bluuebunny/crossref_metadata_2025 huggingface dataset:
CHARACTERIZATION OF PHYCOCYANIN‐DEFICIENT PHYCOBILISOMES FROM A PIGMENT MUTANT OF PORPHYRIDIUM SP. (RHODOPHYTA)
Authors: Ritz Mathilde , Lichtlé Christiane , Spilar Agnès , Joder Annette , Thomas Jean‐Claude , Etienne Anne‐Lise
Published: March 2003

The structure and function of phycobilisomes in the rhodophyte Porphyridium sp. were investigated by comparing the properties of the wild type with a pigment mutant called C12. When grown under low light, cells of C12 were bright orange, while wild‐type cells were deep red. The results obtained from a characterization of purified phycobilisomes of the mutant C12 led us to propose the existence in Porphyridium sp. phycobilisomes of two types of rods, some containing only phycoerythrin and others containing phycoerythrin bound to phycocyanin, which is in turn linked to the core by the linker LRC. By studying the partitioning of phycobiliproteins between phycobilisomes and pools of free phycobiliproteins, we found that phycocyanin in the C12 mutant was only present in the pool of free proteins and that its specific linker, LRC, was totally absent. Phycoerythrin was present in the free pool and in the purified phycobilisomes as well. One of the three specific phycoerythrin linkers γ was missing. In light of the fact that in the C12 mutant, the linker LRC is absent and that there is no phycocyanin bound to the phycobilisomes, we propose that the rods in the mutant contain only phycoerythrin. These phycobilisomes are nevertheless functional and exhibit an efficient excitation transfer from phycoerythrin directly to allophycocyanin. Electron microscopy showed the purified phycobilisomes of C12 to be less dense than those of the wild type. This change was attributed to the disappearance of the rods containing the combination phycocyanin/phycoerythrin. Light still regulates phycobiliprotein synthesis in the mutant, as shown by the change in the color of the culture, which turned green‐yellow when cells were shifted from low light to high light growth conditions. Light also regulates the structure of the phycobilisomes, which have fewer rods under high light growth conditions.
PHYLOGENY OF THE SUBFAMILY SCOTIELLOCYSTOIDEAE (CHLOROPHYCEAE, CHLOROPHYTA) AND RELATED TAXA INFERRED FROM 18S RIBOSOMAL RNA GENE SEQUENCE DATA
Authors: Hanagata Nobutaka
Published: March 2003

Nuclear‐encoded small subunit ribosomal RNA gene (18SrDNA) sequences were determined for Coelastrella multistriata (Trenkwalder) Kalina et Punčochářová, two species of Scotiellopsis (S. oocystiformis (Lund) Kalina et Punčochářová and S. terrestris (Reisigl) Kalina et Punčochářová) and two species of Muriella (M. aurantiaca Vischer and M. terrestris Boye‐ Petersen). Coelastrella and Scotiellopsis are members of the subfamily Scotiellocystoideae, and Muriella is a member of the subfamily Chlorelloideae in the family Chlorellaceae. Phylogenetic trees were constructed based on these sequence data and on previously known 18SrDNA sequences of 25 taxa. Coelastrella and Scotiellopsis were closely related to each other and formed a cluster with Scenedesmus vacuolatus (Shihira et Krauss) Kessler et al. This cluster shared a monophyletic ancestry with other Scenedesmus species. Muriella aurantiaca formed a sister relationship with the monophyletic lineage of Scenedesmus. However, another species, M. terrestris, was placed in the Trebouxiophyceae and was strongly related to Chlorella. The genus Mychonastes belonging to the Scotiellocystoideae was also not monophyletic. This study suggests that the subfamily Scotiellocystoideae should be removed from the Chlorellaceae.
DIVERSITY AMONG TETRASPORALEAN TAXA: EVIDENCE FROM ULTRASTRUCTURE AND MOLECULES
Authors: Moreland A. , Buchheim  , Buchheim J.A.
Published: March 2003

Recent phylogenetic studies of tetrasporalean exemplars using 18S rDNA revealed the extent of diversity among taxa in this non‐monophyletic group (Booton et al. 1998). In particular, two distinct tetrasporalean lineages were identified; one group allied with chlamydomonadalean taxa and the other group comprising taxa now placed in a separate order, the Chaetopeltidales. Using these observations as a framework, a new investigation of diversity among a broader sampling of putative tetrasporalean genera (e.g. Asterococcus, Chloranomala, Chlorophysema, Gloeocystis, Gloeodendron, Palmella, Paulschulzia, Physocytium, Schizochlamys and Tetraspora) was undertaken. Phylogenetic studies of both 18S and 26S rDNA were compared with ultrastructural investigations of vegetative cells. Molecular phylogenetic analyses corroborate the earlier 18S rDNA results, but also reveal additional diversity. The new data raise doubts regarding the monophyly of two genera, Palmella and Tetraspora. The new data also link two enigmatic green algal genera, Physocytium and Heterochlamydomonas, in a long‐branch lineage within the Chlamydomonadales. Another enigmatic genus, Schizochlamys, is allied with Bracteacoccus in the Sphaeropleales. Lastly, Chloranomala is resolved as an ally of Paulschulzia, Tetraspora sp., and the green flagellate, Lobomonas. Comparison of pyrenoid ultrastructure generally supports the molecular phylogenetic analyses, suggesting that this non‐molecular character will be a useful marker for broad phylogenetic studies of chlamydomonadalean taxa. (Supported by NSF grant, DEB 9726588)
MODULATION OF VERY‐LONG CHAIN (C28) HIGHLY UNSATURATED FATTY ACIDS IN PROROCENTRUM MININUM (DINOPHYCEAE) BY SELENIUM
Authors: Place A. , Adolf J.E. , Lund E.
Published: March 2003

Recently, very‐long‐chain (C28) highly unsaturated fatty acids (VLC‐HUFA) were identified in seven marine dinoflagellate species (Manour et al., Phytochemistry, 1999, 50: 541–548). In general, the proportion of these fatty acids accounted for less than 2.3% of the total fatty acids in these species. As part of a study investigating the modulation of the hemolytic fatty acid 18:5n3, cultures of Prorocentrum mininum were grown in artificial seawater with varying molarities of sodium selenite (0, 1, 10, and 100 nM). Optimal growth was observed at 1 nM with this media. As expected, the level of 18:5n3 was modulated by the selenium in the culture medium (7.0 ± 0.2, 14.5 ± 0.6, 7.4 ± 0.8, and 3.9 ± 0.8% of total fatty acid, respectively), with the highest percentage found at 1 nM. Unexpectedly the level of VLC‐HUFA (28:8n3) increased to 7.3 ± 2.8% at 0 nM sodium selenite, while at all other selenite concentrations the VLC‐HUFA was less than 1%. A possible biochemical basis for this finding will be discussed.
A MOLECULAR MOTOR FOR GLIDING MOTILITY IN CYANOBACTERIA
Authors: Hoiczyk E.
Published: March 2003

Motile microorganisms either swim, by using flagella or glide over surfaces by mechanisms that are poorly understood. In cyanobacteria, gliding motility appears as a relatively slow and smooth surface‐associated translocation in the direction of the long axis of the filaments at rates up to a few micrometers a second. Many filamentous species translocate in a highly coordinated manner. Translational movements are usually accompanied by revolutions around the long axis of the filament. While moving, the cyanobacteria secrete slime which is left behind as a twisted and collapsed thin tube. The observation of the slime secretion process shows that the mucilage is formed as fine bands that emerge in close proximity to the cells cross walls. Ultrastructural studies have revealed that the cyanobacteria possess at their cross walls complex, pore‐like organelles, which might be involved in slime secretion. As each cell possess two different sets of pores pointing in opposite direction, the coordinated activity of these structures could explain how the filament can reverse the direction of locomotion. Furthermore, ultrastructural studies have shown that rotating cyanobacteria possess cell surfaces formed by parallel, helically arranged surface fibrils. As the arrangement of these fibrils corresponds with the path of the filaments during locomotion, it might be imaginable that these fibrils serve as screw thread guiding the rotation of the filaments, with the necessary thrust for locomotion being derived from the secretion of slime using the pores at the cross walls.
THE PHENOLOGY OF SEXUAL REPRODUCTION BY GREEN ALGAE (BRYOPSIDALES) ON CARIBBEAN CORAL REEFS
Authors: Clifton Kenneth E. , Clifton Lisa M.
Published: March 2003

Recent field observations of highly organized, species‐ and sex‐specific patterns of synchronous gamete release by tropical green algae (Bryopsidales) invite a variety of future studies into the ecology and life histories of an important component of tropical reef communities. This paper details sexual reproduction by 22 algal species within five common genera (Caulerpa, Halimeda, Penicillus, Rhipocephalus, and Udotea), including field observations on the spatial occurrence, timing, and color changes associated with fertility, data on gamete size and behavior, and descriptions of coincident changes in local species abundances.  Ecologically ephemeral episodes of sexual reproduction involved macroscopic changes that reliably indicated developmental state and sexual identity. The time from onset of fertility to gamete release was 36 h (Halimeda), 48 h (Caulerpa, Penicillus, and Rhipocephalus), or 96 h (Udotea). All species produced flagellated, negatively buoyant, anisogamous gametes. Microgametes of all species were similar in size; however, considerable species‐specific differences were seen in the size of macrogametes. In Caulerpa, Halimeda, and Udotea flabellum (Ellis and Solander) Lamouroux, the volumetric ratio of macrogametes to microgametes ranged from 2:1 to 45: 1, whereas more extreme levels of anisogamy (104: 1) were observed for Penicillus spp., Rhipocephalus phoenix (Ellis and Solander) Kuetzing, and other Udotea spp. The macrogametes of Caulerpa and Halimeda showed strong positive phototaxis.  Although only a subset (generally about 5%) of the thalli representing each species released gametes on a given morning, most species underwent bouts of sexual reproduction on numerous occasions during the seasonal peak of reproductive activity (March–May). As might be expected for holocarpic species, dramatic declines in local algal abundance coincided with these periods. The density of sand‐dwelling genera such as Penicillus fell by 80– 90% during this 3‐month period in 1997. Similar declines in the cover of sprawling species such as Caulerpa racemosa ((Forsskal) J. Agardh) exposed large (35–50 m2) sections of previously overgrown reef substrate.
THE MALATE DEHYDROGENASE GENE FROM BOTRYOCOCCUS BRAUNII (CHLOROPHYTA, CHLOROPHYCEAE): CLONING, SEQUENCE ANALYSIS, AND EXPRESSION IN ESCHERICHIA COLI
Authors: Vioque Javier , Sirakova Tatiana , Kolattukudy Papachan E.
Published: March 2003

The gene for malate dehydrogenase from Botryococcus braunii Kützing (Chlorophyceae) was isolated. The gene codes for a protein of 316 amino acids with a calculated molecular weight of 32.9 kDa. In the N‐terminal region, a pyridine nucleotide‐binding domain was observed. The G+C content of the gene is 65%. Six copies of the (A/G)GGCGG hexanucleotide, which forms the core binding site for the cellular transcription factor Sp1, were observed in the promoter region. Southern blot analysis showed that malate dehydrogenase is encoded by a single gene in B. braunii. Escherichia coli cells in which the B. braunii gene was expressed showed 3.6 times more activity in the conversion of oxaloacetate to malate than the noninduced ones, confirming the identity of the gene. Botryococcus braunii malate dehydrogenase has been subjected to phylogenetic analyses by the neighbor‐joining and parsimony procedures.
EVOLUTIONARY ANALYSES OF SMALL‐SUBUNIT rDNA CODING REGIONS AND THE 1506 GROUP I INTRONS OF THE ZYGNEMATALES (CHAROPHYCEAE, STREPTOPHYTA)
Authors: Besendahl Anja , Bhattacharya Debashish
Published: March 2003

We sequenced the small‐subunit (SSU) rDNA coding region and 1506 group I intron (that interrupts this gene) in Closterium ehrenbergii Menegh. ex Ralfs, Closterium littorale Gay, Cylindrocystis brebissonii (Menegh.) de Bary, Penium margaritaceum (Ehr.) de Bréb. ex Ralfs, and Staurastrum punctulatum de Bréb. and the 1506 intron in Sirogonium sticticum (J.E. Smith) Kütz. (Zygnematales). Reverse transcriptase (RT)/PCR analyses demonstrated that the 1506 introns are not present in vivo in mature rRNA. Splicing analyses in vitro showed, however, that these introns do not catalyze their own excision from the rRNA coding region. Mutation of the conserved G (ωG) to an A at the 3′ terminus of the 1506 intron of Gonatozygon aculeatum Hastings (Zygnematales) restored self‐splicing activity. This mutant intron utilized a new 3′ splice site to facilitate autoexcision. We speculate that the 3′ terminus of the wild‐type 1506 intron may be a target for a “helper” factor that facilitates the second step of splicing (exon ligation) in vivo in the Zygnematales. Phylogenetic analyses showed congruence of rDNA and intron trees confirming an ancient origin of the 1506 intron in the common ancestor of the Zygnematales. The rDNA trees were compared to those inferred from rbcL sequence analyses. These trees were in general agreement and showed polyphyly of the Mesotaeniaceae and the Zygnemataceae. The 1506 introns contain significant evolutionary signal and provided strong phylogenetic support for groups within the Zygnematales when analyzed alone or in combination with the SSU rDNA coding regions. The secondary structure of 1506 group I introns was studied to identify RNA elements that may be useful as systematic markers. This analysis showed an optional helix found in RNA domain P2 that was lost in a monophyletic group of Desmidiaceae. This helix is found in all other 1506 group I introns, including those interrupting red algal and fungal SSU rDNAs.
DEEP‐ETCH ANALYSIS OF ADHESION COMPLEXES BETWEEN GAMETIC FLAGELLAR MEMBRANES OF CHLAMYDOMONAS REINHARDTII (CHLOROPHYCEAE)
Authors: Goodenough Ursula W. , Heuser John E.
Published: March 2003

The ultrastructure of adhesion complexes between gametic flagellar membranes of Chlamydomonas reinhardtii Dangeard was analyzed using the quick‐freeze deep‐etch technique. The sexual agglutinin fibrils interact by forming hybrid fibers that frequently branch, forming extensively cross‐bridged meshworks. This pattern of interaction mimics a prominent mode of cell wall formation in Chlamydomonas, supporting the notion that the agglutinins evolved from cell wall proteins and that sexual adhesion and cell wall assembly are homologous events.
PCNA‐LIKE PROTEINS IN DINOFLAGELLATES
Authors: Leveson Alexis C. , Wong Joseph T. Y.
Published: March 2003

Dinoflagellate chromosomes are permanently condensed and lack nucleosomes. These features suggest that dinoflagellate chromosomes must have an altered structural arrangement when compared to other eukaryotes and some modified DNA replication machinery to accommodate it. To investigate this possibility, proliferating cell nuclear antigen (PCNA), an essential component of the DNA replication machinery, was chosen for closer examination. A protein in the dinoflagellate Crypthecodinium cohnii Biecheler was found to react specifically with two monoclonal antibodies raised against PCNA. The observed band had a size of 55 kDa, which is far in excess of what has been described previously. Another dinoflagellate, Gymnodinium catenatum Bravo, also displayed a band of this size; however, a third species Amphidinium carterae Hulburt, had a band of lower molecular weight. The putative PCNA homolog in C. cohnii showed a nonconstitutive expression pattern. A time‐course western blot using cells from a synchronized G1 population showed that protein levels peak during S phase of the cell cycle. Both C. cohnii and A. carterae displayed a strong nuclear localization as determined by immunofluorescence microscopy. The signal was present in a subpopulation of cells, supporting a cell‐cycle‐specific expression pattern. It is possible that the larger size of this protein in some dinoflagellates reflects the unusual cell cycle and DNA arrangement of this group.
MORPHOLOGY AND MOLECULAR ANALYSES OF THREE TOXIC SPECIES OF GAMBIERDISCUS (DINOPHYCEAE): G. PACIFICUS, SP. NOV., G. AUSTRALES, SP. NOV., AND G. POLYNESIENSIS, SP. NOV.
Authors: Chinain Mireille , Faust Maria A. , Pauillac Serge
Published: March 2003

Three new dinoflagellate species, Gambierdiscus polynesiensis, sp. nov., Gambierdiscus australes, sp. nov., and Gambierdiscus pacificus, sp. nov., are described from scanning electron micrographs. The morphology of the three new Gambierdiscus species is compared with the type species Gambierdiscus toxicus Adachi et Fukuyo 1979, and two other species: Gambierdiscus belizeanus Faust 1995 and Gambierdiscus yasumotoi Holmes 1998. The plate formula is: Po, 3′, 7", 6C, 8S, 5‴, 1p, 2"". Culture extracts of these three new species displayed both ciguatoxin‐ and maitotoxin‐like toxicities. The following morphological characteristics differentiated each species. 1) Cells of G. polynesiensis are 68–85 μm long and 64–75 μm wide, and the cell’s surface is smooth. They are identified by a large triangular apical pore plate (Po), a narrow fish‐hook opening surrounded by 38 round pores, and a large, broad posterior intercalary plate (1p) wedged between narrow postcingular plates 2‴ and 4‴. Plate 1p occupies 60% of the width of the hypotheca. 2) Cells of G. australes also have a smooth surface and are 76–93 μm long and 65–85 μm wide in dorsoventral depth. They are identified by the broad ellipsoid apical pore plate (Po) surrounded by 31 round pores and a long and narrow 1p plate wedged between postcingular plates 2‴ and 4‴. Plate 1p occupies 30% of the width of the hypotheca. 3) Cells of G. pacificus are 67–77 μm long and 60–76 μm wide in dorsoventral depth, and its surface is smooth. They are identified by the four‐sided apical pore plate (Po) surrounded by 30 round pores. A short narrow 1p plate is wedged between the wide postcingular plates 2‴ and 4‴. Plate 1p occupies 20% of the width of the hypotheca. These three newly described species were also characterized by isozyme electrophoresis and DNA sequencing of the D8–D10 region of their large subunit (LSU) rRNA genes. The consistency between species designations based on SEM microscopy and classification inferred from biochemical and genetic heterogeneities was examined among seven isolates of Gambierdiscus. Their classification into four morphospecies was not consistent with groupings inferred from isozyme patterns. Three molecular types could be distinguished based on the comparison of their LSU rDNA sequences. Although G. toxicus TUR was found to be more closely related to G. pacificus, sp. nov. than to other G. toxicus strains, the molecular classification was able to discriminate G. polynesiensis, sp. nov. and G. australes, sp. nov. from G. toxicus. These results suggest the usefulness of the D8–D10 portion of the Gambierdiscus LSU rDNA as a valuable taxonomic marker.
Oxidative metabolism by Thalassiosira weissflogii (Bacillariophyceae) of a diol‐ester of okadaic acid, the diarrhetic shellfish poisoning
Authors: Windust Anthony J. , Hu Tingmo , Wright Jeffrey L. C. , Quilliam Michael A. , McLachlan Jack L.
Published: March 2003

Previous investigations into the comparative toxicity of the diarrhetic shellfish poisoning (DSP) toxins to Thalassiosira weissflogii (Grun.) Fryxell et Hasle found that this diatom oxidatively metabolized okadaic acid diol‐ester (OA diol‐ester) to a more water‐soluble product. This oxidative transformation of OA diol‐ester by the diatom is significant for two reasons. First, it is known that dinophysistoxin‐4 (DTX‐4), the primary DSP toxin produced by the dinoflagellate Exuviaella lima (Ehr.) Butschli, will be hydrolyzed to the diol‐ester following cell rupture (e.g. ingestion by a predator). Second, it implies that the ester, an uncharged, lipophilic intermediate, can easily enter cells and therefore may play an important role in the uptake and transfer of DSP toxins through the food web. It has been suggested that the water soluble DTX‐4 may also be the form in which DSP toxins are excreted from the producing cell. Therefore, the stability of DTX‐4 was examined when incubated either in fresh seawater medium into which washed cells of E. lima were introduced or in seawater medium conditioned by E. lima cells. Rapid hydrolysis of DTX‐4 to the diol‐ester took place in both cases. Thus, regardless of the route by which DTX‐4 is liberated from the cell, either by cell disruption or excretion, the diol‐ester will be the dominant form of the toxin to challenge associated organisms. To examine the metabolism of OA diol‐ester by T. weissflogii in more detail, serial cultures of the diatom were challenged with OA diol‐ester at a concentration of 2.0 μg·mL−1. The metabolism and fate of the diol‐ester in both cellular and medium fractions were monitored over 3 days using liquid chromatography with either ultraviolet (LC‐UV) or mass spectrometric (LC‐MS) detection. During the course of the experiment, all of the diol‐ester was metabolized. LC‐MS analysis revealed the presence of multiple oxidative products of OA diol‐ester in the medium fraction, including a carboxylic acid derivative. The major metabolites were isolated in sufficient quantity to permit structural elucidation by NMR and MS. All the metabolites identified resulted from oxidation of the diol‐ester side chain with the primary sites of attack at the terminal, subterminal, and unsaturated carbons. OA was found in both cellular and medium fractions, and its production was directly correlated with the metabolism of the diol‐ester. The relative partitioning of both OA diol‐ester and its oxidation products between cells and medium supports the contention that OA diol‐ester can readily enter cells, be metabolized, and then excreted in more water‐soluble forms.
ASSAY OPTIMIZATION AND REGULATION OF UREASE ACTIVITY IN TWO MARINE DIATOMS
Authors: Peers Graham S. , Milligan Allen J. , Harrison Paul J.
Published: March 2003

An in vitro urease enzyme assay was developed for the marine diatoms Thalassiosira pseudonana Hasle et Heimdal (clone 3H) and T. weissflogii (Grunow) Fryxell et Hasle (clone Actin). This assay involves the colorimetric measurement of ammonium following the hydrolysis of urea in crude cell homogenates and it is the first assay to account for the rate of nitrogen assimilation in both species grown on urea as the sole nitrogen source. Urease activity was found to be present regardless of nitrogen source, although activities showed distinctly different patterns depending on the species examined and form of nitrogen supplied. Under nitrogen‐replete conditions, urease activity in T. pseudonana was present constitutively when grown on NH4+ and upregulated when grown on NO3− or urea. In nitrogen‐replete T. weissflogii, urease activity was present at high constitutive levels regardless of the nitrogen source and showed no upregulation. Nitrogen starvation did not upregulate activity in either species.
FINE STRUCTURE OF BIFLAGELLATE ZOOSPORES OFASTEROCOCCUS SUPERBUS(TETRASPORALES, CHLOROPHYCEAE), INCLUDING THE ABSOLUTE CONFIGURATION OF THE FLAGELLAR APPARATUS
Authors: Leonardi Patricia I. , Rodríguez María C. , Cáceres Eduardo J.
Published: March 2003

The ultrastructure of zoospores ofAsterococcus superbus(Cienk.) Scherffel was studied to provide ultrastructural data relevant to the systematic position of the genus. Our results demonstrated that the motile cells ofA. superbuswere similar to those of the tetrasporalean algae, such asTetrasporasp. andTetrasporidium javanicumMoebius.The flagellar apparatus ofA. superbushad the same clock‐wise orientation of basal bodies and the V‐shaped alignment of basal bodies asTetraspora cylindrica(Wahlb.) Ag. andT. lubrica(Roth) Ag., but differed by having rhizoplasts.The motile cells ofA. superbusdisplayed chlamydomonadal ultrastructure, similar toChlamydomonas reinhardtiiDangeard,including the absolute configuration of the flagellar apparatus. The pyrenoid matrix inA. superbus,however,showed a large lateral invagination occupied by chloroplast stroma, a characteristic that has never been observed in Chlorophyta.
SMALL SUBUNIT rDNA SEQUENCE ANALYSIS OF SYMBIOTIC DINOFLAGELLATES FROM SEVEN SCLERACTINIAN CORALS IN A TAHITIAN LAGOON
Authors: Darius H. Taiana , Martin Paul M. V. , Grimont Patrick A. D. , Dauga Catherine
Published: March 2003

The diversity of symbiotic dinoflagellates from reef‐building corals collected in the lagoon of Tahiti (South Pacific ocean) was investigated by using a molecular approach. Populations of symbionts (strains or species) of 7 coral species (Fungia scutaria, F. paumotensis Stutchbury, Pavona cactus Forskål, Leptastrea transversa Kluzinger, Pocillopora verrucosa Ellis and Solender, Montastrea curta Dana, and Acropora formosa Dana) were delimited by phylogenetic analysis of small subunit rDNA sequences. Coral P. verrucosa harbored 2 populations of symbiont SSU rDNA sequences that may correspond to two different Symbiodinium species. Corals F. scutaria and M. curta also seemed to contain two different Symbiodinium species. SSU rDNA dinoflagellate sequences from P. cactus, L. transversa, F. scutaria, F. paumotensis, and P. verrucosa were in the same phylogenetic cluster and showed low variability. For these distantly related coral species, dinoflagellate strains from the same species, rDNA paralogues from the same strain, or closely related Symbiodinium species could not be distinguished because monophyletic subgroups were not observed. SSU rDNA dinoflagellate sequences from A. formosa and M. curta were clearly different from the other Symbiodinium sequences and may represent specific species. This molecular approach highlighted a greater diversity of symbiotic dinoflagellates from corals in South Pacific (Symbiodinium groups A, B, and C) than that observed in the rest of the Pacific ocean (Symbiodinium group C). The diversity of symbiotic associations in a restricted area of the lagoon of Tahiti may reflect the complexity of interactions between species of Symbiodinium and corals.
EFFECTS OF TEMPERATURE AND IRRADIANCE ON THE SEASONAL VARIATION OF A SPIROGYRA (CHLOROPHYTA) POPULATION IN A MIDWESTERN LAKE (U.S.A.)
Authors: Berry Holly Adrian , Lembi Carole A.
Published: March 2003

Although Spirogyra Link (1820) is a common mat‐forming filamentous alga in fresh waters, little is known of its ecology. A 2‐year field study in Surrey Lake, Indiana, showed that it grew primarily in the spring of each year. The population consisted of four morphologically distinct filamentous forms, each exhibiting its own seasonal distribution. A 45‐μm‐wide filament was present from February to late April or early May, a 70‐μm‐wide form was present from late April to mid‐June, a 100‐μm‐wide form was present from February to mid‐June, and a 130‐μm‐wide form appeared only in February of 1 of 2 study years. The 70‐ and 100‐μm‐wide forms contributed to the peak amount of biomass observed in late May and early June. Multiple regression analysis indicated that the presence of the 45‐, 70‐, and 100‐μm‐wide forms was negatively correlated with temperature. Presence of the 130‐μm‐wide form was negatively correlated with irradiance. Isolates of these filament forms were exposed to temperature (15, 25, and 35° C)/irradiance (0, 60, 200, 400, 900, and 1500 μmol·m−2·s−1) combinations in the laboratory. Growth rates of the 45‐μm‐wide form were negative at all irradiances at 35° C, suggesting that this form is susceptible to high water temperatures. However, growth rates of the other forms did not vary at the different temperatures or at irradiances of 60 μmol·m−2·s−1 or above. Net photosynthesis was negative at 35° C and 1500 μmol·m−2·s−1 for the 100‐ and 130‐μm‐wide forms but positive for the 70‐μm‐wide form. All forms lost mat cohesiveness in the dark, and the 100‐ and 130‐μm‐wide forms lost mat cohesiveness under high irradiances and temperature. Thus, the morphological forms differed in their responses to irradiance and temperature. We hypothesize that the rapid disappearance of Spirogyra populations in the field is due to loss of mat cohesiveness under conditions of reduced net photosynthesis, for example, at no to low light for all forms or at high light and high temperatures for the 100‐ and 130‐μm‐wide forms. Low light conditions can occur in the interior of mats as they grow and thicken or under shade produced by other algae.
Metabolic rhythms of a diazotrophic cyanobacterium, cyanothece sp. strain atcc 51142, heterotrophically grown in continuous dark
Authors: Schneegurt Mark A. , Tucker Don L. , Ondr Jennifer K. , Sherman Debra M. , Sherman Louis A.
Published: March 2003

Aerobic unicellular cyanobacteria temporally separate nitrogen fixation and photosynthetic activity to protect oxygen‐sensitive nitrogenase. Diurnal metabolic oscillations in the unicellular diazotroph, Cyanothece sp. str. CGD occurred even when cells were grown under continuous dark conditions, as determined in this study. The metabolic processes of nitrogen fixation, respiration, carbohydrate storage, and nitrogen storage all remained highly synchronized during heterotrophic growth, despite the absence of light signals. This shows the importance of circadian regulation in this unicellular cyanobacterium. The nitrogenase complex is apparently tightly regulated at the transcriptional and post‐translational levels. Carbohydrates accumulated during the subjective light phase were metabolized in a burst of respiration in the subjective dark phase. The utilization of carbohydrates occurred at the same time as the intense period of nitrogenase activity and downregulation of the capacity for photosynthetic oxygen evolution. Abundance of the D1 protein of photosystem II in Cyanothece sp. str. CGD remained relatively constant under continuous darkness, but the psbA transcript was more abundant in the subjective light phase. Accumulation of the psaAB gene products in photosystem I was highest in the subjective dark phase. The storage of fixed nitrogen as cyanophycin granules also exhibited periodic changes, with the amount of cyanophycin being greatest after the peak of nitrogenase activity. These results strongly implicate a circadian regulatory mechanism operating on these metabolic processes, independent of light cues, and stress the importance of circadian rhythms in global metabolic regulation in this unicellular cyanobacterium.
The sensitivity of Emiliania huxleyi (Prymnesiophyceae) to ultraviolet‐b radiation
Authors: Buma Anita G. J. , Van Oijen Tim , Van De Poll Willem , Veldhuis Marcel J. W. , Gieskes Winfried W. C.
Published: March 2003

Emiliania huxleyi (Lohm.) Hay et Miller is an important component of the phytoplankton in open ocean waters. The sensitivity of this cosmopolitan alga to natural levels of UVB radiation has never been tested. Since DNA is believed to be a major target of natural UVB radiation (UVBR: 280–315 nm) in living cells, experiments with E. huxleyi were performed using growth rate reduction and DNA damage as indicators of UVBR stress. Specific growth rate, cell volume, pigment content, and CPD (cyclobutane pyrimidine dimer) formation (a measure for DNA damage) were followed during and after prolonged exposure of a series of cultures to a range of UVBR levels. E. huxleyi was found to be very sensitive to UVBR: at a daily weighted UVBR dose of only 400 J·m−2 ·d−1 (BEDDNA300nm), growth was halted. At this UVBR level, both cell volume and contents of the major photosynthetic and photoprotective pigments had increased. The UVBR vulnerability of E. huxleyi cannot be explained by a high potential for cyclobutane thymine dimer formation (the most abundant CPD type) due to a high T content of nuclear DNA: the CG content of this E. huxleyi strain is high (68%) compared with other species. The high UVBR sensitivity may be related to the stage of the cell cycle during UVBR exposure, in combination with low repair capacity. It is concluded that E. huxleyi may experience UVBR stress through the formation of cyclobutane pyrimidine dimers, with subsequent low repair capacity and thereby arrest of the cell cycle.
PHYLOGENETIC POSITION OF KOLIELLA (CHLOROPHYTA) AS INFERRED FROM NUCLEAR AND CHLOROPLAST SMALL SUBUNIT rDNA
Authors: Katana Agnieszka , Kwiatowski Jan , Spalik Krzysztof , Zakryś Bożena , Szalacha Elżbieta , Szymańska Hanna
Published: March 2003

The phylogenetic position of Koliella, a chlorophyte characterized by Klebsormidium type cell division, was inferred from analyses of partial 18S rDNA and partial 16S rDNA. Parsimony and distance analyses of separate and combined data sets indicated that the members of Koliella belonged to Trebouxiophyceae, and high decay indices and bootstrap values supported this affinity. However, the genus appeared to be polyphyletic. Koliella spiculiformis, the nomenclatural type of the genus, was allied with Nannochloris eucaryota and the “true” chlorellas (Chlorella vulgaris, C. lobophora, C. sorokiniana, and C. kessleri). The close relatives of Koliella longiseta (≡Raphidonema longiseta) and Koliella sempervirens appeared to be Stichococcus bacillaris and some species traditionally classified in Chlorella that were characterized by the production of secondary carotenoids under nitrogen‐deficient conditions. This clade was also supported by the presence of a relatively phylogenetically stable group I intron (1506) in the 18S rRNA gene. Because of the presence of Klebsormidium type cell division, some authors regarded the members of Koliella as closely related to charophytes. Molecular analyses, however, did not confirm this affinity and suggested that a Klebsormidium type cell division is homoplastic in green plants.
A REASSESSMENT OF PHYLOGENETIC RELATIONSHIPS WITHIN THE PHAEOPHYCEAE BASED ON RUBISCO LARGE SUBUNIT AND RIBOSOMAL DNA SEQUENCES
Authors: Draisma Stefano G. A. , Prud'Homme van Reine Willem F. , Stam Wytze T. , Olsen Jeanine L.
Published: March 2003

To better assess the current state of phaeophycean phylogeny, we compiled all currently availablerbcL, 18S, and 26S rDNA sequences from the EMBL/GenBank database and added 21 newrbcL sequences of our own. We then developed three new alignments designed to maximize taxon sampling while minimizing information loss due to partial sequences. Phylogenetic analyses were performed on separate and combined data sets (with and without taxa from the sister classes Tribophyceae and Phaeothamniophyceae as outgroups) using a variety of assumption sets, tree‐drawing algorithms (parsimony, neighbor joining, and likelihood), and resampling methods (bootstrap, decay, jackknife). Partition homogeneity testing (PHT) by codon position withinrbcL showed that all positions could be used despite mild third position saturation. PHT by gene and domain within rDNA showed that the 26S D1 and D2 regions do not enhance phylogenetic signal even when combined with the 18S. TherbcL and rDNA (excluding the 26S D1 and D2) could be combined under PHT. The topology of the combined tree was the same as that of therbcL tree alone, but bootstrap support was consistently higher in the combined analysis, applied to more branches, and enabled the establishment of sister group relationships among six orders. Although the taxon sampling for the combination tree was lower (n= 22) than for individual gene analyses (n= 58 forrbcL andn= 59 for rDNA), results show that the Laminariales (previously reported) and Sphacelariales (new) are both paraphyletic.Choristocarpus tenellus(Kützing) Zanardini is the most basal phaeophyte and the Dictyotales the most basal order. In contrast, the Laminarialessensu stricto(s.s.) and Ectocarpalessensu lato(s.l.) are the most derived. For phylogenetic studies in the Phaeophyceae,rbcL has more resolving power than rDNA, though the reason for this is unclear based on the fact that both genes are highly conserved.
HIGH ENCYSTMENT SUCCESS OF THE DINOFLAGELLATESCRIPPSIELLACF.LACHRYMOSAIN CULTURE EXPERIMENTS1
Authors: Olli Kalle , Anderson Donald M.
Published: March 2003

Close to 100% encystment efficiency and a yield above 105cysts·mL−1were routinely achieved in full strength f/2 medium‐based batch cultures (883 μM NO3−and 36 μM PO4−3) of the marine dinoflagellateScrippsiellacf.lachrymosaLewis. Increases in cell density led to nutrient depletion in this enriched medium, which was the most likely cause for initiation of cyst formation. Lowering the concentration of either nutrient to 1/10 the initial levels decreased the encystment efficiency, whereas use of ammonium as the N source resulted in both low cell yield and low encystment efficiency. The mandatory dormancy period was ca. 60 days and was not affected by cold dark storage of the cysts. Cysts produced in the initial phase of sexual reproduction were relatively large (length 47 μm, width 31 μm) with a heavy calcareous cover. Cysts produced thereafter lacked apparent calcareous cover and were smaller (length 29 μm, width 19 μm). The decrease of cyst volume (by a factor of 0.24–0.4) suggested strong resource limitation during the course of encystment. However, after the mandatory dormancy period, germination success of the smaller cysts was higher (80%), compared with the larger cysts that had been produced initially (50%). Germling survival (74%) was independent of cyst type but was enhanced by higher nutrient concentration during incubation. The ratio of initial nutrient concentration in the medium to the cyst yield was used as a proxy to estimate the cellular nutrient quota. The conservative estimates of 9 pmol N·cyst−1and 0.4 pmol P·cyst−1obtained in this manner are at the low end of the range of previous published estimates for other dinoflagellate cysts. Given the high encystment observed in laboratory experiments, we have no reason to assume an inherently lower encystment success in dinoflagellate field populations. Our results do not challenge the low nutrient paradigm for dinoflagellate sexuality. We believe that the high encystment success and cyst yield of this particular species is at least partly due to its ability to achieve very high cell densities in cultures, which evidently leads to nutrient depletion even in f/2 medium.
EVOLUTION OF MICROALGAE IN HIGHLY STRESSING ENVIRONMENTS: AN EXPERIMENTAL MODEL ANALYZING THE RAPID ADAPTATION OF DICTYOSPHAERIUM CHLORELLOIDES (CHLOROPHYCEAE) FROM SENSITIVITY TO RESISTANCE AGAINST 2,4,6‐TRINITROTOLUENE BY RARE PRESELECTIVE MUTATIONS1
Authors: García‐Villada Libertad , López‐Rodas Victoria , Bañares‐España Elena , Flores‐Moya Antonio , Agrelo Mar , Martín‐Otero Luis , Costas Eduardo
Published: March 2003

The increasing rates of global extinction due to human activities necessitate studies of the ability of organisms to adapt to the new environmental conditions resulting from human disturbances. We investigated the evolutionary adaptation of a microalga to sudden environmental change resulting from exposure to novel toxic chemical residues. A laboratory strain of Dictyosphaerium chlorelloides (Naum.) Kom. and Perm. (Chlorophyceae) was exposed to increasing concentrations of the modern contaminant 2,4,6‐trinitrotoluene (TNT). When algal cultures were exposed to 30 mg·L−1 TNT, massive lysis of microalgal cells was observed. The key to understanding the evolution of microalgae in such a contaminated environment is to characterize the TNT‐resistant variants that appear after the massive lysis of the TNT‐sensitive cells. A fluctuation analysis demonstrated unequivocally that TNT did not facilitate the appearance of TNT‐resistant cells; rather it was found that TNT‐resistant cells appeared spontaneously by rare mutations under nonselective conditions, before exposure to TNT. The estimated mutation rate was 1.4 × 10−5 mutants per cell division. Isolated resistant mutants exhibited a diminished fitness in the absence of TNT. Moreover, the gross photosynthetic rate of TNT‐resistant mutants was significantly lower than that of wild‐type cells. Competition experiments between resistant mutants and wild‐type cells showed that in small populations, the resistant mutants were driven to extinction. The balance between mutation rate and the rate of selective elimination determines the occurrence of about 36 TNT‐resistant mutants per million cells in each generation. These scarce resistant mutants are the guarantee of potential for adaptation.
PHYLOGENETIC SYSTEMATICS OF THE ULVACEAE (ULVALES, ULVOPHYCEAE) USING CHLOROPLAST AND NUCLEAR DNA SEQUENCES1
Authors: Hayden Hillary S. , Waaland J. Robert
Published: March 2003

Systematic hypotheses for the Ulvaceae were tested using phylogenetic analysis of sequences for the gene encoding the large subunit of RUBISCO, small subunit rDNA and a combined data matrix. Representatives of eight putative ulvaceous genera and twelve additional taxa from the Ulvophyceae and Trebouxiophyceae were included in analyses using maximum parsimony and maximum likelihood criteria. Molecular data supported hypotheses for the Ulvaceae that are based on the early development of vegetative thalli and motile cell ultrastructure. UlvaceaesensuFloyd and O'Kelly, includingPercursariaBory de Saint‐Vincent,UlvariaRuprecht and a complex of closely related species ofChloropeltaTanner,EnteromorphaLink andUlvaL. was supported; however, monophyly ofEnteromorphaandUlvawas not supported. The Ulvales and UlotrichalessensuFloyd and O'Kelly were monophyletic.BlidingiaKylin andKornmanniaBliding were allied with the former andCapsosiphonGobi with the latter, although relationships among these and other taxa in these orders remain uncertain. The Ulvales are characterized by an isomorphic life history pattern, gametangia and sporangia that are identical in structure and development, motile cells with bilobed terminal caps and proximal sheaths consisting of two equal subunits. Method of motile cell release and the gross morphology of vegetative thalli are not systematically reliable characters.
TWO NEW AUSTRALIAN SPECIES OFPREDAEA(NEMASTOMATACEAE, RHODOPHYTA) WITH TAXONOMIC RECOMMENDATIONS FOR AN EMENDED NEMASTOMATALES AND EXPANDED HALYMENIALES1
Authors: Saunders Gary W. , Kraft Gerald T.
Published: March 2003

Two new species of the red algal genusPredaeaare described from Australia. The first,Predaea auroraKraft et G.W. Saunders, sp. nov., is unusual in its cool‐temperate distribution and in a number of anatomical attributes, most notably the rhizoid‐like habit of the nutritive filaments associated with the auxiliary cells. The second species,Predaea tumescensKraft et G.W. Saunders, sp. nov., inhabits a coral reef habitat more typical of the genus but nonetheless differs in a number of anatomical details from other reported species. Nuclear small subunit rDNA sequences have confirmed the affinity ofP. aurorato other species currently included in this genus. Molecular analyses further indicate thatPredaeabelongs in the Nemastomataceae and that the Nemastomataceae and Schizymeniaceae are sister taxa in an independent clade of “lineage 4” florideophyte algae. As such, a proposal is made to resurrect the Nemastomatales Kylin emend. G.W. Saunders et Kraft to accommodate these two families. Within the Schizymeniaceae, the Australian‐endemicPlatoma australicumandPlatoma foliosumwere only distantly related to the other includedPlatoma,Schizymenia, andTitanophoraspp. We therefore proposeWetherbeellaG.W. Saunders et Kraft, gen. nov., to accommodate these two species. An additional outcome of our molecular analyses is that the genusTsengiais not a member of the Nemastomataceae (where it is currently placed) but rather forms an independent lineage in the Halymeniales that we now designate as the Tsengiaceae G.W. Saunders et Kraft, fam. nov. Finally, the South AfricanNemastoma lanceolatumJ. Agardh is transferred toTsengia.
DETERMINATION OF CELLULAR LEVELS OF NONPROTEIN THIOLS IN PHYTOPLANKTON AND THEIR CORRELATIONS WITH SUSCEPTIBILITY TO MERCURY1
Authors: Satoh Masaya , Hirachi Yoshinobu , Yoshioka Ai , Kobayashi Maki , Oyama Yasuo
Published: March 2003

We determined the intracellular contents and concentrations of cysteine and glutathione in five species of marine phytoplankton, Tetraselmis tetrathele (West) Butcher (Prasinophyceae), Porphyridium purpureum (Bory) Drew et Ross (Rhodophyceae), Pavlova sp. (Haptophyceae), Isochrysis sp. (Haptophyceae), and Pleurochrysis carterae (Braarud et Fagerl) Christensen (Haptophyceae), and examined relationships to mercury susceptibility. Intracellular contents (concentrations) of nonprotein thiols in the five species ranged from 119 to 1210 amol (0.66–12.0 mM) for cysteine, 78 to 719 amol (0.65–2.52 mM) for cystine, 31 to 677 amol (0.13–1.25 mM) for reduced glutathione (GSH), and 12 to 123 amol (0.15–0.26 mM) for oxidized glutathione (GSSG). The intracellular contents of the nonprotein thiols were not proportional to the intracellular concentrations because the cell sizes differed. Oxidation ratios of cysteine:cystine and GSH:GSSG were also wide ranging in the five species, and the higher the concentration of the reduced form of nonprotein thiols, the less they tended to be oxidized. Flow cytometric analyses with fluorescein diacetate were used to monitor the effect of HgCl2 on esterase, and the 50% effect concentrations (EC50) were compared in the five species. The EC50 after 3 h exposure to HgCl2 correlated well with the GSH concentrations but not with those of cysteine. These results indicate that the intracellular concentrations of the nonprotein thiols reflect antioxidant activity and susceptibility to heavy metals.
CERAMIUM INKYUII SP. NOV. (CERAMIACEAE, RHODOPHYTA) FROM KOREA: A NEW SPECIES BASED ON MORPHOLOGICAL AND MOLECULAR EVIDENCE1
Authors: Cho Tae Oh , Fredericq Suzanne , Boo Sung Min
Published: March 2003

Ceramium inkyuii sp. nov. is newly described based on samples collected from the east coast of Korea and compared with similar species such as C. paniculatum and C. tenerrimum. The new species is characterized by pseudo‐dichotomously branched thalli with a twist in the upper part, a single row of spines on the abaxial side, strongly inrolled apices, and the presence of gland cells. In contrast, C. paniculatum has alternate branches and lacks gland cells, and C. tenerrimum is spineless and also lacks gland cells. Ceramium inkyuii was observed to be an annual species producing tetrasporangia in the spring to summer and cystocarps in the fall. Plastid‐encoded rbcL and nuclear small subunit (SSU) rDNA sequences were determined in four samples of C. inkyuii from different locations and six samples of four putative relatives. All four C. inkyuii replicates from three different locations had identical sequences of each gene, and the interspecific sequence divergences were enough to warrant its natural entity. The phylogenies of the rbcL and SSU rDNA sequences also indicate the monophyly of C. inkyuii. The spinous C. inkyuii was more closely related to the spineless C. tenerrimum than to the spinous C. paniculatum.