Accumulation of arsenic in blue-green alga, Phormidium sp

The behavior of a blue-green alga, Phormidium sp., against inorganic arsenic dissolved in media was studied. The Phormidium sp. was shown to have capabilities of endurance against a high concentration stress of arsenic and of accumulation of arsenic. Studies on excretion of arsenic by the alga showed that there were two excretion modes, each of which had a characteristic rate constant and it could be attributed to two types of binding situations between arsenic and the tissues of the alga. The arsenate absorbed by the algae was readily reduced to arsenite within their tissues.     

Antimicrobial and cytotoxic activity produced by an isolate of the thermotolerant cyanobacterium (blue-green alga)Phormidium sp.

Summary Extracellular material from a thermotolerant isolate ofPhormidium sp. from the Azores was chromatographed using Amberlite XAD-7 in conjunction with C₁₈ Sep-Paks to reveal antimicrobial activity. Further examination indicated the possibility of anticancer activity, elucidated using a biochemical induction assay and the inhibition of the V79 cell line.     

Spectrophotometric measurement of plastoquinone photoreduction in the blue-green alga,Phormidium uncinatum

The redox state of plastoquinone was measured in vivo in the blue-green alga, Phormidium uncinatum by means of a double beam UV-spectrophotometer. The difference in absorbance of the oxidized and the reduced forms of plastoquinone was amplified, and stored and averaged in a computer. The redox state was changed by two alternating actinic light beams. When one actinic wavelength was kept constant at 700 nm (PSI) variation of the other yielded an action spectrum representing photosystem II. The inhibitors of the photosynthetic electron transport chain, DCMU and DBMIB, reduced the difference in absorbance between the oxidized and reduced forms of plastoquinone.Abbreviations DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - DCMU 3-(3,4-dichlorophenyl)-1, 1-dimethylurea     

Gated ion fluxes involved in photophobic responses of the blue-green alga,Phormidium uncinatum

The sensory transduction chain of photophobic responses in the blue-green alga, Phormidium uncinatum seems to involve a gating cation transport through membrane bound ion channels which provides an effective amplification.The calcium conducting ionophore A23187 inhibits the photophobic response totally and induces frequent reversals which resemble phobic responses but occur without any light stimulation. This indicates that the electrogenic ion conductance may depend on a gradient of divalent cations, esp. calcium. The calcium conductance during a photophobic response is further confirmed by the inhibitory effect of ruthenium red and lanthanum, blockers of the electrogenic calcium transport. In the case of lanthanum this inhibition is found at a concentration at which neither the number of motile filaments nor the average speed of movement is impaired.Incorporation of ionophores for monovalent cations (gramicidin and valinomycin) only partially impairs the response. Similarly, inhibition of the Na⁺/K⁺ pump by ouabain is less effective. Thus, the existence of a countercurrent of monovalent cations during the response, which has been described for e.g. ciliates, is yet obscure in blue-green algae.     

Plastoquinone as a common link between photosynthesis and respiration in a blue-green alga

The role of plastoquinone in a thermophilic blue-green alga, Shynechococcus sp., was studied by measuring reduction kinetics of cytochrome 553 which was oxidized with red flash preferentially exciting photosystem I. Sensitivity of the cytochrome reduction to DBMIB indicates that cytochrome 553 accepts electrons from reduced plastoquinone. Plastoquinone is in turn reduced in cells without electrons from photosystem II, since DCMU, which inhibited methyl viologen photoreduction more strongly than DBMIB, failed to affect the cytochrome reduction. Participation of cyclic electron transport around photosystem I in cytochrome reduction in the presence of DCMU was excluded, because methyl viologen and antimycin A had no effect on the cytochrome kinetics. On the other hand, electron donation from endogenous substrates to plastoquinone was suggested from decreases in rate of the cytochrome reduction by dark starvation of cells and also from restoration of fast reduction kinetics by the addition of exogenous substrates to or by reillumination of starved cells.KCN, which completely suppressed respiratory O₂-uptake, induced a marked acceleration of the cytochrome reduction in starved cells. The poison was less or not effective in stimulating the cytochrome reduction in more extensively starved or reilluminated cells.Results indicate that plastoquinone is functioning not only in the photosynthetic but also in the respiratory electron transport chain, thereby forming a common link between the two energy conservation systems of the blue-green alga.

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Dependence of the photophobic response of the blue-green alga,Phormidium uncinatum,on cations

It is suggested that photophobic responses caused by a sudden step-down in light intensity require the presence of cations in the blue-green alga, Phormidium uncinatum.Drastic removal of cations abolishes the phobic response, which recovers after addition of Ca²⁺ ions. Calcium can be substituted for partially by other cations with an effectivity following the sequence Ca>Mg>Na>Ba>Co=0. During the photophobic response there is a 25% increase in ⁴⁵Ca binding by the cells related to a step-down in light intensity. Three seconds after a light-dark transition there is a sharp increase in the binding of labelled calcium, followed by a subsequent release.Flushing the filaments with high cation concentrations, esp. calcium causes a reversal of movement in the absence of a light stimulus similar to a photophobic reversal. This stimulus could trigger the same sequence of events in the transduction chain bypassing the primary photoresponse.Abbreviations EDTA Ethylene diaminetetraacetic acid - EGTA ethylene glycol-bis (2-aminoethylether) N,N tetraacetic acid     

Electrical and proton gradients in the sensory transduction of photophobic responses in the blue-green alga,Phormidium uncinatum

The gliding filaments of the blue-green alga Phormidium uncinatum stop their movement almost instantaneously when transfered from their growth pH of 7.2 into a buffer 4.5 or 12.5. A pH jump into the range between 5.6 and 12.0 induces no visible response while in the range between 4.9 and 5.5 the organisms reverse the direction of their movement. The pH jump is believed to simulate an early step during the sensory transduction chain of the photophobic response which eventually results in a reversal of movement.One of the subsequent steps is the inversion of an electric potential gradient existing between the front and rear ends of a filament which dictates the direction of movement. A similar reversal of the naturally existing potential gradient can be provoked by switching on an external do field when the filaments move towards the anode or switching it off when the filaments glide in the opposite direction. Implications of these results on the current model of sensory transduction of the photophobic response in Phormidium uncinatum are being discussed.     

The light-induced oxidation-reduction reaction of cytochrome b-559 in membrane fragments of the blue-green alga Anabaena variabilis

Light-induced oxidation-reduction reactions of cytochrome b-559were investigated with membrane fragments of Anabaena variabilisand supplementarily with Plectonema boryanum. The oxidation-reduction reactions of cytochrome b-559 observedwith membrane fragments were similar in their kinetics to thoseof the cytochrome in aged chloroplasts. The reactions were annihilatedby the addition of Ferro, indicating that the cytochrome ofhigh redox potential (E'_o=+373 mV, pH 6.5) was photoreducedand oxidized. Titration with reducing agents indicated that cytochrome b-559is contained in Anabaena membrane fragments in an amount 1.5times as much as the content of P700 on a molar basis; the contentof the species of high redox potential was estimated to be around70%. Kinetic treatment of the photoreduction indicated that the cytochromewas reduced at some site of the electron transport system betweenthe two photosystems. The photo-oxidation depended on the actionof either photosystem II or I even in the presence of DCMU,indicating that the photooxidation was induced by both photosystems.The oxidation by photosystem I action was inhibited by HgCl₂-treatment,indicating that this reaction is mediated by plastocyanin. EDTA (5?10^-3 M) suppressed the cytochrome photoreduction andenhanced the rapid phase of the photooxidation. The latter effectappeared only when an appropriate dark time (3 min) was insertedafter the cytochrome photoreduction. The phenomenon was interpretedas showing that EDTA modifies the reactivity of the electroncarrier which directly donates electrons to cytochrome b-559.The oxidation, and probably also the reduction of cytochromeb-559, was assumed to be regulated by the oxidation-reductionstate of this carrier. (Received April 26, 1974; )     

Structures in a blue-green alga resembling prolamellar bodies

Summary Cells ofAnabaena (IUCC 380) from soil-water cultures 106 and 168 days after inoculation were fixed in 2% KMnO₄ and studied by electron microscopy. Thylakoid lattices morphologically similar to prolamellar bodies characteristic of etiolated higher plant chloroplasts were discovered. Prefixation sonication and centrifugation were eliminated as factors producing these lattices in the photosynthetic thylakoid system of these prokaryotic cells. Similar lattices are not seen in young cultures in the log phase of growth cultured under the same temperature and light conditions in the same medium. Factors, other than age, producing these lattices are yet to be determined.     

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

The effects of UV irradiation (254 mμ) 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 mμ. 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.     

Alloxan: A growth accelerator for a nitrogen-fixing blue-green alga

Effect of Alloxan was studied on a nitrogen-fixing blue-green alga: Westiellopsis prolifica in pure cultures. Concentrations of Alloxan, 10 g to 50 g/ml stimulate the growth of the alga and increase the chlorophyll, carotin and phycocyanin content of the cultures.     

Algicidal effect of 2,4-dichlorophenoxy acetic acid on blue-green alga Cylindrospermum sp.

The effect of the herbicide 2,4-Dichlorophenoxy acetic acid generally used in agriculture was studied on the nitrogen fixing blue-green alga Cylindrospermum sp. The alga could tolerate up to 150 μg per ml in liquid culture and 100 μg per ml on agar plates without any inhibitory effect on growth and survival. The maximum tolerance was up to 800 μg per ml and higher concentrations were lethal.     

Intracellular localization of glycolate dehydrogenase in a blue-green alga

Glycolate dehydrogenase activity was detected in cell-free extracts of Oscillatoria sp. prepared by osmotic lysis of spheroplasts in 0.05 m potassium phosphate buffer, pH 7.5, containing 0.3 m mannitol. Most of the enzyme activity was found in a particulate fraction and localized in the photosynthetic lamellae after centrifugation in a discontinuous sucrose density gradient. Enzyme activity was detected in this fraction both in the presence and absence of the artificial electron acceptor 2,6-dichlorophenolindophenol (DPIP) and a low rate of O(2) uptake was detected in this lamellar fraction. Activity was lost from the lamellar fraction by repeated washing or by treatment with 0.005% Triton X-100 and the solubilized enzyme activity was DPIP-dependent. The data indicate that both glycolate dehydrogenase and its natural electron acceptor are bound to the photosynthetic lamellae in vivo. In contrast, catalase activity was found in the soluble cytoplasmic fraction.     

The photochemical and fluorescence properties of whole cells, spheroplasts and spheroplast particles from the blue-green alga Phormidium luridum.

The photochemical activities and fluorescence properties of cells, spheroplasts and spheroplast particles from the blue-green alga Phormidium luridum were compared. The photochemical activities were measured in a whole range of wavelengths and expressed as quantum yield spectra (quantum yield vs. wavelength). The following reactions were measured. Photosynthesis (O2 evolution) in whole cells; Hill reaction (O2 evolution) with Fe(CN)63- and NADP as electron acceptors (Photosystem II and photosystem II + Photosystem I reactions); electron transfer from reduced 2,6-dichlorophenolindophenol to diquat (Photosystem I reaction). The fluorescence properties were emission spectra, quantum yield spectra and the induction pattern. On the basis of comparison between the quantum yield spectra and the pigments compositions the relative contribution of each pigment to each photosystem was estimated. In normal cells and spheroplasts it was found that Photosystem I (Photosystem II) contains about 90% (10%) of the chlorophyll a, 90% (10%) of the carotenoids and 15% (85%) of the phycocyanin. In spheroplast particles there is a reorganization of the pigments; they loose a certain fraction (about half) of the phycocyanin but the remaining phycocyanin attaches itself exclusively to Photosystem I (!). This is reflected by the loss of Photosystem II activity, a flat quantum yield vs. wavelength dependence and a loss of the fluorescence induction. The fluorescence quantum yield spectra conform qualitatively to the above conclusion. More quantitative estimation shows that only a fraction (20--40%) of the chlorophyll of Photosystem II is fluorescent. Total emission spectrum and the ratio of variable to constant fluorescence are in agreement with this conclusion. The fluorescence emission spectrum shows characteristic differences between the constant and variable components. The variable fluorescence comes exclusively from chlorophyll a; the constant fluorescence is contributed, in addition to chlorophyll a, by phycocyanine and an unidentified long wavelength component. The variable fluorescence does not change in the transition from whole cells to spheroplasts. However, the constant fluorescence increases considerably. This indicates the release of a small fraction of pigments from the photosynthetic photochemical apparatus which then become fluorescent.     

Evidence for genetic transformation in blue-green alga Anacystis nidulans

Summary Evidence has been presented that blue-green alga Anacystic nidulans can undergo genetic transformation. DNA from erythromycin-, streptomycin-resistant of filamentous strains has been found to transform appropriate markers to a wild type or some other recipients. Favourable conditions for transformation have been described with respect to the revealing of transformants, the concentration of DNA and the competence of cells.