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PubMed1992

The four genomes of the alga Pyrenomonas salina (Cryptophyta).

Cryptomonads are a group of unicellular eukaryotic algae with unusual features. First, their plastids are surrounded by four membranes and second, between the two pairs of membranes there is a plasmatic compartment. This supernumerary eukaryotic compartment of the cryptomonad cell is devoid of mitochondria but contains starch grains, 80S ribosomes and a small vestigial eukaryotic nucleus called the nucleomorph. Isolation and characterization of the four genomes (from mitochondrion, plastid, nucleus and nucleomorph) of one cryptomonad, Pyrenomonas salina, demonstrates that the cryptomonads have originated from an unicellular organism related to green algae which endosymbiotically took up a eukaryotic protist related to the red algae.

Biological Evolution↗
PubMed1992

The yptV1 gene encodes a small G-protein in the green alga Volvox carteri: gene structure and properties of the gene product.

Small G-proteins encoded by ras-like genes are ubiquitous in eukaryotic cells. These G-proteins are believed to play a role in central processes, such as signal transduction, cell differentiation and membrane vesicle transport. By screening genomic and cDNA libraries of the colonial alga, Volvox carteri f. nagariensis, with ypt DNA probes from Zea mays, we have identified the first member of a ypt gene family, yptV1, within a green alga. The 1538-bp yptV1 gene of V. carteri consists of nine exons and eight introns and has three potential polyadenylation sites 210, 420 and 500 bp downstream from the UGA stop codon. The derived 203-amino-acid polypeptide, YptV1, exhibits 81% similarity with Ypt1 from mouse, with the corresponding genes sharing four identical intron positions. Recombinant YptV1 (reYptV1) produced in Escherichia coli retains the ability to bind GTP after SDS-PAGE and immobilization on nitrocellulose. Immunological studies using polyclonal antibodies against reYptV1 indicate that the protein is present in the membrane fraction of a V. carteri extract and is expressed throughout the whole life-cycle of the alga. Similar to other Ras-like proteins, YptV1 contains two conserved C-terminal cysteine residues suggesting post-translational modification(s), such as isoprenylation or palmitoylation, required for membrane anchoring. The presumptive role of YptV1 in cytoplasmic vesicle transport is briefly discussed.

Amino Acid Sequence↗
PubMed2005

Contrasting effects of chloride on the toxicity of silver to two green algae, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii.

Short-term silver toxicity was determined for two freshwater algae, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii, in the presence and absence of chloride. Silver speciation in the exposure media was controlled and algal growth was measured over 6 h. For P. subcapitata, an alga with low Ag uptake fluxes, silver toxicity could be predicted on the basis of the free Ag+ concentration, in the presence or absence of significant complexation by chloride ions, as predicted by the biotic ligand model (BLM). For C. reinhardtii, an alga with high Ag uptake fluxes, silver toxicity was better predicted by the concentration of all labile dissolved Ag species than by free silver, a result that is consistent with diffusion through the unstirred layer surrounding the cell surface being the rate-limiting step in silver uptake. For both species, growth inhibition could be predicted on the basis of the Ag intracellular quota in the presence or absence of chloride, indicating that silver toxicity is a direct result of intracellular accumulation rather than cell surface interactions.

Chlorides↗
PubMed2006

Is prochloraz a potent synergist across aquatic species? A study on bacteria, daphnia, algae and higher plants.

Fungicides inhibiting the biosynthesis of ergostrol, such as the triazoles and imidazoles, have been shown to enhance the effect of insecticides on birds, mammals and invertebrates in the terrestrial environment. The synergy is proposed to be due to an effect on P450 monooxygenase enzymes active in pesticide metabolism in these organisms. Fungicides often enter the aquatic environment jointly with other pesticides. It is therefore possible that they could act as synergists also in the aquatic environment. In this study we tested the joint effect of the imidazole fungicide prochloraz together with the herbicides acifluorfen, diquat and terbuthylazine, the fungicide azoxystrobin and the insecticides chlorfenvinphos, dimethoate, and pirimicarb on the bacteria Vibrio fischeri (six binary mixtures), the crustacean Daphnia magna (four binary mixtures), the algae Pseudokirchneriella subcapitata (four binary mixtures) and the floating plant Lemna minor (three binary mixtures). All the binary mixtures were evaluated both in relation to the model of concentration addition (CA) and independent action (IA) using isobolograms. The study showed strong synergy in relation to CA between prochloraz and azoxystrobin, diquat and esfenvalerat on D. magna with sums of toxic units for the 50:50% effect mixture ( summation TU(50:50)) as low as 0.25. The mixture with dimethoate was however antagonistic with summation TU(50:50) of 2.04. Four out of the six mixtures testes on V. fisheri showed synergy in relation to CA, but for three of the mixtures the response could be explained by IA. Only the mixture with diquat showed synergy in relation to both IA and CA with summation TU(50:50) around 0.50. There was no significant synergy for any of the combinations tested on the plant and the algae species in relation to CA and only for diquat in the algae-test in relation to IA. Hence, prochloraz does synergise the effect of some pesticides in the aquatic environment, but not consistently across species. The organism most susceptible to synergy by prochloraz in this study was D. magna. Especially the combination with insecticides such as esfenvalerate, where the concentration needed to immobilize 50% of the daphnia was reduced from >3microgL(-1) to less than 0.5microgL(-1) when prochloraz was added, could be problematic as these concentrations are environmentally realistic. Furthermore, insecticides and ergostrol-biosynthesis-inhibitors (EBI-fungicides) are often applied together, and are therefore likely to co-exist in surface waters, enhancing the problem of the already very potent insecticides.

Animals↗
PubMed2005

Identification and characterization of heavy metal-resistant unicellular alga isolated from soil and its potential for phytoremediation.

A unicellular alga displaying a high growth rate under heterotrophic growth conditions was isolated from soil and identified as Chlorella sorokiniana. The optimal temperature for growth was 35 degrees C and the optimal pH was 6.0-7.0. Glucose, sucrose, galactose, maltose, and soluble starch served as carbon sources supporting growth under dark conditions. The cell yield was 50 g/l (wet weight) in a heterotrophic medium containing 3% glucose. Isolated unicellular algae were highly resistant to heavy metals such as Cd(2+), of which the minimal inhibitory concentration was 4 mM. Algae were capable of taking up the heavy metal ions Cd(2+), Zn(2+) and Cu(2+) at 43.0, 42.0 and 46.4 microg/mg dry weight, respectively. Growth inhibition of Oryza sative shoots by 5 ppm Cd(2+) in hydroponic medium was completely prevented by the addition of 0.25 mg of wet Chlorella cells. These results indicated that this isolate was potentially useful for phytoremediation by preventing environmental dispersion of heavy metals.

Adsorption↗
PubMed2006

Methodology and evaluation of a highly sensitive algae toxicity test based on multiwell chlorophyll fluorescence imaging.

A new phytotoxicity bioassay based on chlorophyll fluorescence imaging of algae suspensions in multiwell plates is introduced. Phytotoxicity is quantified via inhibition of photosystem II quantum yield, Y(II), assessed with the saturation pulse method. The basics of this approach as well as the factors enhancing and limiting its performance are outlined. Compared to other established techniques the new system allows exceptionally rapid and accurate measurements of phytotoxicity using pulse-amplitude-modulation (PAM) fluorometry. While instrument related errors are negligibly small, optimal performance depends on appropriate choice of algae and illumination conditions. Illustrative examples for the response of Phaeodactylum tricornutum to diuron are presented. The standard deviation involved in the Y(II) determination of a single well amounts to the equivalent of 44 ng/L diuron. A decisive role is played by the light (measuring light, saturation pulses, actinic light) to which samples are exposed during the bioassay: (1) the inhibitor response is enhanced at high measuring light intensity. (2) Saturation pulses may be considered non-invasive only, if applied at low frequency and as long as physiologically healthy algae cultures are used. (3) Continuous actinic light may be problematic, as it induces complex physiological reactions that limit the performance of the approach; it is not required for assessment of diuron-type inhibitors at high measuring light intensity.

Biological Assay↗
PubMed2006

Metabolites from algae with economical impact.

In order to survive in a highly competitive environment, freshwater or marine algae have to develop defense strategies that result in a tremendous diversity of compounds from different metabolic pathways. Recent trends in drug research from natural sources have shown that algae are promising organisms to furnish novel biochemically active compounds. The current review describes the main substances biosynthesized by algae with potential economic impact in food science, pharmaceutical industry and public health. Emphasis is given to fatty acids, steroids, carotenoids, polysaccharides, lectins, mycosporine-like amino acids, halogenated compounds, polyketides and toxins.

Adaptation, Physiological↗
PubMed2005

The effect of solvents on metal ion adsorption by the alga Chlorella vulgaris.

The dead dried alga, Chlorella vulgaris, was used for metal ion sequestering. The uptake of each of Cu(II), Cd(II), Fe(III), and Sn(IV) from their aqueous solutions decreased upon reuse of the biomass. Introducing mixed ethanol/water (50% v/v) metal ion solutions in batch systems enhanced the metal uptake of the exhausted biomass by 90% for iron, 40% for tin and only 14% for cadmium. In the column system, 20% v/v ethanol/water proved to be superior to acetone/water and isopropanol/water metal solutions in enhancing metal uptake. This increase in uptake offers a new method for regeneration of the algal capacity to remove metal ions from their solutions. Mossbauer results of iron and tin loaded algae from aqueous and mixed ethanol water solutions exhibited the characteristic doublet for (FeCl4-) at 0.350-0.565 mms(-1) respectively and the major doublet for inorganic Sn(IV) moieties at -0.217 to -0.365 mms(-1) respectively, excluding the possibility of microprecipitation of iron and tin, which is expected at such high concentrations of metals in the alga.

Adsorption↗
PubMed2004

Differential sensitivity of two green algae, Scenedesmus quadricauda and Chlorella vulgaris, to 14 pesticide adjuvants.

Growth-inhibition tests for 14 pesticide adjuvants which are widely used to manufacture various pesticidal formulations in China, were performed on the green algae Scenedesmus quadricauda, and Chlorella vulgaris to compare differential sensitivity among populations of these algae to the adjuvants. The results showed that the acute toxicities of 700#, 1601#, By-140, and SOPA to S. quadricauda and C. vulgaris were the lowest among all the tested adjuvants. The acute toxicities of Tween 80, O-25, and AEO-13 phosphate to the selected two green algae were intermediate among the tested adjuvants. The acute toxicities of 602#, 500#, OT, NP-10, OP-10, and JFC were the highest. Meanwhile, the algal species vary widely in their response to those adjuvants. The results showed that there was a differential response to various adjuvants among the selected algal species and that the sensitivities of the various algal species exposed to 1601# and OT varied by nearly 1 order and to 700#, and By-140 varied by over 1 order of magnitude. In addition, the NOEC and LOEC values of the selected 14 adjuvants to S. quadricauda and C. vulgaris were tested; the result showed that NOEC < or = EC10<EC20 for 27 of the 28 data sets (96%) and EC10 < or = LOEC < or = EC20 for 20 of the 28 data sets (78%).

Chlorella↗
PubMed2005

Effects of removing symbiotic green algae on the response of Hydra viridissima (Pallas 1776) to metals.

Hydra viridissima is distinctively green due to symbiotic algae within the endodermal cells. The current investigation was designed to see if these algae influenced the response of Hydra to pollutants, by comparing the toxicity of copper, cadmium, and zinc to both symbiotic and aposymbiotic (free of their endosymbiotic algae) H. viridissima. The results demonstrated that the toxicity of the metals was generally similar for both groups of Hydra. However, at the lowest copper concentrations there was a difference between the two group of polyps, with aposymbiotic animals dying at concentrations where symbiotic Hydra survived. The lowest observed effect concentrations were 0.0068 and 0.016 mg/L for aposymbiotic and symbiotic Hydra, respectively. It is suggested that the symbiotic Hydra derive benefits from the association that enable them to better tolerate the toxicant. This work demonstrated that experimental manipulation of symbionts can help to explain their complex interactions and the ways in which they respond to pollutants.

Animals↗
PubMed2006

Toxicity and hazard of selective serotonin reuptake inhibitor antidepressants fluoxetine, fluvoxamine, and sertraline to algae.

The toxicity of SSRIs to algae/phytoplankton was investigated using the US EPA ECOSAR, acute single-species growth inhibition assays, species sensitivity distributions (SSDs), and an outdoor microcosm mixture experiment. Worst-case ECOSAR estimates of SSRI toxicity to algae ranged from 0.73 to 13.08 mg/L. Sertraline was the most toxic SSRI tested in single-species growth inhibition assays followed by fluoxetine and fluvoxamine with worst-case 96-h IC10s of 4.6, 31.3, and 1662 microg/L, respectively. HC5s of 2.4, 3.6, and 1100 microg/L were estimated, respectively, for sertraline, fluoxetine, and fluvoxamine toxicity to algae-using SSDs. Microcosm phytoplankton structural endpoints were more sensitive than functional endpoints in the short term. However, in the long term, structural endpoints were resilient and functional endpoints remained impacted even after a period of recovery. The worst-case EC10 determined from the outdoor microcosm mixture toxicity to phytoplankton communities was 15.2 nM. Although SSRIs are toxic to algae, hazard quotients using worst-case PECs represent a margin of safety of 20 to phytoplankton. Although SSRIs do not appear to pose a hazard to primary production, this assessment is not protective of higher aquatic organisms and further research into the chronic toxicity to low levels of SSRIs to higher-level aquatic species is recommended.

Biomass↗
PubMed2005

Stress-related differential expression of multiple beta-carotene ketolase genes in the unicellular green alga Haematococcus pluvialis.

The unicellular green alga Haematococcus pluvialis is used as a biological production system for astaxanthin. It accumulates large amounts of this commercially interesting ketocarotenoid under a variety of environmental stresses. Here we report the identification and expression of three different beta-carotene ketolase genes (bkt) that are involved in the biosynthesis of astaxanthin in a single strain of the alga. Bkt1 and bkt2 proved to be the crtO and bkt previously isolated from two different strains of H. pluvialis. Bkt3 is a novel third gene, which shared 95% identical nucleotide sequence with bkt2. Nitrogen deficiency alone could not induce the alga cells to produce astaxanthin in 3 days even though it enhances the expression of the bkt genes to three times of that in normal growing cells within 16 h. High light irradiation (125 micromol m(-2)s(-1)) or 45 mM sodium acetate greatly increased the expression of bkt genes to 18 or 52 times of that in normal growing cells, resulting in an accumulation of substantial astaxanthin (about 6 mg g(-1) dry biomass) in 3 days. It is suggested that the existence of the multiple bkt genes and their strong up-regulation by different stress conditions is one of the reasons that H. pluvialis accumulates large amounts of astaxanthin in an instant response to stress environments.

Base Sequence↗
PubMed2005

Microbial modulation in the biomass and toxin production of a red-tide causing alga.

The effect of S10, a strain of marine bacteria isolated from sediment in the Western Xiamen Sea, on the growth and paralytic shellfish poison (PSP) production in the alga Alexandrium tamarense (A. tamarense) was studied under controlled experimental conditions. The results of these experiments have shown that the growth of A. tamarense is obviously inhibited by S10 at high concentrations, however no evident effect on its growth was observed at low concentrations. Its PSP production was also inhibited by S10 at different concentrations, especially at low concentrations. The toxicity of this strain of A. tamarense is about (0.95-12.14) x 10(-6) MU/cell, a peak toxicity value of 12.14 x 10(-6) MU/cell appeared on the 14th day, after which levels decreased gradually. The alga grew well in conditions of pH 6-8 and salinities of 20-34 per thousand. The toxicity of the alga varied markedly at different pH and salinity levels. Toxicity decreased as pH increased, while it increased with salinity and reached a peak value at a salinity of 30 per thousand, after which it declined gradually. S10 at a concentration of 1.02 x 10(9) cells/ml inhibited growth and the PSP production of A. tamarense at different pH and salinity levels. S10 had the strongest inhibitory function on the growth of A. tamarense under conditions of pH 7 and a salinity of 34 per thousand. The best inhibitory effect on PSP production by A. tamarense was at pH 7, this inhibitory effect on PSP production did not relate to salinity. Interactions between marine bacteria and A. tamarense were also investigated using the flow cytometer technique (FCM) as well as direct microscope counting. S10 was identified as being a member of the genus Bacillus, the difference in 16S rDNA between S10 and Bacillus halmapalus was only 2%. The mechanism involved in the inhibition of growth and PSP production of A. tamarense by this strain of marine bacteria, and the prospect of using it and other marine bacteria in the bio-control of red-tides was discussed.

Animals↗
PubMed2006

Tetraprenyltoluquinols from the brown alga Cystophora fibrosa.

Six cyclised tetraprenyltoluquinols and five stereoisomers with the previously reported amentol skeleton have been isolated from the lipophilic extract of the South African brown alga Cystophora fibrosa. Structures and relative stereochemistry were determined using spectrometric techniques, particularly 1D and 2D NMR, and molecular modelling experiments. The compounds isolated appear to be enantiomeric to compounds with the same skeleton isolated from brown algae of the genus Cystoseira collected in northern Africa and the Mediterranean Sea. The isolation of tetraprenyltoluquinols with the amentol skeleton from this alga suggests that C. fibrosa should be moved from the genus Cystophora into the Cystoseira.

Diterpenes↗
PubMed2004

NMR 13C-isotopic enrichment experiments to study carbon-partitioning into organic solutes in the red alga Grateloupia doryphora.

The red alga Grateloupia doryphora Montagne (Howe) (Cryptonemiales, Halymeniaceae) was used as a model to investigate the effects of changes in seawater salinity on the intracellular low-molecular-weight organic compounds. Carbon-partitioning into major organic solutes was followed by 13C nuclear magnetic resonance (NMR) spectroscopy on living algae incubated in NaH13CO3-enriched seawater, and by high resolution 1H and 13C NMR experiments performed on 13C-enriched algal extracts. NMR and high performance liquid chromatography (HPLC) analyses both demonstrated that floridoside level was the most affected by changes in salinity: it rose under the hypersaline treatment and decreased under hyposaline one. Moreover, at low salinity, the high labeling of floridoside (45.3% 13C-enrichment for C1) together with its low concentrations both provided evidence of great increase in the de novo biosynthesis and turnover rate. Our experiments also demonstrated a high incorporation of photosynthetic carbon into amino acids, especially glutamate, under hypoosmotic conditions. On the other hand, isethionic acid and N-methyl-methionine sulfoxide were only partly labeled, which indicates they do not directly derive from carbon photoassimilation. In algae exposed to high salinity, elevated concentrations of floridoside coupled to a low labeling (9.4%) were observed. These results suggest that hyperosmotic conditions stimulated floridoside biosynthesis from endogen storage products rather than from carbon assimilation through photosynthesis.

Amino Acids↗
PubMed2006

Lipids and lipid metabolism in eukaryotic algae.

Eukaryotic algae are a very diverse group of organisms which inhabit a huge range of ecosystems from the Antarctic to deserts. They account for over half the primary productivity at the base of the food chain. In recent years studies on the lipid biochemistry of algae has shifted from experiments with a few model organisms to encompass a much larger number of, often unusual, algae. This has led to the discovery of new compounds, including major membrane components, as well as the elucidation of lipid signalling pathways. A major drive in recent research have been attempts to discover genes that code for expression of the various proteins involved in the production of very long-chain polyunsaturated fatty acids such as arachidonic, eicosapentaenoic and docosahexaenoic acids. Such work is described here together with information about how environmental factors, such as light, temperature or minerals, can change algal lipid metabolism and how adaptation may take place.

Adaptation, Physiological↗
PubMed2004

Biosynthesis of di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) from red alga--Bangia atropurpurea.

The contents of di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) of red alga, Bangia atropurpurea, filaments cultured in artificial sea water medium were similar to those cultured in natural sea water medium. In the culture experiment, B. atropurpurea filaments were found to synthesize de novo phthalate esters. Additionally, DEHP and DBP contents in different species of algae grown in the same environment were different significantly, suggesting that it was due to the intrinsic nature of algae.

Culture Media↗
PubMed2026

Genome-wide insights into the evolutionary and demographic history of the red alga Mazzaella laminarioides: Evidence for speciation with ancient migration along the southeast Pacific coast.

The mechanisms driving lineage divergence in red algae remain unexplored, despite the group's remarkable diversity and ancient evolutionary history. The red alga Mazzaella laminarioides, a Chilean intertidal species complex composed of three parapatric cryptic lineages (North, Center, South), offers a valuable system to evaluate these processes, as its life history combines severe dispersal limitation with a haploid-diploid cycle that may influence the emergence of reproductive barriers. We reconstructed its evolutionary history using whole-genome sequencing and nuclear genome assembly of representative individuals from each lineage. Phylogenomic analyses based on 1,507 single-copy orthologs recovered three deeply divergent lineages with limited nuclear discordance consistent with incomplete lineage sorting. For both splits, demographic modelling was most consistent with an Ancient Migration scenario, although support over strict isolation was moderate, suggesting that divergence may have begun with low asymmetric ancestral gene flow followed by subsequent loss of connectivity, demographic bottlenecks, and later population expansion. Coding sequence analyses revealed lineage-specific dN/dS heterogeneity; only one South-lineage locus passed FDR correction (metaxin-1, mitochondrial protein import), with two further South-lineage candidates in chlorophyll and heme biosynthesis falling below the FDR threshold. Together, these signals suggest that divergent selective pressures on energy acquisition may have contributed to divergence at the southern end of the distribution. These results add to the small but growing body of whole-genome data for red algae and, alongside recent macroalgal studies, suggest that ancestral connectivity could be a recurrent feature of lineage divergence even in marine organisms with extremely restricted dispersal.

Rhodophyta↗