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At least 811 records · Page 45Linked to original sources
PubMed2000

On site photosynthetic performance of Atlantic green algae.

Photosynthetic performance was measured on site in four common Atlantic green algae, Asparagopsis taxiforme, Valonia utricularia, Caulerpa racemosa and Codium taylori, in Gran Canaria, Canary Islands. The photosynthetic quantum yield was determined with a portable PAM instrument and with a diving PAM in the water column. Solar radiation was measured continuously above and in the water column by means of two three-channel dosimeters, ELDONET (Real Time Computer, Möhrendorf, Germany), in the UV-A, UV-B and PAR ranges. The effective photosynthetic quantum yield was found to be affected by exposure to solar radiation in as short as 15 min but recovered in the shade in most species within several hours. Only A. taxiforme failed to recover completely, and a 30-min exposure caused severe photoinhibition from which the algae recovered only partially. While most of the effect was due to the PAR wavelength range, the UV, and especially the UV-B, range considerably enhanced photoinhibition. In all four species, a significant inhibition was found even at their growth sites in the water column, measured with the diving PAM, at high solar angles.

Chlorophyta↗
PubMed2003

The alga Chlamydomonas reinhardtii UVS11 gene is responsible for cell division delay and temporal decrease in histone H1 kinase activity caused by UV irradiation.

The aim of the present work was to study the possible role of the UVS11 gene of the alga Chlamydomonas reinhardtii, in regulation of the cell cycle. To characterize the defect of a uvs11 mutant in respect to DNA damage-dependent cell cycle arrest, we examined first the influence of the tubulin-destabilizing drug methyl benzimidazole-2-yl-carbamate (MBC) on inhibition of mitosis in response to UV 254nm. Then the growth and reproductive processes and activity of cyclin-dependent kinases (CDK)-like kinases during the cell cycle of C. reinhardtii were investigated. In both, the wild type and the uvs11 mutant strain were compared under standard conditions and after DNA damage caused by UV 254nm. We assume the green alga C. reinhardtii possesses control mechanisms allowing to stop the cell cycle progression before mitosis in response to DNA damage. The results indicate that the uvs11 mutant is not able to stop the cell cycle after UV irradiation. We suggest that a product of the UVS11 gene affects cell response to DNA damage and influences a decrease in histone H1 kinase activity.

Animals↗
PubMed1989

Algae columns with anodic stripping voltammetric detection.

The use of silica-immobilized algal cells for on-line column separation in conjunction with continuous monitoring of trace metals is described. Algae-silica preparations are highly suitable for flow analysis as they couple the unique reactivity patterns and high binding capacity of algal biomass with the hydrodynamic and mechanical features of porous silica. Such advantages are illustrated by using on-line anodic stripping voltammetry and the alga Chlorella pyrenidosa. Selective and exhaustive removal of interfering constituents circumvents common problems such as overlapping peaks and intermetallic effects. Effects of flow rate, pH, operation time, and other variables are reported. The system is characterized by high durability, simplicity, and economy and offers an attractive alternative to prevalent columns used for flow analysis.

Chromatography, Liquid↗
PubMed1998

Resonance Raman spectroscopy of a light-harvesting protein from the brown alga Laminaria saccharina.

Resonance Raman spectroscopy of an antenna protein from the brown alga Laminaria saccharina has been used to investigate the molecular structure of this light-harvesting complex (LHC) at the level of its bound pigments, chlorophylls (chl) a and c and the xanthophyll fucoxanthin. Evidence has been obtained for the conservation of pigment structure during the isolation procedure used. Six chl a and two chl c molecules are indicated from the positions and relative contributions of stretching modes of their keto-carbonyl groups. Of special interest is the presence of a population of chls a having a protein-binding conformation highly similar to that seen in antenna proteins from higher plants, possibly indicating a common structural motif within this extended gene family. The eight fucoxanthin molecules evidenced are all in the all-trans conformation; however, one or two have a highly twisted configuration. The results are discussed in terms of common and varying structural features of LHCs in higher plants and algae.

Binding Sites↗
PubMed1998

Structure and orientation of the oxygen-evolving manganese complex of green algae and higher plants investigated by X-ray absorption linear dichroism spectroscopy on oriented photosystem II membrane particles.

X-ray absorption spectroscopy at the Mn K-edge has been performed on multilayers of photosystem II-enriched fragments of the native thylakoid membrane prepared from a higher plant (spinach) and a unicellular green alga (Scenedesmus obliquus). Spectra collected for various angles between the prevailing orientation of the thylakoid membrane normal and the X-ray electric field vector contain information on the atomic structure of the tetranuclear manganese complex of photosystem II (PS II) and its orientation with respect to the membrane normal. The previously used approach for evaluation of the dichroism of extended X-ray absorption fine structure (EXAFS) spectra [George, G. N., et al. (1989) Science 243, 789-791] is modified, and the following results are obtained for PS II in its dark-stable state (S1-state): (1) structure and orientation of the PS II manganese complexes of green algae and higher plants are highly similiar or fully identical; (2) two 2.7-A vectors, which, most likely, connect the Mn nuclei of a planar Mn2(mu-O2) structure, are at an average angle of 80 degrees +/- 10 degrees with respect to the thylakoid normal; (3) the plane of the Mn2(mu-O2) structures is rather in parallel with the thylakoid plane than perpendicular. Structural models for the oxygen-evolving manganese complex and its orientation in the thylakoid membrane are discussed within the context of the presented results.

Chlorophyta↗
PubMed1998

In vivo characterization of the electrochemical proton gradient generated in darkness in green algae and its kinetic effects on cytochrome b6f turnover.

When unicellular algal cells are placed under anaerobic conditions, a large electrochemical gradient is built in darkness across the thylakoid membranes. We have estimated, in vivo, the amplitude of the Delta pH component of this transmembrane potential and shown that the Delta pH is twice as large as the Delta Psi. The amplitude of the Delta mu tildeH+ (approximately 110-140 mV) fits well with estimations based on the ATP/ADP ratio measured in green algae under the same conditions, suggesting that an equilibrium state is established across the thylakoid membrane. Therefore, under anaerobic dark incubation of algae, the electrochemical transmembrane potential is determined only by the cellular ATP content. The existence of this Delta mu tildeH+ is expected to result in a constitutive amount of activated CFo-CF1 ATPase, thereby facilitating ATP synthesis under low light intensity illumination. We report also on the effects of this dark-existing electrochemical gradient on the cytochrome b6f complex turnover kinetics. We show that they are largely slowed by the presence of this electrochemical transmembrane potential. The pH component is mainly responsible for the kinetic slowing down of cytochrome b6f complex turnover, despite the fact that electrogenicity is associated with the reactions taking place within this complex. Therefore, in vivo, owing to the low lumenal pH, the oxidation of plastoquinol at the Qo site is limiting the turnover of the cytochrome b6f complex in the presence of the Delta pH, while in its absence the oxidation rate of the b6 hemes becomes rate-limiting.

Adenosine Triphosphate↗
PubMedDate not supplied

Evaluation of factors promoting astaxanthin production by a unicellular green alga, Haematococcus pluvialis, with fractional factorial design.

Factors affecting the astaxanthin production by a unicellular green alga, Haematococcus pluvialis UTEX 16, were evaluated with sequential fractional factorial design. To simulate an actual production mode, a two-stage process was adapted for astaxanthin production: the alga was first cultivated under vegetative growth conditions, and then astaxanthin production was induced by applying various induction methods. A high dose of irradiation was most effective for the production of astaxanthin both in weight (mg/g) and in cellular (pg/cell) contents. A combination of nitrogen deficiency and acetate addition also significantly increased the astaxanthin content of cells on a dry weight basis. Meanwhile, the acetate addition alone increased only the cellular content of astaxanthin. Although the addition of ferrous ion alone had a negative effect on the weight content of astaxanthin, simultaneous addition of ferrous ion and acetate was effective for increasing the cellular content of astaxanthin.

Acetates↗
PubMed2001

Thiosulfate enhances silver uptake by a green alga: role of anion transporters in metal uptake.

Short-term (< 1 h) silver uptake by the green alga Chlamydomonas reinhardtii was measured in the laboratory in defined inorganic media in the presence or absence of ligands (chloride and thiosulfate). In contradiction to the free-ion model of metal uptake, silver accumulation by the alga proved to be sensitive to the choice of ligand used to buffer the free silver concentration. For a low fixed free Ag+ concentration of 10 nM, silver uptake in the presence of thiosulfate (0.11 microM) was 2x greater than in the presence of chloride (4 mM). When sulfate was removed from the exposure medium (i.e., 81 microM-->0 microM), silver uptake in the presence of thiosulfate was even more markedly enhanced (more than 4x greater than in the presence of chloride). Varying the sulfate concentration in the exposure medium only affected silver uptake if thiosulfate was present. We conclude that silver-thiosulfate complexes are transported across the plasma membrane via sulfate/thiosulfate transport systems and that sulfate acts as a competitive inhibitor of this uptake mechanism.

Animals↗
PubMed2005

Hydroxylated and methoxylated brominated diphenyl ethers in the red algae Ceramium tenuicorne and blue mussels from the Baltic Sea.

Methoxylated polybrominated diphenyl ethers (MeO-PBDEs) and hydroxylated PBDEs (OH-PBDEs) have recently been identified in fish and wildlife from the Baltic Sea. Both OH-PBDEs and MeO-PBDEs are known natural products, while OH-PBDEs also may be metabolites of PBDEs. The aim of the present study was to determine if the red macroalga Ceramium tenuicorne could be a source for MeO- and OH-PBDEs in the Baltic environment. Blue mussels (Mytilus edulis) from the same area were also investigated for their content of MeO- and OH-PBDEs. Seven OH-PBDEs and four MeO-PBDEs were present both in the red macroalga and the blue mussels. The mussels also contained a monochlorinated OH-tetraBDE. One of the compounds, 6-methoxy-2,2',3,4,4',5-hexabromodiphenyl ether, has never been reported to occur in the environment. The identification was based on comparison of relative retention times with reference standards, on two gas chromatographic columns of different polarities, together with comparisons of full-scan electron capture negative ionization (ECNI) and electron ionization (EI) mass spectra. It is shown that MeO-PBDEs and OH-PBDEs are present in algae, but at this stage it could not be confirmed if the compounds are produced by the alga itself or by its associated microflora and/or microfauna.

Animals↗
PubMed2004

Optimization of dynamic headspace extraction of the edible red algae Palmaria palmata and identification of the volatile components.

A new extraction method was applied to the volatile compounds of Palmaria palmata. Dynamic headspace was optimized according to an experimental design, and descriptive sensory analysis and intensity and similarity tests were performed for each extract to assess their respective representativeness. Results showed that extract obtained with crushed algae after a 30 min purge was the most representative. GC-MS analysis was then performed on this extract to identify the volatile components. Seven halogenated compounds, seven aldehydes, two ketones, three alcohols, and four miscellaneous compounds were identified. Among them, halogenated compounds were the most characteristic of red algae, and more particularly, iodoethane and iodopentane, which had yet been found in other seaweeds.

Aldehydes↗
PubMed2004

Bioavailability of cadmium-organic complexes to soil alga--an exception to the free ion model.

It is generally considered that cadmium bioavailability shows a considerable dependence on chemical speciation of Cd in solution, correlates best with the activity of free metal ion (Cd2+) in solution, and is largely indifferent to soluble metal complexes. The role of soluble organic matter (DOM) and soluble metal-organic complexes in metal bioavailability and toxicity, however, is not clear. Growth studies with a soil alga (Chlorococcum sp.) were conducted on a growth medium and pore water of Cookes Plain soil (Paleuxeralf), spiked with Cd as Cd(NO3)2. Speciation of the Cd in pore water, and in growth medium with and without citrate, was performed using the MINTEQA2 computer model incorporating updated values of the stability constants of Cd-DOM complexes, as well as using anode stripping voltammetry. Analysis of the toxicity data showed that Cd-citrate, as well as the Cd-DOM complexes, is bioavailable and contributes toward the toxicity to alga. These data contradict the long-held notion that Cd-DOM complexes are not bioavailable to soil biota although they may increase the mobility of Cd.

Biological Availability↗
PubMed2004

Treatment of dairy manure effluent using freshwater algae: elemental composition of algal biomass at different manure loading rates.

The cultivation of algae on nitrogen (N) and phosphorus (P) in animal manure effluents presents an alternative to the current practice of land application. However, the use and value of the resulting algal biomass as a feed or soil supplement depend, in part, on whether the biomass contains any harmful components such as heavy metals. The objective of this study was to determine how the elemental composition of algae changed in response to different loading rates of anaerobically digested flushed dairy manure effluent. Algal biomass was harvested weekly from laboratory-scale algal turf scrubber (ATS) units using four manure loading rates (2, 4, 6, or 9 L m(-2) day(-1)) corresponding to daily loading rates of 0.8-3.7 g of total N and 0.12-0.58 g of total P. Mean N and P contents in the dried biomass increased 1.6-1.8-fold with increasing loading rate up to maximums of 6.5% N and 0.84% P at 6 L m(-2) day(-1). Concentrations of Al, Ca, Cu, Fe, Mg, Mn, and Zn showed similar 1.4-1.8-fold increases up to maximums at a loading rate of 6 L m(-2) day(-1), followed by plateaus or decreases above this loading rate. Concentrations of Cd, Mo, and Pb initially increased with loading rate but then declined to levels comparable to those at the lowest loading rate. Concentrations of Si and K did not increase significantly with loading rate. The maximum concentrations of individual components in the algal biomass were as follows (in mg kg(-)(1)): 1100 (Al), 9700 (Ca), 0.43 (Cd), 56 (Cu), 580 (Fe), 5.0 (Pb), 2300 (Mg), 240 (Mn), 3.0 (Mo), 14,700 (K), 210 (Si), and 290 (Zn). At these concentrations, heavy metals in the algal biomass would not be expected to reduce its value as a soil or feed amendment.

Biomass↗
PubMed2004

Dibenzyl bromophenols with diverse dimerization patterns from the brown alga Leathesia nana.

Six novel dibenzyl bromophenols (1-6) with different dimerization patterns and two propyl bromophenol derivatives (7 and 8), together with 11 known bromophenol derivatives, were isolated from the ethanolic extract of the brown alga Leathesia nana. On the basis of spectroscopic methods the structures of the new compounds were determined as 5,6'-diethyloxymethyl-3,4,2'-tribromo-2,3',4'-trihydroxydiphenyl ether (1), 2-(2,3-dibromo-4,5-dihydroxybenzyl)-3,5-dihydroxy-4-methoxybenzyl alcohol (2), 6-(2,3-dibromo-4,5-dihydroxybenzyl)-2,3-dibromo-4,5-dihydroxy benzyl methyl ether (3), 9,10-dihydro-9,10-dimethoxy-3,4,7,8-tetrabromo-1,2,5,6-tetrahydroxyanthracene (4), (+)-3-(2,3-dibromo-4,5-dihydroxyphenyl)-4-bromo-5,6-dihydroxy-1,3-dihydroisobenzofuran (5), rel-(4aS,10aR)-(+/-)-6,7-dibromo-4a-hydroxy-3,8-dihydroxymethyl-10a-methoxy-1,4,4a,10a-tetrahydrodibenzo[b,e][1,4]dioxin-1-one (6), (E)-2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propenal (7), and 2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)-1-propanol (8). Some compounds including 3 showed in vitro selective cytotoxicity against several human cancer cell lines. This is the first brown alga to be reported containing bromophenols.

China↗
PubMed2006

Capisterones A and B, which enhance fluconazole activity in Saccharomyces cerevisiae, from the marine green alga Penicillus capitatus.

A whole-cell-based assay using Saccharomyces cerevisiae strains that overexpress Candida albicans CDR1 and MDR1 efflux pumps has been employed to screen natural product extracts for reversal of fluconazole resistance. The tropical green alga Penicillus capitatus was selected for bioassay-guided isolation, leading to the identification of capisterones A and B (1 and 2), which were recently isolated from this alga and shown to possess antifungal activity against the marine pathogen Lindra thallasiae. Current work has assigned their absolute configurations using electronic circular dichroism and determined their preferred conformations in solution based on detailed NOE analysis. Compounds 1 and 2 significantly enhanced fluconazole activity in S. cerevisiae, but did not show inherent antifungal activity when tested against several opportunistic pathogens or cytotoxicity to several human cancer and noncancerous cell lines (up to 35 microM). These compounds may have a potential for combination therapy of fungal infections caused by clinically relevant azole-resistant strains.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2006

Lophocladines, bioactive alkaloids from the red alga Lophocladia sp.

Lophocladines A (1) and B (2), two 2,7-naphthyridine alkaloids, were isolated from the marine red alga Lophocladiasp. collected in the Fijian Islands. Their structures were deduced on the basis of high-resolution mass spectra and one- and two-dimensional NMR spectroscopy. Lophocladine A (1) displayed affinity for NMDA receptors and was found to be a delta-opioid receptor antagonist, whereas lophocladine B (2) exhibited cytotoxicity to NCI-H460 human lung tumor and MDA-MB-435 breast cancer cell lines. Immunofluorescence studies indicated that the cytotoxicity of lophocladine B (2) was correlated with microtubule inhibition. This is the first reported occurrence of alkaloids based on a 2,7-naphthyridine skeleton from red algae.

Alkaloids↗
PubMed1994

Isorawsonol and related IMP dehydrogenase inhibitors from the tropical green alga Avrainvillea rawsonii.

Guided by inhibitory activity against IMP dehydrogenase (IMPDH), a new brominated diphenylmethane derivative, isorawsonol, has been isolated from the tropical green alga Avrainvillea rawsonii. Its structure was determined by detailed spectroscopic analysis including HMQC and HMBC. The known metabolites, avrainvilleol, avrainvilleol methyl ether, 3-bromo-4,5-dihydroxylbenzyl alcohol, and rawsonol, were also isolated from this alga and two of these showed a modest ability to inhibit IMPDH. The formation of isorawsonol is envisioned as being similar to that of rawsonol involving condensation of two molecules of avrainvilleol.

Benzhydryl Compounds↗
PubMed2000

Characterization of the LI818 polypeptide from the green unicellular alga Chlamydomonas reinhardtii.

The LI818 gene from Chlamydomonas encodes a polypeptide that is related to the chlorophyll a/b-binding proteins (CAB) of higher plants and green algae. However, despite this relatedness, LI818 gene expression is not coordinated with that of cab genes and is regulated differently by light, suggesting a different role for LI818 polypeptide. We show here that, in contrast to CAB polypeptides, LI818 polypeptide is not tightly embedded into the thylakoid membranes and is localized in stroma-exposed regions. Moreover, during chloroplast development, LI818 polypeptide accumulates before CAB polypeptides. We also show that the LI818 polypeptide forms with certain chlorophyll a/c-binding proteins (CAC) from the haptophyte Isochrysis galbana and the diatom Cyclotella cryptica a natural group that is distinct from those constituted by CAB, CAC and the chlorophyll a/a-binding proteins (CAA). Such an association suggests a very ancient origin for this group of polypeptides, which predates the division of the early photosynthetic eukaryotes into green (chlorophyte), red (rhodophyte) and brown (chromophyte) algae. Possible roles for the LI818 polypeptide are discussed.

Algal Proteins↗
PubMedDate not supplied

[Polysaccharides of calcareous algae and their effect on calcification process].

The composition and structure of polysaccharides from several groups of calcareous algae (including calcareous cyanobacteria), which differ in the calcification mode (extracellular, cell wall, or intracellular), are reviewed. Two families of marine algae, Corallinaceae (Rhodophyta) and Cocolithophoraceae (Prymnesiophyta = Haptophyta), are considered in detail; they exhibit the cell wall and intracellular calcification modes, respectively, and synthesize unusual polysaccharides that seem to directly participate in the calcification process.

Calcification, Physiologic↗