The sequence of degradation of the photosynthetic apparatus of Anacystia nidulans after virus infection was studied using different methods. In the first stages of pathogenesis changes in the structure and functional activity of the photosynthetic apparatus were shown to be insignificant. At the stages of marked degradation the system of oxygen release and light collecting complex are destroyed gradually. The reaction center of photosystem I is the most resistant to degeneration.

Cyanobacteria↗

PubMedDate not supplied

[Photosynthetic oxygen evolution and CO2 photoassimilation by cyanobacteria that form water-bloom spots in a sulfur spring with a high sulfide content].

Cyanobacteria belonging mainly to the genera Anabaena and Oscillatoria were isolated from water-bloom spots of a sulfur spring in Staraya Matsesta. Their suspensions evolved O2 at a rate of 6--8 nM/min per 1 mg of dry cell weight at an intensity of solar radiation being 60--75 mV/cm2 per 1 sec. The cells were also capable of CO2 photoassimilation in the presence of solfide at a rate of 10(-4) mg C per mg per hour. DCMU at a concentration of 10(-5) M completely inhibited O2 evolution and inhibited CO2 fixation by 80%. Oxygen assimilation in dark by the suspensions did not depend on the addition of cyanide and was caused apparently by nonenzymatic reduction of O2 with sulfide dissolved in the spring water. Oxygen assimilation by the suspensions in light in the presence of DCMU was by 20--30% greater than in dark. Therefore, the cells of cyanobacteria are characterized by photorespiration at the level of photosystem I. Presumably, sulfide at a concentration of 9 mM cannot significantly inhibit the photosynthetic processes in cyanobacteria producing water-bloom spots in the sulfur spring.

Carbon Dioxide↗

PubMedDate not supplied

[Regulation of the differentiation processes in an Anabaena cylindrica culture].

The maximal frequency of heterocysts in the culture of Anabaena cylindrica grown in a nitrogen-free medium was found after 6 days of growth (6%); the number of heterocysts decreased to 1.8% with aging. The quantity of heterocysts in the culture decreased (they could even disappear completely) in the presence of ammonium salts as the source of nitrogen. The index of the shape (the length-to-width ratio of cells, %) decreased under these conditions though it increased in the other variants of the experiment. The incidence of heterocysts in the culture of A. cylindrica increased under the conditions of incubation at low temperature (+4 degrees C) to 8%. The effect was most pronounced when 1% glucose was added to the medium; then, the distance between heterocysts was 5-7 cells. The percentage of heterocysts in filaments increased to 8.3% when vegetative cells were decomposed at elevated temperature (+30 degrees C) in the light. Under the same conditions in the dark, heterocysts degraded and their number decreased to 0.8%. Spore formation in the culture was stimulated by calcium excess and phosphorus deficiency in the medium.

Culture Media↗

PubMedDate not supplied

[Interaction of cyanobacteria cells with methyl viologen].

Oxygen absorption instead of its evolution is induced in cell suspensions of the cyanobacteria Anacystis nidulans and Anabaena variabilis in the presence of methylviologen, an autoxidable electron acceptor, and triphenyltetrazolium chloride which is irreversibly reduced in the cells. The process occurs without addition of exogenous donors and does not depend on DCMU. Dichlorophenolindophenol and ascorbate do not stimulate the absorption. The blue colour of reduced methylviologen was not observed even after argon had been bubbled through a cuvette with the reaction mixture. Cell decoloration and lysis were found upon long contact with methylviologen. Elevated concentrations of DCMU also caused oxygen absorption in the light. Apparently, it is possible to induce oxidation of endogenous donors in the cells of the above cyanobacteria in the presence of methyl-viologen.

Absorption↗

PubMedDate not supplied

[Electron microscopic and biochemical study of spheroplasts of the blue-green alga Anabaena variabilis].

Electron microscopy of the spheroplasts of the blue-green alga Anabaena variabilis revealed damages induced by lysozyme. Biochemical analysis confirmed the data of electron microscopy that the spheroplasts had lost partly the cytoplasmic content of the cells. DNA was preserved in the spheroplasts though the nucleoid was not detected by electron microscopy.

Cyanobacteria↗

PubMedDate not supplied

[Comparative study of the functions of the spheroplasts and cells of the blue-green alga Anabaena variabilis].

The effect of light was studied with the spheroplasts of the blue-green alga Anabaena variabilis. Contrary to the intact cells, the spheroplasts did not synthesize nucleic acids and pigments in the light. These components of the spheroplasts were decomposed in the light, and the remaining chlorophyll was incapable of luminescence. The rate of oxygen uptake increased upon the incubation of the spheroplasts in the light. Changes of the functions induced by lysozyme in the cells of A. variabilis are irreversible, contrary to those which are caused by the incubation in the darkness and can be restored if the cells are transferred into the light.

Chlorophyll↗

PubMedDate not supplied

[Change in the ATP content in the cells of Anabaena variabilis].

The content of ATP in the cells of Anabaena variabilis does not change during one day in the darkness as compared to that in the cells grown in the light, this suggesting the endogenous energy reserve of the cell. The level of ATP gradually decreases when the cells are incubated in the darkness during 25 days, but does not reach zero. The content of ATP increases for a short period in the light in the cells that have been incubated in the darkness during several days (up to 7 days). On the contrary, the level of ATP increases to a small extent and then falls in the cells grown in the light. These differences suggest disturbed coupling of the synthesis and utilization of ATP in the cells grown in the darkness. The content of ATP increases again in the darkness, confirming that the alga is capable of synthesizing ATP in the darkness.

Adenosine Triphosphate↗

PubMedDate not supplied

[Characteristics of oxygen metabolism in the obligate phototrophic blue-green alga Anabaena variabilis in darkness].

The rate of endogenous respiration of the cells of Anabaena variabilis in the mineral medium in the darkness decreases gradually during 30 to 40 days and is then maintained at a low level. The rate of oxygen uptake was the same in the cells grown in aerobic and anaerobic conditions in the darkness. The ability for oxygen evolution in the light is maintained in the anaerobic cells for a longer time, and the biomass yield and the content of phycocyanin in the cells decrease at a lower rate in anaerobic conditions. Therefore, under certain conditions of the medium, the processes related to the cell survival in the darkness are directed to preserve the photosynthesizing apparatus, and oxygen is a factor accelerating the death while anaerobic conditions delay destruction of the cells in the darkness.

Aerobiosis↗

PubMedDate not supplied

[Characteristics of different growth stages of the blue-green alga Anacystis nidulans (Synechococcus)].

The rate of growth of the blue-green alga Anacystis nidulans is highest during the first 5--8 days but the number of the cells increases up to 30 days when the stationary phase takes place (30--60 days). The content of chlorophyll is almost constant during the first 20 days of growth while the content of phycocyanin increases; then the content of the both pigments decreases. The rate of O2 evolution and the rate of electron transport to ferricyanide decrease exponentionally during the first 10 days of growth. The rate of endogenous respiration and the rate of O2 absorption, induced by methylviologen in the light in the presence of DCMU decrease more slowly. At the same time, the rate of O2 absorption in the presence of methylviologen without DCMU and the rate of TTC reduction in the darkness increase and later decrease. The rate of TTC reduction in the light increases up to 30--40 days and then decreases. The rate of the cell death in the darkness decreases when the age of the "light" culture is 50 days. Addition to the medium of its main components does not increase the rate of growth of the culture after 10 days of its growth. Addition of CaCl2, glucose, and asparagic acid increases the rate of growth of the 3-day-old culture. Addition of phosphorus inhibits growth. Argon favours growth of the culture. The cells are rapidly discoloured in conditions of hampered gas exchange; they die rapidly also in the presence of DCMU, methylviologen, and KCN.

Chlorophyll↗