bluuebunny/crossref_metadata_2025_split huggingface dataset:
IMMUNOLOGICAL AND ULTRASTRUCTURAL CHARACTERIZATION OF THE PHOTOSYNTHETIC COMPLEXES OF THE PROCHLOROPHYTE PROCHLOROCOCCUS (OXYCHLOROBACTERIA)
Authors: Lichtlé Christiane , Thomas Jean Claude , Spilar Agnès , Partensky Frédéric 
Published: October 2004

ABSTRACT Ultrastructural features and immunological properties of some thylakoid proteins were examined in two strains of the prochlorophyte Prochlorococcus and compared to those of other photosynthetic prokaryotes and eukaryotes. Both strains exhibited two or three rows of tightly appressed thylakoidal membranes, located at the cell periphery. However, thylakoids were concentrically arranged in the strain from the Sargasso Sea (SARG) and horseshoe‐shaped in the Mediterranean isolate (CCMP 1378). Although lacking phycobilisomes, both cell types shared with cyanobacteria the presence of carboxysome‐like structures and glycogen granules as storage compounds. The main thylakoid polypeptides separated by sodium dodecyl sulfate—polyacrylamide gel electrophoresis were characterized by Western blotting using several antibodies. The 30‐kDa polypeptide of the light‐harvesting complex (LHC) of Prochlorococcus showed a weak positive immunological cross‐reaction with an antibody raised against the 32‐kDa apoprotein of the LHC of the prochlorophyte Prochlorothrix hollandica. In contrast, it showed no immunological relationships with the chlorophyll a/b (Chl a/b) LHCs of green algae and higher plants. Protein membranes from Prochlorococcus strongly cross‐reacted with antibodies raised against reaction center polypeptides of photosystems II and I (PSs II and I) of other photosynthetic organisms, confirming the high degree of conservation of these basic compounds of the photosynthetic machinery during evolution. Immunolocalization of thylakoid proteins showed that the LHC proteins, the major PS II reaction center proteins (CP 43 and D2), and the PS I reaction center proteins were equally distributed within the thylakoid membranes in contrast to the segregation observed in higher plants and green alga thylakoids. We also identified ribulose‐1, 5‐bisphosphate carboxylase/oxygenase in the carboxysomes. These results suggest that Prochlorococcus is more closely related to cyanobacteria than to green plastids even though it contains Chl b.
CHROMOPHYTE PLASTID 16S RIBOSOMAL RNA GENES FOUND IN A CLONE LIBRARY FROM ATLANTIC OCEAN SEAWATER
Authors: Rappe' Michael S. , Kemp Paul F. , Giovannoni Stephen J. 
Published: October 2004

ABSTRACT In recent years, the cloning of ribosomal RNA genes from natural plankton communities has provided insight into the biodiversity of marine bacterioplankton. Small eukaryotic phytoplankton, like bacterioplankton, can be difficult to cultivate or identify routinely by morphological characteristics. We used bacteria‐specific 16S rRNA primers to amplify genes from picoplankton samples collected on 0.2–μm filters by filtration from a depth of 10 m in the pelagic region over the continental shelf off Cape Hatteras, North Carolina. Nucleic acid sequencing and probe hybridization revealed that chromophyte plastid genes comprised 25% of the genes in a library of 170 clones. The plastid genes belonged to two groups within the Chromophyta: the Prymnesiophyceae and the Bacillariophyceae. Comparisons revealed substantial diversity among the bacillariophyte gene sequences, but the species from which the genes originated could not be identified because few sequences from cultured bacillariophytes are available. The prymnesiophyte genes could not be identified either, although they were most similar (similarity = 0.94) to plastid genes from the coccolithophorid Emiliania huxleyi (Lohmann) Hay and Mohler strain PML92D. These results provide evidence of abundant chromophyte plastid 16S rRNA genes in the water over the continental shelf off Cape Hatteras. The results also suggest that plastid 16S rRNA genes may provide suitable genetic markers for studying phytoplankton biodiversity and biogeography.
INTERGENERIC HYBRIDIZATION AMONG FIVE GENERA OF THE FAMILY LESSONIACEAE (PHAEOPHYCEAE) AND EVIDENCE FOR POLYPLOIDY IN A FERTILE PELAGOPHYCUS×MACROCYSTIS HYBRID
Authors: Lewis Raymond J. , Neushul Michael 
Published: October 2004

ABSTRACT Hybridization was attempted by combining gametophytes between intergeneric pairs among the following taxa in the Lessoniaceae: Macrocystis pyrifera (L.) C. Agardh, M. integrifolia Bory, M. angustifolia Bory, Pelagophycus porra (Leman) Setch., Nereocystis luetkeana (Mert.) Post & Rupr., Dictyoneurum californicum Rupr., and Dictyoneuropsis reticulata (Saud.) Smith. Hybrid sporophytes were produced in some combinations involving Macrocystis × Pelagophycus and Macrocystis × Dictyoneurum, and in all combinations of Dictyoneuropsis × Dictyoneurum. This is the first report of intergeneric hybrids involving Dictyoneurum. Gametophytes of P. porra had 16–24 chromosomes. Gametophytes from a fertile Macrocystis‐Pelagophycus hybrid were crossed with Macrocystis and Pelagophycus gametophytes. Hybrid male gametophytes and Pelagophycus female gametophytes produced sporophyte progeny, but hybrid males with Macrocystis females did not. A single hybrid female gametophyte did not produce gametophytes in combination with hybrid males, Pelagophycus males or Macrocystis males. The hybrid gametophytes had approximately 30 chromosomes. It is hypothesized that the hybrid is an alloploid, containing a complete set of Macrocystis and Pelagophycus chromosomes, which may have allowed meiosis and sporogenesis to proceed normally in the hybrid sporophyte found in the sea. Thus, reproductive isolating mechanisms appear to operate at both pre‐ and postzygotic stages, and both can be overcome in intergeneric hybrids.
ISOLATION AND FLOW CYTOMETRIC CHARACTERIZATION OF PROTOPLASTS FROM MARINE MACROALGAE
Authors: Corzo Alfonso , Vergara Juan J. , García‐Jiménez M. Carmen 
Published: October 2004

ABSTRACT Protoplasts were isolated from Ulva rigida C. Agardh (Chlorophyta) and two species of Rhodophyta, Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Folvik and Gracilaria tenuistipitata Chang et Xia var. liui with minor modifications (the inclusion of 0.01% agarase in the set of cell‐wall‐degrading enzymes for the two red algae). Flow cytometric characteristics of freshly isolated protoplasts were determined on a FACScan flow cytometer (FC). The most useful parameters for characterizing protoplasts from marine algae were forward angle light scatter (FSC), orange fluorescence (FL2) and red fluorescence (FL3). Protoplasts from all the species were easily distinguishable when their FSC, FL2, and FL3 signals were combined in the bivariate plots FL3 vs. FSC and FL3 us. FL2. Two alternative techniques to help identify protoplasts from debris in the FC computer screen were developed (for FC without sorting capability). Both techniques were based on the ability of new FCs to record time. The first one was based on the induction of rapid changes of cell volume in response to osmotic stress. Only intact protoplasts responded to changes in the osmotic pressure. The second one was based on the uptake and hydrolysis of fluorescein diacetate by intracellular esterases. Viable protoplasts showed a hyperbolic accumulation of fluorescein with time. Semimaximal fluorescein accumulation was attained in 30.5±9.5 s. Debris was easily recognized since, contrary to protoplasts, it did not show a time‐dependent accumulation of fluorescein.
FACTORS ASSOCIATED WITH HOST SPECIFICITY IN SPOROCLADOPSIS NOVAE‐ZELANDIAE (CHLOROPHYTA)1
Authors: Correa Juan A. , Martínez Enrique A. 
Published: October 2004

ABSTRACTThis study tests the hypotheses that substrate stability and rugose microtopography are the main factors that determine the tissue‐specific epiphytism in the chlorophyte Sporocladopsis novae‐zelandiae Chapman. Both in vitro and field experiments showed that the epiphyte did not develop on stable algal surfaces nor on artificial (smooth or rugose) substrata. In field experiments, however, other macroalgae settled more abundantly on rugose substrata. Similarly, our field experiments did not support the hypothesis that the physical environment provided by the spatial location of the host in the intertidal or subtidal was a relevant factor associated with specificity. In contrast, our laboratory experiments suggested that some component of the host cell wall might trigger the formation of penetrating rhizoids. These did not develop in isolated cultures of the epiphyte but were detected when the epiphyte contacted its natural host. Also, preliminary results showed that rhizoid‐like structures developed, although at very low frequency, only in plants grown in culture medium containing a crude extract of sorus cortical tissue.
RECONSIDERING PREY SPECIALIZATIONS IN AN ALGAL‐LIMPET GRAZING MUTUALISM: EPITHALLIAL CELL DEVELOPMENT INCLATHROMORPHUM CIRCUMSCRIPTUM(RHODOPHYTA, CORALLINALES)1
Authors: Pueschel Curt M. , Miller Theresa J. 
Published: October 2004

ABSTRACTThe association of the limpetTectura testudinalis(Müller 1776) and the crustose coralline red algaClathromorphum circumscriptum(Strömfelt) Foslie (Melobesioideae) is considered a species‐specific mutualism between grazer and prey. Anatomical features ofC. circumscriptum, especially those associated with epithallial cells, have been viewed as being unusual and directly related to the mutualism. Transmission and scanning electron microscopic methods were used to investigate the structure and development of epithallial cells inC. circumscriptum.Contrary to prior reports, terminal cells of the epithallial filaments ofC. circumscriptumundergo senescence and shedding much like epithallial cells in other members of the Corallinales; hence, multicellular epithallial filaments did not evolve in this alga simply because epithallial cells were unable to slough. Although epithallial cells in many coralline algae are lightly calcified, those inC. circumscriptumare heavily mineralized, more so than the underlying initial cells and cells comprising the cortex. As in other coralline algae, starch is absent from the epithallial cells ofC. circumscriptum.The feature of having abundant chloroplasts in the epithallial cells of C. circumscriptum is shared by other species with multi‐cellular epithallial filaments and transiently by species with single epithallial cells. Except for having a thick epithallus, a feature found in other genera and in other species ofClathromorphum, the anatomy ofC. circumscriptumis unexceptional.
LIGHT AND ELECTRON MICROSCOPY OF GRAZING BY POTERIOOCHROMONAS MALHAMENSIS (CHRYSOPHYCEAE) ON A RANGE OF PHYTOPLANKTON TAXA1
Authors: Zhang Xiaoming , Watanabe Makoto M. , Inouye Isao 
Published: October 2004

ABSTRACTGrazing of fluorescent latex beads, bacteria, and various species of phytoplankton by Poterioochromonas malhamensis (Pringsheim) Peterfi (about 8.0 μm in diameter) was surveyed. The alga ingested fluorescent beads and various live or killed and nomnotile or motile organisms including bacteria, blue‐green algae, green algae, diatoms, and chrysomonads. The size range of grazed prey was from 0.1 to 6.0 μm for latex beads and from 1.0 μm (bacteria) to about 21 μm (Carteria inverse) for organisms. As many as 17 latex beads (2.0 μm) or more than 10 Microcystis cells (5–6 μm) were ingested by a single P. malhamensis cell. Following such grazing, the cell increased in volume by up to about 30‐fold. The range of cell volume of ingested prey was from 0.52 μm3 (bacteria) to about 3178 μm3(Carteria inversa). This study demonstrates for the first time that P. malhamensis is capable of grazing algae 2–3 times larger in diameter than its own cell and of grazing intact motile algae. Poterioochromonas malhamensis is an omnivorous grazer. Food vacuole formation and digestion processes were examined. The membrane that was derived from the plasma membrane and surrounded the prey disappeared sometime after ingestion. The food vacuole was then formed by successive fusion of numerous homogeneous vesicles accumulated around the prey. The prey was enclosed in a single membrane‐bound food vacuole and then digested.
EFFECTS OF CADMIUM ON GROWTH AND SUPEROXIDE DISMUTASE ACTIVITY OF THE MARINE MICROALGA TETRASELMIS GRACILIS (PRASINOPHYCEAE)1
Authors: Okamoto Oswaldo Keith , Asano Cristina S. , Aidar Elisabeth , Colepicolo Pio 
Published: October 2004

ABSTRACTMarine planktonic algae are frequently exposed to metallic contaminants. Because heavy metals can be assimilated and accumulated by algal cells, they can then be transferred to higher trophic levels of food chains. We studied the effects of cadmium on protein production and the growth of the marine prasinophyte Tetraselmis gracilis (Kylin) Butcher. By means of toxicological assays, we estimated the LC50 of cadmium as 3.2 ppm and 1.8 ppm after 48 h and 96 h of exposure to this heavy metal, respectively. The growth curves and survival percentages of cell cultures in the presence of cadmium were determined, and a proportional reduction of both parameters with increasing metal concentrations was found. When chronically exposed to sublethal concentrations of cadmium, T. gracilis contained high levels of superoxide dismutase (SOD) activity, one of the main enzymes of the cell's antioxidant defense mechanism. Under these growth conditions, total SOD activity in crude extracts was increased by 41% (at 1.5 ppm) and 107% (at 3.0 ppm). Assays of SOD activity in nondenaturing polyacrylamide gels also showed a similar induction by cadmium. These results show that cadmium has potentially toxic properties since it significantly inhibited the growth of T. gracilis at low concentrations and promoted the induction of SOD activity, suggestive of an oxidative stress state. Besides being the first report of SOD in T. gracilis, this work describes experimental evidence of SOD induction by cadmium in this species.
WHY DO DINOFLAGELLATES HAVE LOWER GROWTH RATES?1
Authors: Tang Evonne P. Y. 
Published: October 2004

ABSTRACTDinoflagellates have substantially lower growth rates than other taxa of similar size. These low growth rates have been suggested to reflect the lower chlorophyll a to carbon ratio (Chl a:C) in dinoflagellates, but that speculation has never been widely tested. This study tests if the variations in growth rates among taxa are related to differences in Chl a:C using published data. I collected 92 data entries from the literature representing 31 species, mostly from two divisions (Chrysophyta and Pyrrophyta), and found a significant relation (r2= 0.39) between growth and Chl a:C. Since Chl a:C is almost independent of C content, I also developed a growth model using both C and Chl a:C. Together, the two variables explain 68% of variation in algal growth. However, a further 6.4% of the variance in growth can still be attributed to phyletic differences. Low Chl a:C is only a partial explanation for the low growth rates of the dinoflagellates.
FLUORESCENT LABELLING OF THE CYTOSKELETON IN CERAMIUM STRICTUM (RHODOPHYTA)1,2
Authors: Garbary David J. , McDonald A. Rosa 
Published: October 2004

ABSTRACTUsing rhodamine‐phalloidin to detect F‐actin/microfilaments and indirect immunofluorescence to detect tubulin/microtubules, we studied the cytoskeleton in axial cells of Ceramium strictum Harv., especially microfilaments and microtubules associated with cytoplasmic strands (trabeculae) that extend longitudinally through the central vacuole. As axial cells attained mature size, trabeculae became progressively thinner, branched, and then broke down. An extensive microfilament array was present in peripheral parts of axial cells as well as in trabeculae. Microfilament arrays were highly disrupted by cytochalasin‐B; this resulted in small irregular actin structures in axial cell peripheries and occasional dense aggregations at the base of cells. No actin‐fluorescence was detected in intact trabeculae after cytochalasin‐B treatment. Microtubules formed a primary structural component in trabeculae, which were disrupted by griseofulvin (5 to 0.005 μM) but reformed after two days in griseofulvin‐free medium.
PLOIDY ANALYSIS OF THE TWO MOTILE FORMS OFCHRYSOCHROMULINA POLYLEPIS(PRYMNESIOPHYCEAE)1
Authors: Edvardsen Bente , Vaulot Daniel 
Published: October 2004

ABSTRACTIn some cultures of the flagellateChrysochromulina polylepisManton et Parke, established from cells isolated from the massive bloom in Skagerrak and Kattegat in 1988, we observed, two motile cell types. They were termed authentic and alternate cells and differed with respect to scale morphology. To investigate whether or not the two cell forms were joined in a sexual life cycle, the relative DNA content per cell and relative size of cells of several clonal cultures ofC. polylepiswere determined by flow cytometry. Percentages of authentic and alternate cells in the cultures were estimated by transmission electron microscopy.Pure authentic cultures (α) contained cells with the lowest level of DNA and were termed haploid. Two pure alternate cultures (β) contained cells with double the DNA content of authentic cells and were termed diploid. Other pure alternate cultures contained haploid cells only, or both haploid and diploid cells. Three cell types were observed, each capable of vegetative propagation: authentic haploid, alternate haploid, and alternate diploid cells. Both the haploid and diploid alternate cells were larger than the haploid authentic cells. Cultures containing diploid cells appeared unstable: cell type ratio and ploidy ratio changed during the experiment where this cell type was present, particularly when grown in continuous light. In contrast, cultures with only haploid cells remained unchanged at all growth conditions tested. Light condition may influence cell type ratio and ploidy ratio. Our attempt to induce syngamy by mixing different authentic haploid clones did not result in mating. Assuming that the authentic and alternate cell types are of the same species, the life cycle ofC. polylepisincludes three flagellated scale‐covered cell forms. Two of the cell types are haploid and may function as gametes, and the third is diploid, possibly being the result of syngamy.
DISCONTINUOUS MITOCHONDRIAL AND CHLOROPLAST LARGE SUBUNIT RIBOSOMAL RNAs AMONG GREEN ALGAE: PHYLOGENETIC IMPLICATIONS1
Authors: Nedelcu Aurora M. , Spencer David F. , Denovan‐Wright Eileen M. , Lee Robert W. 
Published: October 2004

ABSTRACTTo provide insights into the occurrence, evolution, and phylogenetic distribution of discontinuous mitochondrial and chloroplast large subunit ribosomal RNAs (LSU rRNAs) among green algae, we surveyed 12 taxa representing three classes of green algae: the Chlorophyceae, Pleurastrophyceae, and Micromonadophyceae (sensu Mattox and Stewart 1984). We present evidence that discontinuous mitochondrial and chloroplast LSU rRNAs are quite widespread among green algae. Mitochondrial LSU rRNAs appear discontinuous in zoosporic chlorophycean lineages displaying a clockwise or directly opposed configuration in their flagellar apparatus, as well as in chlorococcalean autosporic taxa phylogenetically related to them, but are continuous among zoosporic green algal lineages with a counterclockwise flagellar apparatus configuration, as well as among chlorococcalean autosporic taxa phylogenetically related to them. Chloroplast LSU rRNAs appear discontinuous in all of the lineages investigated. Discontinuous mitochondrial LSU rRNA represents a molecular trait that might have originated at or near the base of Chlorophyceae, whereas discontinuous chloroplast LSU rRNA might have developed very early in the evolutionary history of the green algal group itself. We suggest, therefore, that the presence of discontinuous mitochondrial but not chloroplast LSU rRNA can be used as an additional character in assessing phylogenetic affiliations among green algae.
ASTEROMENIA (RHODYMENIACEAE, RHODYMENIALES), A NEW RED ALGAL GENUS BASED ON FAUCHEA PELTATA1
Authors: Huisman John M. , Millar Alan J. K. 
Published: October 2004

ABSTRACT Asteromenia gen. nov. (Rhodymeniales, Rhodophyta) is proposed with a single species, Asteromenia peltata (W. R. Taylor) comb. nov. (basionym: Fauchea peltata W. R. Taylor). Thalli of the proposed new genus are stipitate with dorsiventral, peltate blades that are initially circular in shape but with age become stellate with ligulate arms. Internally, the blades have a polystromatic medulla of large, hyaline cells, grading into a cortex of smaller, pigmented cells. Clusters of translucent cells occur on the dorsal surface of the blade. Tetrasporangia are formed by transformations of intercalary midcortical cells. Mature tetrasporangia have cruciately arranged spores and are densely aggregated in the cortex, mostly on the ventral surface, but occasional tetrasporangia also arise on the dorsal surface. Carpogonial branches are four‐celled and arise on inner cortical cells. Auxiliary cells are borne on auxiliary mother cells attached to supporting cells of the carpogonial branches. Cystocarps are protuberant, with well‐developed, ostiolate pericarps that often have extended, proboscis‐like necks. The new genus differs from the previously described peltate or dorsiventral taxa in the Rhodymeniaceae by its polystromatic medulla (Maripelta and Sciadophycus have a monostromatic medulla), intercalary tetrasporangia formed in an unmodified cortex, and four‐celled carpogonial branches (Halichrysis, as typified by H. depressa (J. Agardh) F. Schmitz, has terminal tetrasporangia in nemathecia and three‐celled carpogonial branches).
PFIESTERIA PISCICIDA GEN. ET SP. NOV. (PFIESTERIACEAE FAM. NOV.), A NEW TOXIC DINOFLAGELLATE WITH A COMPLEX LIFE CYCLE AND BEHAVIOR1
Authors: Steidinger Karen A. , Burkholder JoAnn M. , Glasgow Howard B. , Hobbs Cecil W. , Garrett Julie K. , Truby Earnest W. , Noga Edward J. , Smith Stephen A. 
Published: October 2004

ABSTRACTThe newly described toxic dinoflagellate Pfiesteria piscicida is a polymorphic and multiphasic species with flagellated, amoeboid, and cyst stages. The species is structurally a heterotroph; however, the flagellated stages can have cleptochloroplasts in large food vacuoles and can temporarily function as mixotrophs. The flagellated stage has a typical mesokaryotic nucleus, and the theca is composed of four membranes, two of which are vesicular and contain thin plates arranged in a Kofoidian series of Po, cp, X, 4′, 1a, 5″, 6c, 4s, 5″′, and 2″″. The plate tabulation is unlike that of any other armored dinoflagellate. Nodules often demark the suture lines underneath the outer membrane, but fixation protocols can influence the detection of plates. Amoeboid benthic stages can be filose to lobose, are thecate, and have a reticulate or spiculate appearance. Amoeboid stages have a eukaryotic nuclear profile and are phagocytic. Cyst stages include a small spherical stage with a honeycomb, reticulate surface and possibly another stage that is elongate and oval to spherical with chrysophyte‐like scales that can have long bracts. The species is placed in a new family, Pfiesteriaceae, and the order Dinamoebales is emended.
AULACOSEIRA SKVORTZOWII SP. NOV. (BACILLARIOPHYTA), A POORLY UNDERSTOOD DIATOM FROM LAKE BAIKAL, RUSSIA1
Authors: Edlund Mark B. , Stoermer Eugene F. , Taylor Christine M. 
Published: October 2004

ABSTRACT Aulacoseira skvortzowii sp. nov. is a diatom taxon present in modern plankton assemblages and sedimentary deposits from Lake Baikal, Russia. It has been previously reported as A. islandica (O. Müll.) Simonsen, A. islandica ssp. helvetica (O. Müll.) Simonsen, a sporangial frustule of A. baicalensis (K. Meyer) Simonsen, and Aulacoseira “spore”. However, its microstructure, ecology, and ability to form true resting spores provide ample criteria to describe this diatom as Aulacoseira skvortzowii sp. nov.