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PubMed1955

Relation between pigment content and photosynthetic characteristics in a blue-green algae.

1. The blue-green alga Anacystis nidulans was cultured under steady state conditions at 25 and 39 degrees C. and under several different light intensities to give five different types of cells. 2. Cells were submitted to pigment analysis based upon acetone extracts and aqueous extracts obtained by sonic disintegration. The different cell types show a threefold range of chlorophyll content and a fourfold range of phycocyanin content with only minor changes in the chlorophyll/phycocyanin ratio. Cells of highest pigment content were estimated to contain 2.8 per cent chlorophyll a and 24 per cent phycocyanin, the latter on a total chromoproteid basis. 3. Light intensity curves of photosynthesis were obtained for each of the cell types at 25 and at 39 degrees C. The slopes of the light-limited regions of the curves are approximately linear functions of chlorophyll and phycocyanin contents. Maximum light-saturated rates of photosynthesis at 25 and 39 degrees show no simple relation to pigment content.

Chlorophyll↗

PubMed1969

Ultrastructure of blue-green algae.

Two freshwater blue-green algae, Tolypothrix tenuis and Fremyella diplosiphon, and an oscillatorialike marine alga, were found to possess structures on the photosynthetic lamellae which appear to correspond to the phycobilisomes of red algae. These homologous structures are important because they contain the phycobilins which are accessory pigments involved in photosynthesis. As in the red algae, the phycobilisomes were attached on the outer side of each lamellae, i.e., the side facing away from its own membrane pair. Although our study on Anacystis nidulans has not thus far revealed the presence of phycobilisomes, some observations were made on the structure of the polyhedral bodies. After negative staining, the polyhedral bodies were seen to be composed of regularly spaced subunits arranged in a crystalline array. Elongated segmented rods, which differed from the polyhedral bodies, were found in the nuclear region of apparently healthy Tolypothrix cells.

Eukaryota↗

PubMed1994

Purification and some properties of a trehalase from a green alga, Lobosphaera sp.

An unicellular green alga identified as Lobosphaera sp. by morphological observations was selected as a source of trehalase. The alga grew well heterotrophically and produced intracellular trehalase using Polypepton, yeast extract, and glycerol as nutrients. The enzyme was highly purified by ammonium sulfate fractionation, column chromatography on DEAE-Toyopearl, Sepharose CL-4B, and SP-Toyopearl. The molecular mass was estimated to be 400 kDa by gel filtration. SDS-PAGE indicated that the enzyme consisted of two subunits with a molecular mass range of 180-220 kDa and it contained carbohydrates. The enzyme was most active at pH 5.5 and at 65 degrees C and stable between pH 4-9 and below 65 degrees C. Fe3+ inactivated the enzyme. Sucrose was a competitive inhibitor with a Ki of 7.5 mM. The enzyme specifically hydrolyzed trehalase with a Km of 0.6 mM.

Carbohydrate Metabolism↗

PubMed2004

Role of a nonselective de novo DNA methyltransferase in maternal inheritance of chloroplast genes in the green alga, Chlamydomonas reinhardtii.

In the green alga, Chlamydomonas, chloroplast DNA is maternally transmitted to the offspring. We previously hypothesized that the underlying molecular mechanism involves specific methylation of maternal gamete DNA before mating, protecting against degradation. To obtain direct evidence for this, we focused on a DNA methyltransferase, DMT1, which was previously shown to be localized in chloroplasts. The full-length DMT1 protein with a molecular mass of 150 kD was expressed in insect cells, and its catalytic activity was determined. In vitro assays using synthetic DNA indicated methylation of all cytosine residues, with no clear selectivity in terms of the neighboring nucleotides. Subsequently, transgenic paternal cells constitutively expressing DMT1 were constructed and direct methylation mapping assays of their DNA showed a clear nonselective methylation of chloroplast DNA. When transgenic paternal cells were crossed with wild-type maternal cells, the frequency of biparental and paternal offspring of chloroplasts increased up to 23% while between wild-type strains it was approximately 3%. The results indicate that DMT1 is a novel type of DNA methyltransferase with a nonselective cytosine methylation activity, and that chloroplast DNA methylation by DMT1 is one of factors influencing maternal inheritance of chloroplast genes.

Animals↗

PubMed1994

Dynamics and pharmacological perturbations of the endoplasmic reticulum in the unicellular green alga Acetabularia.

The giant unicellular green alga Acetabularia was labeled with the lipophilic fluorochrome DiOC6 (3,3'-dihexyloxacarbocyanine) and examined by confocal laser scanning microscopy to study the distribution of the endoplasmic reticulum (ER) and its dynamic changes after the application of inhibitors. In control cells, a two-dimensional polygonal network of ER sheets and tubulus is suspended between parallel, longitudinally oriented bands. These bands coincide with the main physical tracks of organelle transport. All treatments that inhibited organelle motility caused a transformation of the polygonal network into confluent large patches of lamellar ER sheets. The shape of the lamellar sheets and residual activities of the ER were dependent on the inhibitors used. The largest ER lamellae were obtained after cytochalasin D (CD) treatment which effectively stopped cytoplasmic streaming. CD also caused the formation of a network of fine tubules overlapping with the lamellar sheets. Okadaic acid, a specific inhibitor of serine/threonine-protein phosphatases, also caused inhibition of organelle movement and enlargement of lamellar areas. Tension in the cytoplasm appeared to be reduced, as judged from the convexly curved lamellar rims and wavy connecting ER tubules. In contrast, N-ethylmaleimide, a sulfhydryl group blocking reagent, rapidly stopped streaming and halted all activities of the ER in a rigor-like state. These effects are interpreted in the context of actin-based motility phenomena prevalent in Acetabularia, and regulatory principles are discussed that might underlie ER dynamics.

Acetabularia↗

PubMed1980

Ultrastructural aspects of basal body associated fibrous structures in green algae: a critical review.

Ultrastructural aspects of fibrous structures associated with basal bodies of green algae are critically discussed. It is apparent that variation among these structures is much greater than in microtubular flagellar root systems and it is therefore suggested that fibrous structures may be more useful than microtubular roots in elucidating phylogenetic relationships within the Chlorophyceae sensu Stewart and Mattox and the Prasinophyceae sensu Christensen. Two main types of fibrous structures are distinguished: (1) Connecting fibres (these connect different basal bodies); (2) Fibrous roots (these originate at basal bodies and terminate somewhere else in the cell). Fibrous roots are of two types: (a) microtubular-root associated striated fibres (striation pattern 25-35 nm; system I-fibres); (b) striated fibres composed of a bundle of filaments (filament diameter: 5-10 nm; striation pattern greater than 80 nm; system II fibres). Numbers, disposition and substructure of connecting fibres and fibrious roots are variable in different genera of green algae. In the experimental secretion new observations on fibrous roots in the ulvalean genus Enteromorpha as well as preliminary information on fibrous structures in Carteria obtusa and Bryopsis lyngbyei are included. Functional and evolutionary aspects of fibrous structures associated with the flagellar apparatus of green algae are discussed.

Chlorophyta↗

PubMed2025

Genome editing in the green alga Chlamydomonas: past, present practice and future prospects.

The green alga Chlamydomonas is an important and versatile model organism for research topics ranging from photosynthesis and metabolism, cilia, and basal bodies to cellular communication and the cellular cycle and is of significant interest for green bioengineering processes. The genome in this unicellular green alga is contained in 17 haploid chromosomes and codes for 16 883 protein coding genes. Functional genomics, as well as biotechnological applications, rely on the ability to remove, add, and change these genes in a controlled and efficient manner. In this review, the history of gene editing in Chlamydomonas is put in the context of the wider developments in genetics to demonstrate how many of the key developments to engineer these algae follow the global trends and the availability of technology. Building on this background, an overview of the state of the art in Chlamydomonas engineering is given, focusing primarily on the practical aspects while giving examples of recent applications. Commonly encountered Chlamydomonas-specific challenges, recent developments, and community resources are presented, and finally, a comprehensive discussion on the emergence and evolution of CRISPR/Cas-based precision gene editing is given. An outline of possible future paths for gene editing based on current global trends in genetic engineering and tools for gene editing is presented.

Gene Editing↗

PubMed1998

Microcystin toxicosis in cattle due to overgrowth of blue-green algae.

Toxicosis due to microcystin-containing blue-green algae has been sporadically reported in a variety of animal species. Most reports of intoxication involve algal blooms during periods of warm temperatures and abundant sunshine in the spring or early summer. A case of blue-green algae toxicosis with lesions attributable to toxins from Microcystis aeruginosa is described in 4 cattle from southern Georgia during November. The case was unusual in that characteristic hepatic necrosis was accompanied by severe mesenteric edema and peritoneal effusion. In addition, weather conditions and location were not expected to be conducive to algal blooms. Rapid diagnosis and identification of the probable source of intoxication allowed the owner to move the herd away from the affected pond. This action limited losses to only the 4 cattle.

Animals↗

PubMed1988

Purification, properties and complete amino acid sequence of the ferredoxin from a green alga, Chlamydomonas reinhardtii.

The ferredoxin was purified from the green alga, Chlamydomonas reinhardtii. The protein showed typical absorption and circular dichroism spectra of a [2Fe-2S] ferredoxin. When compared with spinach ferredoxin, the C. reinhardtii protein was less effective in the catalysis of NADP+ photoreduction, but its activity was higher in the light activation of C. reinhardtii malate dehydrogenase (NADP). The complete amino acid sequence was determined by automated Edman degradation of the whole protein and of peptides obtained by trypsin and chymotrypsin digestions and by CNBr cleavage. The protein consists of 94 residues, with Tyr at both NH2 and COOH termini. The positions of the four cysteines binding the two iron atoms are similar to those found in other [2Fe-2S] ferredoxins. The primary structure of C. reinhardtii ferredoxin showed a great homology (about 80%) with ferredoxins from two other green algae.

Amino Acid Sequence↗

PubMed1992

Group I introns within the nuclear-encoded small-subunit rRNA gene of three green algae.

Four group I introns from the nuclear-encoded (18S) rRNA genes of three chlorophycean green algae are described; two are in Dunaliella parva, and one each is in D. salina and Characium saccatum. The introns within the gene in the latter two organisms are located at the sites equivalent to the 5' and 3' introns of D. parva, respectively. All four introns lack open reading frames and are relatively small, 381-447 bp. Both primary- and secondary-structural features place these introns within subgroup IC1 described by Michel and Westhof. Phylogenetic relationships of the three intron-containing taxa and their relatives, as inferred from comparisons of 18S rDNA sequences, suggest that inheritance of the introns along with the gene can account for their present distribution. The discovery of these four introns, in addition to two others known to exist in other chlorophycean green algae, suggests that group I introns within the 18S rRNA gene may be relatively common in the green algae.

Base Sequence↗

PubMed1981

Hemagglutination method for detection of freshwater cyanobacteria (blue-green algae) toxins.

Strains of the freshwater cyanobacteria (blue-green algae) Anabaena flosaquae and Microcystis aeruginosa produced toxins that caused intermittent but repeated cases of livestock, waterfowl, and other animal deaths. They also caused illness, especially gastrointestinal, in humans. The most common group of toxins produced by these two species were peptide toxins termed microcystin, M. Aeruginosa type c, and anatoxin-c. A method was found to detect the toxins which utilizes their ability to cause agglutination of isolated blood cells from mice, rats, and humans. The method could detect the toxin in samples from natural algal blooms, laboratory cultures, and toxin extracts. The method consists of: (i) washing lyophilized cyanobacteria cells with physiological saline (0.9% NaCl), (ii) centrifuging the suspension and then mixing portions of the cell-free supernatant with equal volumes of saline-washed erythrocytes in V-shaped microtiter plates, (iii) allowing the mixture to stand for 3 to 4 h, and (iv) scoring the presence of the toxin as indicated by blood cell agglutination. Nontoxic strains, as determined by intraperitoneal mouse bioassay of cyanobacteria or green algae, did not produce an agglutination response.

Bacterial Toxins↗

PubMed1993

Molecular cloning and evolutionary analysis of the calcium-modulated contractile protein, centrin, in green algae and land plants.

Centrin (= caltractin) is a ubiquitous, cytoskeletal protein which is a member of the EF-hand superfamily of calcium-binding proteins. A centrin-coding cDNA was isolated and characterized from the prasinophyte green alga Scherffelia dubia. Centrin PCR amplification primers were used to isolate partial, homologous cDNA sequences from the green algae Tetraselmis striata and Spermatozopsis similis. Annealing analyses suggested that centrin is a single-copy-coding region in T. striata and S. similis and other green algae studied. Centrin-coding regions from S. dubia, S. similis and T. striata encode four colinear EF-hand domains which putatively bind calcium. Phylogenetic analyses, including homologous sequences from Chlamydomonas reinhardtii and the land plant Atriplex nummularia, demonstrate that the domains of centrins are congruent and arose from the two-fold duplication of an ancestral EF hand with Domains 1+3 and Domains 2+4 clustering. The domains of centrins are also congruent with those of calmodulins demonstrating that, like calmodulin, centrin is an ancient protein which arose within the ancestor of all eukaryotes via gene duplication. Phylogenetic relationships inferred from centrin-coding region comparisons mirror results of small subunit ribosomal RNA sequence analyses suggesting that centrin-coding regions are useful evolutionary markers within the green algae.

Amino Acid Sequence↗

PubMed1999

Complete sequence of the mitochondrial DNA of the red alga Porphyra purpurea. Cyanobacterial introns and shared ancestry of red and green algae.

The mitochondrial DNA (mtDNA) of Porphyra purpurea, a circular-mapping genome of 36,753 bp, has been completely sequenced. A total of 57 densely packed genes has been identified, including the basic set typically found in animals and fungi, as well as seven genes characteristic of protist and plant mtDNAs and specifying ribosomal proteins and subunits of succinate:ubiquinone oxidoreductase. The mitochondrial large subunit rRNA gene contains two group II introns that are extraordinarily similar to those found in the cyanobacterium Calothrix sp, suggesting a recent lateral intron transfer between a bacterial and a mitochondrial genome. Notable features of P. purpurea mtDNA include the presence of two 291-bp inverted repeats that likely mediate homologous recombination, resulting in genome rearrangement, and of numerous sequence polymorphisms in the coding and intergenic regions. Comparative analysis of red algal mitochondrial genomes from five different, evolutionarily distant orders reveals that rhodophyte mtDNAs are unusually uniform in size and gene order. Finally, phylogenetic analyses provide strong evidence that red algae share a common ancestry with green algae and plants.

Amino Acid Sequence↗

PubMed2001

Form I Rubiscos from non-green algae are expressed abundantly but not assembled in tobacco chloroplasts.

Non-green algae have Rubiscos that are phylogenetically distinct from their counterparts in green algae and higher plants. Some non-green-algal Rubiscos are more specific for CO2, relative to O2, than higher-plant Rubiscos, sometimes coupled with lower Michaelis constants for CO2. If these Rubiscos could be substituted for the higher-plant enzyme, and if they functioned successfully in the higher-plant chloroplast and were regulated appropriately, they would improve the CO2 use and quantum efficiency of higher-plant photosynthesis. To assess the feasibility of expressing non-green algal Rubiscos in higher-plant chloroplasts, we inserted the rbcLS operons from the rhodophyte Galdieria sulphuraria and the diatom Phaeodactylum tricornutum into the inverted repeats of the plastid genome of tobacco, leaving the tobacco rbcL gene unaltered. Homoplasmic transformants were selected. The transgenes directed the synthesis of abundant amounts of transcripts and both subunits of the foreign Rubiscos. In some circumstances, leaves of the transformants with the P. tricornutum Rubisco contained as much foreign Rubisco protein as endogenous tobacco Rubisco (>30% of the soluble leaf protein). However, the subunits of the foreign Rubiscos were not properly folded and/or assembled. All the foreign large subunits and most of the foreign small subunits were recovered in the insoluble fractions of leaf extracts. Edman sequencing yielded the expected N-terminal sequences for the foreign small subunits but the N-termini of the foreign large subunits were blocked. Accumulation of large amounts of denatured foreign Rubisco in the leaves, particularly of the P. tricornutum transformants, caused a reduction in the amount of tobacco Rubisco present, with concomitant reductions in leaf CO2 assimilation and plant growth.

Amino Acid Sequence↗

PubMed2003

Comparison of plastid 16S rRNA (rrn16) genes from Helicosporidium spp.: evidence supporting the reclassification of Helicosporidia as green algae (Chlorophyta).

The Helicosporidia are invertebrate pathogens that have recently been identified as non-photosynthetic green algae (Chlorophyta). In order to confirm the algal nature of the genus Helicosporidium, the presence of a retained chloroplast genome in Helicosporidia cells was investigated. Fragments homologous to plastid 16S rRNA (rrn16) genes were amplified successfully from cellular DNA extracted from two different Helicosporidium isolates. The fragment sequences are 1269 and 1266 bp long, are very AT-rich (60.7 %) and are similar to homologous genes sequenced from non-photosynthetic green algae. Maximum-parsimony, maximum-likelihood and neighbour-joining methods were used to infer phylogenetic trees from an rrn16 sequence alignment. All trees depicted the Helicosporidia as sister taxa to the non-photosynthetic, pathogenic alga Prototheca zopfii. Moreover, the trees identified Helicosporidium spp. as members of a clade that included the heterotrophic species Prototheca spp. and the mesotrophic species Chlorella protothecoides. The clade is always strongly supported by bootstrap values, suggesting that all these organisms share a most recent common ancestor. Phylogenetic analyses inferred from plastid 16S rRNA genes confirmed that the Helicosporidia are non-photosynthetic green algae, close relatives of the genus Prototheca (Chlorophyta, Trebouxiophyceae). Such phylogenetic affinities suggest that Helicosporidium spp. are likely to possess Prototheca-like organelles and organelle genomes.

Chlorella↗

PubMed1975

Oxygen Isotope Fractionation during Photosynthesis in a Blue-Green and a Green Alga.

Oxygen isotope fractionation ((18)O/(16)O) at the natural abundance level has been measured during photosynthesis of a blue-green and a green alga. When sufficient attention is paid to removal of contaminating air O(2) before and during the experiments, then the photosynthetic O(2) evolved, as compared to the water O(2), had an average difference of -0.36% for a blue-green alga and -0.80% for a green alga. These experiments suggest that there is no reason to invoke an inverse isotope effect in photosynthesis as part of the explanation for the (18)O enrichment in atmospheric O(2) relative to O(2) in oceanic waters. In addition, in an indirect way, the experiments also support the argument that the bulk of O(2) evolved during photosynthesis comes from water. A 10% contribution of O(2) arising from CO(2) would have been detectable in the present work.

Journal Article↗

PubMed1976

Ribonucleotide reductase in blue-green algae: dependence on adenosylcobalamin.

Ten species of freshwater blue-green algae exhibit an adenosylcobalamin-dependent ribonucleotide reductase, thuse explaining the requirement for cobalt by these organisms. The evidence suggests a phylogenetic affinity between the cyanophytes and bacteria, such as Clostridium and Rhizobium, and the euglenoid flagellates, which also use the cofactor-dependent reductase. In contrast, the ribonucleotide reductase reaction in the few green algae surveyed shows no dependence on cobalamins.

Biological Evolution↗

PubMed1980

Strategies of response to copper, cadmium, and lead by a blue-green and a green alga.

The toxic metal ions Cu2+, Cd2+, and Pb2+ inhibited growth of the green alga Ankistrodesmus braunii and the blue-green alga (Cyanobacterium) Anabaena, strain 7120. Some concentrations of Cu lysed Anabaena 7120 at early, but not late, stages of growth. The other metals inhibited growth without causing lysis. Adding the chelating agent nitrilotriacetic acid (NTA) did not reduce, and in some cases increased, metal toxicity to Anabaena 7120. This suggests that these metals do not act on this alga only in the ionic form. When Anabaena 7120 grew in a sublethal concentrations of Cu(NO3)2 (10(-5)M) most of the Cu was found outside the cell, in nonionic form. About half the Cd was found to be cell associated when these algae grew in the presence of 10(-5)M Cd(NO3)2. Ankistrodesmus braunii bound substantial amounts of both Cd and Cu when growing in their presence. At certain Cu levels, the amount bound per cell remained virtually constant during growth. In Cd, the amount bound per cell was highest at the beginning of growth and then fell. Cell-associated metals were found in both wall plus membrane and cytoplasmic fractions of A. braunii after mechanical lysis. When these algae grew over dialysis sacs containing sediment loaded with Cd or Cu, substantial amounts of these metals left the sediment and entered the algal cultures. They were found both cell associated and in the culture medium of A. braunii. In cultures of Anabaena 7120, Cd removed from the sediment was found in both cells and culture medium, but Cu was found almost entirely in the culture medium. The effects that bloom of such algae might have on the mobilization of these metals from sediments in natural waters are discussed.

Cadmium↗