bluuebunny/crossref_metadata_2025 huggingface dataset:
PHYSIOLOGICAL FACTORS THAT AID DIFFERENTIATION OF ZYGOTES AND EARLY JUVENILES OF ACETABULARIA ACETABULUM (CHLOROPHYTA)
Authors: Cooper John J. , Mandoli Dina F.
Published: March 2003

To improve our understanding of early development and to enable standard genetic analyses in Acetabularia acetabulum (L.) Silva, we examined some physiological factors that impact differentiation of young diploid plants. Eighty percent of zygotes differentiated within 6–7 days when they were inoculated at high densities (≥5,000 zygotes·mL−1), and zygote differentiation was independent of the photon flux density of cool white light. In contrast, 90% of juveniles differentiated within 25 days when they were inoculated at medium densities (<1,000 individuals·mL−1) and required >250 μmol·m−2·s−1 cool white light. Both zygotes and juveniles differentiated best at an alkaline pH (7.96), when the temperature was between 18.6° and 23.5° C, and when the external potassium concentration was 1–10 mM. Compared to prior publications, adjustment of these parameters reduced the time to differentiation by 25% (from 8 to 6 days) and more than tripled the percentage of zygotes that developed into healthy juveniles (from 23% to ∼80%).
HETEROGENEITY OF OXYGEN PRODUCTION AND CONSUMPTION IN A PHOTOSYNTHETIC MICROBIAL MAT AS STUDIED BY PLANAR OPTODES
Authors: Glud Ronnie Nøhr , Kühl Michael , Kohls Oliver , Ramsing Niels Birger
Published: March 2003

By applying planar optodes and imaging techniques to a benthic photosynthetic mat, we demonstrated an extensive vertical and horizontal variation in O2 concentrations, O2 consumption, and O2 production. In light, the oxic zone could be divided into three horizons: 1) an upper zone dominated by diatoms that had a moderate net O2 production, 2) another zone dominated by Microcoleus‐like cyanobacteria with a high net O2 production, and 3) a lower zone with disintegrating microalgae and cyanobacteria with a high O2 consumption rate. From the O2 images, the net O2 production/consumption was calculated at a spatial resolution of 130 μM. This allowed us to identify microsites with high rates of O2 turnover within the photic zone. Sites with high net O2 consumption (>1.5 nmol·cm−3·s−1) were typically situated next to sites with a relatively high net production (>2 nmol·cm−3·s−1), revealing a mosaic in which the highest O2 consumption sites were surrounded by the highest O2 production sites. This suggested a tight spatial coupling between production and consumption of O2 within the photic zone. Light stimulated the O2 consumption within the photic zone. At irradiances above 400 μmol photons·m−2·s−1, the stimulated O2 production was almost completely balanced by enhanced O2 consumption at microsites exhibiting net consumption of O2 even at maximum irradiance (578 μmol photons·m−2·s−1). Our observations strongly supported the idea that light‐stimulated respiration was caused by stimulated heterotrophic activity fueled by organic carbon leakage from the phototrophs. Despite microsites with high net O2 consumption, anoxic microniches were not encountered in the investigated mat. Images of gross photosynthetic rates also revealed an extensive horizontal variation in gross rates, with microsites of low or no photosynthesis within the otherwise photic zone. Calculations based on the obtained images revealed that at maximum light (578 μmol photons·m−2·s−1), 90% of the O2 produced was consumed within the photic zone. The presented data demonstrate the great potential offered by planar optode for studies of benthic photosynthetic communities.
RECONSTRUCTION OF THE FEEDING APPARATUS IN PLOEOTIA COSTATA (EUGLENOPHYTA) AND ITS RELATIONSHIP TO OTHER EUGLENOID FEEDING APPARATUSES
Authors: Linton Eric W. , Triemer Richard E.
Published: March 2003

The ultrastructure of the feeding apparatus in Ploeotia costata Farmer and Triemer was determined and compared to other euglenoid feeding apparatuses. The feeding apparatus opened subapically onto the ventral surface and extended nearly the entire length of the cell. It consisted of four parts at the anterior surface: a comb, cytostome/pocket, vanes, and supporting rods. The comb was a multilayered structure of three horizontal microtubular rows encased in cement and formed the dorsal lip of the apparatus. The cytostome/pocket was located between the comb and the supporting rods, tapered into the cell as the cytopharynx and was surrounded by five vanes. The electron‐opaque vanes extended the entire length of the feeding apparatus and were lined with microtubules for most of their length. Finally, two cement supporting rods that were joined by a crosspiece at the anterior end formed the ventral lip. The rods separated briefly before merging with the vanes. As the merged rods and vanes descended into the cell, they gradually narrowed and terminated. Comparisons of the feeding apparatus with Ploeotia vitrea, Diplonema ambulator, Lentomonas applanatum, and other euglenoids have led to the conclusion that the Type II feeding apparatus is found only in Ploeotia species.
EXTENSIVE INTRASPECIFIC MORPHOLOGICAL VARIATION IN ENTEROMORPHA MUSCOIDES (CHLOROPHYTA) REVEALED BY MOLECULAR ANALYSIS
Authors: Blomster Jaanika , Maggs Christine A. , Stanhope Michael J.
Published: March 2003

Enteromorpha muscoides (Clemente y Rubio) Cremades and E. clathrata Roth (Greville) are morphologically variable species that can easily be distinguished from other Enteromorpha species but not from each other. The key morphological character separating the two species is the presence or absence of spine‐like branches: E. muscoides has small spine‐like branches throughout the thallus, whereas E. clathrata lacks spines. The spiny branches in E. muscoides are not as obvious in summer as in winter, so summer samples may be difficult to distinguish from those of E. clathrata. In this study, molecular data were used to investigate whether these two species, as defined by morphological characters, might be conspecific. The sequences of the internal transcribed spacers ITS1 and ITS2 and the 5.8S gene differed by 0%–0.6% between all samples of both E. muscoides and E. clathrata. Phylogenetic analysis of these sequences in an alignment with 13 other representatives of both Enteromorpha and Ulva showed that this highly supported monophyletic E. muscoides/E. clathrata clade is separated by long branch lengths from other Enteromorpha and Ulva clades. Based on these results, we suggest that Enteromorpha muscoides (Clemente y Rubio) Cremades and Enteromorpha clathrata Roth (Greville) are conspecific, with the older name E. muscoides taking priority.
TWO MORPHOLOGICAL FORMS OF CYLINDROSPERMOPSIS RACIBORSKII (CYANOBACTERIA) ISOLATED FROM SOLOMON DAM, PALM ISLAND, QUEENSLAND
Authors: Saker Martin L. , Neilan Brett A. , Griffiths Dilwyn J.
Published: March 2003

Cylindrospermopsis raciborskii Woloszynska is a prominent constituent of a number of water bodies in northern Australia. In Solomon Dam, this species occurs as two distinct morphological forms, one with straight trichomes and one with coiled trichomes. Isolates of the two forms have been grown in pure culture and have been shown to maintain their respective characteristic form over successive generations. Both forms were similar with respect to cylindrospermopsin content expressed as a percentage of freeze‐dried culture material, ranging from 0.14% to 0.20%, depending on the N source provided in the medium. A morphological comparison between natural populations of the two forms showed significant differences in vegetative, heterocyst, and akinete cell dimensions. These characteristics are the primary taxonomic criteria at the species level in this genus. In culture, the coiled form grew slightly faster than the straight form over the range of conditions investigated in this study. The coiled form was better suited to growth under low‐light conditions. These clear and consistent morphological and physiological differences contrast with the 99.8% similarity between the two forms in their 16S rRNA gene nucleotide sequences. It is concluded that although taxonomic separation of the two forms at the species level might not be warranted, the two strains investigated are clearly distinct morphotypes, and it is recommended that they be so recorded in monitoring programs.
IDENTIFICATION OF GREEN ALGAL ENDOPHYTES AS THE ALTERNATE PHASE OF ACROSIPHONIA (CODIOLALES, CHLOROPHYTA) USING ITS1 AND ITS2 RIBOSOMAL DNA SEQUENCE DATA
Authors: Sussmann Andrea V. , Mable Barbara K. , DeWreede Robert E. , Berbee Mary L.
Published: March 2003

The internal transcribed spacer regions of the nuclear ribosomal DNA cistron of green algal endophytes, previously identified as Chlorochytrium inclusum Kjellman and Codiolum petrocelidis Kuckuck, were sequenced. Culture studies have implicated marine Chlorochytrium and Codiolum‐like cells in the life histories of a number of macrophytic green algae. The identity of the endophytes was resolved by comparing DNA sequences from unicells endophytic in the foliose red alga Mazzaella splendens (Setchell et Gardner) Hommersand and in the crustose phase of Mastocarpus papillatus (J. Agardh) Kylin, with sequences from species of Acrosiphonia, Urospora, Ulothrix, and Monostroma. All endophyte isolates were more closely related to species of Acrosiphonia than to those of Urospora, Ulothrix, or Monostroma. The results support previous culture studies, and conclusively identify the endophytes obtained in the field as alternate life history phases of one or more Acrosiphonia species in southern British Columbia, Canada.
KINETICS OF GROWTH AND DEATH IN ANABAENA FLOS‐AQUAE (CYANOBACTERIA) UNDER LIGHT LIMITATION AND SUPERSATURATION
Authors: Lee Dae‐Young , Rhee G‐Yull
Published: March 2003

The kinetics of population growth and death were investigated in Anabaena flos‐aquae (Lyngb.) Bréb grown at light intensities ranging from limitation to photoinhibition (5 W·m−2 to 160 W·m−2) in a nutrient‐replete turbidostat. Steady‐state growth rate (μ, or dilution rate, D) increased with light intensity from 0.44·day−1 at a light intensity of 5 W·m−2 to 0.99·day−1 at 20 W·m−2 and started to decrease above about 22 W·m−2, reaching 0.56·day−1 at 160 W·m−2. The Haldane function of enzyme inhibition fit the growth data poorly, largely because of the unusually narrow range of saturation intensity. However, it produced a good fit (P < 0.001) for growth under photoinhibition. Anabaena flos‐aquae died at different specific death rates (γ) below and above the saturation intensity. When calculated as the slope of a vx−1 and D−1 plot, where vx and D are cell viability (or live cell fraction) and dilution rate, respectively; γ was 0.047·day−1 in the range of light limitation and 0.103·day−1 under photoinhibition. Live vegetative cells and heterocysts, either in numbers or as a percentage of the total cells, showed a peak at the saturation intensity and decreased at lower and higher intensities. The ratio of live heterocysts to live vegetative cells increased with intensity when light was limiting but decreased when light was supersaturating. In cells growing at the same growth rate, the ratio was significantly lower under light inhibition than under subsaturation and the cell N:C ratio was also lower under inhibition. The steady‐state rate of dissolved organic carbon (DOC) production increased with light intensity. However, its production as a percentage of the total C fixation was lowest at the optimum intensity and increased as the irradiance decreased or increased. The rate and percentage was significantly higher under photoinhibition than limitation in cells growing at the same growth rate. About 22% of the total fixed carbon was released as DOC at the highest light intensity. No correlation was found between the number of dead cells and DOC.
ULTRASTRUCTURE AND DESCRIPTION OF CYANOPHORA BILOBA, SP. NOV., WITH ADDITIONAL OBSERVATIONS ON C. PARADOXA (GLAUCOPHYTA)
Authors: Kugrens Paul , Clay Brec L. , Meyer Charles J. , Lee Robert E.
Published: March 2003

The cell structure of Cyanophora biloba, sp. nov. and C. paradoxa Korschikoff was examined using scanning electron microscopy, freeze‐fracture, and sectioned material. The new species description was based on differences in cell micromorphology, in the cell covering, and in cyanelle structure and number. Cyanophora biloba is characterized by having flat, bilobed cells, with each lobe containing a cyanelle. Each cyanelle invariably has a central constriction that probably represents an arrested cytokinesis. A longitudinal groove or furrow is present between the lobes. The flagella arc inserted ventrally and subapically, and the area near the flagellar insertio is flanked by two short folds. Both flagella bear fine fibrillar hairs. The nucleus is horseshoe‐shaped, conforming to the cell shape, and is located in the posterior of the cell. The cell covering in C. biloba consists of overlapping vesicles situated underneath the plasma membrane, and each vesicle contains a thin plate. Freeze fracture revealed that the plates appear to have a crystalline arrangement of subunits. For comparative purposes, the surface architecture and cell covering of C. paradoxa were re‐examined and some features were found to be new or slightly different than previously described. The cell covering of C. paradoxa also consisted of overlapping vesicles with plates, but the vesicles were smaller than those in C. biloba. In addition, the cell had an anterior furrow that can be partially covered by two long folds near the site of flagellar insertion.
CA2+ BINDING PROTEIN CALRETICULIN IN CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA): BIOCHEMICAL CHARACTERIZATION, DIFFERENTIAL EXPRESSION DURING SEXUAL REPRODUCTION, AND PHYLOGENETIC ANALYSIS
Authors: Zuppini Anna , Barbato Roberto , Bergantino Elisabetta , Dainese Paola , Meggio Flavio , Martin William , Mariani Paola
Published: March 2003

The occurrence of calreticulin, the main Ca2+ binding protein in the endoplasmic reticulum of eukaryotic cells, was investigated in the unicellular green alga Chlamydomonas reinhardtii Dangeard. The biochemical characterization of a diethylaminoethyl purified extract highlighted the presence, on SDS‐PAGE, of a 55‐kDa protein that stained blue with the Stains All dye, a diagnostic feature of acidic Ca2+ binding proteins. Immunoblot analyses revealed a strong cross‐reaction of the Chlamydomonas reinhardtii protein with antibodies to plant calreticulins and the endoplasmic reticulum retention signal HDEL. Furthermore, the 55‐kDa protein bound [45Ca2+] and had an acidic isoelectric point (pI = 4.9) but was neither glycosylated nor phosphorylated. N‐terminal sequencing revealed strong amino acid sequence similarity to calreticulin from other sources. The presence of calreticulin in Chlamydomonas reinhardtii suggested that an endoplasmic reticulum Ca2+ buffering mechanism was present in this unicellular chlorophyte. The data suggest an early origin and high conservation of endoplasmic‐reticulum‐mediated Ca2+ functions in eukaryotes, whereby specific posttranslational modifications of the proteinhave been specifically acquired in different lineages of photosynthetic eukaryotes. Moreover, northern and western blot analysis experiments showed a regulation of calreticulin expression during Chlamydomonas sexual reproduction with a high abundance of calreticulin mRNA and protein in reproductive cells.
DIEL PHASING OF THE CELL‐CYCLE IN THE FLORIDA RED TIDE DINOFLAGELLATE, GYMNODINIUM BREVE
Authors: Van Dolah Frances M. , Leighfield Tod A.
Published: March 2003

The diel cycle is a key regulator of the cell‐cycle in many dinoflagellates, but the mechanisms by which the diel cycle entrains the cell‐cycle remain poorly understood. In this study, we describe diel phasing of the cell‐cycle in the Florida red tide dinoflagellate Gymnodinium breve Davis, determine the diel cue which serves to entrain the cell‐cycle, and provide evidence for the presence of cyclin‐dependent kinase (CDK), a cell‐cycle regulator which may be responsive to this cue. Four laboratory isolates from the West Coast of Florida were compared. When grown on a 16:8 h LD cycle, all isolates displayed phased cell division, with the S‐phase beginning 6–8 h into the light phase, and mitosis following 12–14 h later, as determined by flow cytometry. A naturally occurring bloom of G. breve, studied over one diel cycle, displayed diel cell‐cycle phasing similar to that in the laboratory cultures, with the S‐phase beginning during daylight and the peak of mitosis occurring approximately 4 h after sunset. In the laboratory cultures, the dark/light “dawn” transition was found to provide the diel cue which serves to entrain the G. breve cell‐cycle, whereas the light/ dark “dusk” transition did not appear to be involved. Evidence for the presence of CDK in G. breve was obtained using two approaches: (1) identification of a 34‐kDa protein, immunoreactive to an antibody against a conserved amino acid sequence (α‐PSTAIR) unique to the CDK protein family and (2) inhibition of the cell‐cycle by olomoucine, a selective CDK inhibitor. Together, these results provide the basis from which one can begin addressing mechanisms by which the diel cycle regulates the cell‐cycle in G. breve.
MICROPHOTOMETRIC ASSESSMENT OF SPECTRAL ABSORPTION AND ITS POTENTIAL APPLICATION FOR CHARACTERIZATION OF HARMFUL ALGAL SPECIES
Authors: Lohrenz Steven E. , Fahnenstiel Gary L. , Kirkpatrick Gary J. , Carroll Christopher L. , Kelly Kimberly A.
Published: March 2003

A comparison was made of microphotometric measurements and spectrophotometric measurements of particulate spectral absorption of four algal species, including the chlorophyte Dunaliella tertiolecta Butcher; a nontoxic dinoflagellate, Amphidinium carterae Hulburt; a diatom, Chaetoceros gracilis Schütt; and a toxic dinoflagellate, Gymnodinium breve Steidinger. Particulate spectral absorption of monospecies cultures was estimated as the product of the average absorption efficiency factor, Qa, determined by microphotometry, the cellular cross‐sectional area, and the cell number density. Estimates of particulate spectral absorption from microphotometric measurements were, in most cases, within one standard deviation of values determined from spectrophotometric measurements of algal suspensions. Estimates of Qa(675) were shown to be consistent with values reported in previous studies for cells of similar size and pigmentation and were consistent with theoretical predictions. Absorption spectra of mixtures of C. gracilis and G. breve were numerically decomposed into contributions by absorption signatures of monospecies cultures using either spectrophotometric or microphotometric measurements as the basis for end members. Modeled contributions assigned to either species displayed trends consistent with the actual proportions contributed to the spectrum by each algal culture. However, the technique was sensitive to measurement variability, which reduced the level of agreement between modeled and actual contributions. The utility of this approach for identification of algal taxa will depend on the degree to which algal spectral absorption signatures differ and the capabilities for acquiring high‐resolution data with low signal‐to‐noise ratios.
STRUCTURAL FEATURES OF NUCLEAR GENES IN THE CENTRIC DIATOM THALASSIOSIRA WEISSFLOGII (BACILLARIOPHYCEAE)
Authors: Armbrust E. Virginia
Published: March 2003

Thalassiosira weissflogii (Grun.) Fryxell et Hasle is one of the more commonly studied centric diatoms, and yet molecular studies of this organism are still in their infancy. The ability to identify open reading frames and thus distinguish between introns and exons, coding and noncoding sequence is essential to move from nuclear DNA sequences to predicted amino acid sequences. To facilitate the identification of open reading frames in T. weissflogii, two newly identified nuclear genes encoding β‐tubulin and t ‐complex polypeptide (TCP)‐γ, along with six previously published nuclear DNA sequences, were examined for general structural features. The coding region of the nuclear open reading frames had a G + C content of about 49% and could readily be distinguished from noncoding sequence due to a significant difference in G + C content. The introns were uniformly small, about 100 base pairs in size. Furthermore, the 5′ and 3′ splice sites of introns displayed the canonical GT/AG sequence, further facilitating recognition of noncoding regions. Six of the nuclear open reading frames displayed relatively little bias in the use of synonymous codons, as exemplified by the cDNAs encoding β‐tubulin and TCP‐γ. Two open reading frames displayed strong bias in the use of particular codons (although the codons used were different), as exemplified by the cDNA encoding fucoxanthin chlorophyll a/c binding protein. Knowledge of codon bias should facilitate, for example, design of degenerate PCR primers and potential heterologous reporter gene constructs.
Extracellular matrix assembly in diatoms (Bacillariophyceae). iv. ultrastructure of Achnanthes longipes and Cymbella cistula as revealed by high‐pressure freezing/freeze substituton and cryo‐field emission scanning electron microscopy
Authors: Wang Yan , Chen Ya , Lavin Colleen , Gretz Michael R.
Published: March 2003

Extracellular matrix (ECM) polymers secreted by the diatoms Achnanthes longipes Ag. and Cymbella cistula (Ehr.) Kirchn. completely encase the cell and are responsible for adhesion and other interactions with the external environment. To preserve details of the highly hydrophilic ECM in the native state and to preserve, with a high degree of fidelity, the intracellular structures involved in synthesis of extracellular polymers, we applied a suite of cryotechniques. The methods included high‐resolution visualization of surfaces using cryo‐field emission SEM (cryo‐FESEM) and preservation for TEM observation of thin sections by high‐pressure freezing (HPF) and freeze substitution (FS). The extracellular structures of diatoms plunge‐frozen in liquid ethane, etched at low temperature, and observed on a cryostage in the FESEM showed overall dimensions and shapes closely comparable to those observed with light microscopy. Cryo‐FESEM demonstrated the pervasive nature of the extracellular polymers and their importance in cell–substratum and cell–cell associations and revealed details of cell attachment processes not visible using other SEM techniques or light microscopy. The layer of ECM coating the frustule and entirely encapsulating cells of A. longipes and C. cistula was shown to have a significant role in initial cell adhesion and subsequent interaction with the environment. Trails of raphe‐associated ECM, generated during cell motility, were shown at high resolution and consist of anastomoses of coiled and linear strands. Cryo‐FESEM revealed a sheet‐like mucilage covering stalks. HPF/FS of A. longipes resulted in excellent preservation of intra‐ and extracellular structures comparable to previous reports for animals and higher plants and revealed several organelles not described previously. Three distinct vesicle types were identified, including a class closely associated with Golgi bodies and postulated to participate in formation of the extracellular adhesive structures. HPF/FS showed a number of continuous diatotepic layers positioned between the plasma membrane and the silicon frustule and revealed that extracellular adhesive extrusion through frustule pores during stalk production was closely related to the diatotepum. The stalks of A. longipes consist of highly organized, multilayered, fine fibrillar materials with an electron‐opaque layer organized as a sheath at the stalk periphery.
CHARACTERIZATION OF A GENE ENCODING THE LIGHT‐HARVESTING VIOLAXANTHIN‐CHLOROPHYLL PROTEIN OF NANNOCHLOROPSIS SP. (EUSTIGMATOPHYCEAE)
Authors: Sukenik Assaf , Livne Alexander , Apt Kirk E. , Grossman Arthur R.
Published: March 2003

In contrast to vascular plants, green algae, and diatoms, the major light‐harvesting complex of the marine eustigmatophyte genus Nannochloropsis is a violaxanthin–chlorophyll a protein complex that lacks chlorophylls b and c. The isolation of a single polypeptide from the light‐harvesting complex of Nannochloropsis sp. (IOLR strain) was previously reported (Sukenik et al. 1992). The NH2‐terminal amino acid sequence of this polypeptide was significantly similar to NH2‐terminal sequences of the light‐harvesting fucoxanthin, chlorophyll a/c polypeptides from the diatom Phaeodactylum tricornutum Bohlin. Using polyclonal antibodies raised to the Nannochloropsis light‐harvesting polypeptide, a gene encoding this polypeptide was isolated from a cDNA expression library. The deduced amino acid sequence of the Nannochloropsis violaxanthin–chlorophyll a polypeptide reveals a 36 amino acid presequence followed by 173 amino acids that constitute the mature polypeptide. The mature polypeptide has 30%–40% sequence identity to the diatom fucoxanthin–chlorophyll a/c polypeptides and less then 27% identity to the green algal and vascular plant light‐harvesting chlorophyll polypeptides that bind both chlorophylls a and b. Its molecular mass, as deduced from the gene sequence, is 18.4 kDa with three putative transmembrane helices and several residues that may be involved in chlorophyll binding. The cDNA encoding the violaxanthin–chlorophyll a polypeptide was used to isolate and characterize a 10 kb genomic fragment containing the entire gene. The open reading frame was interrupted by five introns ranging in size from 123 to 449 bp. The intron borders have typical eukaryotic GT … AG sequences.
HIERARCHICAL SPATIAL STRUCTURE AND DISCRIMINANT ANALYSIS OF GENETIC DIVERSITY IN THE RED ALGA MAZZAELLA LAMINARIOIDES (GIGARTINALES, RHODOPHYTA)
Authors: Faugeron Sylvain , Valero Myriam , Destombe Christophe , Martínez Enrique A. , Correa Juan A.
Published: March 2003

Our study of the genetic structure of Mazzaella laminarioides (Bory) Fredericq (Gigartinales) in the central Chilean region documented a high level of genetic diversity based on random amplified polymorphic DNA (RAPD) markers and indicated the occurrence of significant genetic structure at different spatial scales. A total of 288 haploid gametophytes was analyzed with 17 polymorphic RAPD bands, which produced 202 distinct multilocus genotypes. Within stands, mean gene diversity ranged from 0.210 to 0.249 and no significant linkage disequilibrium could be detected among pairs of alleles, revealing that recombination (sexual reproduction) regularly shuffles the genes at that scale. Analysis of molecular variance within stands (less than 30 m) showed that the structure was very low, only marginally significant, and did not increase with increasing hierarchical levels at this lowest spatial scale. In contrast, at a larger spatial scale (among stands, from 5 to 60 km), increasing geographical distance seemed to account for increasing isolation between populations even if natural barriers, such as sandy beaches or river estuaries, may play a role in such isolation. Moreover, the strong genetic differentiation occurring between locations separated by 60 km allowed the assignment of individuals to their original population through a canonical discriminant analysis. This approach further allowed the identification of potential recent migrants from one population to the other. Thus, in species like M. laminarioides for which the dominance of RAPD markers can be avoided by selecting haploid individuals, RAPD analysis appeared to be specially appropriate for the study of genetic differentiation.
PRIMARY AND SECONDARY ENDOSYMBIOSIS AND THE ORIGIN OF PLASTIDS
Authors: McFadden Geoffrey Ian
Published: March 2003

The theory of endosymbiosis describes the origin of plastids from cyanobacterial‐like prokaryotes living within eukaryotic host cells. The endosymbionts are much reduced, but morphological, biochemical, and molecular studies provide clear evidence of a prokaryotic ancestry for plastids. There appears to have been a single (primary) endosymbiosis that produced plastids with two bounding membranes, such as those in green algae, plants, red algae, and glaucophytes. A subsequent round of endosymbioses, in which red or green algae were engulfed and retained by eukaryotic hosts, transferred photosynthesis into other eukaryotic lineages. These endosymbiotic plastid acquisitions from eukaryotic algae are referred to as secondary endosymbioses, and the resulting plastids classically have three or four bounding membranes. Secondary endosymbioses have been a potent factor in eukaryotic evolution, producing much of the modern diversity of life.
ADSORPTION OF FULVIC ACID ON ALGAL SURFACES AND ITS EFFECT ON CARBON UPTAKE
Authors: Knauer Katja , Buffle Jacques
Published: March 2003

Adsorption of Suwannee River fulvic acid (SRFA) to algal surfaces of three green algae was studied at environmentally relevant pH values (4 –7) and SRFA concentrations (5–100 mg·L−1). The influence of adsorbed SRFA on carbon uptake of Scenedesmus subspicatus Chodat was also examined. Although no adsorption was observed at neutral pH values (pH 6 and 7), at pH 4 up to 31 mg SRFA·m−2 and at pH 5 up to 4 mg SRFA·m−2 was adsorbed to the algal surfaces. Electrophoretic mobility measurements of S. subspicatus demonstrated an increase in the negative surface charge of the alga in the presence of SRFA at pH 4. The adsorbed SRFA also influenced 14C uptake in S. subspicatus; in this case, enhanced carbon uptake could be related to the amount of adsorbed SRFA. The binding of humic substances by algal surfaces was interpreted as the result of hydrogen bonding and hydrophobic interactions.
CONSUMPTION OF ULVA LACTUCA (CHLOROPHYTA) BY THE OMNIVOROUS MUD SNAIL ILYANASSA OBSOLETA (SAY)
Authors: Giannotti Amy L. , McGlathery Karen J.
Published: March 2003

Marine invertebrate grazing on temperate macroalgae may exert a significant “top‐down” control on macroalgal biomass. We conducted two laboratory experiments to test (1) if consumption by the omnivorous mud snail Ilyanassa obsoleta (Say) on the macroalga Ulva lactuca Linnaeus was a function of food quality (nitrogen content) and (2) if grazing on benthic macroalgae occurred at significant rates in the presence of alternative food sources in the sediment (detritus, larvae, benthic microalgae). Grazing rates were higher for N‐enriched macroalgae; however, all snails lost weight when grazing on macroalgae alone, indicating that U. lactuca was a poor food source. The presence of sediment from two sites, a sandy lagoon and an adjacent organic‐rich muddy tidal creek, did not affect consumption of macroalgae in microcosm experiments, and the grazing snails were capable of significantly reducing macroalgal biomass associated with both sediment types. Grazing rates by this omnivore were as high as 10.83 mg wet weight·individuals−1·d−1 and were similar to those recorded for herbivorous species. In situ loss rates calculated from average grazing rates per individual and snail abundances (up to 3.5 g dry weight·m−2·d−1) also were comparable with those calculated for herbivorous species. This level of grazing could remove up to 88% of new macroalgal growth at the lagoon site where the N supply was relatively low but had a much smaller effect (18% of new growth) at the high‐nutrient creek site. Snails facilitated macroalgal growth at both sites by increasing tissue N content by 40%–80%. Consumption and digestion of macroalgae aided in the recycling of nutrients temporarily bound in the algae and resulted in enrichment of surficial sediments. Increased N sequestration in the sediments also was associated with an interruption of snail burrowing behavior due to persistent anoxia in sediments rich in decaying algal material. Our data suggest that in shallow lagoons where mud snails and benthic macroalgae coexist, grazing may influence N retention in macroalgal biomass.
REAPPRAISAL OF PHYSIOLOGICAL ATTRIBUTES OF NINE STRAINS OF DUNALIELLA (CHLOROPHYCEAE): GROWTH AND PIGMENT CONTENT ACROSS A SALINITY GRADIENT
Authors: Cifuentes Ana S. , González Mariela A. , Inostroza Ingrid , Aguilera Alejandra
Published: March 2003

Among the few taxonomic characters used to circumscribe sections within the subgenus Dunaliella are the physiological response to changes in salt concentration, which define a specific range for optimal growth, and the carotenogenic ability of the vegetative cells, responsible for the change in cell color from green to orange or red, under suboptimal culture conditions. Previous work based on molecular data from seven taxa of different sections of the subgenus showed no correlation between the genetic relationship inferred from the internal transcribed spacer RFLP data and the morphophysiological attributes in use in taxonomy. The present work was performed to experimentally reevaluate the physiological attributes in the same seven previous taxa (D. tertiolecta Butcher UTEX 999 and CCMP 1320, D. parva Lerche UTEX 1983 and CCMP 362, D. salina Teodoresco UTEX 200, D. viridis Teodoresco CONC 002, and D. peircei Nicolai et Baas Becking UTEX 2192) adding D. parva CCAP 19/9 and D. pseudosalina Massyuk et Radchenko CONC 010. Growth responses and pigment content in a wide range of NaCl concentrations were assessed. The results revealed that two strains of D. parva, two strains of D. tertiolecta, and one strain of D. peircei showed similarity in their growth responses to the whole range of salt concentrations. Dunaliella parva UTEX 1983, on the other hand, showed a growth rate pattern very different from those of their conspecifics and similar to those of D. viridis CONC 002 and D. salina UTEX 200. In relation to the pigment content, none of the strains turned orange or red in color under the whole range of salt concentrations assayed, and the total carotenoids to chlorophyll ratios were always lower or equal to 1.0. These results reaffirm the validity of the physiological attributes used to discriminate sections within the subgenus Dunaliella and show correlation with the previous molecular data, but stress the need for relocating some strains into different sections.
CARRAGEENANS BIOSYNTHESIZED BY CARPOSPOROPHYTES OF RED SEAWEEDS GIGARTINA SKOTTSBERGII (GIGARTINACEAE) AND GYMNOGONGRUS TORULOSUS (PHYLLOPHORACEAE)1
Authors: Estevez José Manuel , Ciancia Marina , Cerezo Alberto Saúl
Published: March 2003

Carrageenans biosynthesized by gametophytic and tetrasporic plants of seaweeds belonging to the Gigartinaceae and Phyllophoraceae are different: gametophytes produce carrageenans of the kappa family, whereas lambda‐carrageenans are extracted from tetrasporophytes. For Gigartina skottsbergii Setchell and Gardner and Gymnogongrus torulosus Hooker et Harvey, mature cystocarps were isolated and carrageenans were extracted. Structural determination by methylation analysis, Fourier transform infrared spectroscopy, and 13C‐NMR spectroscopy showed that they were kappa/iota‐carrageenans. For the extract obtained from cystocarps of Gigartina skottsbergii with water at room temperature, the ratio kappa:iota was 1:0.30 and at 90° C was 1:0.43; significant amounts of precursors were also present. The extract obtained from cystocarps of Gymnogongrus torulosus at 90° C showed prevalence of iota‐carrageenans (ratio kappa:iota 1:1.21). These extracts are similar to the polysaccharides produced by gametophytes of these seaweeds. For Gigartina skottsbergii, it was possible to separate the pericarpic tissue from the carposporophyte. Thus, they were extracted separately, and the carrageenans isolated were studied as described before, obtaining similar conclusions. These results clearly show that whereas the carposporophytes are located inside the cystocarp, they produce carrageenans of the kappa family despite of being diploid cells.
β‐TUBULIN GENE OF PORPHYRA PURPUREA ( RHODOPHYTA)1
Authors: MacKay Ron M. , Gallant Jeffrey W.
Published: March 2003

The life cycle of the marine red alga Porphyra purpurea (Roth) C. Agardh includes a shell‐boring filamentous sporophyte and a leafy gametophyte. A single intronless gene for the microtubule protein β‐tubulin was discovered by molecular cloning of P. purpurea cDNA and genomic DNA. This gene, named TubB1, encodes a β‐tubulin with a divergent amino acid sequence, showing 74% identity with the conserved β‐tubulin of Chlamydomonas reinhardtii P. A. Dangeard. Southern hybridization analysis of nuclear DNA confirmed that P. purpurea has a single TubB1 gene. Transcripts (1.8 kb) of TubB1 are present in the sporophyte and gametophyte. Codon bias indicates strong expression of TubB1. The divergent nature of the TubB1 genes suggests that the absence of axonemal structures has allowed substantial genetic drift in red algal β‐tubulin genes.
MOLECULAR EVOLUTION OF EUGLENOZOAN PARAXONEMAL ROD GENES par1 AND par2 COINCIDES WITH PHYLOGENETIC RECONSTRUCTION BASED ON SMALL SUBUNIT rDNA DATA1
Authors: Talke Susanne , Preisfeld Angelika
Published: March 2003

Emergent flagella of Euglenozoa consist of two prominent structural elements: the axoneme built by microtubules with motor proteins to enable the movement of the flagellum and a highly organized protein structure of unknown function, called the paraxonemal rod (PAR), which consists of two major proteins paralleling the axoneme of euglenid and kinetoplastid emergent flagella. These flagellar structures are considered apomorphic characters of Euglenozoa. We examined the evolution of the genes par1 and par2 encoding the two major proteins, where we could show that these proteins are encoded by two very similar genes found in kinetoplastids and euglenids. The branching pattern indicated a gene duplication before the diversification into euglenids and kinetoplastids. In the clades of the genes, subtrees of euglenid and kinetoplastid monophyla arose. Both genes showed strong genetic diversity with biased GC content at taxon rather than at gene level. We also examined phylogenies inferred from PAR genes that are well in agreement with established small subunit rDNA analyses. Both showed further separation of the euglenid subtree into primary osmotrophs and a phototrophic clade, including secondarily derived osmotrophs.
CHEMICAL MEDIATION OF COLONIZATION OF SEAWEED SURFACES1
Authors: Steinberg Peter D. , De Nys Rocky
Published: March 2003

The surfaces of macroalgal thalli are colonized by planktonic propagules (larvae, spores, cells, etc.) from a wide diversity of eukaryotes and prokaryotes. Colonization (here defined broadly to include processes such as settlement, attachment, metamorphosis, biofilm formation, and infection) of seaweed surfaces can be both induced and inhibited by metabolites produced at those surfaces. However, detailed examples of chemically mediated interactions at seaweed surfaces for which chemical cues have been characterized, quantifiedin situ, a biological effect determined, and the consequences to the demography of the seaweeds or colonizers demonstrated are very rare. Here we briefly review the literature on both deterrents (“natural antifoulants”) and inducers of colonization and on interactions at seaweed surfaces between the hosts and associated bacterial biofilms. One theme that emerges is the strong need to integrate ecology, cell biology, and chemistry to understand the distribution of surface‐active moleculesin situand their ecological consequences. This multidisciplinary approach is further emphasized for research on biofilms on seaweeds, where recently developed molecular tools for characterizing bacterial communities are opening up an entire new area of marine chemical ecology. Finally, we emphasize an integrated approach to the topic, as we believe that many aspects of somewhat disparate fields including, for example, induction of larval settlement, algal pathogenesis, and the molecular biology of bacterial signaling can be usefully viewed within the overall framework of chemical mediation of surface colonization.
Phylogeny of the Gracilariaceae (Gracilariales, Rhodophyta) Inferred From rbcL Sequence Analysis: Taxonomic Implications
Authors: Gurgel C. F. D.
Published: March 2003

This research promotes the correlation of molecular phylogenies and morphological data with biogeographic hypotheses for the economically important agarophyte family Gracilariaceae. The generic concepts are evaluated on the basis of chloroplast‐encoded rbcL sequences from 150+ specimens worldwide. The results confirm the monophyly of the family and identifies three large clades, one of which corresponds to the ancestral, antiboreal genera Curdiea and Melanthalia, one to Gracilariopsis, and one to Gracilaria sensu lato which identifies at least nine distinct independent evolutionary lineages, including Hydropuntia. The species currently attributed to Hydropuntia comprise two well‐supported clades with different biogeographic patterns, one composed of Indo‐Pacific species and the other of atlantic species. At least the three most basal clades within Gracilaria sensu lato deserve to be considered distinct genera: (1) a new genus centered around G. chilensis and G. tenuistipitata; (2) Hydropuntia sensu stricto encompassing pacific species (G. urvilleii, G. eucheumatoides, G. edulis), and (3) a new genus composed of atlantic species currently placed in Hydropuntia (G. cornea, G. crassissima, G. usneoides). Cystocarp features within the Gracilaria senso lato clades are more phylogenetically informative than do male characters. The henriquesiana‐type of spermatangial concepacle appeared independently at least four times. The textorii‐type of male apparatus is represented in two distinct clusters of Gracilaria. Several unknown and poorly described species are being described, resurrected from synonymy or re‐circumscribed. G. textorii seems to be part of a major complex of flat species in the Pacific Ocean. The current number of Gracilariaceae is underestimated in the Western Atlantic due to convergence in habit type and the apparent homoplasy in vegetative and reproductive anatomy.
A Randomized Clinical Trial of Outpatient Geriatric Evaluation and Management
Authors: Boult Chad , Boult Lisa B. , Morishita Lynne , Dowd Bryan , Kane Robert L. , Urdangarin Cristina F.
Published: March 2003

OBJECTIVES: To measure the effects of outpatient geriatric evaluation and management (GEM) on high‐risk older persons' functional ability and use of health services.

DESIGN: Randomized clinical trial.

SETTING: Ambulatory clinic in a community hospital.

PARTICIPANTS: A population‐based sample of community‐dwelling Medicare beneficiaries age 70 and older who were at high risk for hospital admission in the future (N = 568).

INTERVENTION: Comprehensive assessment followed by interdisciplinary primary care.

MEASUREMENTS: Functional ability, restricted activity days, bed disability days, depressive symptoms, mortality, Medicare payments, and use of health services. Interviewers were blinded to participants' group status.

RESULTS: Intention‐to‐treat analysis showed that the experimental participants were significantly less likely than the controls to lose functional ability (adjusted odds ratio (aOR) = 0.67, 95% confidence interval (CI) = 0.47–0.99), to experience increased health‐related restrictions in their daily activities (aOR = 0.60, 95% CI = 0.37–0.96), to have possible depression (aOR = 0.44, 95% CI = 0.20–0.94), or to use home healthcare services (aOR = 0.60, 95% CI = 0.37–0.92) during the 12 to 18 months after randomization. Mortality, use of most health services, and total Medicare payments did not differ significantly between the two groups. The intervention cost $1,350 per person.

CONCLUSION: Targeted outpatient GEM slows functional decline.
Geriatricians Health Survey 2000
Authors: Watts David , Damasco‐Ty Edeson , Ryan Frank , Goodman Brian
Published: March 2003

OBJECTIVES: To characterize geriatricians' preventive health behaviors including vitamin/supplement use, exercise, smoking, alcohol use, and weight control.

DESIGN: Mailed questionnaire.

SETTING: United States.

PARTICIPANTS: Two thousand six hundred eleven U.S. physicians certified as having added qualifications in geriatric medicine and who were members in the American Geriatrics Society; 1,524 returned completed questionnaires (58%).

MEASUREMENTS: Rates of supplement use and recommendations, preventive health visits, advance directive completion, exercise, religious service attendance, smoking, alcohol use, and amount of adult weight gain.

RESULTS: Most responding geriatricians took at least one vitamin supplement: 50% vitamin E, 50% a multivitamin (MVI), and 31% vitamin C. Calcium ingestion was common among women. Other supplement use was uncommon: ginkgo compounds were consumed by 47 (3%), and 77 (5%) took a variety of other nonvitamin supplements. Over 90% recommended vitamins, especially multivitamins and vitamin E, at least sometimes. Recommendations for ginkgo (38%) and St. John's wort (33%) were also common. Almost half of respondents had completed a formal advance directive. Exercise was practiced at least weekly by 88%. Cigarette smoking was rare (1%), but at least occasional alcohol use was common (85%). Most of respondents were men (74%), and 35% had completed fellowship training.

CONCLUSION: Vitamin/supplement use was common among responding geriatricians but not universal. Respondents often recommended MVI, vitamin E, and vitamin C, but were less likely to consume or recommend other supplements. The most common preventive health behavior among our respondents was exercise.
Persistent Mobility Deficit in the Absence of Deficits in Activities of Daily Living: A Risk Factor for Mortality
Authors: Khokhar Shafiq R. , Stern Yaakov , Bell Karen , Anderson Karen , Noe Enrique , Mayeux Richard , Albert Steven M.
Published: March 2003

OBJECTIVES:

To investigate the extent to which self‐reported mobility deficit in the absence of impairment in activities of daily living (ADL) is associated with elevated mortality risk.

DESIGN:

Prospective cohort study, with annual assessments of mobility and ADL status and ongoing monitoring of vital status.

SETTING:

Population‐based cohort drawn from Medicare enrollees in New York City.

PARTICIPANTS:

One thousand two hundred ninety‐eight older adults reporting functional status at baseline (1992–1994) and 2 years later.

MEASUREMENTS:

Subjects reported mobility (e.g., walking, climbing stairs, and rising from a chair) and ADL (e.g., bathing, toilet use, dressing, grooming, and feeding) limitations. Two‐year functional status trajectories were noted. We used two additional follow‐up periods, at 2 and 4 years, to examine the likelihood that older people with mobility deficit may face an increased risk of death without first passing through a state of enduring ADL disability.

RESULTS:

At 2 years, 12.7% had incident mobility deficit without ADL disability, and 21.3% were persistently disabled in mobility without ADL disability. Relative to subjects free of disability at baseline and follow‐up, risk of mortality in the incident mobility deficit group was elevated at 2 and 4 years but did not achieve statistical significance. By contrast, for subjects with persistent mobility impairment who did not report ADL impairment, the mortality risk was significantly elevated both at 2 years (relative risk (RR) = 2.5; 95% confidence interval (CI) = 1.1–5.7)) and 4 years (RR = 2.9; 95% CI = 1.7–4.9)) of follow‐up. Mortality was significantly elevated in this group in analyses restricted to respondents with no or only one comorbid condition.

CONCLUSION:

Continuing, self‐reported mobility impairment in the absence of ADL deficit is a risk factor for mortality. Older people with self‐reported mobility deficit face an increased risk of mortality without first passing through enduring states of ADL disability. J Am Geriatr Soc 49:1539–1543, 2001.