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PubMed2006

A novel obligate cultivation mutualism between damselfish and Polysiphonia algae.

In cultivation mutualisms, farming animals prepare fields for cultivars, enhance their growth and harvest them. For example, in terrestrial ecosystems, plant-herbivore cultivation mutualisms arose between humans and their crops only relatively recently. We discovered an obligate cultivation mutualism between a damselfish and an alga in a coral reef ecosystem. The damselfish, Stegastes nigricans, manages algal farms through territorial defence against the invading grazers and through weeding of unpalatable algae. As a result, the algal farms of S. nigricans are dominated by one species, Polysiphonia sp. We performed an exhaustive survey of algal assemblages inside and outside the territories of five damselfish species around the Ryukyu Islands, Japan, using molecular and morphological characteristics. Polysiphonia sp. 1 grew exclusively inside the farms of S. nigricans, and never elsewhere. Since only Polysiphonia sp. 1 is harvested and consumed by the damselfish as a staple food, this interdependent relationship is an obligate cultivation mutualism. This is the first record of an obligate plant-herbivore cultivation mutualism in a marine ecosystem. Our data also suggest that three other Polysiphonia species are facultatively mutual with, commensal with, or parasitic on other damselfish species.

Animals↗

PubMed1979

Regulation of numbers of intracellular algae.

Members of three classes of unicellular algae have exploited an intracellular habitat and occur as endosymbionts in aquatic invertebrates, including Protozoa. Such associations manifest a range of host--symbiont cellular interactions and achieve stability through the regulation of symbiont numbers. The mechanism of regulation is poorly understood. Steady-state algae:host cell ratios might be achieved by expulsion, digestion, or inhibition of growth of algal symbionts. Digestion and expulsion have been observed directly in some associations but their role in regulating numbers is circumstantial. Inhibition of growth as a result of nutrient limitation or inhibitor secretion is an attractive, but inadequately tested, hypothesis. The relation between the host cell mitosis and algal proliferation is a potential focal point for further study.

Animals↗

PubMed2002

Endolithic algae: an alternative source of photoassimilates during coral bleaching.

Recent reports of worldwide coral bleaching events leading to devastating coral mortality have caused alarm among scientists and resource managers. Differential survival of coral species through bleaching events has been widely documented. We suggest that among the possible factors contributing to survival of coral species during such events are endolithic algae harboured in their skeleton, providing an alternative source of energy. We studied the dynamics of photosynthetic pigment concentrations and biomass of endoliths in the skeleton of the encrusting coral Oculina patagonica throughout a bleaching event. During repeated summer bleaching events these endolithic algae receive increased photosynthetically active radiation, increase markedly in biomass, and produce increasing amounts of photoassimilates, which are translocated to the coral. Chlorophyll concentrations and biomass of endoliths were 4.6 +/- 1.57 and 1570 +/- 427 microg cm(-2) respectively, in skeletons of relatively healthy colonies (0-40% bleaching) but up to 14.8 +/- 2.5 and 4036 +/- 764 microg cm(-2) endolith chlorophyll and biomass respectively, in skeletons of bleached colonies (greater than 40% bleaching). The translocation dynamics of (14)C-labelled photoassimilates from the endoliths to bleached coral tissue showed significantly higher 14C activity of the endoliths harboured within the skeletons of bleached corals than that of the endoliths in non-bleached corals. This alternative source of energy may be vital for the survivorship of O. patagonica, allowing gradual recruitment of zooxanthellae and subsequent recovery during the following winter.

Animals↗

PubMed2002

Pseudoalteromonas issachenkonii sp. nov., a bacterium that degrades the thallus of the brown alga Fucus evanescens.

Eleven non-pigmented strains of gram-negative, aerobic, marine bacteria with polar flagella were isolated from the thallus of the brown alga Fucus evanescens collected in the Kraternaya Bight of the Kurile Islands in the Pacific Ocean. These organisms were conspecific and exhibited high levels of genetic relatedness (up to 91%). The G+C contents of the DNAs of these strains were 42.9-43.3 mol%. These halophilic bacteria had bacteriolytic, proteolytic and haemolytic activities and degraded algal polysaccharides, synthesizing a number of glycoside hydrolases (fucoidanases, laminaranases, alginases, agarases, pullulanases, beta-glucosidases, beta-galactosidases, beta-N-acetylglucosaminidases and beta-xylosidases). By 16S rDNA analysis, the bacteria were shown to belong to the genus Pseudoalteromonas, a member of the gamma-subclass of the Proteobacteria. DNA from the strains isolated from the brown alga showed 27-54% genetic relatedness with respect to DNAs of other type strains of the genus Pseudoalteromonas. The phenotypic characteristics, together with the genetic evidence, indicate that this group of epiphytic bacteria represents a distinct species, Pseudoalteromonas issachenkonii sp. nov., for which the type strain is KMM 3549T (= LMG 19697T = CIP 106858T).

Gammaproteobacteria↗

PubMed2004

Formosa algae gen. nov., sp. nov., a novel member of the family Flavobacteriaceae.

Four light-yellow-pigmented, Gram-negative, short-rod-shaped, non-motile isolates were obtained from enrichment culture during degradation of the thallus of the brown alga Fucus evanescens. The isolates studied were chemo-organotrophic, alkalitolerant and mesophilic. Polar lipids were analysed and phosphatidylethanolamine was the only phospholipid identified. The predominant cellular fatty acids were 15 : 0, i15 : 0, ai15 : 0, i15 : 1 and 15 : 1(n-6). The DNA G+C contents of the four strains were 34.0-34.4 mol%. The level of DNA relatedness of the four isolates was conspecific (88-98 %), indicating that they belong to the same species. The 16S rDNA sequence of strain KMM 3553(T) was determined. Phylogenetic analysis revealed that KMM 3553(T) formed a distinct phyletic line in the phylum Bacteroidetes, class Flavobacteria in the family Flavobacteriaceae and that, phylogenetically, this strain could be placed almost equidistant from the genera Gelidibacter and Psychroserpens (16S rRNA gene sequence similarities of 94 %). On the basis of significant differences in phenotypic and chemotaxonomic characteristics, it is suggested that the isolates represent a novel species in a new genus; the name Formosa algae gen. nov., sp. nov. is proposed. The type strain is KMM 3553(T) (=CIP 107684(T)).

Base Composition↗

PubMed2003

Characterization of mannuronan C-5-epimerase genes from the brown alga Laminaria digitata.

Alginate is an industrially important polysaccharide obtained commercially by harvesting brown algae. The final step in alginate biosynthesis, the epimerization of beta-1,4-d-mannuronic acid to alpha-1,4-l-guluronic acid, a structural change that controls the physicochemical properties of the alginate, is catalyzed by the enzyme mannuronan C-5-epimerase. Six different cDNAs with homology to bacterial mannuronan C-5-epimerases were isolated from the brown alga Laminaria digitata (Phaeophyceae). Hydrophobic cluster analysis indicated that the proteins encoded by the L. digitata sequences have important structural similarities to the bacterial mannuronan C-5-epimerases, including conservation of the catalytic site. The expression of the C-5-epimerase genes was examined by northern-blot analysis and reverse transcriptase-polymerase chain reaction in L. digitata throughout a year. Expression was also monitored in protoplast cultures by northern and western blot, reverse transcriptase-polymerase chain reaction, and activity measurements. From both the structural comparisons and the expression pattern, it appears that the cDNAs isolated from L. digitata encode functional mannuronan C-5-epimerases. The phylogenetic relationships of the bacterial and brown algal enzymes and the inferences on the origin of alginate biosynthetic machinery are discussed.

Amino Acid Sequence↗

PubMed2003

Characterization of salt-regulated mannitol-1-phosphate dehydrogenase in the red alga Caloglossa continua.

Mannitol-1-phosphate (M1P) dehydrogenase (M1PDH; EC 1.1.1.17), an enzyme catalyzing the reduction of Fru-6-phosphate (F6P) to M1P in algal mannitol biosynthesis, was purified to homogeneity from a cell homogenate of the eulittoral red alga Caloglossa continua (Okamura) King et Puttock. The enzyme was a monomer with an apparent molecular mass of 53 kD, as determined by gel filtration and SDS-PAGE, and exhibited an pI of approximately 5.5. The substrate specificity was very high toward F6P and M1P for respective reductive and oxidative reactions. The enzyme was found to be a sulfhydryl-type, because its activity was inhibited by N-ethylmaleimide and p-hydroxymercuribenzoate, and the inhibition by p-hydroxymercuribenzoate was rescued by 2-mercaptoethanol. Some unknown factors in the extract may also have inhibited the activity, because the total activity was greatly increased through the purification procedure. The optimum pH for F6P reduction was changed from 6.0 or lower to 7.2 by the addition of 200 mm NaCl. The reduction of F6P showed strong substrate inhibition above 0.5 mm. However, Km(F6P) of M1PDH was increased eight times by the addition of 200 mm NaCl, whereas Vmax was in a similar range with the avoidance of substrate inhibition by F6P. These results indicate that the enzyme was finely and directly regulated by the salt concentration without the requirement for gene expression. M1PDH can therefore be a key enzyme for regulating mannitol biosynthesis when the alga is stressed by a salinity change.

Kinetics↗

PubMed2005

Inhibition of target of rapamycin signaling by rapamycin in the unicellular green alga Chlamydomonas reinhardtii.

The macrolide rapamycin specifically binds the 12-kD FK506-binding protein (FKBP12), and this complex potently inhibits the target of rapamycin (TOR) kinase. The identification of TOR in Arabidopsis (Arabidopsis thaliana) revealed that TOR is conserved in photosynthetic eukaryotes. However, research on TOR signaling in plants has been hampered by the natural resistance of plants to rapamycin. Here, we report TOR inactivation by rapamycin treatment in a photosynthetic organism. We identified and characterized TOR and FKBP12 homologs in the unicellular green alga Chlamydomonas reinhardtii. Whereas growth of wild-type Chlamydomonas cells is sensitive to rapamycin, cells lacking FKBP12 are fully resistant to the drug, indicating that this protein mediates rapamycin action to inhibit cell growth. Unlike its plant homolog, Chlamydomonas FKBP12 exhibits high affinity to rapamycin in vivo, which was increased by mutation of conserved residues in the drug-binding pocket. Furthermore, pull-down assays demonstrated that TOR binds FKBP12 in the presence of rapamycin. Finally, rapamycin treatment resulted in a pronounced increase of vacuole size that resembled autophagic-like processes. Thus, our findings suggest that Chlamydomonas cell growth is positively controlled by a conserved TOR kinase and establish this unicellular alga as a useful model system for studying TOR signaling in photosynthetic eukaryotes.

Algal Proteins↗

PubMed1994

Two Distinct Aldolases of Class II Type in the Cyanoplasts and in the Cytosol of the Alga Cyanophora paradoxa.

Two aldolases from the alga Cyanophora paradoxa (Glaucocystophyta) can be separated by chromatography on diethylaminoethyl-Fractogel. The two aldolases are inhibited by 1 mM ethylene-diaminetetraacetate (EDTA) and, therefore, are class II aldolases. When cells of C. paradoxa were fractionated, one aldolase was associated with the cytosol fraction and the other was associated with the cyanoplast fraction. The Km(fructose-1,6-bisphosphate) was 600 [mu]M for the cytosolic aldolase and 340 [mu]M for the cyanoplast aldolase. The activity of the cytosolic aldolase was increased up to 4-fold by 100 mM K+ and slightly inhibited by Li+ and Cs+, whereas the cyanoplast aldolase was not affected by these ions. Inactivation by 1 mM EDTA could be partly restored by the addition of Co2+ or Mn2+ and to a lesser extent by Zn2+ or Mg2+. The molecular masses of the native cytosolic and cyanoplast aldolases are about 90 and 85 kD, respectively, as estimated by velocity centrifugation in sucrose gradients. Implications for the evolution of class I and II aldolases in chloroplasts of higher plants and algae will be discussed.

Journal Article↗

PubMed1995

Isolation and Characterization of a Protein Associated with Carotene Globules in the Alga Dunaliella bardawil.

The halotolerant alga Dunaliella bardawil accumulates very large amounts of [beta]-carotene when exposed to high light intensity. The accumulated [beta]-carotene is concentrated in small, oily globules within the chloroplast and has been suggested to protect the alga against photodamage by high irradiation (A. Ben-Amotz, A. Katz, M. Avron [1982] J Phycol 18:529-537;A. Ben-Amotz, M. Avron [1983] Plant Physiol 72: 593-597; A. Ben-Amotz, A. Shaish, M. Avron [1989] Plant Physiol 91: 1040-1043). A 38-kD protein was identified and purified from [beta]-carotene globules and was designated carotene globule protein (Cgp). Induction of Cgp occurs in parallel with [beta]-carotene accumulation in D. bardawil grown under different inductive conditions. Cgp is overproduced in a constitutive mutant strain that overproduces [beta]-carotene and is not detected in Dunaliella salina, a species that does not accumulate [beta]-carotene. Cgp production was not suppressed by norflurazon, an inhibitor of [beta]-carotene synthesis that leads to accumulation of the carotenoid precursor phytoene. Immunogold-labeling analysis by electron microscopy demonstrates that the protein is localized at the periphery of the globules. Proteolytic cleavage by trypsin enhances the coalescence and destruction of the globules, in parallel with Cgp disappearance. It is suggested that the function of Cgp is to stabilize the structure of the globules within the chloroplast.

Journal Article↗

PubMed2000

Characterization of sulfate assimilation in marine algae focusing on the enzyme 5'-adenylylsulfate reductase.

5'-Adenylylsulfate (APS) reductase was characterized in diverse marine algae. A cDNA encoding APS reductase from Enteromorpha intestinalis (EAPR) was cloned by functional complementation of an Escherichia coli cysH mutant. The deduced amino acid sequence shows high homology with APS reductase (APR) from flowering plants. Based on the probable transit peptide cleavage site the mature protein is 45.7 kD. EAPR expressed as a His-tagged recombinant protein catalyzes reduced glutathione-dependent reduction of APS to sulfite, exhibiting a specific activity of approximately 40 micromol min(-1) mg protein(-1) and Michealis-Menten kinetic constants of approximately 1.4 mM for reduced glutathione and approximately 6.5 microM for APS. APR activity and expression were studied in relation to the production of 3-dimethylsulfoniopropionate (DMSP), a sulfonium compound produced by many marine algae. A diverse group of DMSP-producing species showed extremely high enzyme activity (up to 400 times that found in flowering plants). Antibodies raised against a conserved peptide of APR strongly cross-reacted with a protein of 45 kD in several chlorophytes but insignificantly with chromophytes. In the chlorophyte Tetraselmis sp., APR activity varies significantly during the culture cycle and does not follow the changes in cellular DMSP content. However, a positive correlation was found between cell-based APR activity and specific growth rate.

Amino Acid Sequence↗

PubMed1966

Respiratory chain of colorless algae. II. Cyanophyta.

Whole cell difference spectra of the blue-green algae, Saprospira grandis, Leucothrix mucor, and Vitreoscilla sp. have one, or at the most 2, broad alpha-bands near 560 mmu. At -190 degrees these bands split to give 4 peaks in the alpha-region for b and c-type cytochromes, but no alpha-band for a-type cytochromes is visible. The NADH oxidase activity of these organisms was shown to be associated with particulate fractions of cell homogenates. The response of this activity to inhibitors differed from the responses of the NADH oxidase activities of particulate preparations from the green algae and higher plants to the same inhibitors, but is more typical of certain bacteria. No cytochrome oxidase activity was present in these preparations. The respiration of Saprospira and Vitreoscilla can be light-reversibly inhibited by CO, and all 3 organisms have a CO-binding pigment whose CO complex absorbs near 570, 535, and 417 mmu. The action spectrum for the light reversal of CO-inhibited Vitreoscilla respiration shows maxima at 568, 534, and 416 mmu. The results suggest that the terminal oxidase in these blue-greens is an o-type cytochrome.

Eukaryota↗

PubMed1968

The effects of ultraviolet irradiation on a coccoid blue-green alga: survival, photosynthesis, and photoreactivation.

The effects of UV irradiation (254 mmu) on a coccoid blue-green alga Agmenellum quadruplicatum, Strain PR-6, have been examined in terms of the survival curve and measurement of short time photosynthetic rates. From study of survival evidence has been found for a strong photoreactivation centered near 430 mmu. Measurements of photosynthetic rate suggest that there is a correlation between decay of photosynthesis and survival after UV exposure. The UV induced decay in photosynthetic activity is reversed by the identical photoreactivation conditions that increase the survival level. The photosynthetic data are interpreted as demonstrating a photoreactivation of photosynthesis in blue-green algae.

Journal Article↗

PubMed1969

Carbonic anhydrase in marine algae.

An electrometric system for determination of carbonic anhydrase activity was constructed. Enzyme activity was assayed in homogenates of marine macroscopic Chlorophyta, Rhodophyta, and Phaeophyta. Plants surveyed included Ulva expansa (Setchell) Setchell and Gardner, Codium fragile (Suringar) Hariot, Enteromorpha sp., Chaetomorpha torta (Farlow) McClatchie (Chlorophyta); Laurencia papillosa (Greville). Plocamium coccineum var. pacificum (Kylin) Dawson, Pterocladia capillacea (Gmelin) Bornet and Thuret. Gigartina armata J. Agardh (Rhodophyta); Eisenia arborea Areschoug and Macrocystis pyrifera (Linnaeus) C. A. Agardh (Phaeophyta). Activity was present in all algae; in the Phaeophyta this could be demonstrated only after dialysis. p-Chloromercuriphenylsulfonic acid (10(-4)m) decreased activity in 1 species, Plocamium; this inhibition could be almost completely overcome with the addition of 10(-3)m dithiothreitol. In 2 green and 2 red algae assayed for sensitivity to acetazolamide (Diamox), inhibition was complete at 10(-4)m concentration of inhibitor. Dithiothreitol at a concentration of 10(-3)m did not enhance activity in any of the homogenates, and was not necessary for enzyme expression.

Carbonic Anhydrases↗

PubMed1970

Defined Media for Growth and Gamete Production by the Green Alga, Oedogonium cardiacum.

Defined media consisting of inorganic salts and vitamin B(12) are described for the male and female filaments of the green alga, Oedogonium cardiacum. These media provide for a maximal growth rate and for the induction of oogonia and antheridia under the prescribed conditions. The maximal amounts of growth, based on dry weight measurements, compare favorably with other green algae.

Journal Article↗

PubMed1972

Studies with deoxyribonucleic Acid from blue-green algae.

DNA from two blue-green algae was isolated and characterized. The buoyant densities, thermal denaturation and renaturation, thermal melting values, base compositions, sedimentation coefficients, and molecular weights were determined. Blue-green algal DNA renatured extensively and at a comparable rate to that of bacterial DNA. The similarities among the kinds of DNA from bacteria and blue-green algae were interpreted to reflect a close relationship.

Journal Article↗

PubMed1975

Regulation of glucose 6-phosphate dehydrogenase in blue-green algae.

Glucose 6-phosphate dehydrogenase (EC 1.1.1.49) has been partially purified from Anacystis nidulans and Anabaena flos-aquae by means of ammonium sulfate fractionation and exclusion gel chromatography and the kinetic properties determined.Glucose 6-phosphate dehydrogenase from these blue-green algae exhibits Michaelis-Menten kinetics at pH 6.7. At this pH, Km values of 0.37 mm for glucose 6-phosphate and 10 mum for NADP were determined. At a pH above 7.4, the enzyme exhibits sigmoidal kinetics with respect to glucose 6-phosphate saturation but the saturation curve for NADP remains hyperbolic.ATP is an inhibitor of the enzyme competitively with NADP with a Ki of 2 to 5 mm. NADPH inhibits the enzyme competitively with glucose 6-phosphate. The inhibition curves for NADPH are hyperbolic at pH 6.7 and sigmoidal at pH 8.6.The significance of these in vitro kinetics are discussed relative to in vivo data on the control of glucose 6-phosphate turnover in blue-green algae.

Journal Article↗

PubMed1976

Specificity for Nicotinamide Adenine Dinucleotide and Nicotinamide Adenine Dinucleotide Phosphate of Nitrate Reductase from the Salt-tolerant Alga Dunaliella parva.

Nitrate reductase of the salt-tolerant alga Dunaliella parva could utilize NADPH as well as NADH as an electron donor. The two pyridine nucleotide-dependent activities could not be separated by either ion exchange chromatography on DEAE-cellulose or gel filtration on Sepharose 4B. The NADPH-dependent activity was not inhibited by phosphatase inhibitors. NADPH was not hydrolyzed to NADH and inorganic phosphate in the course of nitrate reduction. Reduction of nitrate in vitro could be coupled to a NADPH-regenerating system of glycerol and NADP-dependent glycerol dehydrogenase. It is concluded that the nitrate reductase of D. parva will function with NADPH as well as NADH. This is a unique characteristic not common to most algae.

Journal Article↗