bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE IDENTIFICATION AND PURIFICATION OF A CELL‐SURFACE ALKALINE PHOSPHATASE FROM THE DINOFLAGELLATE PROROCENTRUM MINIMUM (DINOPHYCEAE)1
Authors: Dyhrman Sonya T. , Palenik Brian P. 
Published: October 2004

ABSTRACTTwo cell‐surface proteins were identtjied in the dinoflagellate Prorocentrum minimum (Pavillard) Schilkr strain CCMP 1329 that are evident in phosphate‐limited cultures, but not in nitrate‐limited cultures or cultures growing exponentially in complete media. These proteins were detected by labeling cell‐surface proteins with the biotinylating reagent succinimidyl 6‐(biotinamido) hexanoate. One protein, of appoximately 200,000 daltons was purified using differential centrifugation, detergent extraction, and gel filtration chromatography. This purified protein was able to hydrolyze orthophosphate groups from p‐nitrophenylphosphate at pH 8, indicating it is an alkaline phosphatase, although it is larger than other alkaline phosphatases isolated to date tom most microorganisms. This protein may be induced to help P. minimum cleave orthophosphate groups from organic forms of phosphate in marine environments. Ultimately, this protein could represent a unique antigen for developing an antibody probe for examining the relationships between phosphate stress and bloom formation in P. minimum, and perhaps other dinoflagellates, in the field.
IDENTIFICATION OF CYLINDROSPERMOPSIN IN APHANIZOMENON OVALISPORUM (CYANOPHYCEAE) ISOLATED FROM LAKE KINNERET, ISRAEL1
Authors: Banker R. , Carmeli S. , Hadas O. , Teltsch B. , Porat R. , Sukenik A. 
Published: October 2004

ABSTRACTAphanizomenon ovalisporum (Forti) was identified and isolated from Lake Kinneret upon its first appearance as a dominant bloom in late 1994. This cyanobacterial species, not previously known to be toxic, was evaluated by a commonly used mouse bioassay and was demonstrated to induce toxic symptoms that were distinguishable from the typical symptoms of the neurotoxins previously reported in Aphanizomenon flos‐aquae (L.) Ralfs. Mice died 5–24 h after crude extracts were injected intraperitoneally, and the LD50 value was estimated as 465 mg dry wt biomass · kg−1 mouse. A toxicity‐guided fractionation of the active extract indicated that the potent substance is polar an nature. The structure of the active compound was determined by its mass spectrometry and NMR data. The compound was found to be the sulfate‐guanidinium zwitterion, cylindrospermopsin, previously isolated from the cyanobacterium Cylindrospermopsis raciborskii (Woloszynska) and recently also reported in Umezakia natans (Watanabe). This is the first time that Aphanizomenon ovalisporum has been reported to contain a toxic compound.
GROWTH, PHYSIOLOGY, AND ULTRASTRUCTURE OF A DIAZOTROPHIC CYANOBACTERIUM, CYANOTHECE SP. STRAIN ATCC 51142, IN MIXOTROPHIC AND CHEMOHETEROTROPHIC CULTURES1
Authors: Schneegurt Mark A. , Sherman Debra M. , Sherman Louis A. 
Published: October 2004

ABSTRACTThe growth, physiology, and ultrastructure of the marine, unicellular, diazotrophic cyanobacterium, Cyanothece sp. strain ATCC 51142, was examined under mixotrophic and chemoheterotrophic conditions. Several organic substrates were tested for the capacity to support heterotrophic growth. Glycerol was the only substrate capable of enhancing mixotrophic growth in the light and supporting chemoheterotrophic growth in the dark. Dextrose enhanced mixotrophic growth but could not support chemoheterotrophic growth. Chemoheterotrophic cultures in continuous darkness grew faster and to higher densities than photoautotrophic cultures, thus demonstrating the great respiratory capacity of this cyanobacterial strain. Only small differences in the pigment content and ultrastructure of the heterotrophic strains were observed in comparison to photoautotrophic control strains. The chemoheterotrophic strain grown in continuous darkness and the mixotrophic strain grown in light/dark cycles exhibited daily metabolic oscillations in N2 fixation and glycogen accumulation similar to those manifested in photoautotrophic cultures grown in light/dark cycles or continuous light. This “temporal separation” helps protect O2‐sensitive N2 fixation from photosynthetic O2 evolution. The rationale for cyclic glycogen accumulation in cultures with an ample source of organic carbon substrate is unclear, but the observation of similar daily rhythmicities in cultures grown in light/dark cycles, continuous light, and continuous dark suggests an underlying circadian mechanism.
THE ZYGOSPORE WALL OF CHLAMYDOMONAS MONOICA (CHLOROPHYCEAE): MORPHOGENESIS AND EVIDENCE FOR THE PRESENCE OF SPOROPOLLENIN1
Authors: VanWinkle‐Swift Karen P. , Rickoll Wayne L. 
Published: October 2004

ABSTRACTChlamydomonas monoica Strehlow is being developed as a model for genetic analysis of zygospore morphogenesis, and many relevant mutant strains are available. To provide the basis for interpreting the ultrastructural phenotypes of zygospore mutants, an analysis of wall morphogenesis in wildtype zygospores of C. monoica was undertaken. Following synthesis of a thick, fibrous, primary zygote wall, granular material accumulated between the plasma membrane and the primary zygote wall and aggregated into a repetitive array of electron‐opaque fibrous stripes. A new wall layer, the outer layer of the secondary zygospore wall, first appeared as segments with a fibrous outer surface overlying a well‐defined band of electron‐translucent material. These segments gave rise to an intact sheath adjacent to the plasma membrane. Beneath this sheath, electron‐opaque material (forming the inner layer of the secondary zygospore wall) accumulated unevenly and forced the surface sheath to undulate, creating a pattern of peaks and valleys that was exposed to the external environment 4 rupture and release of the primary zygote wall. The zygospore wall included material resistant to degradation by potassium hydroxide, 2‐aminoethanol, and acetolysis, but it was destroyed by exposure to chromic acid. These characteristics, in combination with the autofluorescence of untreated zygospore walls and their failure to stain with phloroglucinol, suggest that sporopollenin may be responsible for many of the resistant properties associated with the mature zygospore of Chlamydomonas.
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 value 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.
SEASONAL EFFECT ON THE RELATIONSHIP BETWEEN THE PHOTOSYNTHETIC CAPACITY OF INTERTIDAL MICROPHYTOBENTHOS AND TEMPERATURE1
Authors: Blanchard Gérard F. , Guarini Jean‐Marc , Gros Philippe , Richard Pierre 
Published: October 2004

ABSTRACTThe response of the photosynthetic capacity (Pmax) of microphytobenthos to short‐term variations of temperature (in the range 5–35° C) was assessed on a seasonal basis. The relationship is described mathematically, and relevant physiological parameters are identified: PMAX, the maximum value of Pmax achieved at Topl, the optimum temperature. Estimated values of Topt do not change significantly throughout the year and remain close to 25° C. It is thus concluded that Topt is not influenced by seasonal variations in the daily range of mud surface temperature. Identical conclusions hold for Tmax (ca. 38° C), the thermal threshold beyond which no photosynthesis occurs. Conversely, PMA estimates exhibit substantial variability: PMAX (mean ± root mean square error) is highest in April (11.18 ± 0.42 [μg C · [μg Chl a]−1· h−1) during the beginning of the annual increase in temperature, photoperiod, and maximum irradiance and is lowest in December (3.04 ± 0.16 μg C · [μg Chl a]−1· h−l). From an ecological point of view, the short‐term and seasonal variations of PMAX suggest that the microphytobenthic community takes advantage of the abiotic spring environmental conditions, allowing the onset of the bloom. Nevertheless, no “acclimation strategy” (i.e. shifts in Topt and Tmax that prevent temperature inhibition in summer or improve photosynthetic rates in winter) is apparent from our results.
PRIMARY PRODUCTION, CALCIFICATION, AND AIR‐SEA CO2 FLUXES OF A MACROALGAL‐DOMINATED CORAL REEF COMMUNITY (MOOREA, FRENCH POLYNESIA)1
Authors: Gattuso Jean‐Pierre , Payri Claude E. , Pichon Michel , Delesalle Bruno , Frankignoulle Michel 
Published: October 2004

ABSTRACTCommunity metabolism and air‐sea carbon dioxide (CO2) fluxes were investigated in July 1992 on a fringing reef at Moorea (French Polynesia). The benthic community was dominated by macroalgae (85% substratum cover) and comprised of Phaeophyceae Padina tenuis (Bory), Turbinaria ornata (Turner) J. Agardh, and Hydroclathrus clathratus Bory (Howe); Chlorophyta Halimeda incrassata f. ovata J. Agardh (Howe); and Ventricaria ventricosa J. Agardh (Olsen et West), as well as several Rhodophyta (Actinotrichia fragilis Forskál (Børgesen) and several species of encrusting coralline algae). Algal biomass was 171 g dry weight· m−2. Community gross production (Pg), respiration (R), and net calcification (G) were measured in an open‐top enclosure. Pg and R were respectively 248 and 240 mmol Co2·m−2·d−1, and there was a slight net dissolution of CaCO3 (0.8 mmol · m−2·d−1). This site was a sink for atmospheric CO2 (10 ± 4 mmol CO2·m−2·d−1), and the analysis of data from the literature suggests that this is a general feature of algal‐dominated reefs. Measurement of air‐sea CO2 fluxes in open water close to the enclosure demonstrated that changes in small‐scale hydrodynamics can lead to misleading conclusions. Net CO2 evasion to the atmosphere was measured on the fringing reef due to changes in the current pattern that drove water from the barrier reef (a C02 source) to the study site.
PATTERNS OF REPRODUCTION, GENETIC DIVERSITY, AND GENETIC DIFFERENTIATION IN CALIFORNIA POPULATIONS OF THE GENICULATE CORALLINE ALGA LITHOTHRIX ASPERGILLUM (RHODOPHYTA)1
Authors: Pearson Elizabeth A. , Murray Steven N. 
Published: October 2004

ABSTRACTThe reproductive composition and genetic diversity of populations of the red seaweed Lithothrix aspergillum Gray (O. Corallinales) were studied at three southern California sites (Shaw's Cove and Treasure Island, Laguna Beach; Indian Rock, Santa Catalina Island) and at a fourth site (Bodega Bay) located in northern California. Sexually reproducing populations were confined to southern California. Diploid individuals were numerically dominant over haploid (gametophytic) individuals at all sites. Intertidal and subtidal subpopulations from Shaw's Cove differed in their reproductive profiles. Most intertidal specimens found on emersed surfaces were densely branched, turf‐forming, and bore tetrasporangial (68.6%), carposporangial (11.4%), or spermatangial (5.7%) conceptacles, reflecting a sexual life history; none produced asexual bispores. In contrast, 74.3% of the larger, loosely branched subtidal specimens bore bisporangial conceptacles indicative of asexual reproduction. Nearly 70% of the Indian Rock thalli showed no evidence of conceptacle formation. Only asexual, diploid bispore‐producing thalli were obtained from the Bodega Bay site. Genetic diversity (mean number of alleles per locus, percent of polymorphic loci, and average expected heterozygosity) of diploid L. aspergillum populations varied with life‐history characteristics and geographic location. A total of 30 alleles was inferred from zymograms of 16 loci examined by starch‐gel electrophoresis; of these loci, 11 were polymorphic. The genetic diversity of sexual, diploid populations of L. aspergillum (alleles per locus [A/L] = 1.4‐1.5; percent polymorphic loci [%P] = 37.5‐50.0) was relatively high compared with other red seaweeds. Lowest diversity (A/L = 1.0; %P = 0.0) occurred in the exclusively asexual Bodega Bay population which consisted of genetic clones. All sexual L. aspergillum populations deviated significantly from Hardy‐Wein‐berg expectations due to lower than expected heterozygosity. Genetic differentiation (Wright's Fstatistic [FST]; Nei's Genetic Distance [D]) among sexually reproducing southern California populations was low (FST= 0.030) on a local scale (ca. 5 km), suggesting high levels of gene flow, but high genetic differention (FST= 0.390 and 0.406) occurred among southern California populations separated by ca. 70 km. Very high genetic differentiation (FST= 0.583–0.683) was obtained between northern and southern California populations separated by 700–760 km. Our genetic and reproductive data suggest that the L. aspergillum population from Bodega Bay is sustained by perennation, vegetative propagation, or asexual reproduction by bispores and may represent an isolated remnant or a population established by a founder event.
BIOMASS AND DYNAMICS OF GROWTH OF ULVA SPECIES IN PALMONES RIVER ESTUARY1
Authors: Hernández Ignacio , Peralta Gloria , Pérez‐Lloréns J. Lucas , Vergara Juan J. , Niell F. Xavier 
Published: October 2004

ABSTRACTDuring the last decade, the Palmones River estuary has undergone severe eutrophication followed by a green tide episode; two species of Ulva, rotundata Blid. and Ulva curvata (Kütz.) De Toni, were the main macroalgae responsible for this bloom. From November 1993 to December 1994, we followed the biomass, the growth dynamics, and tissue elemental composition (C:N:P)of Ulva species, as well as some physicochemical variables in the estuary. Maximum biomass (up to 375 g dry wt·m−2 in some spots, corresponding to a thallus area index of nearly 17 m2Ulva·m−2 sediment) were observed in June and December. However, the biomass varied among the sampling stations. Water nitrate, ammonia, and phosphate showed high concentrations throughout the year, with extremely high transient pulses, sustaining the high growth rates observed. Growth rates were estimated directly in the field. The rates were generally higher in Ulva discs maintained in net cages than those estimated by changes in biomass standing stock between two consecutive samplings. The difference between both estimates was used to quantify the importance of the processes causing loss of biomass, which were attributable to grazing, exported biomass, and thallus decomposition under anaerobic conditions resulting from extreme self‐shading. Maximum chlorophyll content was found in winter, whereas the minimum was in spring. Atomic N:P ratios were generally higher in the algae than in the water. However, the absolute concentrations of tissue N and P were always higher than the critical levels for maximum growth, which suggests that growth was not limited by inorganic N or P availability. The results suggested that the increase in nutrient loading in the river may have triggered the massive development of green algae and that light limitation and temperature stress in summer seem to be the main factors controlling the abundance of Ulva in the estuary. In addition to light availability and thermal stress, the different loss processes may have a decisive role in the dynamics of Ulva biomass.
THE ROLE OF NITROGEN NUTRITION IN HIGH‐TEMPERATURE TOLERANCE OF THE KELP, LAMINARIA SACCHARINA (CHROMOPHYTA)1
Authors: Gerard Valrie A. 
Published: October 2004

ABSTRACTMechanisms of high‐temperature tolerance in the kelp Laminaria saccharina (L.) Lamour. were examined by comparing a heat‐tolerant ecotype from Long Island Sound (LIS), New York, and a population from the Atlantic (ATL) coast of Maine. Greater heat tolerance was not attributable to greater thermal stability of the photosynthetic apparatus: LIS and ATL plants exhibited similar short‐term effects of high temperature on photosynthetic capacity (Pmax) and quantum yield (estimated as the ratio of variable to maximum chlorophyll fluorescence, Fv/Fm. As LIS plants had consistently higher N and protein content than ATL plants, the interaction between nitrogen nutrition and high‐temperature tolerance was examined. When grown under high N supply and optimal temperature (12° C), LIS plants had a higher density of photosystem II reaction centers (RCII), higher activity of two Calvin cycle enzymes (ribulose bisphosphate carboxylase oxygenase [RUBISCO] and NADP‐dependent glyceraldehyde‐3‐phosphate dehydrogenase [G3PDH]), and higher Pmax and Fv/Fm than ATL plants. Individual ATL plants, furthermore, exhibited close correlations of RCII density and enzyme activity with N and/or protein content. Variation in RCII density and enzyme activity, in turn, largely accounted for plant‐to‐plant differences in Pmax and Fv/Fm. Relationships among these parameters were generally weak or lacking among individual LIS plants grown under optimal conditions, apparently because luxury N consumption resulted in excess reserves of photosynthetic apparatus components. Exposure of N‐replete LIS and ATL plants to a superoptimal temperature (22° C) for 4 days caused an increase in the minimum turnover time of the photosynthetic apparatus (tau) and a decrease in Pmax, but had no consistent effect on Fv/Fm RCII density, PSU size (chlorophyll a/RCII), or enzyme activities. When plants were subjected to concurrent N limitation and heat stress, however, LIS and ATL populations exhibited quite different responses. All photosynthetic parameters of N‐limited ATL plants declined sharply in response to high temperature, resulting in a negative rate of daily net C fixation. In contrast, LIS plants showed a reduction in PSU size, but maintained other parameters, including daily C fixation, at levels similar to those of N‐limited plants at optimal temperature. Overall, the ability of LIS plants to accumulate and maintain high N reserves appears to be critical for heat tolerance and, therefore, for survival during summer periods of simultaneous low N supply and superoptimal temperature. ATL plants, which also experience low summer N supply but not superoptimal temperatures, do not accumulate large reserves of nitrogenous components and are unable to tolerate the combined stress. Because low N supply often co‐occurs with high temperatures in temperate marine systems, large‐scale declines in algal productivity, such as during El Niño events, are probably due to the interactive effect of N limitation and heat stress.
ABUNDANT PLASMID‐LIKE DNA IN VARIOUS MEMBERS OF THE ORDERS SIPHONOCLADALES AND CLADOPHORALES (CHLOROPHYTA)1
Authors: La Claire John W. , Zuccarello Giuseppe C. , Tong Shun 
Published: October 2004

ABSTRACTIn all seven genera belonging to the order Siphonocladales and in two genera of the Cladophorales (Chlorophyta) that were examined, extracts of total DNA contained abundant low molecular weight (LMW) molecules. This DNA typically ranged in size from 1.5 to 3.0 kb among the different genera studied. The complexity of the populations of molecules found in different genera also varied with regard to sizes and numbers of bands evident in electrophoresis gels. Our data suggest that the LMW DNA is ubiquitous among these algae since it occurred in each of our six isolates of Ernodesmis verticillata (Kützing) Børgesen collected in both the Caribbean and the Gulf of California. The LMW DNA from Ernodesmis and Ventricaria ventricosa (J. Agardh) Olsen et J. West was denser than high molecular weight (HMW) DNA in CsCl/bisbenzimide gradients. Ultrastructurally, the LMW DNA molecules were linear, averaging 0.65 μm (Ernodesmis) and 1.0 μm (Ventricaria) in length. Approximately 2%–5% of the former possessed an apparent loop or lariat at one end, as visualized in the electron microscope after rotary shadowing. The LMW DNA molecules appeared to be predominantly double‐stranded DNA based upon staining with acridine orange. The 2.2‐kb DNA from Ernodesmis has features typical of plasmids in that it rapidly reannealed after heat denaturation, and it was selectively enriched in an alkaline‐lysis extraction procedure. In denaturing gels, this DNA migrated at >4.0 kb, indicating that the molecules may actually be single‐stranded DNA species with intramolecular base pairing, each containing a long inverted repeat folded back on itself in a hairpin conformation in the native state. Digestion with mung bean nuclease revealed that additional single‐stranded regions may occur in many of the LMW molecules, in addition to the hairpin loop. Although the endonuclease DNase I rapidly digested the LMW DNA, neither exonuclease III nor lambda exonuclease digested it. This suggests that the ends of these DNA molecules are protected. Collectively, the data indicate that members of the Siphonocladales and Cladophorales contain linear plasmid‐like DNA molecules that appear to have a novel combination of features.
THREE NEW BENTHIC SPECIES OF PROROCENTRUM (DINOPHYCEAE) FROM BELIZE: P. NORRISIANUM SP. NOV., P. TROPICALIS SP. NOV., and P. RETICULATUM SP. NOV.1
Authors: Faust Maria A. 
Published: October 2004

ABSTRACTThree new benthic, photosynthetic dinoflagellate species, Prorocentrum norrisianum, Prorocentrum tropicalis, and Prorocentrum reticulatum, from floating detritus and coral rubble of Central America are described from scanning electron micrographs. Species were identified based on shape, size, surface micromorphology, thecal plate ornamentation, and architecture of the periflagellar area and intercalary band.Cells of P. norrisianum are ovate with a cell size of 20–25 μm long and 13–16 μm wide. The theca is delicate, its surface smooth, pores species specific with 95 to 105 pores per valve. Pores are round with a diameter of about 0.1 μm. The periflagellar area is V‐shaped, located on the right valve in a shallow depression. It has no ornamentation. The flagellar and auxiliary pores are unequal in size. The intercalary band is smooth. Prorocentrum tropicalis cells are ovoid, 50–55 μm long and 40–45 μm wide in valve view with maximum width behind the middle region, narrow at the anterior end. The periflagellar area, situated in the right valve, is a V‐shaped wide triangle with a deeply indented depression; the left valve exhibits a flat ridge. The periflagellar area is unornamented, and the flagellar and auxiliary pores are unequal in size. The valve surface is rugose with evenly distributed valve poroids. Each poroid appears to have a small dome in the center. The intercalary band is rimlike around the cell margin, granulated, and horizontally striated. Prorocentrum reticulatum cells are oblong in valve view; cells are 55–60 μm long and 40–45 μm wide. Thecal surface is reticulated; it is composed of a labyrinth of ridges with alternating depressions that vary in size and shape. Each depression has a narrow, oblong‐kidney‐shaped opening about 0.6 μm long. The periflagellar area is a deep, V‐shaped triangle. The right valve of P. reticulatum is excavated, and contains a large flagellar pore and a smaller auxiliary pore surrounded by a narrow apical collar. The left valve margin exhibits a curved flat ridge. The intercalary band is smooth.