Particle aggregation in photosynthetic membranes of the blue-green alga Anacystis nidulans.

Freeze-fracture electron microscopy demonstrates that in photosynthetic membranes of the blue-green alga Anacystis nidulans quenched from a temperature below growth temperature, areas devoid of membrane particles occur. We suggest that this phenomenon is related to phase transitions in the photosynthetic membrane.     

Ethionine-resistant mutants of the filamentous blue-green alga Plectonema boryanum.

Plectonema boryanum mutants that are resistant to ethionine are unable to incorporate ethionine into acid-precipitable material. Ethionine causes bleaching of chlorophyll in sensitive cells.     

Particle aggregation in photosynthetic membranes of the blue-green alga Anacystis nidulans

Freeze-fracture electron microscopy demonstrates that in photosynthetic membranes of the blue-green alga Anacystis nidulans quenched from a temperature below growth temperature, areas devoid of membrane particles occur. We suggest that this phenomenon is related to phase transitions in the photosynthetic membrane.     

Phosphomonoesterase activity of the cyanobacterium (blue-green alga) Calothrix parietina

Cellular and extracellular phosphomonoesterase activities were compared in Calothrix parietina D550, a strain whose original environment has been studied in detail. Activity in both fractions became detectable at about the same stage in batch culture. Differences in the influence of environmental factors between the two were slight, suggesting a common origin. The optimum temperatures for cellular and extracellular activities were 40 degrees C and 30 degrees C, respectively, and the upper limits for detectable activity were 80 degrees C and 65 degrees C. The pH optimum for both cellular and extracellular activity was 10.0-10.2. When P-limited cultures were tested with p-nitrophenyl phosphate (pNPP) as substrate, Km values for cellular and extracellular activities were 43 and 33 microM pNPP, respectively. Eleven ions were tested for their influence on activity. In most cases the effect was low or negligible at concentrations likely to be present in nature or freshwater laboratory media. Where obvious effects occurred, these were usually apparent at lower concentrations with extracellular than cellular activity. One mM Ca led to a 40% increase in extracellular activity in comparison with 0.1 mM Ca, but had no effect on cellular activity. However, inorganic phosphate, which had a marked inhibitory effect at concentrations above 10 microM, brought about a similar response with cellular and extracellular activities (approximately 60% decrease with 100 microM).     

Superoxide dismutases from a blue-green alga, Plectonema boryanum.

Iron-containing and manganese-containing superoxide dismutases were found in Plectonema boryanum. The Mn-enzyme occupies about 10% of total activity. The Fe-enzyme was purified to near homogeneity. It contains 2 atoms of iron per mol. Its molecular weight is 41,700 and it is composed of two subunits of identical molecular weight without disulfide linkage. Amino acid composition is presented. Electron paramagnetic resonance spectrum revealed that iron occurs in a high spin ferric form and in some anisotropic environment. The absorption spectrum and the absence of acid-labile enzymes are insensitive to cyanide. Although the Fe-enzyme is sensitive to hydrogen peroxide, the Mn-enzyme is not.     

Nitrogenase activity in the blue-green alga Plectonema boryanum strain 594

Summary The non-heterocystous filamentous blue-green alga, Plectonema boryanum strain 594 reduces acetylene to ethylene, incorporates ¹⁵N₂ into cell protoplasm, and grows readily in medium free of combined nitrogen, when incubated in a gas phase without added oxygen. Cells grown in the presence of 50 mg/l of ammonium-nitrogen do not reduce acetylene, and a concentration of 0.015 atm. CO in the gas phase inhibits nitrogenase activity completely but inhibits ¹⁴CO₂ incorporation by only 28%. Nitrogenase activity is inhibited after 2 h treatment with 3×10^-5 M DCMU and is inhibited completely in air.     

Isolation and characterization of three types of membranes from the cyanobacterium (blue-green alga) Synechocystis PCC 6714

Three types of membranes were separated from the cyanobacterium Synechocystis PCC 6714 by mechanical disruption and density gradient centrifugation. Orange-colored membranes contained xanthophylls but little -carotene or chlorophyll a, green-colored membranes contained chlorophyll a, -carotene and xanthophylls, and another type of orange-colored membranes contained unknown xanthophylls. These membrane preparations were similar to those from Anacystis nidulans in pigmentation and buoyant density and were identified as purified preparations of the cytoplasmic membranes, thylakoid membranes and cell walls of Synechocystis PCC 6714, respectively.Abbreviations SDS sodium dodecyl sulfate - Tes N-tris[hydroxymethyl]methyl-2-aminoethanesulfonic acid - TLC thin-layer chromatography     

Cytochromes and prenylquinones in preparations of cytoplasmic and thylakoid membranes from the cyanobacterium (blue-green alga) Anacystis nidulans

The cytochrome and prenylquinone compositions were compared for cytoplasmic membranes and thylakoid membranes from the cyanobacterium (blue-green alga) Anacystis nidulans. Reduced-minus-oxidized difference absorption spectra at ?196°C indicated that the thylakoid membranes contained photosynthetic cytochromes such as cytochrome ?, cytochrome b-559 and cytochrome b₆, while cytochromes c-549 and c-552 were detected spectrophotometrically only after their release by sonic oscillation. The cytoplasmic membrane preparation contained one or two low-potential cytochrome(s) with α-band maxima at 553 and 559 nm at ?196°C, which differed from the cytochromes in the thylakoid membranes. A cytochrome specific to the cytoplasmic membranes was also found by heme-staining after lithium dodecyl sulfate-polyacrylamide gel electrophoresis. Both types of membranes contained the three prenylquinones plastoquinone-9, phylloquinone and 5′-monohydroxyphylloquinone, but in different proportions.     

Temperature dependence of the photosynthetic activities in the thylakoid membranes from the blue-green alga Anacystis nidulans.

The effects of temperature and ethidium bromide on the banding of heat-denatured DNA was studied during equilibrium centrifugation in density gradients of NaI. Centrifugation at 10 degrees C prevents the partial renaturation of Escherichia coli DNA and Clostridium perfringens DNA that occurs at 20 degrees C. A centrifugation temperature of --5 degrees C is required to prevent renaturation of T7 phage DNA. Ethidium bromide decreases renaturation of Escherichia coli DNA during centrifugation at 20 degrees C and causes a small shift in the buoyant density of both denatured and native DNA. Equilibrium centrifugation at lower temperatures prevents DNA renaturation and permits increased utilization of the large buoyant density difference between native and heat-denatured DNA in gradients of NaI.     

Regulatory effect of hydrogen on nitrogenase activity of the blue-green alga (cyanobacterium) Nostoc muscorum.

Preincubation of the blue-green alga (cyanobacterium) Nostoc muscorum under an atmosphere of argon plus acetylene in the light led to a greater than fourfold increase of light-induced hydrogen evolution and to a 50% increase of acetylene reduction, as compared to cells that had not been preconditioned. The basic and the increased hydrogen evolution were both due to nitrogenase activity. Furthermore, after preincubation the hydrogen uptake, usually observed with unconditional cells, was abolished. Nostoc preincubated under acetylene evolved hydrogen in the light even in the presence of nitrogen for at least 2 h, with a 15-fold increase as compared to the unconditioned cells. These acetylene effects could be completely abolished by the presence of hydrogen during acetylene preincubation. These findings indicate that the hydrogen concentration in N. muscorum cells plays a role in regulation of nitrogenase activity.     

Fine structure of developing polyphosphate bodies in a blue-green alga,Plectonema boryanum

Summary Stages in the development of polyphosphate bodies in the blue-green alga, Plectonema boryanum, grown under continuous illumination in the presence of excess phosphate, are reported. During the first stage, an electronlucent area appears near the nucleoplasm or cross walls; it gradually increases to a size approximately equal to that of the final polyphosphate body. In this area a porous structure of medium electron density develops, while simultaneously electron-dense material, interpreted as polyphosphate, is deposited in the adjacent cytoplasm. Eventually, this material seems to penetrate into the porous structure. When the polyphosphate bodies are fully formed, the surrounding cytoplasm does not contain detectable amounts of polyphosphate.The formation of polyphosphate bodies in P. boryanum is compared with that in some bacterial species.     

Energy metabolism in the cyanobacterium Plectonema boryanum. Oxidative phosphorylation and respiratory pathways

The filamentous cyanobacterium Plectonema boryanum catalyzes efficient dark oxidative phosphorylation of exogenous ADP during NADPH consumption after a lysozyme treatment of only 30 min and subsequent dilution in hypoosmotic medium. It is shown that the thylakoid membranes and membrane areas bearing the terminal oxidase (presumably the cell membrane with cytochrome c:O₂ oxidoreductase) and easily soluble cytoplasmic proteins are involved in KCN-sensitive dark oxidative phosphorylation. The dinitrophenyl ether of 2-iodo-4-nitrothymol, 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone and KCN are inhibitors of dark respiratory ATP synthesis. Dependent on the physiological condition, other more or less KCN-insensitive respiratory pathways towards O₂ may be present. A tentative scheme of the respiratory pathways is proposed.     

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.     

Temperature dependence of the photosynthetic activities in the thylakoid membranes from the blue-green alga Anacystis nidulans

The photosynthetic electron transport and phosphorylation reactions were measured in the room temperature region in the thylakoid membranes prepared from the blue-green alga, Anacystis nidulans. The Arrhenius plot of the Hill reaction with 2,6-dichlorophenolindophenol showed a distinct break of straight lines at 21°C in the membranes from cells grown at 38°C, and at 12°C in those from cells grown at 28°C. The Arrhenius plot of the Hill reaction with ferricyanide showed a break at 13°C in the membranes from cells grown at 38°C, and at 7°C in those from cells grown at 28°C. On the other hand, the Arrhenius plot of the System I reaction with methylviologen as an electron acceptor and 2,6-dichlorophenolindophenol and ascorbate as an electron donor system was composed of a straight line in the membranes from cells grown at 28°C as well as at 38°C. The Arrhenius plot of the System II reaction measured by the ferricyanide reduction mediated by silicotungstate in the presence of 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea also showed a break at 11°C in the membranes from cells grown at 38°C.The Arrhenius plot of the phosphorylation mediated by N-methylphenazonium methylsulfate showed a break at 21°C in the membranes from cells grown at 38°C and at 12°C in those from cells grown at 28°C. The Arrhenius plot of the phosphorylation mediated by the System I reaction showed a break at 24°C in the membranes from cells grown at 38°C.The characteristic features in the Arrhenius plots of the photosynthetic electron transport and phosphorylation reactions are discussed in terms of the transition of physical phase of the thylakoid membrane lipids.     

Components of natural gas resulting from thermal degradation of the blue-green alga (cyanobacterium)Oscillatoria tenuis

Cultures of the blue-green alga (cyanobacterium)Oscillatoria tenuis were used to simulate thermal degradation and gas formation by heating without oxygen at 250° and 350 °C for 100 h. Analysis through gas chromatography showed that the gases were mainly CH₄, C₂H₆, C₃H₈, iC₄ (isobutane), nC₄ (normal butane), iC₅ (isopentane), nC₅ (normal pentane), H₂, C0₂ and N₂. The volume of gases per g dry weight of alga was 44 ml at 250 °C and 100 ml at 350 °C. Alkane gas comprised only 2.04% of the total at 250 °C and rising to 40.0% at 350 °C. The fraction of C0₂ decreased from 83.3% at 250 °C to 40.0% at 350 °C. The quantity of alkane in the soluble organic matter doubled with rising temperature but the H/C atomic ratio in the ‘kerogen’, insoluble organic matter, decreased sharply. Infrared spectra of the ‘kerogen’ showed that the peak of adipose radical at 2900 cm⁻¹ disappeared gradually with rising temperature, which reflects the gradual break of CH₄ or C₂H₆ from ‘kerogen’. This demonstrates that insoluble organic matter rather than soluble organic matter in blue-green algae are the main sources of the gas alkanes in the process of simulated thermal degradation.     

Energy transduction in photosynthetic bacteria IV. Light-dependent ATPase in photosynthetic membranes from Rhodopseudomonas capsulata

ATPase activity of photosynthetic membrane fragments from the bacterium Rhodopseudomonas capsulata can be stimulated by continuous illumination under conditions of active cyclic electron flow. The activation corresponds to an increase in the maximum velocity of the reaction and does not affect the apparent K_m for ATP (0.11 mM). No stimulation in the light is observed in the presence of classical uncouplers or oxidized 2,6-dichlorophenolindophenol (DCIP), which, per se, stimulate ATPase in the dark. It is demonstrated, however, that oxidized DCIP acts as an uncoupler of bacterial photophosphorylation.

The effect of light is elicited after a few minutes of preillumination, or in a much shorter time if an ADP trapping system is supplied. Activation does not occur if ADP is added during the preillumination (apparent K_m for inhibition by ADP = 1 μM). The effect of ADP is not related to competitive inhibition with ATP, which can be observed at higher concentrations (apparent K_i = 0.26 mM). ADP, however, is not effective if added after some minutes of preillumination.