Heat-stabilities of cytochromes and ferredoxin isolated from a thermophilic blue-green alga

Two C-type cytochromes and ferredoxin were isolated and purifiedfrom the thermophilic blue-green alga Synechococcus sp. Theirheat-stabilities were studied in relation to the thermophilyof the alga. (Received May 23, 1979; )     

ADAPTATION OF A BLUE-GREEN ALGA TO SODIUM SELENATE AND CHLORAMPHENICOL

The pattern of growth of the unicellular blue-green alga Anacystisnidulans in gradually increasing concentrations of sodium selenateand chloramphenicol during successive subcultures was studied.An increase in tolerance to sodium selenate of about twelvetimes occurred during ten transfers of the alga in increasingconcentrations of the drug. The tolerance was partially lostafter the resistant cells had been given the same number oftransfers in a selenate-free medium. ¹ Present address: Botany Department, The University, Udaipur,Raj., India.     

Enhanced Model for Photophobic Responses of the Blue-Green Alga, Phormidium uncinatum

An improved computer-based mathematical model of photophobicresponses in the blue-green alga, Phormidium uncinatum, hasbeen used to simulate the behavior of the alga under variouslight and dark conditions. Under high light intensities, themodel predicts the induction of step-up phobic responses. Thisnovel result could be varified experimentally in vivo. Appropriatefeatures have been incorporated to simulate the effects of ionophoresand the application of external electrical fields; results ofthe computer simulation and in vivo experiments are compared.Several parameters of the model have been varied to specifythe range in which phobic responses are permitted. These parametersallow conclusions to be drawn on the functional correlates inthe living organism. (Received July 13, 1982; Accepted October 9, 1982)     

Growth and Nitrogen Fixation by Westiellopsis prolifica Janet

The blue-green alga Westiellopsis prolifica Janet has been isolatedin unialgal bacteria-free culture. Evidence of the ability ofthis algs to fix elementary nitrogen was obtained by demonstrationof increase in total combined nitrogen in cultures by the micro-Kjeldahlmethod and also by the uptake of ¹⁵N as demonstrated by theuse of the mass spectrometer. The growth and nitrogen-fixingcapacity of the alga was studied in relation to temperatureand light intensity. Increase in dry weight was greatest at40° C but the optimum for nitrogen fixation was between30 and 35°C. A considerable proportion of the nitrogen fixedwas released in soluble organic form into the medium.     

Chromatographic separation of photosystems I and II from the thylakoid membrane isolated from a thermophilic blue-green alga

The thylakoid membrane of a thermophilic blue-green alga, Synechococcussp., was separated into four chlorophyll-containing fractionsby a single chromatographic manipulation with a diethylaminoethyl-cellulosecolumn after digitonin treatment. Photosystems I and II, orchlorophyll a forms, were unevenly distributed among the fourfractions, which were designated F-1, F-2, F-3 and F-4 in theorder of elution from the column. F-1 has a simple composition of the chlorophyll a form and totallylacks photochemical activity. This fraction may be an antennachlorophyll a-protein in the blue-green alga. F-2 is rich inshorter wavelength chlorophyll a forms and shows the three-bandedfluorescence emission spectrum characteristic of photosystemII at liquid nitrogen temperature. This fraction is highly activein 2,6-dichloroindophenol photoreduction and contains one photooxidizablecytochrome b₅₅₉ per 50–100 chlorophyll a, whereas theP-700 content is as low as one P-700 per 2,000 chlorophyll a.Thus, F-2 represents photosystem II in a highly purified state.F-3 is rich in photosystem I, since this fraction is inactivein 2,6-dichloroindophenol photoreduction, and contains one P-700per 200 chlorophyll a and smaller amounts of cytochrome b₅₅₉.Longer wavelength chlorophyll a forms are abundant and a peakat 730 nm is the most prominent in the low-temperature fluorescencespectrum in this fraction. F-4, which consists of larger membranefragments shows spectral and photochemical features similarto those of F-3. (Received August 8, 1979; )     

Ascorbate photo-oxidation by a photochemically active chromoprotein isolated from the blue-green alga Anabaena cylindrica: the effect of monochromatic illumination

Ascorbate photo-oxidation by a photochemically active chromoproteinisolated from the blue-green alga Anabaena cylindrica was studiedunder monochromatic illumination. Results indicate that die chromoprotein consists of at leasttwo pigments, both of which act as light-energy receptors forascorbate photo-oxidation. (Received May 11, 1971; )     

Electron donor-specificity observed in photosystem I reactions of membrane fragments of the blue-green alga Anabaena variabilis and the higher plant Spinacea oleracea

Electron donating activities of plastocyanins and c-type cytochromesof various organisms for photosystem I reactions were studiedwith membrane fragments of the blue-green alga Anabaena variabilisand the higher plant Spinacea oleracea. In the Anabaena photosystem I reaction, basic but not acidicplastocyanin and c-type cytochromes acted as efficient electrondonors, while only acidic redox proteins were active in thespinach photosystem I reaction. The selective reactivity ofredox proteins in the two photosystem I reactions was observedwith both plastocyanin (or cytochrome) limited and saturatedconditions. These data support our previous observation that photosystemI of blue-green algae differs from those of other green plantswith respect to specificity to the proteinous electron donor(1). (Received August 17, 1971; )     

Effects of Radiations on Blue-green Algae: II. Effects in Growth

The unicellular blue-green alga Anacystis nidulans was repeatedlytreated with X-rays and radiophosphate (32P) during successivesubcultures. The strains so obtained were characterized by comparisonwith the untreated control strain, with respect to their resistanceto ultraviolet light, X-rays, streptomycin, and isoniazid. The³²P-treated strain was found to be relatively more resistantto streptomycin than the untreated strain and the X-rayed strainwas found to be relatively rnore sensitive to isoniazid thanthe control. In old cultures, cells of the X-rayed strain weresignificantly smaller than those of the untreated strain. The effects of X-rays on cell- and heterocyst dimensions ofthe nitrogen-fixing alga Chlorogloea fritschii Mitra were studied.In the irradiated material the cell diameter and heterocystbreadth were greater, rather than smaller, than in unirradiatedmaterial.     

THE EFFECT OF PROFLAVINE ON DIFFERENT STRAINS OF THE BLUE-GREEN ALGA ANACYSTIS NIDULANS

The growth of the blue-green alga Anacystis nidulans was inhibitedby relatively low concentrations of proflavine. The durationof the lag phase increased linearly with increasing proflavineconcentrations. The alga neither acquired increased toleranceto the drug during the course of six subcultures in proflavine-supplementedmedia nor was there any shortening of lag-phase or increasein final population density following repeated subculture inproflavine medium. The strain obtained after six subcultures in proflavine wasfound to have become more sensitive to streptomycin than theuntreated stock strain. A comparison of sensitivity to proflavine of two streptomycin-resistantstrains and of untreated stock strain of the alga revealed thatthe streptomycin-resistant strains were less sensitive to proflavinethan the untreated strain. The resistance of a strain resistant to 200 µg streptomycin/mlwas lost after it had been cultured once in streptomycin-freebasal medium that had been supplemented with 1 µg proflavineµml.The results obtained provide some indirect evidence for theexistence of episome in A. nidulans. ¹Present temporary address: Division of Biosciences, NationalResearch Council, Ottawa-2, Canada.     

Purification of C-Type Cytochromes from a Thermophilic Blue-Green Alga, Synechococcus vulcanus, by Hydrophobic Column Chromatography using Toyopearls

Two C-type cytochromes, c-550 and c-553, were extracted by animproved procedure from a thermophilic blue-green alga, Synechococcusvulcanus, and effectively purified by a two-step hydrophobicchromatography. The first step was performed with a ToyopearlHW-65C :ammonium sulfate-66 column and the second with a butyl-Toyopearl650 column. This work is the first to apply butyl-toyopearl650 to protein purification. (Received July 2, 1984; Accepted September 13, 1984)     

Chromatic adaptation and photoreversal in blue-green algaCalothrix clavata West

Complementary chromatic adaptation, a well-established phenomenon in some blue-green algae, has been observed inCalothrix clavata, a heterocystous blue-green alga of the family Rivulariaceae. The chromatic adaptation has been observed for fluorescent and incandescent light by measuring the absorption spectra. The material grown in fluorescent light forms more of phycoerythrin whereas more of phycocyanin tends to be formed in incandescent light. Besides this, photoreversal was observed by transferring the incandescent light grown alga to fluorescent light conditions and vice-versa. Effect of photoreversal and chromatic adaptation has also been discussed for this alga under different monochromatic light conditions. The influence of different light conditions on morphological changes, heterocysts and hormogonia formation has also been investigated. Both chromatic adaptation and photomorphogentic phenolmena in this alga show the involvement of some photoreversible (red:green) pigment.     

FREQUENT HETEROCYST GERMINATION IN THE BLUE-GREEN ALGA GLOEOTRICHIA GHOSEI SINGH1

A unique feature, frequent heterocyst germination, has been observed in a nonsporulating mutant clone (of spontaneous origin) of the blue-green alga Gloeotrichia ghosei Singh. The controlling factor seems to be the presence of ammoniacal nitrogen in the medium. In addition, such a medium supports differentiation of successive crops of new heterocysts and their germination in the name medium and in the same algal culture. Contrary to previous observations with oilier blue-green algae, ammoniacal nitrogen does not seem to inhibit heterocyst differentiation in this alga. Both the parent alga and its mutant clone grow poorly in a nitrogen-free medium, which, although they are not completely free from bacteria, may indicate that they tire poor fixers or nonfixers. However, they form a large number of heterocysts under these conditions. The general conclusion is that the heterocysts of blue-green algae show a multiplicity of structure and function. In the present case they have reproductive function leading to direct propagation of the alga. The bearing of these findings on the interrelationships of the genera Gloeotrichia and Rivularia has been discussed. It has been concluded that the distinction between them is purely artificial.     

Polyphosphate metabolism in the blue-green alga Microcystis aeru-ginosa

The uptake of inorganic phosphorus was studied in an axenicstrain of phosphorus-starved cells of the blue-green alga Microcystisaeruginosa, an organism often causing blooms in freshwater bodies.Rates of growth and of cellular polyphosphate content as a functionof initial orthophosphate in the medium indicate the operationof the ‘phosphorus overplus’ phenomenon in M. aeruginosa,accompanied by formation of volutin granules. The granules wereisolated by a non-aqueous centrifugation method, and identifiedas polyphosphate bodies.     

Quantitative relationship between two reaction centersin the photosynthetic system of blue-green algae

The quantitative relationship between reaction centers I andII was studied with blue-green algae Anabaena cylindrica, Anabaenavariabilis and Anacystis nidulans grown under different lightconditions. The number of reaction centers I was estimated fromthe P700 content and that of reaction centers II, from the O₂yield of repetitive short flashes. Supplementary determinationswere done with three other blue-green algae and one red alga.The maximum number of reaction centers II counted from the O₂yield of repetitive short flashes was markedly smaller thanthe total number of P700 in all algae tested when the algaewere grown under weak light; in the extreme case (Anabaena cylindrica),the ratio was only 0.258?0.015. This ratio became larger andclose to unity when the algae were grown under stronger light.Variation in the number of reaction centers in a single cellsuggested that reaction center I was a variable component. Ourresults indicate that the proportion of the two reaction centersmay markedly vary in blue-green algae depending on the growthconditions (Received November 13, 1978; )     

Effect of carbon dioxide concentration on pigmentation in the blue-green alga Anacystis nidulans

The pigment content in the blue-green alga Anacystis nidulanswas found to be dependent upon CO₂ concentration during growth.In cells grown with 1% CO₂ in air the total pigment constituted20.5% of the dry weight while it was only 11.1% of dry weightof cells grown in air (0.03% CO₂). This decrease in total pigmentwas found to be almost entirely ascribable to decrease in phycocyanin.Since light absorbed by phycocyanin has been shown to providenearly equal rates of photoreactions I and II, the "CO₂ control"of phycocyanin is viewed as an effective means of regulationof the photoreactions without upsetting the balance of operationof the two photoreactions. (Received December 25, 1970; )     

Nitrogen Fixation by the Blue-green Alga Anabaena flos-aquae A-37

Nitrogen fixation has been demonstrated in a bacteria-free culture of a semithermophilic blue-green alga, Anabaena flos aquae A-37, employing the criterion of an increase in cellular nitrogen as a basis for determining nitrogen fixation. This is apparently the first time that nitrogen fixation has been demonstrated in a pure culture of a blue-green alga which grows at 40 C and which produces abundant quantities of an extracellular heteropolysaccharide.     

Immunological identification of pigment component of a photochemically active chromoprotein (AGP) isolated from the blue-green alga Anabaena cylindrica

Pigment constitution of a photochemically active chromoprotein(ACP) isolated from the blue-green alga Anabaena cylindrica,was immunologically studied. Results confirmed our previousview that ACP is a complex of c-phycocyanin and a pigment havingabsorption peaks at 480 and 695 nm. Antisera of both ACP andphycocyanin did not significantly affect the photochemical activityof ACP. (Received August 15, 1972; )     

Effects of Radiations on Blue-green Algae: I. The Production and Characterization of a strain of Anacystis nidulans resistant to Ultraviolet radiation

The unicellular blue-green alga Anacystis nidulans was exposedto ultraviolet radiation during several successive subcultures.The ultraviolet-trained strain so obtained was then comparedwith the untrained control and found to be relatively more resistantto ultraviolet, penicillin, and streptomycin, and more sensitiveto isoni-azid. It was further characterized by decreased carotenoid/chlorophyllratio and by not having fully overcome the division-inhibitingeffect of ultraviolet radiation. It was able to grow betterthan the untrained strain in a medium containing high concentrationsof nitrite as the sole nitrogen source.     

The Lipid Phase of Thylakoid and Cytoplasmic Membranes from the Blue-Green Algae (Cyanobacteria), Anacystis nidulans and Anabaena variabilis

The lipid phases of the thylakoid and cytoplasmic membranesfrom the blue-green alga, Anacystis nidulans, were studied bya spin-probe method using 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxyl.The thylakoid and cytoplasmic membranes of this alga were bothin the liquid crystalline state at growth temperature, and inthe phase separation state at about 0?C. The thylakoid membranesentered the phase separation state at a temperature higher thanthe cytoplasmic membranes. The lipid phase of the thylakoidmembranes from Anabaena variabilis was studied in a similarway, and these membranes were found also to undergo the phasetransition. The temperature for the onset of the phase separationand the fluidity of the membrane lipids of both algae dependedon the growth temperature of the culture. (Received April 9, 1984; Accepted June 1, 1984)     

Phycoerythrin of the marine blue-green alga Trichodesmium thiebautii

Spectroscopic characteristics of the phycoerythrin obtainedfrom the marine blue-green alga Trichodesmium thiebautii wereinvestigated. The algal sample was collected at its naturalhabitat, the East China Sea. The phycoerythrin showed an absorptionspectrum and a fluorescence excitation spectrum with three peaksin the visible wave-length region at 500, 547 and 565 nm. Thisproperty is very different from that of the cyanophycean phycoerythrin,which has a single peak at 565 nm, but it is similar to thatof the rhodophycean phycoerythrin with three peaks at 500, 550and 565 nm. (Received April 20, 1974; )