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PubMed1976

An NADP-dependent Glutamate Dehydrogenase in Chloroplasts from the Marine Green Alga Caulerpa simpliciuscula.

NADP-dependent glutamate dehydrogenase was partially purified from extracts of the marine siphonous green alga Caulerpa simpliciuscula. The enzyme had an apparent Km NH(4) (+) of 0.4 to 0.7 mm and was highly specific for NADPH, alpha-ketoglutarate, and ammonium ions.The bulk of the NADP-glutamate dehydrogenase was isolated with the chloroplast fraction in cell-free preparations of this alga and was released from these "chloroplast fractions" as a soluble enzyme on gentle lysis of chloroplast membranes.

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PubMed1977

Diurnal variation in n(2) fixation and photosynthesis by aquatic blue-green algae.

Rates of (14)CO(2) fixation, O(2) evolution, and N(2) fixation (acetylene reduction) by natural populations of blue-green algae recovered from Lake Mendota were measured at frequent intervals between sunrise and sunset. Photosynthesis and N(2) fixation were depressed during midday when light intensity was greatest. As the light intensity rose, most of the algal population migrated to deeper, light-limited waters where radiation damage would be diminished. As the relative rate of N(2) fixation compared to CO(2) fixation increases with depth, it is suggested that the algae maintain balanced growth by migrating vertically via buoyancy regulation. High concentrations of dissolved O(2) in lake water may inhibit N(2) fixation by enhancing photorespiration. Several factors such as photosynthetic rate, light intensity, dissolved O(2), species composition, and vertical and horizontal migration all affect observed rates of in situ N(2) fixation.

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PubMed1978

Biosynthesis of dolichyl phosphate: characterization and site of synthesis in algae.

This is the first report not only on the presence of polyprenyl phosphates and their site of synthesis in algae, but also on the formation of their sugar derivatives in this system.A glucose acceptor lipid was isolated from the nonphotosynthetic alga Prototheca zopfii. The lipid was acidic and resistant to mild acid and alkaline treatments. The glucosylated lipid was labile to mild acid hydrolysis and resistant to phenol treatment and catalytic hydrogenation, as dolichyl phosphate glucose is. These results are consistent with the properties of an alpha-saturated polyprenyl phosphate.The polyprenylic nature of the lipid was confirmed by biosynthesis from radioactive mevalonate. The [(14)C]lipid had the same chromatographic properties as dolichyl phosphate in DEAE-cellulose and Sephadex LH-20. Strong alkaline treatment and enzymic hydrolysis liberated free alcohols with chain lengths ranging from C(90) to C(105), C(95) and C(100) being the most abundant molecular forms. The glucose acceptor activity of the biosynthesized polyprenyl phosphate was confirmed.The ability of different subcellular fractions to synthesize dolichyl phosphate was studied. Mitochondria and the Golgi apparatus were the sites of dolichyl phosphate synthesis from mevalonate.

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PubMed1978

Two Biosynthetic Pathways to delta-Aminolevulinic Acid in a Pigment Mutant of the Green Alga, Scenedesmus obliquus.

Pigment mutant C-2A' of the unicellular green alga Scenedesmus obliquus develops only traces of chlorophyll and has no detectable amount of delta-aminolevulinic acid (ALA) when grown in the dark. In light it develops ALA and in the presence of levulinic acid (LA), a competitive inhibitor of ALA dehydratase, it accumulates 0.18 mmoles of ALA per 10 microliters of packed cell volume per 12 hours. This amount could be increased up to 15 times by feeding precursors and cofactors.Incubation with [U-(14)C]glutamate, [1-(14)C]glutamate, and [2-(14)C]glycine yielded significantly labeled ALA, whereas [1-(14)C]glycine did not label the ALA specifically. Thus, two pathways using either glycine/succinyl-coenzyme A or incorporating the whole C-5-skeleton of glutamate into ALA are present in this alga. The efficiency of the glycine/succinyl-coenzyme A pathway seems to be three times higher than that of the glutamate pathway. Incubation with [5-(14)C]2-ketoglutarate, which can serve both pathways as a precursor, resulted in radioactivity of ALA as high as the sum of both labeling with [1-(14)C]glutamate and [2-(14)C]glycine.Since the newly synthesized chlorophyll was radioactive regardless of labeled substrate employed, both pathways culminate in chlorophyll formation.

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PubMed1980

Evidence for HCO(3) Transport by the Blue-Green Alga (Cyanobacterium) Coccochloris peniocystis.

The possibility of HCO(3) (-) transport in the blue-green alga (cyanobacterium) Coccochloris peniocystis has been investigated. Coccochloris photosynthesized most rapidly in the pH range 8 to 10, where most of the inorganic C exists as HCO(3) (-). If photosynthesis used only CO(2) from the external solution the rate of photosynthesis would be limited by the rate of HCO(3) (-) dehydration to CO(2). Observed rates of photosynthesis at alkaline pH were as much as 48-fold higher than could be supported by spontaneous dehydration of HCO(3) (-) in the external solution. Assays for extracellular carbonic anhydrase were negative. The evidence strongly suggests that HCO(3) (-) was a direct C source for photosynthesis.Weakly buffered solutions became alkaline during photosynthesis with a one-to-one stoichiometry between OH(-) appearance in the medium and HCO(3) (-) initially added. Alkalization occurred only during photosynthesis and was blocked by 3-(3,4-dichlorophenyl)-1, 1-dimethylurea, diuron. It is suggested that HCO(3) (-) was transported into cells of Coccochloris in exchange for OH(-) produced as a result of HCO(3) (-) fixation in photosynthesis.The inorganic C concentration required to support a rate of photosynthesis of half the maximum rate (K(m)) was 6 micromolar at pH 8.0 or, in terms of available CO(2), a K(m) of 0.16 micromolar. This value is two orders of magnitude lower than reported K(m) values for the d-ribulose-1,5-bisphosphate carboxylase for blue-green algae. It is suggested that the putative HCO(3) (-) transport by Coccochloris serves to raise the CO(2) concentration around the carboxylase to levels high enough for effective fixation.

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PubMed1980

The Absence of Protochlorophyll(ide) Accumulation in Algae with Inhibited Chlorophyll Synthesis.

Golenkinia, Chlorella protothecoides, and mutant C-2A' of Scenedesmus were grown in darkness and on media in which chlorophyll synthesis is reduced significantly. The pigments were analyzed by spectrophotometry or by paper chromatography and compared with similar extracts from light-grown algae and dark-grown beans. No protochlorophyll(ide) was present in the dark-grown algae indicating that chlorophyll synthesis is blocked by a mechanism other than feedback regulation of aminolevulinic acid synthesis by protochlorophyll(ide) which has been proposed for flowering plants.

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PubMed1980

Effect of temperature on glycerol retention in the halotolerant algae dunaliella and asteromonas.

Algae of the genera Dunaliella and Asteromonas can maintain extremely high concentration gradients (>10(4)) of glycerol between the intracellular space and the medium. This unique ability is highly temperature-dependent. Treating the algae for several minutes at temperatures exceeding 60 C causes complete release of all the internally held glycerol; 50% release occurs around 50 C, but essentially none is released below 40 C. A similar behavior was observed in several species of Dunaliella, and one of Asteromonas and is independent of the salt concentration of the medium. The underlying mechanism may involve a temperature-dependent conformational transition of a component of the cellular membrane which is essential for glycerol impermeability.

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PubMed1981

Inorganic Carbon Accumulation and Photosynthesis in a Blue-green Alga as a Function of External pH.

The blue-green alga Coccochloris peniocystis photosynthesizes optimally over the pH range of 7.0 to 10.0, but the O(2)-evolution rate is inhibited below pH 7.0 and ceases below pH 5.25. Measurement of the inorganic carbon pool in this alga in the light, using the silicone-fluid filtration technique demonstrated that the rate of accumulation of dissolved inorganic carbon remained relatively constant over a wide pH range. At external dissolved inorganic carbon concentrations of 0.56 to 0.89 millimolar the internal concentration after 30 seconds illumination was greater than 3.5 millimolar over the entire pH range. Intracellular pH measured in the light using [(14)C]5,5-dimethyloxazolidine-2,4-dione and [(14)C]methylamine dropped from pH 7.6 at an external pH of 7.0 to pH 6.6 at an external pH of 5.25. Above an external pH of 7.0 the intracellular pH rose gradually to pH 7.9 at an external pH 10.0. Ribulose-1,5-bisphosphate carboxylase activity of cell-free algal extracts exhibited optimal activity at pH 7.5 to 7.8 but was inactive below pH 6.5. It is suggested that the inability of Coccochloris to maintain its intracellular pH when in an acidic environment restricts its photosynthetic capacity by a direct pH effect on the principal CO(2) fixing enzyme.

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PubMed1981

Kinetic Complexity, Homogeneity, and Copy Number of Chloroplast DNA from the Marine Alga Olisthodiscus luteus.

The kinetic complexity of chloroplast DNA isolated from the chromophytic alga Olisthodiscus luteus has been determined. Using optical reassociation techniques, it was shown that the plastid DNA of this alga reacted as a single component with a second order rate constant of 4.1 molar(-1) and second(-1) (Cot((1/2)) 0.24 molar second) under conditions equivalent to 180 millimolar Na(+) and 60 degrees C. Given the 92 x 10(5) dalton complexity calculated for this chloroplast genome, an Olisthodiscus cell contains 650 plastome copies. Although this complement remains constant throughout the growth cycle of the organism, the ploidy level of an individual chloroplast shows significant plasticity and is dependent upon the number of chloroplasts present per cell. Experiments with the DNA fluorochrome Hoechst dye 33258 (bisbenzimide) demonstrate that plastids isolated from all phases of cell growth each possess a ring-shaped nucleoid containing detectable DNA. Olisthodiscus chloroplast DNA showed no sequence mismatch when thermal denaturation profiles of reassociated chloroplast DNA were examined, thus all plastome copies are essentially identical. Finally, reassociation studies demonstrated that no foldback (short inverted repeat) sequences were present in the plastid genome although significant hairpin loop structures were observed in control nuclear DNA samples.

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PubMed1982

Chilling-Susceptibility of the Blue-Green Alga Anacystis nidulans: III. LIPID PHASE OF CYTOPLASMIC MEMBRANE.

The lipid phase of cytoplasmic membrane was studied by freeze-fracture electron microscopy in the chilling-susceptible blue-green alga, Anacystis nidulans. At growth temperatures, intramembrane particles were distributed at random in the fracture faces of cytoplasmic membrane, whereas, at chilling temperatures, the fracture faces were composed of particle-free and particle-containing regions. These findings indicate that lipids of the cytoplasmic membrane were in the liquid-crystalline state at the growth temperatures and in the phase-separation state at the chilling temperatures. Temperatures for the onset of phase separation were 5 and 16 degrees C in cells grown at 28 and 38 degrees C, respectively.In comparison, another blue-green alga, Anabaena variabilis, which is not susceptible to chilling, was also examined by the freeze-fracture electron microscopy. The intramembrane particles were distributed at random in the fracture faces of cytoplasmic membrane at the growth, as well as at the chilling, temperatures.The results in this and previous studies suggest that the chilling susceptibility of A. nidulans is a result of irreversible leakage of ions from the cytoplasm when the lipids of cytoplasmic membrane are in the phase-separation state at low temperatures.

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PubMed1982

Oxidation of c-Type Cytochromes by the Membrane-Bound Cytochrome Oxidase (Cytochrome aa(3)) of Blue-Green Algae.

Respiratory particles containing an aa(3)-type cytochrome oxidase were prepared from Anacystis nidulans, Synechocystis 6714, Synechococcus lividus, Anabaena variabilis, Nostoc sp. strain MAC, Nostoc muscorum, and Mastigocladus laminosus. Oxidation of c-type cytochromes by membrane preparations of the different blue-green algae was observed using purified cytochromes from horse heart, Candida krusei, tuna, Saccharomyces oviformis, Rhodospirillum rubrum, Rhodospirillum molischianum, Rhodopseudomonas palustris, Rhodocyclus purpureus, Paracoccus denitrificans, Anacystis nidulans, Anabaena variabilis, Euglena gracilis, and Scenedesmus obliquus. Rapid oxidations were consistently observed with the mitochondrial c-type cytochromes (horse heart cytochrome c reacts most rapidly) and with cytochromes c(2) from Rhodopseudomonas palustris and Rhodocyclus purpureus; in contrast, the cytochrome c(2) from Rhodospirillum rubrum and the plastidic cytochromes from E. gracilis and Scendesmus obliquus were inactive with all membrane preparations. All reactions were inhibited by low concentrations of KCN, NaN(3), and CO, and they were activated by Tween 80, thus indicating participation of the terminal oxidase. The results are discussed in view of the spectral similarities between the terminal oxidase of blue-green algae and the mitochondrial aa(3)-type cytochrome oxidase of plants and other eukaryotes.

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PubMed1983

Phosphofructokinase activities in photosynthetic organisms : the occurrence of pyrophosphate-dependent 6-phosphofructokinase in plants and algae.

A pyrophosphate-dependent phosphofructokinase (PPi-PFK) activity is detectable in extracts of a wide variety of primitive and advanced plants, the Charalean algae, and in the photosynthetic bacterium, Rhodospirillum rubrum. Angiosperms with extractable PPi-PFK activities 4- to 70-fold higher than the respective ATP-PFK activities tend to be succulent and to exhibit CAM. Even though PPi-PFK activity is not detected in crude extracts of some well known CAM plants, e.g. plants in the Crassulaceae, gel filtration of the extract and/or inclusion of the PPi-PFK activator, fructose 2,6-bisphosphate, in the assay reveals that a PPi-PFK activity is present in these species. Fructose 2,6-bisphosphate likewise activates PPi-PFK activities in extracts of C(3) and C(4) plants. C(3) and C(4) plant PPi-PFK activities are roughly equivalent to ATP-PFK activities in the same species. PPi-PFK activity is also detected in some bryophytes, lower vascular plants, ferns, and gymnosperms. The Charophytes, advanced algae presumed to be similar to species ancestral to vascular plants, exhibit at least 4-fold higher PPi-PFK than ATP-PFK activities. R. rubrum also exhibits a much higher PPi-PFK activity than ATP-PFK activity. These data indicate that PPi-PFK may serve as an alternate enzyme to ATP-PFK in glycolysis in a wide range of photosynthetic organisms.

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PubMed1983

Photosynthetic Unit Organization in a Red Alga : Relationships between Light-Harvesting Pigments and Reaction Centers.

The relative concentration of biliproteins, phycobilisomes, chlorophyll a, and reaction centers I and II are reported for Neoagardhiella bailyei, a macrophytic red alga collected in the field and compared with Anacystis nidulans, a cyanobacterium cultured in the laboratory. The ratios of chlorophyll to reaction center I, of chlorophyll to reaction center II, and the mass of phycobiliprotein per reaction center II are quite similar in Neoagardhiella and Anacystis, supporting the concept that the red algal chloroplast is derived from a cyanobacterial progenitor. The ratios of reaction center I to reaction center II are about 2.3 in both species. The Anacystis phycobilisome has about 40% of the mass of the Neoagardhiella phycobilisome, 4.9 and 14.9 x 10(6) daltons, respectively. The reaction center II/phycobilisome ratio is about 1.7 in Anacystis and 4.1 in Neoagardhiella. Phycobilisome size and physical restrictions on phycobilisome packing may be a major constraint on the reaction center II-phycobilisome association and the assembly of the photosynthetic membrane in both the red algae and cyanobacteria.

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PubMed1983

On the Factors Which Determine Massive beta-Carotene Accumulation in the Halotolerant Alga Dunaliella bardawil.

Dunaliella bardawil, a beta-carotene-accumulating halotolerant alga, has been analyzed for the effect of various growth conditions on its pigment content, and compared with Dunaliella salina, a beta-carotene nonaccumulating species. In D. bardawil, increasing light intensity and light period or inhibiting growth by various stress conditions such as nutrient deficiency or high salt concentration caused a decrease in the content of chlorophyll per cell and an increase in the amount of beta-carotene per cell. As a result, the beta-carotene-to-chlorophyll ratio increased from about 0.4 to 13 grams per gram and the alga changed its visual appearance from green to deep orange. D. salina grown similarly decreased in content of both chlorophyll and beta-carotene per cell and the culture turned from green to yellowish. Low chlorophyll-containing cells of D. bardawil or D. salina exhibit very high photosynthetic rates when expressed on a chlorophyll basis ( approximately 600 micromoles O(2) evolved per milligram chlorophyll per hour).Variation of pigment content in D. bardawil by a large variety of environmental agents has been correlated with the integral irradiance received by the algal culture during a division cycle. The higher the integral irradiance per division cycle, the lower the chlorophyll content per cell; the higher the beta-carotene content per cell, and therefore the higher the beta-carotene-to-chlorophyll ratio. The results are interpreted as indicating a protecting effect of beta-carotene against injury by high irradiance under conditions of impairment in chlorophyll content per cell.

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PubMed1983

State 1-State 2 Transitions in a Unicellular Green Algae : Analysis of In Vivo Chlorophyll Fluorescence Induction Curves in the Presence of 3-(3,4-Dichlorophenyl)-1, 1-dimethylurea (DCMU).

A study has been made on the State 1-State 2 transitions exhibited by the unicellular green algae Chlorella pyrenoidosa. Chlorophyll fluorescence induction curves from algae adapted to State 1 or State 2 have been analyzed and a comparison made with similar curves produced by decreasing the intensity of light going to the photosystem II reaction centers. In both cases, quenching of the maximum fluorescence yield (F(m)) and the initial fluorescence yield (F(o)) were observed so that the F(v)/F(m) ratio and the area above the induction curve (A(max)) remained constant. The State 1-State 2 transition also produced changes in the beta(max) component indicative of some alteration within photosystem II organization. The implications of these experiments on the in vivo mechanism for energy redistribution between the two photosystems are discussed in terms of changes in absorption cross-section rather than being due to spillover from photosystem II to photosystem I. These changes may reflect the phosphorylation of the light-harvesting chlorophyll a/b protein complex and its subsequent migration away from the photosystem II core leading to its closer association with photosystem I.

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PubMed1983

Light-Harvesting System of the Red Alga Gracilaria tikvahiae: I. Biochemical Analyses of Pigment Mutations.

Wild type Gracilaria tikvahiae, a macrophytic red alga, and fourteen genetically characterized pigment mutants were analyzed for their biliprotein and chlorophyll contents. The same three biliproteins, phycoerythrin, phycocyanin, and allophycocyanin, which are found in the wild type are found in all the Mendelian and non-Mendelian mutants examined. Some mutants overproduce R-phycoerythrin while others possess only traces of phycobiliprotein; however, no phycoerythrin minus mutants were found. Two of the mutants are unique; one overproduces phycocyanin relative to allophycocyanin while the nuclear mutant obr synthesizes a phycoerythrin which is spectroscopically distinct from the R-phycoerythrin of the wild type. The phycoerythrin of obr lacks the typical absorption peak at 545 nanometers characteristic of R-phycoerythrin and possesses a phycoerythrobilin to phycourobilin chromophore ratio of 2.6 in contrast to a ratio of 4.2 found in the wild type. Such a lesion provides evidence for the role of nuclear genes in phycoerythrin synthesis. In addition, comparisons are made of the pigment compositions of the Gracilaria strains with those of Neoagardhiella bailyei, a macrophytic red alga which has a high phycoerythrin content, and Anacystis nidulans, a cyanobacterium which lacks phycoerythrin. The mutants described here should prove useful in the study of the genetic control of phycobiliprotein synthesis and phycobilisome structure and assembly.

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PubMed1983

Effects of Salinity on Primary Processes of Photosynthesis in the Red Alga Porphyra perforata.

The effects of salinity on the primary processes of photosynthesis were studied in the red alga Porphyra perforata. The results show that there are at least three sites in the photosynthetic apparatus of this alga that were affected by increased salinity. The first site, photoactivation and dark-inactivation of electron flow on the reducing side of photosystem I, was completely inhibited at high salinity. The second site, electron flow on the oxidizing side (water side) of photosystem II, was inhibited as was the re-oxidation of Q in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The third site affected by high salinity was the transfer of light energy probably from pigment system II to I. High salinity reduced the amount of light energy that reached the reaction centers of photosystem II.These effects are discussed in relation to the mechanisms available to this plant to avoid photoinhibition when it is exposed to stresses such as high light and high salinity which are conditions that are commonly found in the intertidal habitat.

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PubMed1985

Photosynthesis and Inorganic Carbon Accumulation in the Acidophilic Alga Cyanidioschyzon merolae.

The intracellular pH and membrane potential were determined in the acidophilic algae Cyanidoschyzon merolae as a function of extracellular pH. The alga appear to be capable of maintaining the intracellular pH at the range of 6.35 to 7.1 over the extracellular pH range of 1.5 to 7.5. The membrane potential increase from -12 millivolts (negative inside) to -71 millivolts and thus DeltamuH(+) decreased from -300 to -47 millivolts over the same range of extracellular pH. It is suggested that the DeltamuH(+) may set the upper and lower limits of pH for growth. Photosynthetic performance was also determined as a function of pH. The cells appeared to utilize CO(2) from the medium as the apparent K(m(co(2))) was 2 to 3 micromolar CO(2) over the pH range of 1.5 to 7.5 C. merolae appear to possess a ;CO(2) concentrating' mechanism.

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