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At least 127 records · Page 7Linked to original sources
PubMed2006

Predicting understorey structure from the presence and composition of canopies: an assembly rule for marine algae.

Assembly rules provide a useful framework for predicting patterns of community assembly under defined environmental conditions. Habitat created by canopy-forming algae (such as kelps) provides a promising system for identifying assembly rules because canopies typically have a large and predictable influence on understorey communities. Across >1,000 km of subtidal South Australian coastline, we identified natural associations between assemblages of understorey algae and (1) monospecific canopies of Ecklonia radiata, (2) canopies comprised of E. radiata mixed with Fucales (Cystophora spp. and Sargassum spp.), and (3) gaps among canopies of algae. We were able to recreate these associations with experimental tests that quantified the assembly of understorey algae among these three habitat types. We propose the assembly rule that understorey communities on subtidal rocky coast in South Australia will be (1) monopolised by encrusting coralline algae beneath monospecific canopies of E. radiata, (2) comprised of encrusting corallines, encrusting non-corallines, and sparse covers of articulated corallines, beneath mixed E. radiata-Fucales canopies, and (3) comprised of extensive covers of articulated corallines and filamentous turfs, as well as sparse covers of foliose algae and juvenile canopy-formers, within gaps. Consistencies between natural patterns and experimental effects demonstrate how algal canopies can act as a filter to limit the subsets of species from the locally available pool that are able to assemble beneath them. Moreover, the subsets of species that assemble to subtidal rocky substrata in South Australia appear to be predictable, given knowledge of the presence and composition of canopies incorporating E. radiata.

Analysis of Variance↗
PubMed1992

Degradation of azo dyes by algae.

The degradation of azo dyes by algae was evaluated and it was found that certain algae can degrade a number of azo dyes to some extent. The reduction rate appears to be related to the molecular structure of the dyes and the species of algae used. The azo reductase of algae is responsible for degrading azo dyes into aromatic amine by breaking the azo linkage. The aromatic amine is then subjected to further metabolism by algae. It is proposed in this paper that in stabilization ponds, algae can play a direct role in the degradation of azo dyes, rather than only providing oxygen for bacterial growth.

Journal Article↗
PubMedDate not supplied

Differentiation of Candida guilliermondii varieties by lectin-like substances from marine algae.

Lectin-like substances of 54 marine algae, corresponding to 30 red algae and 24 brown algae, were studied to estimate the agglutination activity against Candida guilliermondii. Extracts of Dictyopteris membranacea, Bifurcaria bifurcata, Halidrys siliquosa, Ascophyllum nodosum, Fucus serratus and F. spiralis algae showed selective agglutinating activities for C. guilliermondii "sensu stricto" and some of its varieties. According to their response to agglutination (positive or negative), certain algal extracts enabled the differentiation of varieties of C. guilliermondii independently of the titre values. Three extracts of brown algae were sufficient to identify 4 varieties of C. guilliermondii. The results suggest that lectin-like substances from marine algae may be valuable reagents as assistant tools for the identification of yeast strains.

Agglutination↗
PubMed2005

Divergence of the mitochondrial electron transport chains from the green alga Chlamydomonas reinhardtii and its colorless close relative Polytomella sp.

Compelling evidence exists that the colorless algae of the genus Polytomella arose from a green Chlamydomonas-like ancestor by losing its functional photosynthetic apparatus. Due to the close relationship between the colorless and the green chlorophyte, Polytomella sp. appeared as a useful indicative framework for structural studies of Chlamydomonas reinhardtii mitochondria. However, comparative studies reported here unexpectedly revealed significant differences between the mitochondrial respiratory systems of the two algae. Two-dimensional blue native/SDS-PAGE of isolated mitochondria indicated that cytochrome-containing respiratory complexes III and IV in the two chlorophytes contrast in size, subunit composition and relative abundance. Complex IV in Polytomella is smaller than its counterpart in C. reinhardtii and occurs in two forms that differ presumably in the presence of subunit COXIII. The cytochrome c and the iron-sulfur Rieske protein of both chlorophytes revealed structural differences on the amino acid sequence level. Under comparable culture conditions, the colorless alga exhibits lower levels of cytochrome c and complex IV but a higher respiratory activity than the green alga. Cytochrome c levels were also found to be differently regulated by the growth conditions in both algae. The divergence between the respiratory systems in the two related chlorophytes can be viewed as a consequence of the loss of photosynthetic activity and/or of the adaptation to the environment via the acquisition of a more flexible, heterotrophic metabolism. Our understanding of mitochondrial function and evolution is expected to be greatly enhanced via further parallel studies of photosynthetic/non-photosynthetic algae, for which this study forms an incentive.

Amino Acid Sequence↗
PubMed2004

Biokinetics of cadmium, selenium, and zinc in freshwater alga Scenedesmus obliquus under different phosphorus and nitrogen conditions and metal transfer to Daphnia magna.

The uptake of Cd, Se(IV) and Zn by the freshwater alga Scenedesmus obliquus and the subsequent transfer and release budget in Daphnia magna were investigated under different nutrient additions and cell incubation conditions. An increase in ambient phosphate concentrations from 0.5 micromol l(-1) to 50 micromol l(-1) significantly increased the intracellular accumulation of Cd (by 18x) and Zn (by 5x), but decreased the accumulation of Se (by 126x) in the alga. The percentage of these metals distributing in the intracellular pool of algae also increased substantially with increasing ambient P concentrations. Nitrate addition from 5.0 to 200 micromol l(-1) did not influence the uptake of any of the three metals, although a significant decrease in the intracellular Se distribution was observed. Radiolabeled algae under different nutrient manipulations (semi-continuous culture, starvation, and P-pulse treatments) were used to measure trophic transfer assimilation efficiency (AE) in Daphnia. When the algal cells were grown in a semi-continuous culture, starved for N and P, or were treated with P-pulse, the AEs of Cd and Zn were generally independent of the nutritional conditions, but the Se AE was significantly affected by different P levels. The efflux rate constants, determined during 10 d depuration following 7 days of dietary uptake, decreased significantly for Cd and Zn, but were relatively constant for Se with increasing P concentration. N-addition caused no effect on the metal efflux rate constants. P- or N-additions did not influence the release budget (including molting, neonates, excretion and feces) for all three elements in Daphnia. Our study indicated that phosphate enrichment may substantially increase metal uptake in green alga S. obliquus. Responses of trophic transfer in Daphnia to nutrient enrichment were metal specific. P-enrichment can possibly lead to considerable decrease on Se transfer from algae to zooplankton.

Animals↗
PubMed2005

Algae and UV irradiation: effects on ultrastructure and related metabolic functions.

The effects of ultraviolet radiation in the biological relevant wavebands of UV-A (315-400 nm) and UV-B (280-315 nm) on algae have become an important issue as a man-made depletion of the protecting ozone layer has been reported. However, experimental designs to investigate this issue are manifold and the target organisms are extremely diverse. Data are included from the prokaryotic cyanobacteria, haptophytes, diatoms, brown algae to green algae (fresh water, snow algae and marine species) including different habitats from marine littoral and open ocean to freshwater ponds, lakes and snow fields. A broad overview on UV effects on algae is given, with a focus on structurally visible changes. Here we report on destruction in chloroplasts, mitochondria, and the occurrence of structures that are likely to be related to the UV stress. In addition several new data are presented from organisms that have to face naturally high UV irradiation due to their habitats. As no disturbances are reported in these organisms, they obviously have a set of protective mechanisms allowing survival in extreme habitats such as snow fields. Physiological changes as a consequence of UV irradiation are included, effects on the DNA level are summarized, and avoidance strategies are discussed. Every effort has been made to summarize the diverse observations and critically evaluate and compare the different experimental strategies to study UV effects in algae.

Adaptation, Physiological↗
PubMed1997

Determining surface areas of marine alga cells by acid-base titration method.

A new method for determining the surface area of living marine alga cells was described. The method uses acid-base titration to measure the surface acid/base amount on the surface of alga cells and uses the BET (Brunauer, Emmett, and Teller) equation to estimate the maximum surface acid/base amount, assuming that hydrous cell walls have carbohydrates or other structural compounds which can behave like surface Brönsted acid-base sites due to coordination of environmental H2O molecules. The method was applied to 18 diverse alga species (including 7 diatoms, 2 flagellates, 8 green algae and 1 red alga) maintained in seawater cultures. For the species examined, the surface areas of individual cells ranged from 2.8 x 10(-8) m2 for Nannochloropsis oculata to 690 x 10(-8) m2 for Dunaliella viridis, specific surface areas from 1,030 m2.g-1 for Dunaliella salina to 28,900 m2.g-1 for Pyramidomonas sp. Measurement accuracy was 15.2%. Preliminary studies show that the method may be more promising and accurate than light/electron microscopic measurements for coarse estimation of the surface area of living algae.

Cell Division↗
PubMed2001

Phytochelatin production in freshwater algae Stigeoclonium in response to heavy metals contained in mining water; effects of some environmental factors.

Production of phytochelatins (PC) in two freshwater, filamentous green algae of the genus Stigeoclonium, in response to heavy metals contained in mining water was studied. Stigeoclonium sp. grown abundantly in ditches with the mining water (southern Poland) accumulated high amounts of heavy metals. The other studied alga Stigeoclonium tenue Kütz. was isolated from unpolluted lake water in the Netherlands. Both algae exposed to the heavy metal mixture (17 microM; mainly zinc) contained in the hard, alkaline (pH 8.2) mining water produced similar amounts of phytochelatins (PC2 and PC3): 500-600 nmol SH g(-1) dry weight. After water acidification to pH 6.8, a > 2-fold increase of the total phytochelatin level as well as the appearance of longer chain peptide PC4 in the cells of both algae was observed. The concentration of labile forms of zinc in the acidified mining water was four times as high as that in the alkaline water. The heavy metal mixture (17 microM) in non-complexing solution of pH 6.8 caused a comparable phytochelatin production in both Stigeoclonium strains as the same mixture present in the acidified mining water. However, in the non-complexing solution of pH 8.2, the metal mixture induced in algae more PCs than at pH 6.8. A positive effect of bicarbonate enrichment in the solution on the PC production in S. tenue was also observed. Stigeoclonium sp. exposed to high concentrations (10 microM) of individual metals (Zn, Pb and Cd available as free cations) synthesised much higher amounts of phytochelatins (PC2-PC4) than in response to the metal mixture contained in the mining water. The order of PC induction by the studied metals in the Stigeoclonium sp. was Cd > Pb > Zn. Addition of suspended solid matter to the heavy metal solution resulted in essential quantitative changes in phytochelatins in algal cells; a considerable decrease of PC2, PC3 and PC4 levels was observed. The PC production in algae of the genus Stigeoclonium exposed to the heavy metal mixture is discussed in the context of various metal bioavailability and the algal adaptation to complex aquatic environment.

Bicarbonates↗
PubMed2003

Radionuclides and trace metals in eastern Mediterranean Sea algae.

Three types of sea alga distributed along the Syrian coast have been collected and analyzed for radioactivity and trace elements. Results have shown that (137)Cs concentrations in all the analyzed sample were relatively low (less than 1.2 Bq kg(-1) dry weight) while the levels of naturally occurring radionuclides, such as (210)Po and (210)Pb, were found to be high in most samples; the highest observed value (27.43 Bq kg(-1) dry weight) for (210)Po being in the red Jania longifurca alga. In addition, most brown alga species were also found to accumulate (210)Po, which indicates their selectivity to this isotope. On the other hand, brown alga (Cystoseira and Sargassum Vulgare) have shown a clear selectivity for some trace metals such as Cr, As, Cu and Co, this selectivity may encourage their use as biomonitor for pollution by trace metals. Moreover, the red alga species were found to contain the highest levels of Mg while the brown alga species were found to concentrate Fe, Mn, Na and K and nonmetals such as Cl, I and Br.

Cesium Radioisotopes↗
PubMed1986

Use of the beta-carotene rich alga Dunaliella bardawil as a source of retinol.

Dunaliella bardawil, a beta-carotene accumulating halotolerant alga, has been tested as a source of retinol in a chick diet. Chicks were fed diets deficient in retinol or supplemented with retinol, synthetic beta-carotene or dry algae. After an initial lag, chicks grew equally well on diets supplemented with algae, retinol or beta-carotene. Serum and liver analyses revealed a normal content of retinol in all chicks except those grown on the retinol-deficient diet. Chicks fed the algae-supplemented diet contained lutein but no beta-carotene in their serum, even though the ratio of beta-carotene to lutein in the algae was over 15:1. Laying hens fed with an algae-supplemented diet showed enhanced egg yolk colour attributable to a higher lutein content. No beta-carotene was present in the egg-yolk. These studies demonstrate the possibility of using dried Dunaliella bardawil as a dietary supplement which can fully satisfy the retinol requirement and also serve as a yolk-colour enhancing agent.

Animal Nutritional Physiological Phenomena↗
PubMed2006

Influence of the drying conditions of Sargassum sp. alga on the bioadsorption of hexavalent chromium.

Industrial wastes containing synthetic organic compounds and heavy metals are among the most dangerous residues, whose growth has followed the increase in industrial activity. Heavy metals are readily assimilated into the food chain and therefore easily accumulated in the ecosystem. To remove heavy metals from aqueous solutions, marine algae may be used as adsorbents either in their natural form or after treatments by a cross-linking process to improve their mechanical resistance. Drying of biosorbents, such as marine algae, is mentioned in many previous works as a step preceding the adsorption/dessorption cycle. Concerning algae, drying of its fresh biomass allows for proper storage and enhances performance in the sorption of heavy metals. In this work, physical and morphological analyses of fresh and dried Sargassum sp. marine algae, harvested offshore São Sebastião, São Paulo state, Brazil, were performed in order to assess the influence of drying conditions on the biosorption process. Chromium concentrations were also determined in different parts of the algal structure before and after the biosorption process. The drying promoted structural changes in the algae, like shrinkage and porosity reduction. It was also observed that the chromium retention was dependent on the structural arrangement of the alga parts, in which the leaf was the major biosorbent.

Adsorption↗
PubMed2005

Effects of enhanced ultraviolet-B radiation on algae and cyanobacteria.

This article provides an overview of existing literature on the ultraviolet-B (UV-B) radiation effects on algae and cyanobacteria. We report on the effects of UV-B radiation to the growth and development, biomass, sensitivity, photosynthetic pigments, UV-B absorbing compounds, photosynthesis, protein and DNA damage, enzyme activity, nitrogen fixation and assimilation of nitrogen, protective mechanisms of algae and cyanobacteria, the accommodation of algae and cyanobacteria to environmental stress, and the effects to ecology system. Many of the studies show the dramatic effects of UV-B radiation; but typically these studies were conducted under conditions with supplemental UV-B irradiance that was higher than would ever occur outside experimental conditions or natural condition. A few of the studies reviewed used experimental conditions and supplemental UV-B irradiance that approached realism. Enhanced UV-B generally decreased chlorophyll content, whereas it increased UV-B absorbing compounds in many algae. Decrease in photosynthesis, particularly at higher UV-B doses, was due to both direct (effect on photosystem) and indirect (decrease in pigments) effects. The decreases in chlorophyll pigments and photosynthesis resulted in lower biomass. However, algae and cyanobacteria have evolved various avoidance and repair mechanisms to protect themselves against the damaging effects of UV radiation to acclimate to enhanced UV-B radiation. The review points to areas where further studies on the relationships among nitrogenase, Rubisco, antioxidase activity, signal, antioxidants, and free radicals under enhanced UV-B are needed to quantify the effects of UV-B radiation on algae and cyanobacteria. These studies are needed in order to develop dose response functions that can facilitate development of dynamic simulation models for use in UV-B and other environmental impact assessments.

Cyanobacteria↗
PubMed2002

Inhibition of mast cells by algae.

There is a history of use of algae as foods and as food additives, or nutraceuticals. Although algae are a safe component of human foods and animal feeds, the effects of the algae other than as a source of protein are not clear. We examined the prevalence of an antiinflammatory activity in selected algae using, as an assay system, the inhibition of histamine release from mast cells. Methanolic extracts of eleven algae were examined for activity to inhibit the release of histamine from mast cells in vitro. This activity was found widely among the samples tested. The activities of these extracts were not uniformly stable in acid methanol. Selected extracts studied further did not separate with the use of size-exclusion filtration filters. LH-20 chromatography suggested at least two main elution areas of activity of the Chlorella extract. In summary, we saw wide phylogenetic dispersion of mast cell inhibition activity, suggesting that this antiinflammatory property is common in algae. This effect was apparently due to multiple activities within the algal extracts.

Algal Proteins↗
PubMed2003

Phragmoplastin, green algae and the evolution of cytokinesis.

Phragmoplast-mediated cell division characterizes the land plants in the streptophyte lineage and some species of the green algal orders Coleochaetales, Charales and Zygnematales that are basal to that lineage. This type of cell division is generally not found in the other green plant lineage, the chlorophyte algae. A well-developed phragmoplast-type cell division has been documented, however, in two subaerial green algae (Cephaleuros parasiticus and Trentepohlia odorata) belonging to the order Trentepohliales--an order that molecular sequence data place unequivocally within the chlorophytes rather than streptophytes. Is the phragmoplast-mediated cell division of the Trentepohliales a case of homology or non-homology? To gain more insight into this question, we are exploring the potential phylogenetic information inferred from gene sequences of phragmoplastin, a dynamin-like protein that has been associated with cell-plate formation during phragmoplast-mediated cytokinesis in land plants. Primers for green algae were designed based on an available phragmoplastin sequence from soybean and yielded PCR amplifications from the trentepohlialean green algae Trentepohlia and Cephaleuros and the leafy liverwort Bazzania: These are the first published data for phragmoplastins in algae and liverworts. Analysis of phragmoplastin gene sequences in chlorophyte and streptophyte green algae may help to chart the evolution of the development of the phragmoplast.

Cell Division↗
PubMed1967

Glycolate pathway in algae.

No glycolate oxidase activity could be detected by manometric, isotopic, or spectrophotometric techniques in cell extracts from 5 strains of algae grown in the light with CO(2). However, NADH:glyoxylate reductase, phosphoglycolate phosphatase and isocitrate dehydrogenase were detected in the cell extracts. The serine formed by Chlorella or Chlamydomonas after 12 seconds of photosynthetic (14)CO(2) fixation contained 70 to 80% of its (14)C in the carboxyl carbon. This distribution of label in serine was similar to that in phosphoglycerate from the same experiment. Thus, in algae serine is probably formed directly from phosphoglycerate. These results differ from those of higher plants which form uniformly labeled serine from glycolate in short time periods when phosphoglycerate is still carboxyl labeled. In glycolate formed by algae in 5 and 10 seconds of (14)CO(2) fixation, C(2) was at least twice as radioactive as C(1). A similar skewed labeling in C(2) and C(3) of 3-phosphoglycerate and serine suggests a common precursor for glycolate and 3-phosphoglycerate. Glycine formed by the algae, however, from the same experiments was uniformly labeled. Manganese deficient Chlorella incorporated only 2% of the total (14)CO(2) fixed in 10 minutes into glycolate, while in normal Chlorella 30% of the total (14)C was found in glycolate. Manganese deficient Chlorella also accumulated more (14)C in glycine and serine.Glycolate excretion by Chlorella was maximal in 10 mm bicarbonate and occurred only in the light, and was not influenced by the addition of glycolate. No time dependent uptake of significant amounts of either glycolate or phosphoglycolate was observed. When small amounts of glycolate-2-(14)C were fed to Chlorella or Scenedesmus, only 2 to 3% was metabolized after 30 to 60 minutes. The algae were not capable of significant glycolate metabolism as is the higher plant. The failure to detect glycolate oxidase, the low level glycolate-(14)C metabolism, and the formation of serine from phosphoglycerate rather than from glycolate are consistent with the concept of an incomplete glycolate pathway in algae.

Carbon Isotopes↗
PubMed1980

Thermotropic Properties of Thermophilic, Mesophilic, and Psychrophilic Blue-green Algae.

Thermotropic properties of blue-green algae grown at high, room, and low temperatures in H(2)O and D(2)O media were studied by highly sensitive differential scanning microcalorimetry. The thermograms of these organisms contain an endothermal peak in the temperature range of 50 to 70 C with an endothermal heat ranging from 0.14 to 1.91 joules per gram organism. The temperature at which the endothermal peak occurs is comparable with the thermal denaturation temperature of phycocyanin, the major biliprotein isolated from these algae. A good correlation can be found for the relative thermal stability of various organisms with that of the isolated biliproteins. The ability of these algae to resist thermal disruption is correlated with the thermal environments in which these algal cells grow. The thermal stability of normal algae is in the order of thermophile > mesophile > psychrophile. It was found that the deuterated mesophilic algae were less able to resist thermal disruption than ordinary mesophilic algae.

Journal Article↗
PubMed1982

Measurement of photorespiration in algae.

The rates of true and apparent photosynthesis of two unicellular green algae, one diatom and four blue-green algae were measured in buffer at pH 8.0 at subsaturating concentrations of dissolved inorganic carbon (13-27 micromolar). Initial rates of depletion from the medium of inorganic carbon and (14)C activity caused by the algae in a closed system were measured by gas chromatography and by liquid scintillation counting, respectively. The rate of photorespiration was calculated as the difference between the rates of apparent and true photosynthesis. The three eucaryotic algae and two blue-green algae had photorespiratory rates of 10 to 28% that of true photosynthesis at air levels of O(2). Reduction of the O(2) level to 2% caused a 52 to 91% reduction in photorespiratory rate. Two other blue-green algae displayed low photorespiratory rates, 2.4 to 6.2% that of true photosynthesis at air levels of O(2), and reduction of the O(2) concentration had no effect on these rates.

Journal Article↗
PubMed2003

The mitochondrial genome of Chara vulgaris: insights into the mitochondrial DNA architecture of the last common ancestor of green algae and land plants.

Mitochondrial DNA (mtDNA) has undergone radical changes during the evolution of green plants, yet little is known about the dynamics of mtDNA evolution in this phylum. Land plant mtDNAs differ from the few green algal mtDNAs that have been analyzed to date by their expanded size, long spacers, and diversity of introns. We have determined the mtDNA sequence of Chara vulgaris (Charophyceae), a green alga belonging to the charophycean order (Charales) that is thought to be the most closely related alga to land plants. This 67,737-bp mtDNA sequence, displaying 68 conserved genes and 27 introns, was compared with those of three angiosperms, the bryophyte Marchantia polymorpha, the charophycean alga Chaetosphaeridium globosum (Coleochaetales), and the green alga Mesostigma viride. Despite important differences in size and intron composition, Chara mtDNA strikingly resembles Marchantia mtDNA; for instance, all except 9 of 68 conserved genes lie within blocks of colinear sequences. Overall, our genome comparisons and phylogenetic analyses provide unequivocal support for a sister-group relationship between the Charales and the land plants. Only four introns in land plant mtDNAs appear to have been inherited vertically from a charalean algar ancestor. We infer that the common ancestor of green algae and land plants harbored a tightly packed, gene-rich, and relatively intron-poor mitochondrial genome. The group II introns in this ancestral genome appear to have spread to new mtDNA sites during the evolution of bryophytes and charalean green algae, accounting for part of the intron diversity found in Chara and land plant mitochondria.

Base Sequence↗