bluuebunny/crossref_metadata_2025_split huggingface dataset:
STRESS TOLERANCE IN INTERTIDAL SEAWEEDS
Authors: Davison Ian R. , Pearson Gareth A. 
Published: October 2004

ABSTRACTIntertidal seaweeds are periodically exposed to air where they experience a variety of potentially stressful environmental conditions, including nutrient limitation, high light, high and low temperature, desiccation, and osmotic stress. This paper considers the current understanding of stress tolerance in intertidal seaweeds and discusses ways in which future research could increase our understanding of the role of environmental factors in the ecology and physiology of these algae. We believe research is required in at least three areas. 1) Laboratory physiological studies have established that correlations exist between stress tolerance and the vertical distribution of species. However, little information is available on the importance of stress in determining community structure in nature. Field experiments are essential to relate the impact of single or multiple stresses on the survival, growth, and reproductive output of macroalgae. In paticular, it is necessary to clarify the role of sublethal stress in determining the outcome of competitive interactions. 2) With the exception of obvious lethal effects or damage associated with extreme environmental conditions, such as unusually hot and dry weather, it is difficult to evaluate the occurrence and severity of stress in natural populations of seaweeds. There is a need to develop molecular and biochemical markers specific for individual stresses or groups of stresses to allow the unambiguous and direct determination of stressin situ.3) Despite the apparent importance of stress in intertidal seaweeds, we are largely ignorant of the mechanistic basis of tolerance. The application of currently available tools of molecular and cell biology to the investigation of stress‐induced transcriptional and translational changes could enormously increase our understanding of both the sites of, and pathways involved in, stress tolerance. In summary, there are numerous unanswered fundamental questions about the stress tolerance of intertidal seaweeds, providing opportunities for research ranging from field ecology to molecular biology and biochemistry.
SHORT‐TIME SCALE DEVELOPMENT OF A GYMNODINIUM CATENATUM POPULATION IN THE RIA DE VIGO (NW SPAIN)1
Authors: Fermín Eglée Gómez , Figueiras Francisco G. , Arbones Belén , Villarino María Luisa 
Published: October 2004

ABSTRACTWind direction and fresh water runoff determine the circulation pattern of the Ría de Vigo (NW Spain), which in turn influence the selection and distribution of its phytoplankton populations. Coastal winds with a south–southwesterly component reverse the positive estuarine circulation in the Ría, causing an off‐shore to in‐shore flow of surface waters and, consequently, the outflow of inner waters via deeper layers. We found that this reversal imposed a selective force on the phytoplankton population: diatoms, which could not counteract the sinking movement of the surface waters, were diminished, while dinoflagellates remained in the water column. From the end of September to the beginning of October 1993, an accumulation of Gymnodimium catenatum Graham was observed coinciding with an intrusion of coastal water induced by westerly winds which provoked a reversal in the circulation of the Ría. The slow reestablishment of the positive estuarine circulation pattern, which was due to a weak coastal upwelling and considerable fresh water runoff, allowed the population of G. catenatum to flourish.
BIOENERGETIC PROCESSES ARE MODIFIED DURING NITROGEN STARVATION AND RECOVERY IN PHORMIDIUM LAMINOSUM (CYANOPHYCEAE)1
Authors: Ochoa de Alda Jesús A. G. , Tapia María I. , Llama María J. , Serra Juan L. 
Published: October 2004

ABSTRACTIn the non‐N2‐fixing cyanobacterium Phormidium laminosum (Agardh) Gomont (strain OH‐I‐pCl1), N starvation induced an increase in the rate of respiration and a decrease in the rate of O2 evolution. When NO3− was added to illuminated N‐starved cells, O2 evolution immediately increased to levels shown by NO3− grown cells, even though N‐starved cells had lost most of their in vitro photosynthetic activities. Stimulation of noncyclic electron flow was maximal under light‐saturating conditions and after 2–3 days of N starvation. The respiratory rate of N‐starved cells was stimulated by the addition of NO3− or NH4+ and partially inhibited at very low irradiances, even in the presence of DCMU (3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea). Results indicate that N‐starved cells obtain the energy supply for N assimilation through a process different from that used by N‐sufficient cells. N‐starved cells were able to take up NO3− in the dark and when illuminated in the presence of DCMU under anaerobiosis. Following NO3− addition, the photosynthetic yield of the in vivo noncyclic electron transport slightly increased, whereas it decreased after NH4+ addition. Addition of NO3− or NH4+ favored photoinhibition of photosystem II, the effect being faster after NH4+ addition.
SYNTHESIS AND BINDING OF PHYCOERYTHRIN AND ITS ASSOCIATED LINKERS TO THE PHYCOBILISOME IN RHODELLA VIOLACEA (RHODOPHYTA): COMPARED EFFECTS OF HIGH LIGHT AND TRANSLATION INHIBITORS1
Authors: Bernard Cécile , Etienne Anne‐Lise , Thomas Jean‐Claude 
Published: October 2004

ABSTRACTWe studied the synthesis and binding of phycoerythrin and its associated linkers to the phycobilisome (PBS) in Rhodella violacea (Kornmann) Wehrmeyer and compared the effects of high light and translation inhibitors on these processes. Rhodella violacea has a simple hemidiscoidal PBS structure with a well‐known composition. The number of PBSs per cell decreases when irradiance is increased, and at higher irradiances the rods are shortened with a specific loss of the terminal hexamer of phycoerythrin (PE) and its associated linker. To test whether or not the observed variations were due to a coordination between the expression of the chloroplast‐encoded PE and the nuclear‐encoded linkers, we inhibited the expression of the chloroplast genes by the translation inhibitor chloramphenicol. In the few PBSs synthesized, the linker associated to the terminal PE hexamer was missing while that associated with the intermediate PE hexamer was still present. The inhibition by cycloheximide of the translation of the nuclear‐encoded linkers did not influence the synthesis of the chloroplast‐encoded phycobiliproteins. The absence of linkers prevented the formation of PE hexamers and their binding to the PBSs.We therefore propose the existence of two levels of regulation for PE and associated linkers: the intermediate PE hexamer and associated linker are always present even though their amount is reduced when irradiance is increased. In contrast, the terminal hexamer of PE and its associated linker are no longer present under high light. Their absence can be due to a feedback control between the level of PE and the synthesis of the linker: when the level of PE is lowered below a given value by the action of light on the chloroplast, a signal coming from the chloroplast reaches the nucleus and the synthesis of the linker is repressed. There is no sign of nuclear regulation of the synthesis of PE, but the nuclear‐encoded linkers have a structural role in the formation of PE hexamers.
EFFECT OF LOW TEMPERATURE ON THE STEREOISOMER COMPOSITION OF β‐CAROTENE IN THE HALOTOLERANT ALGA DUNALIELLA BARDAWIL (CHLOROPHYTA)1
Authors: Ben‐Amotz Ami 
Published: October 2004

ABSTRACT Dunaliella bardawil Ben‐Amotz & Avron, a β‐carotene‐accumulating halotolerant alga, was analyzed for the effect of growth temperatures on its pigment content and on the stereoisomeric composition of β‐carotene by the use of advanced liquid chromatography and photodiode array detection. Decreasing culture temperature from 30° to 10°C increased the β‐carotene content twofold and the ratio of 9‐cis to all‐trans β‐carotene fourfold, with no significant changes in the other cell pigments. The variation of total β‐carotene content by temperature was correlated with the integral irradiance received by the algal culture during a cell division cycle, whereas the 9‐cis stereoisomer increased over the amount expected by that integration. The massive accumulation of 9‐cisβ‐carotene within the β‐carotene globules is interpreted as indicating that the oily 9‐cis stereoisomer protects against the crystallization of all‐trans β‐carotene at low temperatures.
EFFECT OF TEMPERATURE ON TWO ENZYMES FROM A PSYCHROPHILIC CHLOROMONAS (CHLOROPHYTA)1
Authors: Loppes Roland , Devos Nathalie , Willem Sabine , Barthélemy Pascal , Matagne René F. 
Published: October 2004

ABSTRACTA psychrophilic green alga belonging to the Chloromonas genus and here named ANT1 was collected in Antarctica. The activities of two enzymes, nitrate reductase and argininosuccinate lyase, were measured at various temperatures and compared to the corresponding enzyme activities in the mesophilic species Chlamydomonas reinhardtii Dangeard. For both enzymes, the temperature for apparent optimal activity was about 20°C lower in ANT1 than in C. reinhardtii. The enzymes were also submitted to various heat treatments before measuring their activities. Both psychrophilic enzymes were more sensitive to heat than the corresponding mesophilic enzymes. It is worth stressing, however, that in both species nitrate reductase was much more sensitive to heat than argininosuccinate lyase, which probably indicates that the peculiar structure of each protein primarily determines its dependence to temperature. Secondary adaptations to low temperatures should then occur to confer the psychrophilic character.
WIDESPREAD PHAGOCYTOSIS OF CILIATES AND OTHER PROTISTS BY MARINE MIXOTROPHIC AND HETEROTROPHIC THECATE DINOFLAGELLATES1
Authors: Jacobson Dean M. , Anderson Donald M. 
Published: October 2004

ABSTRACTAn electron microscopic examination of large amorphous inclusions located in a variety of photosynthetic thecate dinoflagellates (Alexandrium ostenfeldii (Paulsen) Balech et Tangen, Gonyaulax diegensis Kofoid, Scrippsiella sp., Ceratium longipes (Bailey) Gran, and Prorocentrum micans Ehrenberg) and a nonphotosynthetic thecate species (Amylax sp.) revealed each inclusion to be a food vacuole, the majority of which were ingested ciliate prey. Recognizable features of these ciliates included linear arrays of basal bodies and cilia consistent with oligotrich polykinetid structure, characteristic macronuclei, chloroplasts (evidently kleptoplastids), cup‐shaped starch plates, and cylindrical extrusomes. Three species contained (apparent) nonciliate prey: Scrippsiella sp., whose food vacuoles consistently contained unusual and complex extrusome‐like cylindrical bodies having a distinctive six‐lobed, multilayered structure; P. micans, which contained an unidentified encysted cell; and a single A. ostenfeldii cell, containing a Dinophysis sp. dinoflagellate cell. Several food vacuoles of ciliate origin had a red hue. This, together with the resemblance of A. ostenfeldii cells to planozygotes, suggests that similar structures previously identified as accumulation bodies may in fact be food vacuoles and that feeding may in some cases be associated with sexual processes.
MOLECULAR IDENTIFICATION OF A BACTERIUM ASSOCIATED WITH GALL FORMATION IN THE MARINE RED ALGA PRIONITIS LANCEOLATA1
Authors: Ashen Jon B. , Goff Lynda J. 
Published: October 2004

ABSTRACTThe polymerase chain reaction (PCR) was used to amplify eubacterial small‐subunit (16S) ribosomal DNA (rDNA) genes from galls of the marine red alga Prionitis lanceolata Harvey (Gigartinales). These tumors consist of hypertrophied algal cells containing large numbers of intercellular bacteria that remain uncultivable. PCR‐amplified 16S rDNAs from surface‐sterilized gall tissue plugs were cloned, sequenced, and analyzed by alignment to available small‐subunit rRNA sequences (University of Illinois Ribosomal Database Project). Variable regions were identified and used to construct a fluorescently labeled, species‐specific oligodeoxynucleotide probe for whole cell in situ hybridization to the gall symbiont. Probe 949 (PLANC.949) localized the P. lanceolata bacterial symbiont in preparations from mature gall tissue. This probe did not hybridize to the rDNA of closely related bacteria included as controls in the same hybridization reactions, In situ hybridization revealed the presence of the same bacterium in association with P. lanceolata gall formation from three central California localities. Distance and parsimony analyses suggest that this organism is a member of the Proteobacteria (alpha subdivision; Rhodobacter group) and is most closely related to Roseobacter denitrificans.
SPORELING COALESCENCE AND INTRACLONAL VARIATION IN GRACILARIA CHILENSIS (GRACILARIALES, RHODOPHYTA)1
Authors: Santelices Bernabé , Correa Juan A. , Meneses Isabel , Aedo Diego , Varela Daniel 
Published: October 2004

ABSTRACTThis study evaluates the hypothesis that spore coalescence may cause intraclonal variation. Spore coalescence might allow the occurrence of unitary thalli that in fact correspond to genetically different, coalesced individuals. Plant portions simultaneously derived from these chimeric individuals may exhibit dissimilar growth responses even when incubated under similar abiotic conditions. Testing of the hypothesis included various approaches. Transmission electron microscopy observations of early stages of sporeling coalescence indicated that polysporic plantlets were formed by groups of spores and their derivatives. Even though adjacent cells in two different groups may fuse, these groups maintained an independent capacity to grow and form uprights. Laboratory‐grown plantlets showed a significant correlation between the initial number of spores and the total number of erect axes differentiated from the sporeling. Construction and growth of bicolor individuals indicated the chimeric nature of the coalesced individuals. Coalesced, bicolor holdfasts had green and red cells, which subsequently produced green and red uprights, respectively. Individuals fronds were also chimeric, as indicated by the production of green and red branchlets from single, red uprights. The existence of mixed tissues was further substantiated by random amplified polymorphic DNA analysis. The banding pattern produced by branchlets of a unisporic thallus was consistently monomorphic, whereas the patterns produced by the polysporic thallus were polymorphic. Growth rates of polysporic thalli had larger data dispersal and variation coefficients than oligosporic or monosporic thalli. Therefore, all results support the original hypothesis and suggest that coalescence might be ecologically more important than previously thought.
FURTHER OBSERVATIONS AND SOME COMMENTS ON THE FINE STRUCTURE OF THE CENTRIC DIATOM AULACOSEIRA ISLANDICA (BACILLARIOPHYCEAE)1
Authors: Le Cohu René 
Published: October 2004

ABSTRACTUsing light and electron microscopy, the diatom species Aulacoseira islandica (O. Müll.) Sim. was examined with special emphasis on the following characteristics: structure of the valve areolae, heterovalvy, and distribution of the rimoportulae. The mantle and valve face areolae were pores containing volate occlusions. However, observations only using transmission electron microscopy may result in an incomplete interpretation because of the fragility of the dissected system of volae. Relief valves with a stepped mantle and intaglio valves with a plain mantle occurred. Another form of heterovalvy resulted from the formation of separation valves. Linking valves had spatulate spines while separation valves bore tapering spines. In Aulacoseira, the rimoportulae usually occurred near the “Ringleiste.” The presence of several rimoportulae on the mantle was one of the most striking features in Aulacoseira islandica.
DOES LIGHT QUALITY AFFECT THE SINKING RATES OF MARINE DIATOMS?1
Authors: Fisher Anne E. , Berges John A. , Harrison Paul J. 
Published: October 2004

ABSTRACTAlthough the spectral quality of light in the ocean varies considerably with depth, the effect of light quality on different physiological processes in marine phytoplankton remains largely unknown. In cases where experiments are performed under full spectral irradiance, the meaning of these experiments in situ is thus unclear. In this study, we determined whether variations in spectral quality affected the sinking rates of marine diatoms. Semicontinuous batch cultures of Thalassiosira weissflogii (Gru.) Fryxell et Hasle and Ditylum brightwellii (t. West) Grunow in Van Huerk were grown under continuous red, white, or blue light. For T. weissflogii, sinking rates (SETCOL method) were twice as high (∼0.2 m·d−1)for cells grown under red light as for cells grown under white or blue light (∼0.08 m·d−1), but there were no significant differences in carbohydrate content (∼105 fg·μm−3) or silica content (∼ 17 fg·μ−3) to account for the difference in sinking rates. Thalassiosira weissflogii grown under blue light was significantly smaller (495 μm3) than cells grown under red light (661 μm3), which could contribute to its reduced sinking rate. However, cells grown under white light were similar in size to those grown under red light but had sinking rates not different from those of cells grown under blue light, indicating the involvement of factors other than size. There were no significant differences in sinking rate (∼0.054 m·d−1) or silica content (∼20 fg·μm−3) in D. brightwellii grown under red, white, or blue light, but cells grown under red light were significantly (20%) larger and contained significantly (20%) more carbohydrate per μm3 than cells grown under white or blue light. Spectral quality had no consistent effect on sinking rate, biochemical composition (carbohydrate or silica content), or cell volume in the two diatoms studied. The similarity in sinking rate of cells grown under white light compared to those grown under blue light supports the ecological validity of sinking rate studies done under white light.
DOES CARBOHYDRATE CONTENT AFFECT THE SINKING RATES OF MARINE DIATOMS?1
Authors: Fisher Anne E. , Harrison Paul J. 
Published: October 2004

ABSTRACTWe tested the hypothesis that positive relationships between sinking rate and irradiance were due to increases in cell density caused by accumulations of carbohydrate. In semicontinuous batch cultures of Thalassiosira weissflogii (Gru.) Fryxell el Hasle and Ditylum brightwellii (t. West) Grunow in Van Huerk, carbohydrate content was varied by growing cells under diel cycles of high or low light. Sinking rate was measured at the end of the light period and the end of the dark period, on live and heat‐killed cells. No positive correlations were found between sinking rate (which varied from – 0.060 to 0.13 m·d−1) and carbohydrate content (which varied from 10 to 950 pg · cell−1), indicating that accumulations of carbohydrate did not significantly affect sinking rate. There were no large diel variations in the sinking rate of T. weissflogii, but sinking rates of D. brightwellii grown under high light ranged from being negative (i.e. cells were floating) at the end of the light period to positive at the end of the dark period. This is the first report of positive buoyancy in vegetative D. brightwellii, a phenomenon that may only occur in D. brightwellii grown under diel cycles.
OCCURRENCE OF A TEMPERATE CYANOPHAGE LYSOGENIZING THE MARINE CYANOPHYTE PHORMIDIUM PERSICINUM1
Authors: Ohki Kaori , Fujita Yoshihiko 
Published: October 2004

ABSTRACTA temperate cyanophage was found to lysogenize the marine cyanophyte Phormidium persicinum (Reinke) Com. (Provasoli strain). The lytic cycle was induced by the addition of mitomycin C or by brief illumination with ultraviolet light. The lytic process observed under the electron microscope showed that phage particles appeared in a nucleoplasm region 15 to 24 h after the addition of mitomycin C. The induction of the lytic process occurred simultaneously in almost all cells of every trichome. Matured phage particles were released to the medium 30 to 50 h after the addition of mitomycin C. Phage particles isolated from algal lysates had a polyhedral head (about 40 nm in diameter) with a long (about 300 nm) and noncontractile tail. The most abundant protein, presumably a structural protein, had an apparent molecular mass of about 38 kDa. The genome size estimated from restriction analysis was about 50 kbp. Phage DNA was digested with several restriction endonucleases including Sau3AI and DpnI. However, MboI failed to digest the phage DNA, suggesting that the phage DNA is highly methylated. Southern blot analysis suggested that some part of the phage was in the lytic cycle in algal cells growing under normal conditions. A possible role of temperate cyanophages in the regulation of cyanophyte populations in the marine environment is discussed.
CHANGES IN DOMOIC ACID PRODUCTION AND CELLULAR CHEMICAL COMPOSITION OF THE TOXIGENIC DIATOM PSEUDO‐NITZSCHIA MULTISERIES UNDER PHOSPHATE LIMITATION1
Authors: Pan Youlian , Subba Rao Durvasula V. , Mann Kenneth H. 
Published: October 2004

ABSTRACTProduction of domoic acid (DA), a neurotoxin, by the diatom Pseudo‐nitzschia multiseries (previously Nitzschia pungens f. multiseries) Hasle and its cellular chemical composition were studied in phosphate‐limited chemostat continuous cultures and in subsequent batch cultures. Under steady‐state chemostat conditions, DA production increased from 0.01 to 0.26 pg DA · cell−1· d−1 as the growth rate decreased. When the nutrient supply was discontinued (to produce a batch culture), DA production was enhanced by a factor of ca. 3. DA production was temporarily suspended upon addition of phosphate to the batch cultures but resumed 1 d later at a higher rate coincident with the decline of phosphate uptake. In both steady‐state continuous culture and batch culture, more DA was produced when alkaline phosphatase activity (APA) was high. The association of high DA production with high levels of APA and high cellular N:P ratios strongly suggests that phosphate limitation enhances DA production. Also, DA production was high when other primary metabolism (e.g. uptake of carbon, nitrogen, phosphorus and silicon, and cell division) was low, but chlorophyll a and adenosine triphosphate were generally high. This suggests that the synthesis of DA requires a substantial amount of biogenic energy.
CHLAMYDOMONAS EUGAMETOS (CHLOROPHYTA) STORES PHOSPHATE IN POLYPHOSPHATE BODIES TOGETHER WITH CALCIUM1
Authors: Siderius Marco , Musgrave Alan , van den Ende Herman , Koerten Henk , Cambier Piet , van der Meer Pieter 
Published: October 2004

ABSTRACTWhen Chlamydomonas eugametos Moewus cells are starved of phosphate, they accumulate 32Pi much faster than before starvation. Phosphate accumulation is stimulated by calcium. Less than 5% of the 32Pi taken up by the cell is present in soluble molecules, suggesting that most is in a metabolically inactive, storage form. Nuclear magnetic resonance and X‐ray microanalysis data are presented to show that it is stored as polyphosphate in electron‐dense bodies hi the cytoplasm. The same bodies accumulate divalent cations, in particular calcium. The P/Ca ratio in the bodies was maintained between 5.4 (1‐week‐old cells) and 3.3 (5‐week‐old cells) during cultivation, suggesting that the calcium and phosphorus relations of the bodies are coupled. The possibility that these electron‐dense bodies represent calcium stores that can be released to activate calcium signaling is discussed.