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.     

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.     

The effect of osmotic stress on the oxidation of glycolate by the blue-green alga Anacystis nidulans

Planta - Anacystis nidulans Richt. was shown to assimilate glycolic acid, and uptake was light-stimulated. In the dark 90% of the glycolate taken up was oxidised to CO2. Both light and dark uptake...     

Photosynthetic electron transport and phosphorylation reactions in thylakoid membranes from the blue-green alga Anacystis nidulans.

Thylakoid membranes were prepared from the blue-green alga, Anacystis nidulans with lysozyme treatment and a short period of sonic oscillation. The thylakoid membrane preparation was highly active in the electron transport reactions such as the Hill reactions with ferricyanide and with 2,6-dichlorophenolindophenol, the Mehler reaction mediated by methyl viologen and the system 1 reaction with methyl viologen as an electron acceptor and 2,6-dichlorophenolindophenol and ascorbate as an electron donor system. The Hill reaction with ferricyanide and the system 1 reaction was stimulated by the phosphorylating conditions. The cyclic and non-cyclic phosphorylation was also active. These findings suggest that the preparation of thylakoid membranes retained the electron transport system from H2O to reaction center 1, and that the phosphorylation reaction was coupled to the Hill reaction and the system 1 reaction.     

Mutations arising during transformation in the blue-green alga Anacystis nidulans

Summary Genetic transformation experiments have been performed in Anacystis nidulans using donor material from two sources, namely chemically extracted DNA and extracellular nucleic acids. A high proportion of the transformants became mutant at sites which were wild type in both parental strains. Linkage was less extensive in transformation mediated by chemically extracted DNA, and this increased frequency of recombination was associated with enhanced mutation frequencies. The frequencies of recombination and mutation were varied to the same extent by changing the DNA concentration, and both processes were prevented by pretreatment of donor DNA with DNase. Mutational events are, therefore, closely associated with recombination in A. nidulans.     

Synchronous growth and genome replication in the blue-green alga Anacystis nidulans

Summary Following the induction of synchronous growth of Anacystis nidulans by light and CO₂ deprivation, cell mass and RNA and DNA content during two cell cycles were measured. Both RNA and DNA synthesis were discontinuous and marked variation in survival to ultraviolet light was related to the state of replication. A model is presented which accounts for the proportion of cells (66%) induced into synchronous genome replication which is also related to the state of replication at the onset of pre-synchrony treatment.     

Fluorescence from sensitizing phycobilin chromophores in the blue-green alga Anacystis nidulans

Regeneration of the pigment system of Anacystis nidulans was studied following nitrate starvation. Three new, distinct fluorescence bands, at 596, 615 and 636 nm attributed to sensitizing phycobilin chromophores were detected. They each possess a separate excitation band at 425, 395 and 410 nm, respectively.     

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.     

The relationship between carbonic anhydrase activity and glycolate excretion in the blue-green alga Coccochloris peniocystis

Summary The rate of glycolate excretion by Coccochloris peniocystis Kütz. cells incubated under conditions of low bicarbonate concentration and high light intensity was linear for only the initial 15 min of incubation and no additional glycolate accumulated in the medium after 20 min. Excretion was maximal in cells grown on 5% CO₂ in air when transferred to an incubation medium containing no added bicarbonate. The inhibitor INH (isonicotinyl hydrazide) had no measurable effect on the amount of glycolate released whereas HPMS (-hydroxy-2-pyridyl methanesulfonate) stimulated excretion 3-fold. Cells transferred to air from growth on 5% CO₂ in air increased in carbonic anhydrase activity, while a decrease occurred in the cells' ability to excrete glycolate. Cells grown on air and switched to 5% CO₂ in air showed an increase in their ability to excrete glycolate with a concomitant decrease in carbonic anhydrase activity. Diamox, a specific inhibitor of carbonic anhydrase, was found to stimulate excretion with both airgrown and 5% CO₂-grown cells which had been off 5% CO₂ for approximately 30 min. The rate of carbon fixation by 5% CO₂-grown cells put on air was found to rise over a 110 min period, corresponding to both the induction period of carbonic anhydrase and the period of decline in the ability of the cells to excrete glycolic acid. These results suggest that the absence of carbonic anhydrase in 5% CO₂-grown cells causes a stimulation of glycolate excretion when these cells are transferred to a low bicarbonate medium, because of an increased rate of glycolate formation due to the oxidation of ribulose diphosphate by molecular oxygen at low internal CO₂ concentrations.Abbreviations INH isonicotinyl bydrazide - HPMS -hydroxy-2-pyridyl methanesulfonate     

The characterization of the RNAs and aminoacyl-tRNA synthetases of the blue-green alga, Anacystis nidulans

The tRNA and aminoacyl-tRNA synthetases of the blue-green alga, Anacystis nidulans have been isolated and studied. The distribution of some algal tRNA species on BD-cellulose chromatography has been determined. One tRNA^Met species has been isolated in 80% purity by a single chromatography on a BD-cellulose column developed with a modified salt gradient. The number of different tRNA isoacceptors for Met, Ser, and Leu has been ascertained by RPC-5 chromatography. The recognition of algal tRNAs by the homologous algal synthetase preparation as well as the heterologous Escherichia coli preparation was studied by the aminoacylation tests. Since all of the isoaccepting species of the tRNAs tested behaved almost identically in presence of the two enzyme preparations, a conservation of the recognition site during the evolutionary divergence of bacteria and algae is strongly suggested.     

Photosystem I and photophosphorylation-dependent leucine incorporation in the blue-green alga Anacystis nidulans

L-Leucine uptake and incorporation in the blue-green alga Anacystisnidulans were measured during illumination with monochromaticlight of 630 and 717 nm. With near as well as far red light,an enhanced uptake of ¹⁴C-L-leucine was observed. In far redlight, the leucine uptake depended on light intensity and pHvalue. After the first few minutes, the uptake remained constantfor more than one hour. The rate of uptake in light was thesame in air as in nitrogen. The incorporation of ¹⁴C-leucinein the soluble fraction decreased in the presence of chloramphenicolwhich prevents protein synthesis. In far red light, its incorporationwas insensitive to DCMU (5 ? 10^–6 M) but was depressedby uncouplers like CCCP or desaspidin. These effects are takenas evidence that leucine incorporation under the conditionsused is dependent on photosystem I reactions and cyclic photophosphorylation.DBMIB and KCN in high concentrations decrease the leucine incorporationin far red light and indicate that plastoquinone and plastocyaninare members of the cyclic electron flow also in intact cellsof Anacystis. Antimycin A has no inhibitory effect. The inhibitionby other less specific inhibitors like salicylaldoxime, desaspidinand DSPD is discussed. (Received August 19, 1978; )     

The regulation of the energy-dependent phosphate uptake by the blue-green alga Anacystis nidulans

Investigations of the energy-dependent accumulation of orthophosphate by the blue-green alga Anacystis nidulans have established: 1. The transport through the cell membrane is the rate-limiting step in the incorporation of phosphate.-2. This transport is facilitated by a carrier that can be activated by Ca²⁺ and Mg²⁺ and inhibited by EDTA.-3. The activation of the carrier in the light is associated with changes of the cytoplasmic Mg²⁺ content.-4. Intracellular phosphate is shown to be present in bound form.-5. The energy-dependent accumulation of orthophosphate within the cell depends strictly on the cytoplasmic pH and not on the energy conversion at the thylakoid membrane which is responsible for the energy supply. The cytoplasmic pH is different in the light, in the dark, and in the presence of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). Orthophosphate accumulation can most readily be explained in terms of a pH dependent precipitation into a complex with bivalent cations rather than by an active transport against a concentration gradient.Abbreviation CCCP Carbonyl cyanide m-chlorophenylhydrazone     

The assimilation of nucleic acid precursors by intact cells and protoplasts of the blue-green alga Anacystis nidulans

Summary The entry of both nucleotides and base precursors into whole cells and the nucleic acid fraction of the blue-green alga Anacystis nidulans has been examined. Very slow rates of uptake were observed with intact organisms but protoplast preparations assimilated the nucleic acid precursors much more readily.     

Coupling between the initiation of DNA replication and cell division in the blue-green alga Anacystis nidulans

The effect of mitomycin C on cell mass increase, cell division, RNA synthesis and DNA synthesis in the blue-green alga Anacystis nidulans has been examined. Data suggests that the initiation of DNA replication, rather than its termination was the necessary event for cell division to occur.     

Fluorescence from sensitizing phycobilin chromophores in the blue-green alga Anacystis nidulans.

Regeneration of the pigment system of Anacystis nidulans was studied following nitrate starvation. Three new, distinct fluorescence bands, at 596, 615 and 636 nm attributed to sensitizing phycobilin chromophores were detected. They each possess a separate excitation band at 425, 395 and 410 nm, respectively.