibiont population increase at the beginning of the intermolt period. Cell division was the major contributor to epibiont increase at the end of the intermolt period.
MICROENVIRONMENTS AND MICROSCALE PRODUCTIVITY OF CYANOBACTERIAL DESERT CRUSTS1
Authors: Garcia‐Pichel Ferran , Belnap Jayne 
Published: October 2004

ABSTRACTWe used microsensors to characterize physicochemical microenvironments and photosynthesis occurring immediately after water saturation in two desert soil crusts from southeastern Utah, which were formed by the cyanobacteria Microcoleus vaginatus Gomont, Nostoc spp., and Scytonema sp. The light fields within the crusts presented steep vertical gradients in magnitude and spectral composition. Near‐surface light‐trapping zones were formed due to the scattering nature of the sand particles, but strong light attenuation resulted in euphotic zones only ca. 1 mm deep, which were progressively enriched in longer wavelengths with depth. Rates of gross photosynthesis (3.4–9.4 mmol O2·m−2·h−1) and dark respiration (0.81–3.1 mmol O−2·m−2·h−1) occurring within 1 to several mm from the surface were high enough to drive the formation of marked oxygen microenvironments that ranged from oxygen supersaturation to anoxia. The photosynthetic activity also resulted in localized pH values in excess of 10, 2–3 units above the soil pH. Differences in metabolic parameters and community structure between two types of crusts were consistent with a successional pattern, which could be partially explained on the basis of the microenvironments. We discuss the significance of high metabolic rates and the formation of microenvironments for the ecology of desert crusts, as well as the advantages and limitations of microsensor‐based methods for crust investigation.
LECTIN‐LIKE COMPOUNDS AND LECTIN RECEPTORS IN MARINE MICROALGAE: HEMAGGLUTINATION AND REACTIVITY WITH PURIFIED LECTINS1
Authors: Hori Kanji , Ogata Takehiko , Kamiya Hisao , Mimuro Mamoru 
Published: October 2004

ABSTRACTWe detected lectin‐like compounds and lectin receptors in microalgae by hemagglutination, competitive inhibition with sugars, and reactivity with lectins isolated from other sources. Cell extracts from eight species of Dinophyceae and from one species each of Raphidophyceae and Bacillariophyceae exhibited hemagglutination toward trypsinized rabbit erythrocytes. In addition, the culture media of the dinoflagellateAlexandrium cohorticulaand the raphidophyteChattonella antiquadisplayed similar hemagglutination. These activities were not inhibited by any monosaccharides or oligosaccharides tested but were inhibited by some specific glycoproteins. This suggests that the active factors were lectin‐like compounds. Upon exposing intact, healthy cells of 12 species of Dinophyceae and one species each of Raphidophyceae, Cryptophyceae, Bacillariophyceae, and Chlorophyceae to lectins isolated from either macroalgae or terrestrial plants, most species were adversely affected. The negative effects included one or more of the following: impaired motility, disappearance of motility, agglutination, abnormal morphology, and cell rupture or lysis. Some species, even after freezing, thawing, and washing with saline solution, still agglutinated with macroalgal or terrestrial plant lectins. This study suggests that lectins and carbohydrate‐containing lectin receptors may commonly occur on the cell surfaces of various species of microalgae.
MICROENVIRONMENTAL CONTROL OF PHOTOSYNTHESIS AND PHOTOSYNTHESIS‐COUPLED RESPIRATION IN AN EPILITHIC CYANOBACTERIAL BIOFILM1
Authors: Kühl Michael , Glud Ronnie Nøhr , Ploug Helle , Ramsing Niels Birger 
Published: October 2004

ABSTRACTThe photosynthetic performance of an epilithic cyano‐bacterial biofilm was studied in relation to the in situ light field by the use of combined microsensor measurements of O2, photosynthesis, and spectral scalar irradiance. The high density of the dominant filamentous cyanobacteria (Oscillatoria sp.) embedded in a matrix of exopolymers and bacteria resulted in a photic zone of < 0.7 mm. At the biofilm surface, the prevailing irradiance and spectral composition were significantly different from the incident light. Multiple scattering led to an intensity maximum for photic light (400–700 nm) of ca. 120% of incident quantum irradiance at the biofilm surface. At the bottom of the euphotic zone in the biofilm, light was attenuated strongly to < 5–10% of the incident surface irradiance. Strong spectral signals from chlorophyll a (440 and 675 nm) and phycobilins (phycoerythrin 540–570 nm, phycocyanin 615–625 nm) were observed as distinct maxima in the scalar irradiance attenuation spectra in the upper 0.0–0.5 mm of the biofilm. The action spectrum for photosynthesis in the cyanobacterial layer revealed peak photosynthetic activity at absorption wavelengths of phycobilins, whereas only low photosynthesis rates were induced by light absorption of carotenoids (450–550 nm).Respiration rates in light‐ and dark‐incubated biofilms were determined using simple flux calculations on measured O2 concentration profiles and photosynthetic rates. A significantly higher areal O2 consumption was found in illuminated biofilms than in dark‐incubated biofilms. Although photorespiration accounted for part of the increase, the enhanced areal O2 consumption of illuminated biofilms could also be ascribed to a deeper oxygen penetration in light as well as an enhanced volumetric O2 respiration in and below the photic zone. Gross photosynthesis was largely unaffected by increasing flow velocities, whereas the O2 flux out of the photic zone, that is, net photosynthesis, increased with flow velocity. Consequently, the amount of produced O2 consumed within the biofilm decreased with increasing flow velocity. Our data indicated a close coupling of photosynthesis and respiration in biofilms, where the dissolved inorganic carbon requirement of the photo‐synthetic population may largely be covered by the respiration of closely associated populations of heterotrophic bacteria consuming a significant part of the photosynthetically produced oxygen and organic carbon.
PHYSIOLOGICAL RESPONSES TO PHOSPHORUS LIMITATION IN BATCH AND STEADY‐STATE CULTURES OF DUNALIELLA TERTIOLECTA (CHLOROPHYTA): A UNIQUE STRESS PROTEIN AS AN INDICATOR OF PHOSPHATE DEFICIENCY1
Authors: Graziano Lisa M. , La Roche Julie , Geider Richard J. 
Published: October 2004

ABSTRACTA protein unique to phosphorus stress observed in Dunaliella tertiolecta Butcher was studied in the context of phosphate‐limited cell physiology and is a potential diagnostic indicator of phosphate deficiency in this alga. Cells were grown over a range of limited, steady‐state growth rates and at maximum (replete) and zero (phosphate‐starved) growth rates. The stress protein, absent in nutrient‐replete cells, was produced under all steady‐state phosphate‐limited conditions and increased in abundance with increasing limitation (decreasing growth rate). Cellular carbon: phosphorus ratios and the maximum uptake rate of phosphate (Vm) increased with increasing limitation, whereas the ratio of chlorophyll a: carbon decreased. Alkaline phosphatase activity did not respond to limitation but was measurable in starved, stationary‐phase cells. Fv/Fm, a measure of photochemical efficiency, was a nonlinear, saturating function of p, as commonly observed under N limitation. The maximum Fv/Fm of 0.64 was measured in nutrient‐replete cells growing at μmax, and a value of zero was measured in stationary‐phase starved cells. When physiological parameters were compared, the P‐stress protein abundance and Fv/Fm were the most sensitive indicators of the level of deficiency. The stress protein was not produced under N‐ or Fe‐limited conditions. It is of high molecular weight (>200) and is associated with internal cell membranes. The stress protein has several characteristics that make it a potential diagnostic indicator: it is 1) unique to phosphorus limitation (i.e. absent under all other conditions), 2) present under limiting as well as starved conditions, 3) sensitive to the level of limitation, and 4) observable without time‐course incubation of live samples.
EFFECT OF MALTOSE RELEASE ON UPTAKE AND ASSIMILATION OF AMMONIUM BY SYMBIOTIC CHLORELLA (CHLOROPHYTA)1
Authors: McAuley Paul J. , Dorling Matthew , Hodge Harry 
Published: October 2004

ABSTRACTWhen incubated at pH 4–5, Chlorella freshly isolated from symbiosis with Hydra viridissima PALLAS 1766 (green hydra) release large amounts of photosynthetically fixed carbon in the form of maltose, and assimilation of inorganic N is inhibited. Physiological responses to N starvation of the cultured 3N813A strain of maltose‐releasing Chlorella differed from those caused by 48 h of maltose release induced by low pH. N starvation increased rates of ammonium assimilation at pH 7.0 in light or darkness, and ammonium assimilation in darkness stimulated cell respiration. In contrast, cells pretreated at pH 5.0 to induce maltose release were unable to take up ammonium at pH 7.0 unless supplied with an external carbon source such as bicarbonate, acetate, or succinate, and rates of uptake were similar to control cells. Freshly isolated symbionts displayed a similar dependency. Rates of ammonium uptake by cells pretreated at pH 5.0 were reduced in darkness and did not stimulate cell respiration. N‐starved cells supplied with ammonium also showed a large short‐term increase in glutamine pools at the expense of glutamate, as might be expected if large amounts of ammonium were rapidly assimilated via glutamine synthetase/glutamate synthase, whereas after long‐term maltose release cells showed only a small increase in glutamine when supplied with ammonium. Furthermore, maltose release caused a fall in pool sizes of a number of amino acids, including glutamine and glutamate, and also caused a decrease in pool sizes of 2‐oxoglutarate and phospho‐enol‐pyruvate, which are required for ammonium assimilation into amino acids.Cells stimulated to synthesize and release maltose may be unable to assimilate ammonium and synthesize amino acids because of diversion of fixed carbon from N metabolism. We estimate that 40–50% affixed C is required for maximal maltose synthesis, whereas up to 30% fixed C is required for ammonium assimilation. These results are discussed in the context of host regulation of symbiotic algal growth.
DISTINCTIVE LECTIN LABELING OF THE FLAGELLAR APPARATUS OF TETRASELMIS (PRASINOPHYCEAE) AND DUNALIELLA (CHLOROPHYCEAE)1
Authors: Costas Eduardo , Hevia Elena , Carretero Yolanda , López‐Rodas Victoria 
Published: October 2004

ABSTRACTFluorescent labeling of the flagellar apparatus of Tetraselmis (Prasinophyceae) and Dunaliella (Polyblepharidaceae, Chlorophyceae) were successfully performed using fluorescein isothiocyanate–labeled lectins from Arachis hypogaea and Glycine maxima. These lectins specifically bound to the flagella and kinetosome of the cell but did not bind to the cell surface. Lectin binding on the flagellar apparatus remained constant under different culture media, temperatures, irradiances, cell division cycle, and culture aging. All the Tetraselmis and Dunaliella analyzed (five species, 20 clones) showed intense labeling of the flagellar apparatus. In contrast, no other species analyzed (46 clones of 25 species from four classes) showed binding to their flagellar apparatus. After the lectin treatment, many cells remained alive, and they were able to swim with the flagellar apparatus intensely labeled. The lectin binding indicates that the flagella and kinetosome of Tetraselmis are rich in Gal and GalNH2 moieties and that the flagella of Dunaliella are rich in Gal and GalNAc moieties. Apparently, this feature seems to be specific to these species.
IDENTIFICATION OF THE CLASS PRYMNESIOPHYCEAE AND THE GENUSPHAEOCYSTISWITH RIBOSOMAL RNA–TARGETED NUCLEIC ACID PROBES DETECTED BY FLOW CYTOMETRY1
Authors: Lange Martin , Guillou Laure , Vaulot Daniel , Simon Nathalie , Amann Rudolf I. , Ludwig Wolfgang , Medlin Linda K. 
Published: October 2004

ABSTRACTTarget regions specific for the class Prymnesiophyceae and the genusPhaeocystis(Har.) Lag. were identified from 18S ribosomal RNA coding regions, and two complementary probes were designed (PRYMN01 and PHAEO01). Detection of whole cells hybridized with these probes labeled with fluorescein isothiocyanate was difficult using epifluorescence microscopy because autofluorescence of the chlorophylls seriously interfered with the fluorescence of the probes. In contrast, flow cytometry proved very useful to detect and quantify the fluorescence of the hybridized cells. Hybridization conditions were optimized, especially with respect to formamide concentration. Both probes were tested on a large array of both target and nontarget strains. Positive and negative controls were also analyzed. Specificity was tested by adding a competing nonlabeled probe. Whereas probe PHAEO01 seems to have good specificity, probe PRYMN01 appeared less specific and must be used with stringent positive and negative controls.
ANALYSIS OF THE EXPRESSION OF GENES FOR P‐TYPE ATPASE IN THE HALOTOLERANT ALGA DUNALIELLA SALINA (CHLOROPHYCEAE)1
Authors: Wada Masato , Hirokawa Aki , Fukumoto Ryou‐hei , Shono Mariko 
Published: October 2004

ABSTRACTA partial complementary DNA (cDNA) (DSA8) for a P‐type ATPase was obtained from the halotolerant alga Dunaliella salina (Dunal) Teod. (Chlorophyceae). The cDNA exhibited greater than 90% homology to the cDNA for a H+‐ATPase in D. bioculata Butcher. The expression of the gene that corresponded to DSA8 was decreased strongly by increases in NaCl concentration. The expression of a gene that corresponded to another ATPase (DSA1; possibly for a Ca2+‐ATPase) from D. salina did not show the same decrease as did the DSA8. However, increased osmotic pressure due to glycerol resulted in the same decrease in the DSA8 gene. Under salt or osmotic stress, the activity of a H+‐ATPase from microsomes of this alga also decreased. We suggest that expression of the gene for the plasma membrane H+‐ATPase of D. salina is regulated by osmotic pressure rather than by the concentration of NaCl.
A SPECTROPHOTOMETRIC ASSAY FOR RUBISCO ACTIVITY: APPLICATION TO THE KELP LAMINARIA SACCHARINA AND IMPLICATIONS FOR RADIOMETRIC ASSAYS1
Authors: Gerard Valrie A. , Driscoll Timothy 
Published: October 2004

ABSTRACTWe optimized a spectrophotometric method for measuring ribulose‐l,5‐bisphosphate carboxylase oxygenase (Rubisco) activity in crude extracts of the kelp Laminaria saccharina Lamour. Activity exhibited a decline during the assays, such that rates determined over a 10‐min period were only 70% of activity during the first minute. Activity was significantly enhanced by addition of HCO3− to the extraction buffer and was stable for at least 4 h. Highest activities were determined using small extract loads (1–2.5 mg fresh weight·mL−1 of assay mixture); extract loads of 10 mg·mL−1caused a 25% decrease in activity. Rubisco activities determined for individual kelp plants using the spectrophotometric method were significantly correlated with total protein and gross photo synthetic capacity (Pmax) and were 1.5–2 times higher than Pmax. Low Rubisco activities relative to photosynthetic rates reported in many previous studies of macroalgae and microalgae may have resulted at least partly from underestimation of enzyme activity by radiometric assays using relatively large volumes of un‐activated crude extract and assay periods longer than 1 min.
GROWTH AND NITROGEN FIXATION OF THE DIAZOTROPHIC FILAMENTOUS NONHETEROCYSTOUS CYANOBACTERIUM TRICHODESMIUM SP. IMS 101 IN DEFINED MEDIA: EVIDENCE FOR A CIRCADIAN RHYTHM1
Authors: Chen Yi‐Bu , Zehr Jonathan P. , Mellon Mark 
Published: October 2004

ABSTRACT Trichodesmium sp. IMS 101, originally isolated from coastal western Atlantic waters by Prufert‐Bebout and colleagues and maintained in seawater‐based media, was successfully cultivated in two artificial media. Its characteristics of growth, nitrogen fixation, and regulation of nitrogen fixation were compared to those of natural populations and Trichodesmium sp. NIBB 1067. Results indicate that the culture grown in artificial media had nitrogen fixation characteristics similar to those when the culture is grown in seawater‐based medium and to those of Trichodesmium sp. in the natural habitat. The study provides practical artificial media to facilitate the physiological studies of these important diazotrophic cyanobacteria, as well as the cultivation of other Trichodesmium species in future studies. Manipulations of the light/dark cycle were performed to determine whether or not the daily cycle of nitrogen fixation is a circadian rhythm. Cultures grown under continuous light maintained the cycle for up to 6 days. We demonstrated that the daily cycle of nitrogen fixation in Trichodesmium sp. IMS 101 was at least partially under the control of a circardian rhythm.
CORRELATED BIOCHEMICAL AND ULTRASTRUCTURAL CHANGES IN NITROGEN‐STARVED EUGLENA GRACILIS1
Authors: García‐Ferris Carlos , de los Ríos Asunción , Ascaso Carmen , Moreno Joaquín 
Published: October 2004

ABSTRACTGrowth of Euglena gracilis Z Pringsheim under photoheterotrophic conditions in a nitrogen‐deprived medium resulted in progressive loss of chloroplastic material until total bleaching of the cells occurred. Biochemical analysis and ultrastructural observation of the first stages of the starvation process demonstrated an early lag phase (from 0 to 9 h) in which cells increased in size, followed by a period of cell division, apparently supported by the mobilization of some chloroplastic proteins such as the photosynthetic CO2‐fixing enzyme ribulose‐1,5‐bisphosphate carboxylase/oxygenase. The degradation of the enzyme started after 9 h of starvation and was preceded by a transient concentration of this protein in pyrenoidal structures. Protein nitrogen and photosynthetic pigments as well as number of chloroplasts per cell decreased during proliferation through mere distribution among daughter cells. However, after 24 h, when cell division had almost ceased, there was a slow but steady decline of photosynthetic pigments. This was paralleled by observable ultrastructural changes including progressive loss of chloroplast structure and accumulation of paramylon granules and lipid globules in the cytoplasm. These findings reinforce the role of chloroplastic materials as a nitrogen source during starvation of E. gracilis in a carbon‐rich medium. The excess of ribulose‐1,5‐bisphosphate carboxylase/oxygenase acts as a first reservoir that, once exhausted, is superseded by the generalized disassembly of the photosynthetic structures, if the adverse environment persists more than 24 h.