bluuebunny/crossref_metadata_2025 huggingface dataset:
A MOLECULAR AND PHENOTYPIC ANALYSIS OF NODULARIA (CYANOBACTERIA) FROM THE BALTIC SEA
Authors: Barker Gary L. A. , Hayes Paul K. , O’Mahony Sarah L. , Vacharapiyasophon Panmuk , Walsby Anthony E.
Published: March 2003

The filamentous diazotrophic cyanobacterium Nodularia forms water blooms each year in the Baltic Sea. Filaments isolated from such water blooms vary in their trichome width, degree of coiling, and properties of their gas vesicles; previously, these characters have been used to classify individuals to species level. To test the validity of such a phenotypic classification, we determined the nucleotide sequences for a region of the phycocyanin locus that includes a noncoding intergenic spacer (PC‐IGS), the IGS between two adjacent copies of the gvpA gene (which encodes the main structural gas vesicle protein) and the rDNA internal transcribed spacer (rDNA‐ITS), for 13 clonal Nodularia isolates from the Baltic Sea during August 1994. The complete 16S‐rDNA sequence was determined for three isolates and was found to be identical in each of them. Molecular sequences for noncoding regions of the genome were used to assign isolates to three groups on the basis of PC‐IGS, two groups on the basis of gvpA‐IGS, and three groups on the basis of rDNA‐ITS. No consistent correlation was found between genotype and any of the phenotypic features examined, and no link was found between any of these features themselves, indicating that these characters are not useful for placing Nodularia isolates into meaningful taxonomic groups. The PC‐IGS, gvpA‐IGS, and rDNA‐ITS genotypic groupings were not congruent. This might indicate that gene flow occurs between individuals in Nodularia populations.
FATTY ACIDS AND HYDROXY FATTY ACIDS IN THREE SPECIES OF FRESHWATER EUSTIGMATOPHYTES
Authors: Volkman John K. , Barrett Stephanie M. , Blackburn Susan I.
Published: March 2003

The monocarboxylic fatty acids and hydroxy fatty acids of three species of freshwater microalgae—Vischeria punctata Vischer, Vischeria helvetica (Vischer et Pascher) Taylor, and Eustigmatos vischeri (Hulbert) Taylor, all from the class Eustigmatophyceae— were examined. Each species displayed a very similar distribution of fatty acids, the most abundant of which were 20:5n‐3, 16:0, and 16:1n‐7; C18 polyunsaturated fatty acids were minor components. These fatty acid distributions closely resemble those found in marine eustigmatophytes but are quite distinct from those found in most other algal classes. These microalgae also contain long‐chain saturated and unsaturated monohydroxy fatty acids. Two distinct types of hydroxy fatty acids were found: a series of saturated α‐hydroxy acids ranging from C24 to C30 with a shorter series of monounsaturated α‐hydroxy acids ranging from C26 to C30 together with a series of saturated β‐hydroxy acids ranging from C26 to C30. The latter have not previously been reported in either marine or freshwater microalgae, although C30 to C34 midchain (ω‐18)‐hydroxy fatty acids have been identified in hydrolyzed extracts from marine eustigmatophytes of the genus Nannochloropsis, and C22 to C26 saturated and monounsaturated α‐hydroxy fatty acids have been found in three marine chlorophytes. These findings have provided a more complete picture of the lipid distributions within this little studied group of microalgae as well as a range of unusual compounds that might prove useful chemotaxonomic markers. The functions of the hydroxy fatty acids are not known, but a link to the formation of the lipid precursors of highly aliphatic biopolymers is suggested.
PSEUDO‐NITZSCHIA SPECIES (BACILLARIOPHYCEAE) IN LOUISIANA COASTAL WATERS: MOLECULAR PROBE FIELD TRIALS, GENETIC VARIABILITY, AND DOMOIC ACID ANALYSES
Authors: Parsons Michael L. , Scholin Christopher A. , Miller Peter E. , Doucette Gregory J. , Powell Christine L. , Fryxell Greta A. , Dortch Quay , Soniat Thomas M.
Published: March 2003

An 18‐month field survey of the Pseudo‐nitzschia population present in Louisiana coastal waters was conducted comparing species abundance estimates by novel fluorescent molecular probes (16S large subunit rDNA oligonucleotide sequences) with traditional electron and differential‐interference light microscopy. While the probe and microscopic analyses agreed on the presence or absence of four common Pseudo‐nitzschia species (P. multiseries (Hasle) Hasle, P. pseudodelicatissima (Hasle) Hasle, P. delicatissima (P.T. Cleve) Heiden, and P. pungens (Grunow) Hasle in 66% of the samples analyzed, the probes gave conflicting results with the microscopic methods in the remaining 34% of the samples. The majority of the discrepancies appear to be because of genetic variation within the Pseudo‐nitzschia population, especially in P. pseudodelicatissima, indicating that the Monterey Bay Pseudo‐nitzschia spp. may not be appropriate reference strains for distinguishing Louisiana Pseudo‐nitzschia spp. Additionally, P. pseudodelicatissima has been associated with domoic acid (DA) activity in three field samples, at levels up to 22 times higher than the highest value given inother published reports of DA production by this species. The contemporaneous existence of multiple strains of P. pseudodelicatissima (toxic and non‐toxic) presents new challenges to the study of the ecophysiology and population dynamics of this bloom‐forming species.
Tn5 MUTAGENESIS OF PSEUDOMONAS STUTZERI SF/PS, A BACTERIUM ASSOCIATED WITH ALEXANDRIUM LUSITANICUM (DINOPHYCEAE) AND PARALYTIC SHELLFISH POISONING
Authors: Plumley F. Gerald , Wei Zhengyu , Toivanen Tracie B. , Doucette Gregory J. , Franca Susana
Published: March 2003

It is becoming increasingly clear that bacteria can play an important role in the toxin and population dynamics of harmful algal bloom (HAB) events. In this paper, we document protocols and strategies that can be used to identify bacterial genes involved in either the production of toxic compounds and/or the establishment and maintenance of relationships between bacteria and algae. The protocols we tested involved transposon mutagenesis and complementation with broad‐host‐range plasmids. We tested six bacterial strains thought to be involved, either directly or indirectly, in the production of toxins associated with paralytic shellfish poisoning (PSP). Five strains were resistant to transformation under the growth conditions used. However, a single strain, Pseudomonas stutzeri SF/PS, was readily transformed when grown under appropriate conditions. This bacterium has been shown to accumulate PSP toxins and to increase toxin production when added to axenic cultures of a toxic dinoflagellate, Alexandrium lusitanicum. We conclude that a transposon mutagenesis strategy can be used to identify genes involved in HAB events.
ISOLATION OF ccmKLMN GENES FROM THE MARINE CYANOBACTERIUM, SYNECHOCOCCUS SP. PCC7002 (CYANOPHYCEAE), AND EVIDENCE THAT CcmM IS ESSENTIAL FOR CARBOXYSOME ASSEMBLY
Authors: Ludwig Martha , Sültemeyer Dieter , Price G. Dean
Published: March 2003

A high CO2 requiring mutant of the marine cyanobacterium Synechococcus PCC7002 was generated using a random gene‐tagging procedure. This mutant demonstrated a reduced photosynthetic affinity for inorganic carbon (Ci) and accumulated high internal levels of Ci that could not be used for photosynthesis. Analysis of the mutant genomic DNA showed that the mutagenesis had disrupted a cluster of genes involved in the cyanobacterial CO2 concentrating mechanism (CCM), the so‐called ccm genes. These characteristics are consistent with a cyanobacterial mutant with defects in carboxysome assembly and/or functioning. Further genomic analyses indicated that the genes of the Synechococcus PCC7002 operon, ccmKLMN, are structurally similar to those of two closely related cyanobacteria, Synechococcus PCC7942 and Synechocystis PCC6803. The Synechococcus PCC7002 ccmM gene, which encodes a polypeptide with a predicted size of 70 kDa, was the direct target of the mutagenesis event. The CcmM protein has two distinct regions: an N‐terminal region that shows similarity to an archaeon gamma carbonic anhydrase and a C‐terminal region that contains repeated domains demonstrating sequence similarity to the small subunit of Rubisco. Physiological analysis of a ccmM‐defined mutant showed that these cells were essentially identical to the original mutant; they required high CO2 concentrations for growth, they had a low photosynthetic affinity for Ci, and they internalized Ci to high levels. Moreover, ultrastructural examination showed that both the original and the defined mutants lack carboxysomes. Thus, our results demonstrate that the ccmM gene of Synechococcus PCC7002 encodes a polypeptide that is essential for carboxysome assembly and therefore for proper functioning of the cyanobacterial CCM.
RAMET DYNAMICS FOR THE CLONAL SEAWEED PTEROCLADIELLA CAPILLACEA (RHODOPHYTA): A COMPARISON WITH CHONDRUS CRISPUS AND WITH MAZZAELLA CORNUCOPIAE (GIGARTINALES)
Authors: Scrosati Ricardo , Servière‐Zaragoza Elisa
Published: March 2003

Little is known about the dynamics and the ecological interactions among ramets (fronds) from populations of clonal red seaweeds. Small ramets are very difficult to tag, so their growth cannot be monitored directly. The temporal variation of the relationship between stand biomass and ramet density offers information on ramet performance. We calculated this relationship for an intertidal population of Pterocladiella capillacea (Gmelin) Santelices et Hommersand (Gelidiales) from Baja California, Mexico. Biomass and density were positively correlated on an annual basis, indicating that biomass accumulated without involving self‐thinning among ramets. This contrasts with nonclonal seaweeds, for which self‐thinning among individuals occurs during growth, but agrees with other clonal red seaweeds, such as Chondrus crispus Stackhouse and Mazzaella cornucopiae (Postels et Ruprecht) Hommersand (both Gigartinales). The growth pattern for these members of the Gelidiales and of the Gigartinales holds despite differences in holdfast morphology and ramet branching degree and despite differences in the capacity of coalescence during early stages, known only for the Gigartinales. The positive slope for the dynamic biomass–density relationship, on a bilogarithmic scale, was statistically steeper for M. cornucopiae than for P. capillacea and for C. crispus. This suggests that the addition of new ramets during the growth season may be relatively more beneficial for biomass accumulation rates for M. cornucopiae. This would be expected for high‐intertidal species subjected to strong abiotic stress, for which ramet crowding constitutes a key protection. Pterocladiella capillacea occurs at the mid‐intertidal zone and C. crispus at the subtidal zone, so ramets would be relatively less important in that respect.
INFLUENCE OF UV‐B RADIATION ON NITROGEN UTILIZATION BY A NATURAL ASSEMBLAGE OF PHYTOPLANKTON
Authors: Fauchot Juliette , Gosselin Michel , Levasseur Maurice , Mostajir Behzad , Belzile Claude , Demers Serge , Roy Suzanne , Villegas Piedad Zulema
Published: March 2003

A 7‐day mesocosm experiment was conducted in July 1996 to investigate the effects of ambient UV‐B radiation (UVBR) exclusion and two UVBR enhancements above ambient levels on NO3−, NH4+ and urea utilization in a natural plankton community (<240 μm) from the Lower St. Lawrence Estuary. The phytoplankton community was dominated by diatoms during the first 3 days and, afterward, by flagellates and dinoflagellates. The results of 4‐h incubations just below the water surface show that, compared with ambient UVBR conditions, UVBR exclusion generally increased NO3−, NH4+, and urea uptakes. During the last 4 days of the experiment, the percent increase in the specific uptake rate of urea under excluded UVBR conditions varied between 17% and 130% and was a linear function of the ambient UVBR dose removed. During the first 3 days, the phytoplankton community dominated by diatoms was able to withstand UVBR enhancements without any perceptible effect on nitrogen uptake. However, during the post‐diatom bloom period, UVBR enhancements resulted in decreases in NO3−, NH4+, and urea uptake compared with ambient UVBR conditions. The reduction of urea uptake under UVBR enhancements during the last 3 days varied between 23% and 64% and was linearly related to the enhanced UVBR dose. However, the different UVBR treatments did not affect the internal organic nitrogen composition (internal urea, free amino acids, and proteins) of the phytoplankton community experiencing vertical mixing in the mesocosms. The discrepancy between short‐term uptake measurements at the surface and long‐term effects in the mesocosms emphasizes the importance of vertical mixing on UVBR effects in natural ecosystems. This suggests that an increase in ambient UVBR would have a minimal effect on nitrogen utilization by natural phytoplankton assemblages if these are vertically mixed.
Transformation of the diatom Phaeodactylum tricornutum (Bacillariophyceae) with a variety of selectable marker and reporter genes
Authors: Zaslavskaia Lioudmila A. , Lippmeier J. Casey , Kroth Peter G. , Grossman Arthur R. , Apt Kirk E.
Published: March 2003

A general purpose transformation vector, designated pPha‐T1, was constructed for use with the diatom Phaeodactylum tricornutum Bohlin. This vector harbors the sh ble cassette for primary selection on medium containing the antibiotic zeocin, and a multiple cloning site flanked by the P. tricornutum fcpA promoter. pPha‐T1 was used to establish the utility of three selectable marker genes and two reporter genes for P. tricornutum transformation. The nat and sat‐1 genes confer resistance to the antibiotic nourseothricin, and nptII confers resistance to G418. Each of these genes was effective as a selectable marker for identifying primary transformants. These markers could also be used for dual selections in combination with the sh ble gene. The reporter genes uidA and gfp were also introduced into P. tricornutum using pPha‐T1. Gus expression in some transformants reached 15 μg·μg−1 of total soluble protein and permitted excellent cell staining, while GFP fluorescence was readily visible with standard fluorescence microscopy. The egfp gene, which has optimal codon usage for expression in human cells, was the only version of gfp that produced a strong fluorescent signal in P. tricornutum. The codon bias of the egfp gene is similar to that of P. tricornutum genes. This study suggests that codon usage has a significant effect on the efficient expression of reporter genes in P. tricornutum. The results presented here demonstrate that a variety of selectable markers and reporter genes can be expressed in P. tricornutum, enhancing the potential of this organism for exploring basic biological questions and industrial applications.
THE FRESHWATER CYANOBACTERIUM PLANKTOTHRIX SP. FP1: MOLECULAR IDENTIFICATION AND DETECTION OF PARALYTIC SHELLFISH POISONING TOXINS
Authors: Pomati Francesco , Sacchi Silvia , Rossetti Carlo , Giovannardi Stefano , Onodera Hideyuki , Oshima Yasukatsu , Neilan Brett A.
Published: March 2003

A filamentous cyanobacterium, belonging to the Order of Oscillatoriales, was found to be responsible for a toxic algal bloom in Lake Varese, Italy, during the summer of 1997. Morphological characters, as well as near complete 16S rRNA gene sequencing, revealed that the dominant species of the bloom was most closely related to the genus Planktothrix. In addition, genetic analysis of the phycocyanin operon of Planktothrix sp. FP1 revealed a novel primary structure, previously undescribed within the cyanobacteria, which was used as a genetic marker for rapid detection and identification of this toxic strain. The occurrence of saxitoxin (STX), a principal toxin in paralytic shellfish poisoning (PSP), was confirmed in the natural bloom sample by both pre‐column and post‐column derivatization high‐performance liquid chromatography (HPLC) analyses, and eventually by liquid chromatography/mass spectrometry (LC/MS). The toxicity of this field sample was also revealed by electrophysiological assays in which the extract inhibited 90% of the voltage‐dependent Na+ current in human neuroblastoma cells at the STX concentration of 80 nM. The cultured strain showed a lower physiologic activity than the bloom sample (67% blockage of Na+ current at a toxin concentration of 200 nM), and STX was detected only by pre‐column HPLC, indicating the presence of a compound structurally close to STX. Chemical and molecular genetic analyses performed here add Planktothrix sp. FP1 to the growing list of diverse cyanobacterial species capable of synthesizing STX and its related compounds.
Temperature dependence of nitrate reductase activity in marine phytoplankton: biochemical analysis and ecological implications
Authors: Gao Yu , Smith G. Jason , Alberte Randall S.
Published: March 2003

The temperature dependence of NADH:NR activity was examined in several marine phytoplankton species and vascular plants. These species inhabit divergent thermal environments, including the chromophytes Skeletonema costatum (12–15° C), Skeletonema tropicum (18–25° C), Thalassiosira antarctica (−2 to 4° C), and Phaeocystis antarctica (−2 to 4° C), the green alga Dunaliella tertiolecta (14–28° C), and the vascular plants Cucurbita maxima (20–35° C) and Zea mays (20–25° C). Despite the difference in growth habitats, similar temperature response curves were observed among the chromophytic phytoplankton, with temperatures optimal for NR activity being between 10–20° C. In contrast, the chlorophyll b‐containing alga and vascular plants exhibited optimal temperatures for NR activity above 30° C. Such dramatic differences in NR thermal characteristics from the two taxonomic groups reflect a divergence in NR structure that may be associated with the evolutionary diversification of chromophytes and chlorophytes. Further, it suggests a potential contribution of the thermal performance of NR to the geographic distributions, seasonal abundance patterns, and species composition of phytoplankton communities. NR partial activities, which assess the individual functions of Mo‐pterin and FAD domains, were evaluated on NR purified from S. costatum to determine the possible causes for high temperature (>20° C) inactivation of NR from chromophytes. It was found that the FAD domain and electron transport among redox centers were sensitive to elevated temperatures. S. costatum cells grown at 5, 15, and 25° C exhibited an identical optimal temperature (15° C) for NADH:NR activity, whereas the maximal NR activity and NR protein levels differed and were positively correlated with growth temperature and growth rate. These findings demonstrate that thermal acclimation of NO3− reduction capacity is largely at the level of NR protein expression. The consequences of these features on NO3− utilization are discussed.
CIRCADIAN RHYTHM OF PHOTOSYNTHETIC OXYGEN EVOLUTION IN KAPPAPHYCUS ALVAREZII (RHODOPHYTA): DEPENDENCE ON LIGHT QUANTITY AND QUALITY
Authors: Granbom Malena , Pedersén Marianne , Kadel Petra , Lüning Klaus
Published: March 2003

The rate of oxygen evolution of the tropical red alga Kappaphycus alvarezii (Doty) Doty was measured for 6 days in the laboratory using a computer‐aided method for long‐term recording. In cool white light, Kappaphycus exhibited a robust circadian rhythm of O2 evolution in the irradiance range of 100 to 1000 μmol photons·m−2·s−1. With increasing irradiance, the period of the free‐running rhythm, τ, decreased in blue and increased in red light but did not change significantly in green light. The accelerating or slowing action of blue or red light, respectively, points to two photoreceptors used in the light transduction pathway of the circadian oscillator controlling oxygen evolution or the light reactions of photosynthesis in Kappaphycus. No significant changes of τ were observed with increasing irradiance in cool white light, possibly due to the additive opposing responses caused by blue and red light.
15N MEASUREMENTS OF AMMONIUM AND NITRATE UPTAKE BY ULVA FENESTRATA (CHLOROPHYTA) AND GRACILARIA PACIFICA (RHODOPHYTA): COMPARISON OF NET NUTRIENT DISAPPEARANCE, RELEASE OF AMMONIUM AND NITRATE, AND 15N ACCUMULATION IN ALGAL TISSUE1
Authors: Naldi Mariachiara , Wheeler Patricia A.
Published: March 2003

Ammonium and nitrate uptake rates in the macroalgae Ulva fenestrata (Postels and Ruprecht) (Chlorophyta) and Gracilaria pacifica (Abbott) (Rhodophyta) were determined by 15N accumulation in algal tissue and by disappearance of nutrient from the medium in long‐term (4–13 days) incubations. Nitrogen‐rich algae (total nitrogen> 4% dry weight [dw]) were used to detect isotope dilution by release of inorganic unlabeled N from algal thalli. Uptake of NH4+ was similar for the two macroalgae, and the highest rates were observed on the first day of incubation (45 μmol N·g dw−1·h−1 in U. fenestrata and 32 μmol N·g dw−1·h−1 in G. pacifica). A significant isotope dilution (from 10 to 7.9 atom % enrichment) occurred in U. fenestrata cultures during the first day, corresponding to a NH4+ release rate of 11 μmol N·g dw−1·h−1. Little isotope dilution occurred in the other algal cultures. Concurrently to net NH4+ uptake, we observed a transient free amino acid (FAA) release on the first day in both macroalgal cultures. The uptake rates estimated by NH4+ disappearance and 15N incorporation in algal tissue compare well (82% agreement, defined as the percentage ratio of the lower to the higher rate) at high NH4+ concentrations, provided that isotope dilution is taken into account. On average, 96% of added 15NH4+ was recovered from the medium and algal tissue at the end of the incubation. Negligible uptake of NO3− was observed during the first 2–3 days in both macroalgae. The lag of uptake may have resulted from the need for either some N deprivation (use of NO3− pools) or physiological/metabolic changes required before the uptake of NO3−. During the subsequent days, NO3− uptake rates were similar for the two macroalgae but much lower than NH4+ uptake rates (1.97–3.19 μmol N·g dw−1·h−1). Very little isotope dilution and FAA release were observed. The agreement between rates calculated with the two different methods averaged 91% in U. fenestrata and 95% in G. pacifica. Recovery of added 15NO3− was virtually complete (99%). These tracer incubations show that isotope dilution can be significant in NH4+ uptake experiments conducted with N‐rich macroalgae and that determination of 15N atom % enrichment of the dissolved NH4+ is recommended to avoid poor isotope recovery and underestimation of uptake rates.
APPARENT LIGHT REQUIREMENT FOR ACTIVATION OF PHOTOSYNTHESIS UPON REHYDRATION OF DESICCATED BEACHROCK MICROBIAL MATS1
Authors: Schreiber Ulrich , Gademann Rolf , Bird Paul , Ralph Peter J. , Larkum Anthony W. D. , Kühl Michael
Published: March 2003

Photosynthetic electron transport of beachrock microbial mats growing in the intertidal zone of Heron Island (Great Barrier Reef, Australia) was investigated with a pulse amplitude modulation chl fluorometer providing four different excitation wavelengths for preferential excitation of the major algal groups (cyanobacteria, green algae, diatoms/dinoflagellates). A new type of fiberoptic emitter‐detector unit (PHYTO‐EDF) was used to measure chl fluorescence at the sample surface. Fluorescence signals mainly originated from cyanobacteria, which could be almost selectively assessed by 640‐nm excitation. Even after desiccation for long time periods under full sunlight, beachrock showed rapid recovery of photosynthesis after rehydration in the light (t1/2∼ 15 min). However, when rehydrated in the dark, the quantum yield of energy conversion of PSII remained zero over extended periods of time. Parallel measurements of O2concentration with an oxygen microoptode revealed zero oxygen concentration in the surface layer of rehydrated beachrock in the dark. Upon illumination, O2concentration increased in parallel with PSII quantum yield and decreased again to zero in the dark. It is proposed that oxygen is required for preventing complete dark reduction of the PSII acceptor pools via the NADPH‐dehydrogenase/chlororespiration pathway. This hypothesis is supported by the observation that PSII quantum yield could be partially induced in the dark by flushing with molecular oxygen.

Abbreviations:EDF, emitter‐detector unit; Fo, fluor‐escence yield of dark‐adapted sample; Fm, maximal fluorescence yield measured during saturation pulse; Fv, variable fluorescence yield; LED, light‐emitting diode; PAM, pulse amplitude modulation; PQ, plastoquinone
MORPHOLOGICAL, TOXICOLOGICAL, AND GENETIC DIFFERENCES AMONG PSEUDO‐NITZSCHIA (BACILLARIOPHYCEAE) SPECIES IN INLAND EMBAYMENTS AND OUTER COASTAL WATERS OF WASHINGTON STATE, USA1
Authors: Stehr Carla M. , Connell Laurie , Baugh Keri A. , Bill Brian D. , Adams Nicolaus G. , Trainer Vera L.
Published: March 2003

Plankton samples from three inland embayments and several outer coastal sites of Washington State were collected from 1997 through 1999 and were examined for the presence of diatoms of the genus Pseudo‐nitzschia and levels of the toxin, domoic acid (DA). Seven species were observed, including Pseudo‐nitzschia pungens (Grunow ex Cleve) Hasle, P. multiseries (Hasle) Hasle, P. australis Frenguelli, P. fraudulenta (Cleve) Hasle, P. cf. heimii Manguim, P. pseudodelicatissima (Hasle) Hasle, and P. delicatissima (Cleve) Heiden. The coastal Pseudo‐nitzschia species assemblages differed significantly from those observed within embayments. The dominant species observed at coastal sites were P. pseudodelicatissima and P. cf. heimii. Pseudo‐nitzschia assemblages found in embayments included one or more of the following species: P. pungens, P. multiseries, P. australis, P. pseudodelicatissima, and P. fraudulenta. The nuclear large subunit rRNA gene was sequenced for six of the seven species identified. This sequence revealed that P. multiseries, P. pungens, P. australis, and P. heimii were genetically similar to those found in California, whereas P. delicatissima and P. pseudodelicatissima were distinct from the California isolates. Although the concentrations of DA in razor clams along Washington State coasts have exceeded regulatory limits several times since 1991, levels of DA in shellfish from Washington State embayments have not yet exceeded regulatory limits. The widespread presence of toxin‐producing Pseudo‐nitzschia species suggests, however, that toxic blooms are likely to occur within embayments in the future. In conjunction with the monitoring of environmental conditions conducive to toxic bloom formation, the development of species‐specific probes for rapid and accurate detection of potentially toxic Pseudo‐nitzschia species in this region would enable the forecasting of a toxic event before DA accumulates in shellfish, thereby reducing the impacts to coastal communities.
NITROGEN STARVATION INDUCES THE ACCUMULATION OF ARACHIDONIC ACID IN THE FRESHWATER GREEN ALGA PARIETOCHLORIS INCISA (TREBUXIOPHYCEAE)1
Authors: Khozin‐Goldberg Inna , Bigogno Chiara , Shrestha Pushkar , Cohen Zvi
Published: March 2003

The Chlorophyte Parietochloris incisa comb. nov (Trebuxiophyceae) was found to be the richest plant source of the pharmaceutically valuable long‐chain polyunsaturated fatty acid (PUFA), arachidonic acid (20:4ω6, AA). Over 90% of total AA are deposited in triacylglycerols (TAG). Under nitrogen starvation, the fatty acid content constituted over 35% of dry weight and the proportion of AA exceeded 60% of total fatty acids. Consequently, we obtained an AA content of over 20%. This is, to the best of our knowledge, the highest reported content of any PUFA in algae. Increasing the biomass concentration resulted in an enhancement of both the proportion of AA and the fatty acid content. We hypothesize that one of the roles of TAG in P. incisa is to serve as a reservoir of AA that can be used for the construction of membranal lipids.
ISOLATION AND CHARACTERIZATION OF A VIRUS THAT INFECTS EMILIANIA HUXLEYI (HAPTOPHYTA)1
Authors: Castberg Tonje , Thyrhaug Runar , Larsen Aud , Sandaa Ruth‐Anne , Heldal Mikal , Van Etten James L. , Bratbak Gunnar
Published: March 2003

The isolation and characterization of a virus (designated EhV) that infects the marine coccolithophorid Emiliania huxleyi (Lohmann) Hay & Mohler are described. Three independent clones of EhV were isolated from Norwegian coastal waters in years 1999 and 2000. EhV is a double‐stranded DNA‐containing virus with a genome size of ∼415 kilo‐base pairs. The viral particle is an icosahedron with a diameter of 160–180 nm. The virus particle contains at least nine proteins ranging from 10 to 140 kDa; the major capsid protein weighs ∼54 kDa. EhV has a latent period of 12–14 h and a burst size of 400–1000 (mean, 620) viral particles per cell. A phylogenetic tree based on DNA polymerase amino acid sequences indicates EhV should be assigned to the Phycodnaviridae virus family and that the virus is most closely related to viruses that infect Micromonas pusilla and certain Chlorella species.
A SMALLER AND IMPAIRED XANTHOPHYLL CYCLE MAKES THE DEEP SEA MACROALGAE LAMINARIA ABYSSALIS (PHAEOPHYCEAE) HIGHLY SENSITIVE TO DAYLIGHT WHEN COMPARED WITH SHALLOW WATER LAMINARIA DIGITATA1
Authors: Rodrigues Marcoaurélio Almenara , Dos Santos César Pereira , Young Andrew John , Strbac Dragana , Hall David Oakley
Published: March 2003

Pigment composition, fluorescence parameters, and oxygen evolution of the deep water Laminaria abyssalis Oliveira and of the shallow water L. digitata Lamoroux were determined in response to high irradiances. This was performed in the presence and absence of an inhibitor of violaxanthin de‐epoxidase (dithiothreitol) or an inhibitor of the chloroplast‐encoded protein synthesis (chloramphenicol). Photochemical quenching in L. digitata was almost 3‐fold that seen in L. abyssalis, whereas both nonphotochemical quenching and PSII photochemical yield were doubled. Laminaria digitata possessed a xanthophyll‐cycle pool nearly double that of L. abyssalis. After photoinhibitory treatment, L. digitata displayed substantial violaxanthin de‐epoxidation, whereas in L. abyssalis de‐epoxidation only took place in limited amounts. Both species were able to fully recover their epoxidation status after transfer back to dim light. Overnight incubation with dithiothreitol fully blocked de‐epoxidation in both species, and both displayed similar fluorescence properties. Chloramphenicol caused no change in their fluorescence parameters. With high light treatment, L. abyssalis was completely and irreversibly inhibited both in the presence and absence of inhibitors, whereas L. digitata showed 60% inhibition of its photosynthetic activity and full recovery in the absence of inhibitors. In the presence of dithiothreitol, L. digitata did not recover to the preillumination conditions and chloramphenicol delayed the recovery of the oxygen evolution activity. We suggest that the xanthophyll cycle is the main mechanism of photoprotection of these Laminaria species and that the higher susceptibility of L. abyssalis to photoinhibition may be due to its limited de‐epoxidation capacity and reduced xanthophyll‐cycle pool size.
Mycosporine‐Like Amino Acid Intercalibration Effort Using Replicate Samples
Authors: Zimba P. V. , Boue S.
Published: March 2003

The measurement of mycosporine‐like amino acids (MAAs) has several inherent problems, including the lack of commercial standards for identification and quantification. This symposium provided the opportunity to coordinate analyses with six laboratories actively involved in MAA research. Two samples were provided to each laboratory and included freeze‐dried nori (Porphyra sp.) and a freeze‐dried (filtered) sample of the cyanobacteria Microcystis aeruginosa Kützing. Each laboratory provided extraction methodologies, chromatograms of the identified peaks, as well as estimates of the concentration of each analyte. All laboratories were able to identify major chromatographic components of the samples (Porphyra: shinorine, porphyra, mycosporine 2‐glycine, asterina, palythine; Microcystis: shinorine, porphyra). Sequential cold (4 °C for 18 h) and hot (45 °C for 2 h) extractions of the same sample resulted in differing analyte recovery. Several currently unidentified compounds were observed in freshwater samples.
Origin and Early Evolution of Plant Body Symmetry and Gravity Responses
Authors: Cook M. E. , Graham L. E.
Published: March 2003

Land plant bodies exhibit both apical–basal and radial symmetry, and they are able to detect and respond to gravitational forces. These attributes were, likely important factors in the success of earliest plants on land. This study focuses on features of charophycean green algae likely to have been pre‐adaptive to early establishment of plant symmetry and gravitational responses, though most modern charophyceans occupy aquatic habitats where the buoyancy of water counteracts the effects of gravity. Trait mapping suggests that even the earliest‐divergent modern members of the streptophyte clade have bodies whose symmetry departs significantly from the spherical condition, and that cellular mechanisms defining aspects of radial symmetry and polarized tip growth originated early. Genes, cell biological approaches, and taxa are identified for which further exploration is likely to illuminate early evolution of plant body symmetry and gravity responses.
Post‐European Sedimentation and Nutrient Loading in Lake St. Croix: A Natural Impoundment on the St. Croix River, USA
Authors: Edlund M. B. , Triplett L. , Engstrom D. R.
Published: March 2003

The final 37 km of the St. Croix River were naturally dammed by the Mississippi River to form Lake St. Croix approximately 9500 years ago. The St. Croix River is currently regarded as having ‘exceptional resource value’, as one of the least impacted large Midwest river systems. Twenty‐four 2‐m piston cores were recovered in 1999–2001 from Lake St. Croix sub‐basins to identify post‐European settlement signals of land use, trophic change, and sedimentation using a whole‐basin approach to reconstruct loading history of nutrients, sediments, heavy metals, and organics. Dating chronologies based on 210Pb inventories indicated both cores recovered a sediment sequence dating from pre‐ and post‐European settlement (c. 1850) in the St. Croix River basin. Select cores were subjected to magnetic susceptibility, loss‐on‐ignition, and diatom microfossil analysis. Sedimentary increases in magnetic susceptibility were indicative of increased erosion and transport of ferromagnetic mineral grains due to initiation of settlement, logging, and agricultural activities in the basin. A three‐fold increase in sediment accumulation began in the mid‐1800s in the northern basin and by 1900 in the southern basin. Diatom accumulation increased 20–50‐fold since settlement with a shift from benthic‐ to planktonic‐dominated assemblages. Simultaneous with the assemblage shift were the introduction and establishment of many planktonic diatoms considered ubiquitous indicators of eutrophy. The fossil diatom assemblages were further analyzed using weighted‐averaging calibration and reconstruction of historical water column total phosphorus (TP). Reconstructed TP values showed that water column nutrient values have increased 2.5–3‐fold since presettlement times. Presettlement values of about 0.02 mg/L TP were found in both cores with TP increases beginning c. 1910 and especially dramatic increases after World War II. Modern reconstructed TP values (about 0.055 mg/L) were similar to TP concentrations reported from monitoring during the last few decades; however, the river was clearly impacted well before monitoring efforts were begun.
Differences Among Coccoid Green Algal Communities in Minnesota and North Dakota Lakes
Authors: Fawley P. K. , Fawley M. W.
Published: March 2003

Very little is known about the diversity and distribution of freshwater unicellular coccoid green algae. The simple morphology and small size of these organisms make reliable identification extremely difficult. Current hypotheses suggest that species of coccoid algae are widely distributed, opportunistic organisms that are always present in aquatic systems. These hypotheses are based on the assumption that phytoplankton communities include only one or a few species of coccoid algae. We examined the diversity and distribution of green‐colored autosporic coccoid algae in Itasca State Park in Minnesota and Arrowwood National Wildlife Refuge in North Dakota using molecular techniques and light microscopy. Our preliminary results indicate a higher level of diversity of coccoid green algae than has been reported in regional flora. Contrary to current hypotheses, communities of coccoid green algae vary among the different lakes.
Species Diversity of Microbial Communities in a Northern Temperate Humic Lake
Authors: Graham J. M. , Kent A. D. , Lauster G. H. , Yannarell A. C. , Graham L. E. , Kratz T. K. , Triplett E. W.
Published: March 2003

Species richness and species diversity of bacterioplankton, phytoplankton and protoplankton were examined in Crystal Bog, a humic lake in northern Wisconsin, as part of an NSF sponsored Microbial Observatory Program. Crystal Bog is part of the North Temperate Lakes Long‐Term Ecological Research site. Automated ribosomal intergenic spacer analysis (ARISA) was used to assess bacterial diversity. Phytoplankton and protoplankton were enumerated in a settling chamber with an inverted microscope. Four distinct phases in the ice‐free season of the bog can be recognized based on microbial populations. The first phase extends from ice‐out until about the first week of April. During this phase three species of dinoflagellates come to dominate the phytoplankton, with Glenodinium quadridens representing 60% of total phytoplankton biovolume. By mid‐April the spring dinoflagellate blooms collapse. The second phase is a period of instability as a series of species dominates the phytoplankton. In mid‐July dinoflagellates again dominate the third phase, and Peridinium limbatum alone represents 90% of the bog phytoplankton. The fourth phase is a stable period as P. limbatum slowly declines in late summer and fall. A strong correlation was found between bacterial and phytoplankton diversity (Shannon–Weaver Index) in this bog, suggesting the two microbial communities are linked. The protoplankton, however, were relatively uniform throughout the ice‐free period. The ice‐covered period may be treated as a fifth phase. When snow accumulates over the ice‐covered bog, light penetration is blocked and photosynthesis shut off. Heterotrophic protozoa assume dominance in the plankton.
The Plastid of Dinophysis (Dinophyceae): Phylogenetic Evidence for a Permanent Replacement
Authors: Hackett J. D. , Maranda L. , Bhattacharya D.
Published: March 2003

In the photosynthetic dinoflagellate Dinophysis, pigment composition and ultrastructural characters place the origin of the chloroplast with the cryptophytes. Presented here is the first molecular data from the plastid of Dinophysis. We cloned and sequenced the coding regions of psbA and small subunit (SSU) rDNA from four populations of D. acuminata and from D. acuta. These data were used to test two hypotheses about Dinophysis plastid evolution: (1) The plastid is of cryptophyte origin; and (2) The plastid is a permanent replacement. The psbA‐coding region was identical among the populations of D. acuminata and between this species and D. acuta. On the other hand, the SSU rDNA showed polymorphisms, both between species and among populations. Phylogenetic analysis shows that both psbA and SSU rDNA sequences firmly place the Dinophysis spp. plastid within the cryptophytes, confirming its origin through plastid replacement. The polymorphic SSU rDNA sequences group together and are sister to a cryptophyte ultraplankter (OCS20). The SSU rDNA sequence heterogeneity between species (about 1%) is comparable to the heterogeneity among different isolates of D. acuminata, suggesting these are population‐level differences and not indicative of different plastid captures by Dinophysis. Interestingly, a second class of cloned coding regions was also isolated from each population. These psbA and SSU rDNA sequences were evolutionarily more divergent and specifically related to florideophyte red algae. Given the mixotrophic habit of Dinophysis, the possibility arises that this second class may have come from red algal preys in the food vacuoles of our single‐cell isolates. These results highlight the importance of sampling multiple genes and populations in determining the complex evolutionary history of the Dinophysis plastid.
A New Method for Studying Nutrient Limitation of Periphyton: A Case Study From Acid Mine Drainage Streams
Authors: Hamsher S. E. , Casamatta D. A. , Filkin N. R. , McClintic A. S. , Chiasson W. B. , Verb G. R. , Vis M. L.
Published: March 2003

Acid mine drainage (AMD) affects about 16 900 km of streams in the Appalachian region, but little is known about the biology of these habitats. Typically, these habitats have low primary productivity most likely due to metal stress. However, these streams are also very low in nutrients. Traditionally, nutrient limitation studies of periphyton have been conducted employing terracotta pots. Recently, research has concluded that this methodology may have inherent flaws due to variable porosity. Therefore, development of new nutrient diffusing substrates is needed. To test a new approach for nutrient diffusion, Petri dishes were filled with agar and the nutrient of choice. A Whatman glass microfiber filter (GF/F) was attached to the top of the dish, which served as the medium through which the nutrients diffused and as a uniform surface area for periphyton colonization. Before testing in a stream impacted by acid mine drainage, laboratory studies were conducted to simulate field conditions. The Petri dishes readily diffused the nutrients and were durable to the acid conditions. Six replicates with a control, nitrogen (0.5 M), phosphorus (0.5 M), and nitrogen + phosphorus (0.5 M of each) Petri dishes were deployed in four AMD impacted streams for the month of February. Samples were analyzed for chlorophyll a, ash‐free dry mass (AFDM), and taxa present. The chlorophyll a analyses showed the phosphorus treatment to be significantly (P < 0.05) greater than all other treatments and the nitrogen treatment was significantly (P < 0.05) lower. However, these trends were not seen in the AFDM results with no difference among treatments detected. Seasonal assessment of this approach is currently under way.
Intraspecific Genetic Variation in H. Irritans, a Fungal Endosymbiont of Marine Brown Algae on the North American Pacific Coast
Authors: Harvey J. B. J.
Published: March 2003

The marine ascomycete genus Haloguignardia occurs endophytically in members of the marine brown algal family Sargassaceae globally. This example of endosymbiosis has been morphologically described: the fungal component internally infects the algal host resulting in prolific cell growth, forming galls composed chiefly of host algal cells but containing fungal reproductive structures and vegetative hyphae. H. irritans induces the formation of galls in the brown algae Cystoseira osmundacea and Halidrys dioica along the Pacific coast from Oregon to Baja California, Mexico. Using culture‐independent molecular techniques, I sequenced the 18S rDNA gene region for H. irritans and generated a 18S‐based taxonomy consistent with the current taxonomy for this morphological species. In order to study intraspecific genetic variation in H. irritans, I have sequenced the ITS rDNA (ITS 1, 2 and the 5.8 s) regions for five separate gall‐tissue samples from Santa Rosa Island in southern California and for five samples from Monterey and Carmel in central California. Intraspecific DNA sequence variation in the ITS regions of H. irritans reveals consistent sequence divergence between sites sampled. The fungal ITS regions for H. irritans total 613 bp in length and contain 40 synapomorphic characters for a total of 6.5% variation in informative loci between southern and central Californian sites. This value is similar to those found for the ITS and other gene regions previously used by researchers investigating species boundaries at the intraspecific level in symbiotic, terrestrial fungi. In addition to ITS 1, 2 and the 5.8 s gene regions, I am currently using the 5’ end of the EF1a coding region to construct intraspecific genealogies for H. irritans. By comparing these genealogies to each other and to the geographic distribution of samples, I aim to determine if more than one genetic species is present within the morphological species H. irritans.
Phylogenetic Analysis of the Mischococcales, Tribonematales, and Vaucheriales (Xanthophyceae) Inferred from 18S rRNA Gene Sequences
Authors: McElhinney A. , Bailey J. C. , Andersen R. A.
Published: March 2003

The Xanthophyceae have traditionally been classified using a phenetic classification system based upon vegetative cell structure. Species belonging to the class are placed in one of six orders corresponding to amoeboid, coccoid, filamentous, flagellate, palmelloid, or siphonous organization. Nuclear 18S rRNA gene sequences were determined for 29 species and aligned with 10 previously determined sequences. Parsimony and maximum likelihood trees inferred from these data imply that the orders Mischococcales (coccoid), Tribonematales (filamentous), and Vaucheriales (siphonous) are not monophyletic. The majority of species are divided between two clades defined by the presence or absence of a bipartite cell wall. Also, several families, particularly those placed in the Mischococcales, are resolved as polyphyletic. Results indicate that coccoid and filamentous life forms may have arisen independently at least three times, and some coccoid and filamentous life forms are resolved as closely related. For example, Heterococcus (filamentous) is more closely related to Mischococcus and Pseudopleurochloris (coccoid) than it is to other members of the Tribonematales. Our data strongly support the contention that Bumilleriopsis and Pseudobumilleriopsis are congeneric with Bumilleria. The siphonous xanthophytes including Asterosiphon, Botrydium, and Vaucheria probably do not form a monophyletic group although robust bootstrap support for this conclusion is low. Our results indicate that the generic, familial, and ordinal classification of the Xanthophyceae requires major revision.
Validation of an Instrument Designed to Assess Medical Student Attitudes Toward Home Care
Authors: Boal Jeremy , Fabacher Diane , Miller Roberta , Siu Albert , Kantor Bonnie , Flaherty Joseph
Published: March 2003

OBJECTIVES: To develop and validate an instrument to assess medical students' attitudes toward home care.

DESIGN: Survey administration before and following participation in a home care training program.

SETTING: Five medical schools in the United States.

PARTICIPANTS: 326 third and fourth year medical students.

MEASUREMENTS: Factor analysis was performed on all posttests. Domains were tested for internal reliability (Chronbach's α). Interdomain correlation was tested. One‐way analysis of variance (ANOVA) was used to determine whether the results for each domain differed among the five programs.

RESULTS: Using exploratory factor analysis, the original 20‐item survey was revised to yield a 14‐item survey consisting of four domains (general attitudes, home‐based therapies, home care training, and time and reimbursement). Domain intra‐item reliability ranged from 0.60 to 0.82. Interdomain correlations were found to be significant with the exception of one comparison (time and reimbursement and home care training). One‐way ANOVA showed significant differences between the training programs for two of the four domains (home‐based therapies and home care training). For a third domain, time and reimbursement, there was a trend toward differences across the schools (P = 0.06).

CONCLUSION: The instrument described in this paper is a reliable and valid instrument for assessing the impact of home care training on medical student attitudes across a series of important domains.