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Green Algae (green + alga)
Kinds of Green Algae Terms modified by Green Algae Selected AbstractsREDOX PROPERTIES ARE CONSERVED IN RUBISCOS FROM DIATOMS AND GREEN ALGAE THROUGH A DIFFERENT PATTERN OF CYSTEINES,JOURNAL OF PHYCOLOGY, Issue 3 2010Julia Marín-Navarro Eukaryotic RUBISCO appears in two sequence-diverging forms, known as red-like (present in nongreen algae) and green-like (of green algae and higher plants) types. Oxidation of cysteines from green-like RUBISCOs is known to result in conformational changes that inactivate the enzyme and render a relaxed structure more prone to proteolytic attack. These changes may have regulatory value for green algae and higher plants, promoting RUBISCO catabolism under stress conditions. We compare here red-like RUBISCOs from several diatoms with a representative green-like RUBISCO from Chlamydomonas reinhardtii, paying special attention to the cysteine-dependent redox properties. Purified diatom RUBISCO preparations displayed a specific carboxylase activity about one order of magnitude lower than that of the C. reinhardtii P. A. Dang. enzyme. Despite having different patterns of cysteine residues in their primary sequence, the red-like enzymes from diatoms inactivated also through oxidation of cysteine sulfhydryls to disulfides with a transition midpoint identical to that of the green-like forms. Cysteine oxidation resulted also in structural modifications of the diatom RUBISCOs, as recognized by a higher sensitivity of the oxidized enzyme to in vitro proteolysis. The coincident redox properties of red- and green-like RUBISCO types suggest that these changes are part of a physiologically significant regulatory mechanism that has been convergently implemented in both groups with a different set of cysteine residues. [source] PHYLOGENETIC ANALYSIS OF PSEUDOCHLORODESMIS STRAINS REVEALS CRYPTIC DIVERSITY ABOVE THE FAMILY LEVEL IN THE SIPHONOUS GREEN ALGAE (BRYOPSIDALES, CHLOROPHYTA),JOURNAL OF PHYCOLOGY, Issue 3 2009Heroen Verbruggen The genus Pseudochlorodesmis (Bryopsidales) is composed of diminutive siphons of extreme morphological simplicity. The discovery of Pseudochlorodesmis -like juveniles in more complex Bryopsidales (e.g., the Halimeda microthallus stage) jeopardized the recognition of this genus. Confronted with this uncertainty, taxonomists transferred many simple siphons into a new genus, Siphonogramen. In this study, we used a multimarker approach to clarify the phylogenetic and taxonomic affinities of the Pseudochlorodesmis-Siphonogramen (PS) complex within the more morphologically complex bryopsidalean taxa. Our analyses reveal a new layer of diversity largely distinct from the lineages containing the structurally complex genera. The PS complex shows profound cryptic diversity exceeding the family level. We discuss a potential link between thallus complexity and the prevalence and profundity of cryptic diversity. For taxonomic simplicity and as a first step toward clarifying the taxonomy of these simple siphons, we propose to maintain Pseudochlorodesmis as a form genus and subsume Siphonogramen and Botryodesmis therein. [source] FERRIC CHELATE REDUCTASE ACTIVITY AS AFFECTED BY THE IRON-LIMITED GROWTH RATE IN FOUR SPECIES OF UNICELLULAR GREEN ALGAE (CHLOROPHYTA)1JOURNAL OF PHYCOLOGY, Issue 3 2002Harold G. Weger Four species of green algae (Chlorella kessleri Fott et Nováková, Chlorococcum macrostigmatum Starr, Haematococcus lacustris[Girod-Chantrans] Rostaf., Stichococcus bacillaris Näg.) were grown in iron-limited chemostats and under phosphate limitation and iron (nutrient) sufficiency. For all four species, steady-state culture density declined with decreasing degree of iron limitation (increasing iron-limited growth rate), whereas chl per cell or biovolume increased. Plasma membrane ferric chelate reductase activity was enhanced by iron limitation in all species and suppressed by phosphate limitation and iron sufficiency. These results confirm previous work that C. kessleri uses a reductive mechanism of iron acquisition and also suggest that the other three species use the same mechanism. Although imposition of iron limitation led to enhanced activities of ferric chelate reductase in all species, the relationship between ferric chelate reductase activity and degree of iron limitation varied. Ferric chelate reductase activity in C. macrostigmatum and S. bacillaris was an inverse function of the degree of iron limitation, with the most rapidly growing iron-limited cells exhibiting the highest ferric chelate reductase activity. In contrast, ferric chelate reductase activity was only weakly affected by the degree of iron limitation in C. kessleri and H. lacustris. Calculation of ferric reductase activity per unit chl allowed a clear differentiation between iron-limited and iron-sufficient cells. The possible extension of the ferric chelate reductase assay to investigate the absence or presence of iron limitation in natural waters may be feasible, but it is unlikely that the assay could be used to estimate the degree of iron limitation. [source] GREEN ALGAE AND LAND PLANTS,AN ANSWER AT LAST?JOURNAL OF PHYCOLOGY, Issue 2 2002Russell L. Chapman First page of article [source] Equal Sex Ratios of a Marine Green Alga, Bryopsis plumosaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2008Tatsuya Togashi Abstract By finding some important culture conditions as below, we succeeded in experimentally controlling the whole life history of a dioecious marine green alga, Bryopsis plumosa (Hudson) C. Agardh. In this study, we focused on the primary and secondary sex ratios (i.e. at inception and maturity) using these culture techniques. Gametogenesis was induced by culturing haploid gametophytes with Provasoli's enriched seawater (PES) medium under a 14:10 h light : dark cycle at 14 °C. Formed zygotes grew into diploid sporophytes, which were cultured for 3 months with PES medium under a 14:10 h light : nbsp;dark cycle at 18 °C. Then they were transferred into Schreiber medium and cultured under a 10:14 h light : dark cycle at 22 °C. Within 1 week, zoosporogenesis was observed. Zoospores were released within a couple of days. Each zoospore soon germinated and grew into a unisexual gametophyte. The primary sex ratio was examined in gametophytes that originated from a single sporophyte. The secondary sex ratio was studied in the field. Both were estimated as 1:1. Synchronized meiotic cell divisions might occur during zoosporogenesis dividing each sex-determining factor evenly among zoospores. Given the equal sex ratio at maturity, there seems to be no environmental factor that differentially affects the survival of male or female gametophytes in nature. [source] Photosynthetic Eukaryotes of Freshwater Wetland Biofilms: Adaptations and Structural Characteristics of the Extracellular Matrix in the Green Alga, Cosmarium reniforme (Zygnematophyceae, Streptophyta)THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 4 2009DAVID S. DOMOZYCH ABSTRACT. Cosmarium reniforme (Zygnematophyceae, Streptophyta) is a green alga that is commonly found in biofilms of wetlands of the Adirondack region, NY (USA). Two distinctive characteristics that are critical to this alga's survival in a benthic biofilm are its elaborate cell morphology and extracellular matrix (ECM). In this study, ultrastructural, immunocytochemical, and experimental methodologies were employed in order to elucidate the cellular characteristics that are critical for survival in a biofilm. The ECM consists of a thick, outwardly lobed cell wall (CW), which contains a patterned network of structurally complex pores. Each pore consists of a narrow channel, terminating internally at a bulb that invaginates localized regions of the plasma membrane. The outer region of the pore contains arabinogalactan protein-like and extensin epitopes that are likely involved in adhesion mechanisms of the cell. External to the CW is the extracellular polymeric substance that is employed in ensheathment of the cell to the substrate and in gliding motility. The architectural design/biochemical make-up of the CW and a secretory system that encompasses the coordinated activities of the endomembrane and cytomotile/cytoskeletal systems provide the organism with effective mechanisms to support life within the biofilm complex. [source] Engineering photosynthetic light capture: impacts on improved solar energy to biomass conversionPLANT BIOTECHNOLOGY JOURNAL, Issue 6 2007Jan H. Mussgnug Summary The main function of the photosynthetic process is to capture solar energy and to store it in the form of chemical ,fuels'. Increasingly, the photosynthetic machinery is being used for the production of biofuels such as bio-ethanol, biodiesel and bio-H2. Fuel production efficiency is directly dependent on the solar photon capture and conversion efficiency of the system. Green algae (e.g. Chlamydomonas reinhardtii) have evolved genetic strategies to assemble large light-harvesting antenna complexes (LHC) to maximize light capture under low-light conditions, with the downside that under high solar irradiance, most of the absorbed photons are wasted as fluorescence and heat to protect against photodamage. This limits the production process efficiency of mass culture. We applied RNAi technology to down-regulate the entire LHC gene family simultaneously to reduce energy losses by fluorescence and heat. The mutant Stm3LR3 had significantly reduced levels of LHCI and LHCII mRNAs and proteins while chlorophyll and pigment synthesis was functional. The grana were markedly less tightly stacked, consistent with the role of LHCII. Stm3LR3 also exhibited reduced levels of fluorescence, a higher photosynthetic quantum yield and a reduced sensitivity to photoinhibition, resulting in an increased efficiency of cell cultivation under elevated light conditions. Collectively, these properties offer three advantages in terms of algal bioreactor efficiency under natural high-light levels: (i) reduced fluorescence and LHC-dependent heat losses and thus increased photosynthetic efficiencies under high-light conditions; (ii) improved light penetration properties; and (iii) potentially reduced risk of oxidative photodamage of PSII. [source] Effect of temperature and phytoplankton concentration on Nile tilapia Oreochromis niloticus (L.) filtration rateAQUACULTURE RESEARCH, Issue 6 2003Hakan Turker Abstract Nile tilapia Oreochromis niloticus (L.) held in timed-pulse feeding chambers, were provided with algal-rich water dominated by either green algae (Scenedesmus, Ankistrodesmus, Chlorella and Tetraedron) or cyanobacteria (Microcystis) to determine the effect of temperature and phytoplankton concentration on filtration rates. Green algae and cyanobacteria filtration rates were measured as suspended particulate organic carbon (POC) kg,1 wet fish weight h,1. Ivlev's filter-feeding model described the relationships between filtration rates and suspended POC concentration of green algae and cyanobacteria. Filtration rates of both green algae and cyanobacteria increased linearly as water temperature increased from 17 °C to 32 °C and were significantly higher in the warm-water regime (26,32 °C) than in the cool-water regime (17,23 °C). Filtration rates at 95% saturation POC (FR95) in green algal and cyanobacterial waters were 700 mg C kg,1 h,1 and 851 mg C kg,1 h,1 in the warm-water regime and 369 mg C kg,1 h,1 and 439 mg C kg,1 h,1 in the cool-water regime respectively. The FR95 in warm water were achieved at lower POC concentrations than in cool water. [source] Ecological niche partitioning in the picoplanktonic green alga Micromonas pusilla: evidence from environmental surveys using phylogenetic probesENVIRONMENTAL MICROBIOLOGY, Issue 9 2008Elodie Foulon Summary Very few studies have analysed the niches of pelagic protist in details. This is because for most protists, both an accurate species definition and methods for routine detection and quantification of cells are lacking. The morphospecies Micromonas pusilla, a marine unicellular green alga, is the most ubiquitous and cosmopolitan picoeukaryote described to date. This species comprises several independent genetic lineages or clades, which are not currently distinguishable based on comparison of their morphology or biogeographical distribution. Molecular probes were used to detect and quantify the genetic clades of M. pusilla in samples from temperate, polar and tropical environments in order to assess potential ecological niche partitioning. The three clades were detected in all biogeographical regions studied and were commonly found in sympatry. Cell abundances recorded for clades A and B were high, especially at coastal stations. Clade C, when detected, was always at low abundances and is suggested to be a low-light clade. Shifts in the contribution of clades to total M. pusilla abundance were observed along environmental gradients, both at local and basin-wide scales. This suggests that the phylogenetic clades occupy specific niches and confirms the existence of cryptic species within the morphospecies M. pusilla. Parameters which can precisely explain the distribution of these cryptic species remain to be elucidated. [source] Phylogenetic relationship and antifouling activity of bacterial epiphytes from the marine alga Ulva lactucaENVIRONMENTAL MICROBIOLOGY, Issue 3 2000Brief report It is widely accepted that bacterial epiphytes can inhibit the colonization of surfaces by common fouling organisms. However, little information is available regarding the diversity and properties of these antifouling bacteria. This study assessed the antifouling traits of five epiphytes of the common green alga, Ulva lactuca. All isolates were capable of preventing the settlement of invertebrate larvae and germination of algal spores. Three of the isolates also inhibited the growth of a variety of bacteria and fungi. Their phylogenetic positions were determined by 16S ribosomal subunit DNA sequencing. All isolates showed a close affiliation with the genus Pseudoalteromonas and, in particular, with the species P. tunicata. Strains of this bacterial species also display a variety of antifouling activities, suggesting that antifouling ability may be an important trait for members of this genus to be highly successful colonizers of animate surfaces and for such species to protect their host against fouling. [source] Metal toxicity inferred from algal population density, heterotrophic substrate use, and fatty acid profile in a small streamENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2000Robert B. Genter Abstract The purpose of this study was to examine relations between metal concentrations in periphyton and the abundance of algal species, heterotrophic use of 95 carbon sources, and phospholipid fatty acids (PLFA) of the periphyton in a small stream spanning a mine in Lemhi County, Idaho, USA. Two upstream, two mine, and two downstream sites were examined. Elevated concentrations of As and Cu at the mine sites were associated with communities that were depleted of diatoms and filamentous blue-green algae and characterized by a low-diversity community dominated by a single blue-green alga and patchy populations of the diatom Achnanthidium minutissimum and a filamentous green alga. Carbon source use and PLFA profiles provided a rapid assessment of stream conditions that were consistent with algal taxonomy and with our hypotheses constructed from previous reports on periphyton responses to metal stress. [source] THE ECOLOGY AND GENETICS OF FITNESS IN CHLAMYDOMONAS.EVOLUTION, Issue 1 2002VIII. Abstract According to classical evolutionary theory, sexual recombination can generate the variation necessary to adapt to changing environments and thereby confer an evolutionary advantage of sexual over asexual reproduction. Using the green alga, Chlamydomonas reinhardtii, we investigated the effect of a single sexual episode on adaptation of heterotrophic growth on different carbon sources. In an initial mixture of isolates, sex was induced and the resulting offspring constituted the sexual populations, along with any unmated vegetative cells; the unmated mixture of isolates represented the asexual populations. Mean and variance in division rates (i.e., fitness) were measured four times during approximately 50 generations of vegetative growth in the dark on all possible combinations of four carbon sources. Consistent with effects of recombination of epistatic genes in linkage disequilibrium, sexual populations initially had a higher variance in fitness, but their mean fitness was lower than that of asexual populations, possibly due to recombinational load. Subsequently, fitness of sexual populations exceeded that of asexual ones, but finally they regained parity in both mean and variance of fitness. Although recombination was not more effective on more complex substrates, these results generally support the idea that sex can accelerate adaptation to novel environments. [source] Temperature- and pH-dependent accumulation of heat-shock proteins in the acidophilic green alga Chlamydomonas acidophilaFEMS MICROBIOLOGY ECOLOGY, Issue 3 2006Antje Gerloff-Elias Abstract Chlamydomonas acidophila, a unicellular green alga, is a dominant phytoplankton species in acidic water bodies, facing severe environmental conditions such as low pH and high heavy metal concentrations. We examined the pH-, and temperature-dependent accumulation of heat-shock proteins in this alga to determine whether heat-shock proteins play a role in adaptation to their environment. Our results show increased heat-shock proteins accumulation at suboptimal pHs, which were not connected with any change in intracellular pH. In comparison to the mesophilic Chlamydomonas reinhardtii, the acidophilic species exhibited significantly higher accumulations of heat-shock proteins under control conditions, indicating an environmental adaptation of increased basal levels of heat-shock proteins. The results suggest that heat-shock proteins might play a role in the adaptation of C. acidophila, and possibly other acidophilic algae, to their extreme environment. [source] Light acclimation of Chlamydomonas acidophila accumulating in the hypolimnion of an acidic lake (pH 2.6)FRESHWATER BIOLOGY, Issue 8 2005ANTJE GERLOFF-ELIAS Summary 1. The unicellular green alga Chlamydomonas acidophila accumulates in a thin phytoplankton layer in the hypolimnion (deep chlorophyll maximum, DCM) of an extremely acidic lake (Lake 111, pH 2.6, Lusatia, Germany), in which the underwater light spectrum is distorted and red-shifted. 2. Chlamydomonas acidophila exhibited a significantly higher absorption efficiency and a higher cellular chlorophyll b content when incubated in the red shifted underwater light of Lake 111 than in a typical, blue-green dominated, light spectrum. 3. Chlamydomonas acidophila has excellent low light acclimation properties (increased chlorophyll b content, increased oxygen yield and a low light saturation point for photosynthesis) that support survival of the species in the low light climate of the DCM. 4. In situ acclimation to the DCM under low light and temperature decreased maximum photosynthetic rate in autotrophic C. acidophila cultures, whereas the presence of glucose under these conditions enhanced photosynthetic efficiency and capacity. 5. The adaptive abilities of C. acidophila to light and temperature shown in this study, in combination with the absence of potent competitors because of low lake pH, most probably enable the unusual dominance of the green alga in the DCM of Lake 111. [source] Equal Sex Ratios of a Marine Green Alga, Bryopsis plumosaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2008Tatsuya Togashi Abstract By finding some important culture conditions as below, we succeeded in experimentally controlling the whole life history of a dioecious marine green alga, Bryopsis plumosa (Hudson) C. Agardh. In this study, we focused on the primary and secondary sex ratios (i.e. at inception and maturity) using these culture techniques. Gametogenesis was induced by culturing haploid gametophytes with Provasoli's enriched seawater (PES) medium under a 14:10 h light : dark cycle at 14 °C. Formed zygotes grew into diploid sporophytes, which were cultured for 3 months with PES medium under a 14:10 h light : nbsp;dark cycle at 18 °C. Then they were transferred into Schreiber medium and cultured under a 10:14 h light : dark cycle at 22 °C. Within 1 week, zoosporogenesis was observed. Zoospores were released within a couple of days. Each zoospore soon germinated and grew into a unisexual gametophyte. The primary sex ratio was examined in gametophytes that originated from a single sporophyte. The secondary sex ratio was studied in the field. Both were estimated as 1:1. Synchronized meiotic cell divisions might occur during zoosporogenesis dividing each sex-determining factor evenly among zoospores. Given the equal sex ratio at maturity, there seems to be no environmental factor that differentially affects the survival of male or female gametophytes in nature. [source] LIPID COMPOSITION OF CHLORARACHNIOPHYTES (CHLORARACHNIOPHYCEAE) FROM THE GENERA BIGELOWIELLA, GYMNOCHLORA, AND LOTHARELLA,JOURNAL OF PHYCOLOGY, Issue 2 2005Jeffrey D. Leblond The Chlorarachniophyceae are unicellular eukaryotic algae characterized by an amoeboid morphology that may be the result of secondary endosymbiosis of a green alga by a nonphotosynthetic amoeba or amoeboflagellate. Whereas much is known about the phylogeny of chlorarachniophytes, little is known about their physiology, particularly that of their lipids. In an initial effort to characterize the lipids of this algal class, four organisms from three genera were examined for their fatty acid and sterol composition. Fatty acids from lipid fractions containing chloroplast-associated glycolipids, storage triglycerides, and cytoplasmic membrane-associated polar lipids were characterized. Glycolipid-associated fatty acids were of limited composition, principally eicosapentaenoic acid [20:5(n-3)] and hexadecanoic acid (16:0). Triglyceride-associated fatty acids, although minor, were found to be similar in composition. The polar lipid fraction was dominated by lipids that did not contain phosphorus and had a more variable fatty acid composition with 16:0 and docosapentaenoic acid [22:5(n-3)] dominant along with a number of minor C18 and C20 fatty acids. Crinosterol and one of the epimeric pair poriferasterol/stigmasterol were the sole sterols. Several genes required for synthesis of these sterols were computationally identified in Bigelowiella natans Moestrup. One sterol biosynthesis gene showed the greatest similarity to SMT1 of the green alga, Chlamydomonas reinhardtii. However, homologues to other species, mostly green plant species, were also found. Further, the method used for identification suggested that the sequences were transferred to a genetic compartment other than the likely original location, the nucleomorph nucleus. [source] NITROGEN LIMITATION EFFECTS OF DIFFERENT NITROGEN SOURCES ON NUTRITIONAL QUALITY OF TWO FRESHWATER ORGANISMS, SCENEDESMUS QUADRICAUDA (CHLOROPHYCEAE) AND SYNECHOCOCCUS SP. (CYANOPHYCEAE)JOURNAL OF PHYCOLOGY, Issue 5 2003Gunnel Ahlgren Food quality for grazers has been related to mineral (nitrogen, phosphorus) and biochemical (amino acids, fatty acids) constituents. The aim of the study was to examine the influence of different nitrogen sources on these constituents in two organisms, the green alga Scenedesmus quadricauda Turp. and the cyanobacterium Synechococcus sp., commonly used in feeding experiments. The two organisms were grown in continuous cultures at different growth rates. Nitrate or ammonium salts were used as nitrogen sources under both replete and limited conditions. Carbon content (mg·g,1 dry weight) was stable in both organisms independent of nitrogen source, nitrogen limitation, and growth rate. Nitrogen content decreased with limitation and growth rate in Scenedesmus and to a lesser degree in Synechococcus, whereas changes in phosphorus content were not statistically significant. The relative proportions of amino acids (% of total amino acids) were relatively stable in both organisms, whereas the proportions of fatty acids varied with growth rate and limitation. Fatty acid content was much lower in Synechococcus than in Scenedesmus. At N limitation, polyunsaturated fatty acids (PUFAs) showed lower levels in both organisms. The change occurred in the ,3 PUFA (linolenic acid) of the green alga and in the ,6 PUFA (linoleic acid) of the cyanobacterium. The difference in the response of N limitation in the two organisms may be traced to the different composition of the chloroplast membranes (the prokaryotic way) and the microsomal membranes (the eukaryotic way) where the desaturation takes place. [source] 28 Lipid composition of members of the algal class chlorarachniophyceaeJOURNAL OF PHYCOLOGY, Issue 2003J. L. Dahmen The algal class Chlorarachniophyceae is comprised of a small group of unicellular eukaryotic algae that are often characterized by an unusual amoeboid morphology. This morphology is hypothesized to be the result of a secondary endosymbiosis in which a green alga was engulfed as prey by a nonphotosynthetic amoeba or amoebaflagellate. Whereas much is known about the phylogenetic relationships of individual chlorarachniophytes to one another, and to possible ancestral host organisms in the genera Cercomonas and Heteromita, little is known about their physiology, particularly that of their lipids. In an initial effort to characterize the lipids of this algal class, seven organisms were examined for their fatty acid and sterol composition. These included Bigelowiella natans, Chlorarachnion globusum, Chlorarachnion reptans, Gymnochlora stellata, Lotharella amoeboformis, Lotharella globosa, and Lotharella sp. Fatty acids associated with chloroplast-associated glycolipids, cytoplasmic membrane-associated phospholipids, and storage triglycerides were characterized. Glycolipid fatty acids were found to be of limited composition, containing principally eicosapentaenoic acid [20:5(n-3)] and hexadecanoic acid (16:0), which ranged in relative percentage from 67,90% and 10,29%, respectively, in these seven organisms. Triglyceride-associated fatty acids were found to be similar. Phospholipid fatty acid composition was more variable. The principal phospholipid fatty acids, 16:0 (25,32%) and a compound tentatively identified as docosapentaenoic acid [22:5(n-3)] (26,35%), were found along with a number of C18 and C20 fatty acids. All organisms contained two sterols as free sterols. These were tentatively identified as 24-ethylcholesta-5,22E-dien-3b-ol (stigmasterol; 70,95%) and 24-methylcholesta-5,22E-dien-3b-ol (brassicasterol; 5,30%). [source] PRELIMINARY STUDIES OF SEASONALITY, ECOLOGY, AND SPECIES COMPOSITION OF ULVOID ALGAL BLOOMS IN WASHINGTON STATEJOURNAL OF PHYCOLOGY, Issue 2000T.A. Nelson Blooms of green macroalgae can devastate important finfish and shellfish habitats. Ulvaria obscura, a relatively unstudied green alga, is a major contributor to these blooms in the San Juan Islands, Washington State, USA. The biomass and productivity of this and other ulvoid algae were measured seasonally for two years. Experiments comparing the growth rates, responses to desiccation, photoacclimation, and grazer preference of U. obscura and Ulva fenestrata were conducted. Ulvaria blooms tended to occur in the subtidal while Ulva blooms were often intertidal. Both genera bloomed between late June and September. Despite their superficial similarity, Ulvaria and Ulva display markedly different physiological and ecological responses. Ulva was capable of faster growth, had higher rates of photosynthesis, and was more desiccation tolerant than Ulvaria. Ulvaria, however, appears to be more resistant to grazing than Ulva. [source] pH regulation in an acidophilic green alga , a quantitative analysisNEW PHYTOLOGIST, Issue 2 2009Birgit Bethmann Summary ,,Short-term cytosolic pH regulation has three components: H+ binding by buffering groups; H+ transport out of the cytosol; and H+ transport into the vacuole. To understand the large differences plants show in their tolerance to acidic environments, these three components were quantified in the acidophilic unicellular green alga Eremosphaera viridis. ,,Intracellular pH was recorded using ion-selective microelectrodes, whereas constant doses of weak acid were applied over different time intervals. A mathematical model was developed that describes the recorded cytosolic pH changes. Recordings of cytosolic K+ and Na+ activities, and application of anion channel inhibitors, revealed which ion fluxes electrically compensate H+ transport. ,,The cytosolic buffer capacity was , = 30 mM. Acidification resulted in a substantial and constant H+ efflux that was probably driven by the plasmalemma H+ -ATPase, and a proportional pH regulation caused by H+ pumped into the vacuole. Under severe cytosolic acidification (, 1 pH) more than 50% of the ATP synthesized was used for H+ pumping. While H+ influx into the vacuole was compensated by cation release, H+ efflux out of the cell was compensated by anion efflux. ,,The data presented here give a complete and quantitative picture of the ion fluxes during acid loading in an acidophilic green plant cell. [source] Morphology and molecular phylogeny of Prasiola sp. (Prasiolales, Chlorophyta) from MyanmarPHYCOLOGICAL RESEARCH, Issue 3 2002Moat War Dine Naw SUMMARY Morphological and molecular phylogenetic studies were carried out on a freshwater green alga from Myanmar. Most specimens exhibited a gross morphology similar to Enteromorpha, however, their thalli were basically monostromatic and chloroplasts were axile and stellate. In addition, the phylogenetic analysis inferred from the 18S rRNA gene strongly supported a monophyly with Prasiola japonica and a more distant relationship with other chlorophytan taxa, including Enteromorpha. From our results, it has been shown that this alga belongs to Prasiola and has a close phylogenetic relationship with P. japonica. [source] Carbonic anhydrases in plants and algaePLANT CELL & ENVIRONMENT, Issue 2 2001J. V. Moroney ABSTRACT Carbonic anhydrases catalyse the reversible hydration of CO2, increasing the interconversion between CO2 and HCO3, + H+ in living organisms. The three evolutionarily unrelated families of carbonic anhydrases are designated ,-, ,-and ,-CA. Animals have only the ,-carbonic anhydrase type of carbonic anhydrase, but they contain multiple isoforms of this carbonic anhydrase. In contrast, higher plants, algae and cyanobacteria may contain members of all three CA families. Analysis of the Arabidopsis database reveals at least 14 genes potentially encoding carbonic anhydrases. The database also contains expressed sequence tags (ESTs) with homology to most of these genes. Clearly the number of carbonic anhydrases in plants is much greater than previously thought. Chlamydomonas, a unicellular green alga, is not far behind with five carbonic anhydrases already identified and another in the EST database. In algae, carbonic anhydrases have been found in the mitochondria, the chloroplast thylakoid, the cytoplasm and the periplasmic space. In C3 dicots, only two carbonic anhydrases have been localized, one to the chloroplast stroma and one to the cytoplasm. A challenge for plant scientists is to identify the number, location and physiological roles of the carbonic anhydrases. [source] Photosynthetic Eukaryotes of Freshwater Wetland Biofilms: Adaptations and Structural Characteristics of the Extracellular Matrix in the Green Alga, Cosmarium reniforme (Zygnematophyceae, Streptophyta)THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 4 2009DAVID S. DOMOZYCH ABSTRACT. Cosmarium reniforme (Zygnematophyceae, Streptophyta) is a green alga that is commonly found in biofilms of wetlands of the Adirondack region, NY (USA). Two distinctive characteristics that are critical to this alga's survival in a benthic biofilm are its elaborate cell morphology and extracellular matrix (ECM). In this study, ultrastructural, immunocytochemical, and experimental methodologies were employed in order to elucidate the cellular characteristics that are critical for survival in a biofilm. The ECM consists of a thick, outwardly lobed cell wall (CW), which contains a patterned network of structurally complex pores. Each pore consists of a narrow channel, terminating internally at a bulb that invaginates localized regions of the plasma membrane. The outer region of the pore contains arabinogalactan protein-like and extensin epitopes that are likely involved in adhesion mechanisms of the cell. External to the CW is the extracellular polymeric substance that is employed in ensheathment of the cell to the substrate and in gliding motility. The architectural design/biochemical make-up of the CW and a secretory system that encompasses the coordinated activities of the endomembrane and cytomotile/cytoskeletal systems provide the organism with effective mechanisms to support life within the biofilm complex. [source] Effect of inorganic carbon on photoautotrophic growth of microalga Chlorococcum littoraleBIOTECHNOLOGY PROGRESS, Issue 2 2009Masaki Ota Abstract The growth rate of a highly CO2 -tolerant green alga, Chlorococcum littorale, was investigated in semi-batch cultures at a temperature of 22°C, a light intensity of 170 ,mol-photon m,2 s,1 and CO2 concentrations ranging from 1 to 50% (v/v) at atmospheric pressure. In the experiments, solutions were bubbled with CO2 and N2 gas mixtures to adjust CO2 concentrations to minimize the influence of O2. Growth rate, which was defined in terms of a specific growth rate ,, decreased with increasing CO2 concentration at the conditions studied. The inhibition of growth by CO2 gas could be attributed to the concentration of inorganic carbon in the culture medium. A growth model is proposed where key assumptions are the formation of bicarbonate ion HCO as substrate for algal growth and equilibrium between CO2 inhibitor. The proposed growth model based on the Monod equation agreed with the experimental data to within 5% and provides better correlation than the conventional inhibition model, especially in the high CO2 concentration region. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Meteorological factors affecting the diversity of airborne algae in an urban atmosphereECOGRAPHY, Issue 5 2006Naveen K. Sharma Aeroalgal sampling of Varanasi City, India, was done using a Tilak Rotorod sampler and exposing agarised Bold basal medium Petri plates during March 2003 to February 2005. Amongst the 34 airborne algal genera recorded, cyanobacteria dominated the aero-algal flora, followed by green algae and diatoms. The generic diversity of airborne algae as well as the constituting groups exhibited seasonal variation. The most favored period for the appearance of cyanobacteria in the air was summer, while winter favored green algae. Presence of diatoms was almost uniform throughout the year. The presence of algal particles in the air depended upon the abundance and dynamics of algal source and their release and dispersal in the atmosphere. Best model selection with Akaike information criteria indicated temperature, relative humidity, rainfall, wind velocity as the most important climatic factors determining algal diversity. These factors exert their effect both directly by influencing entrainment and dispersal of algae from the source, and indirectly by regulating the dynamics of the possible algal source (soil, water, plant body, wall and roof of the building) by supporting or inhibiting the algal growth. In a closed environment and at low altitude sampling site characteristic is also an important factor. Open area near to the countryside had maximal aero-algal diversity. [source] Soil CO2 flux and photoautotrophic community composition in high-elevation, ,barren' soilENVIRONMENTAL MICROBIOLOGY, Issue 3 2009Kristen R. Freeman Summary Soil-dominated ecosystems, with little or no plant cover (i.e. deserts, polar regions, high-elevation areas and zones of glacial retreat), are often described as ,barren', despite their potential to host photoautotrophic microbial communities. In high-elevation, subnival zone soil (i.e. elevations higher than the zone of continuous vegetation), the structure and function of these photoautotrophic microbial communities remains essentially unknown. We measured soil CO2 flux at three sites (above 3600 m) and used molecular techniques to determine the composition and distribution of soil photoautotrophs in the Colorado Front Range. Soil CO2 flux data from 2002 and 2007 indicate that light-driven CO2 uptake occurred on most dates. A diverse community of Cyanobacteria, Chloroflexi and eukaryotic algae was present in the top 2 cm of the soil, whereas these clades were nearly absent in deeper soils (2,4 cm). Cyanobacterial communities were composed of lineages most closely related to Microcoleus vaginatus and Phormidium murrayi, eukaryotic photoautotrophs were dominated by green algae, and three novel clades of Chloroflexi were also abundant in the surface soil. During the light hours of the 2007 snow-free measurement period, CO2 uptake was conservatively estimated to be 23.7 g C m,2 season,1. Our study reveals that photoautotrophic microbial communities play an important role in the biogeochemical cycling of subnival zone soil. [source] Photodynamic therapy against cyanobacteriaENVIRONMENTAL TOXICOLOGY, Issue 1 2007M. Drábková Abstract This study explores the use of photosensitizers and reactive oxygen species (ROS) to limit growth of cyanobacteria. We chose 12 phthalocyanines, tetraphenol porphyrine, and methylene blue as compounds producing singlet oxygen. Hydrogen peroxide was chosen as another source of ROS. These compounds were tested using algal toxicity tests in microplates on three cultures of green algae (Pseudokirchneriella subcapitata, Scenedesmus quadricauda, and Chlorella kessleri) and on three cultures of cyanobacteria (Synechococcus nidulans, Microcystis incerta, and Anabaena sp.). Results indicate that photosensitizers and singlet oxygen could be highly toxic for some selected phytoplankton species. Green alga Scenedesmus quadricauda was highly sensitive (EC50 = 0.07 mg/L) to compounds producing singlet oxygen, although it was not sensitive to hydrogen peroxide, which was about 10 times more toxic for cyanobacteria. We conclude that the compounds producing hydroxyl radical species seems to be more promising to treat cyanobacterial blooms than the compounds producing the singlet oxygen. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 112,115, 2007. [source] Effects of dietborne copper and silver on reproduction by Ceriodaphnia dubia,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2009Jason M. Kolts Abstract Recent studies have indicated the potential for dietborne metals as an important exposure pathway for metal toxicity in freshwater organisms. We conducted a study in which freshwater cladocerans (Ceriodaphnia dubia) were fed green algae (either Pseudokirchneriella subcapitata or Chlorella vulgaris) that were grown in Ag- or Cu-contaminated media. In one series of toxicity tests patterned after the U.S. Environmental Protection Agency's three-brood C. dubia chronic toxicity test, we exposed C. dubia to waterborne Ag or Cu while feeding them normal amounts of uncontaminated yeast,Cerophyll®,trout chow (YCT) slurry and either algae grown in standard media or algae grown in standard media supplemented with Ag or Cu (added as AgNO3 or CuSO4·5H2O). These parallel tests demonstrated that dietborne metal did not contribute to survival or reproduction effects beyond the effects caused by waterborne metal alone. We also conducted dietborne-only toxicity tests patterned after two other recently published experimental designs in which 1) C. dubia were fed only metal-contaminated algae for 4 h, transferred to fresh water, and fed uncontaminated algae and YCT slurry for the duration of the three-brood test or 2) C. dubia were fed standard amounts of metal-contaminated algae and uncontaminated YCT slurry for the entire three-brood test. In contrast to previous studies, we did not find consistent dietborne metal toxicity or standard concentration,response relationships in those two experiments. Instead, among-experiment variation in intracellular partitioning of metals in the algae fed to the C. dubia, among-laboratory differences in experimental procedures, selective feeding by C. dubia to avoid metal-contaminated algae, an interaction between reproductive status of the C. dubia and dietborne metal concentration, or a combination of these might help explain the apparently inconsistent results. [source] Rock weathering promoted by embryonic soils in surface cavitiesEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2002G. Certini Summary The upper surfaces of trachyte outcrops and boulders in Tuscany and Latium have numerous cavities. The cavities have formed from the dislodgement of xenoliths and, if properly oriented, they collect water and accumulate mineral and organic debris. There is no drainage, and water stays in them for a long time, inducing a severe hydrological regimen, but supporting a variety of living organisms such as cyanobacteria, green algae and insects. The humic substances produced by the humification of organic matter and the organic acids released by organisms alter the underlying rock, thereby deepening and enlarging the cavities. Following the dissolution of the glassy cements, crystals detach from the matrix to join the accumulated material, where they are progressively comminuted and partly changed into clay minerals. With time, these accumulations increase in thickness sufficiently to allow the establishment of vascular plants and the development of horizons so as to become embryonic soils. We sampled the material from several such cavities and determined its chemical and mineralogical composition. We conclude that cavities contain miniature ecosystems supported by the tiny bodies of soil in them. [source] Functional characterization of the evolutionarily divergent fern plastocyaninFEBS JOURNAL, Issue 16 2004José A. Navarro Plastocyanin (Pc) is a soluble copper protein that transfers electrons from cytochrome b6f to photosystem I (PSI), two protein complexes that are localized in the thylakoid membranes in chloroplasts. The surface electrostatic potential distribution of Pc plays a key role in complex formation with the membrane-bound partners. It is practically identical for Pcs from plants and green algae, but is quite different for Pc from ferns. Here we report on a laser flash kinetic analysis of PSI reduction by Pc from various eukaryotic and prokaryotic organisms. The reaction of fern Pc with fern PSI fits a two-step kinetic model, consisting of complex formation and electron transfer, whereas other plant systems exhibit a mechanism that requires an additional intracomplex rearrangement step. The fern Pc interacts inefficiently with spinach PSI, showing no detectable complex formation. This can be explained by assuming that the unusual surface charge distribution of fern Pc impairs the interaction. Fern PSI behaves in a similar way as spinach PSI in reaction with other Pcs. The reactivity of fern Pc towards several soluble c -type cytochromes, including cytochrome f, has been analysed by flavin-photosensitized laser flash photolysis, demonstrating that the specific surface motifs for the interaction with cytochrome f are conserved in fern Pc. [source] | |||||||||||||||||||||||||||||||||||||||||||