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At least 505 records · Page 28Linked to original sources
PubMed1976

Effect of some environmental factors on cyanophage AS-1 development in Anacystis nidulans.

The development cycle of the cyanophage AS-1 was studied in the host blue-green alga, Anacystis nidulans, under conditions that impair photosynthesis and under various light/dark regimes. Under standard conditions of incubation the 16-h development cycle consisted of a 5-h eclipse period and an 8-h latent period. Burst size was decreased by dark incubation to 2% of that observed in the light. An inhibitor of photosystem II, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), reduced the burst size to 27% of that of the uninhibited control, whereas cyanophage production was completely abolished by carbonyl-cyanide m-chlorophenyl hydrazone (CCCP), an inhibitor of photosynthetic electron transport. Dark incubation of infected cells decreased the latent period by 1-2 h and the eclipse period by 1 h, once the cultures were illuminated. This suggests that adsorption took place in the dark. Intracellular growth curves indicated that light is necessary for viral development. Infected cells must be illuminated at least 13 h to produce a complete burst at the same rate as the continuously illuminated control. Low light intensities retarded the development cycle, and at lowest light intensities no phage yield was obtained. AS-1 is highly dependent on host cell photophosphorylation for its development.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMed1976

[The metabolic interactions between Paramecium bursaria Ehrbg. and Chlorella spec. in the Paramecium bursaria-symbiosis. I. The nitrogen and the carbon metabolism (author's transl)].

Symbiotic Chlorellae have been isolated from Paramecium bursaria Ehrbg. and cultivated under conditions of nitrogen deficiency. Reinfection of Chlorella-free Paramecium bursaria with these nitrogen-deficient algae resulted in a complete regeneration and multiplication of the algae within the host cells. The endosymbiotic algal cells of the Paramecium bursaria-symbiosis can be supplied by their host with nitrogen. The inhibition of photosynthesis by 3-(3,4-Dichlorophenyl)-1,1-dimethylurea (DCMU) leads in green Paramecium bursaria to a breakdown of the symbiotic steady state-system resulting in a loss of algal cells. Obviously the endosymbiotic algae cannot be fed heterotrophically by their host to such an extent that a stable symbiosis is maintained. The application of 3-(3,4-Dichlorophenyl)-1,1-dimethylurea (DCMU) can be used as a new method for culturing Chlorella-free Paramecium bursaria.

Chlorella↗
PubMed1977

Adaptation by hot spring phototrophs to reduced light intensities.

Photosynthesis was measured by the 14C method on natural as well as low light adapted populations of Chloroflexus (a photosynthetic bacterium) and Synechococcus (a blue-green alga) from hot springs in Yellowstone National Park (Wyoming U.S.A.), to test the ability of these phototrophs to photosynthesize at a variety of light intensities. The herbicide 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) was used to distinguish uptake of the blue-green alga from that of the photosynthetic bacterium, while measurements of chlorophyll a and bacteriochlorophyll c served to quantitate the standing crops of these organisms. Natural populations of Synechococcus were found to be slightly inhibited by full sunlight intensities (summer values can surpass 90000 Lux), whereas the Chloroflexus populations were not. Populations of both phototrophs subjected to reduced light intensities through the use of neutral density filters were found to adapt to low light, and then become severely inhibited by high light intensities. Adaptation to various light regimes may be an important ecological phenomenon to the survival of these hot spring phototrophs.

Adaptation, Biological↗
PubMed1977

Dependence of sulphate uptake by Anacystis nidulans on energy, on osmotic shock and on sulphate stravation.

Sulphate uptake by Anacystis nidulans under aerobic conditions in the light was found to be sensitive to metabolic poisons, such as N,N'-dicyclohexylcarbodiimide and carbonyl cyanide m-chlorophenyl hydrazone. It was also depressed by darkness. The sulphate absorption is an energy-dependent process. Sulphate uptake was also inhibited by chromate and selenate. Osmotic shock strongly affected sulphate uptake. This effect could be interpreted by a loss of a binding protein involved in the absorption of sulphate. Osmotic shock also depressed oxygen production in light and oxygen consumption in darkness; however, shocked cells were able to grow normally. Sulphate uptake was strongly enhanced by sulphate starvation, but this enhancement was partly prevented by chloramphenicol. Apparently sulphate starvation depressed the synthesis of a carrier involved in the transport of sulphate. During sulphate starvation the membrane potential, measured by the uptake of triphenylmethylphosphonium, increases. This may be due to changes in the membrane.

Aerobiosis↗
PubMed1975

The effect of inhibitors on the electron flow triggering photo-phobic reactions in Cyanophyceae.

1. Since photo-phobic reactions in the blue green alga Phormidium uncinatum seem to be triggered by changes of electron flow rates into or out of an electron pool situated in the electron transport chain between photo-system II and I, the effect of inhibitors affecting the electron transport chain has been studied. 2. Dose response curves of the phobic reaction have been measured by varying the trap energy in double beam light trap experiments with constant pairs of monochromatic light. From these dose response curves the effects of the inhibitors on both types of phobic reactions, i.e. exit reactions and entrance reactions, have been calculated. 3. Dibromothymoquinone (DBMIB) inhibits the electron transport between the electron pool and photosystem I by preventing the reoxidation of plastoquinone. The phobic entrance reaction, which results in an emptying of the light trap, is triggered by changes in the electron flow out of the pool; thus it is more effected by DBMIB than the exit reaction, which is mediated by the electron transport into the pool. 4. The phobic exit reaction, which results in accumulations in the light trap, is triggered by changes in the electron flow into the electron pool via photosystem II. 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) inhibits the electron transport near photosystem II; thus it affects the exit reaction more than the entrance reaction.

Cell Movement↗
PubMed1977

Photooxidation reactions of diphenylcarbazide and their DCMU-sensitivity in thylakoids of the blue-green alga Oscillatoria chalybea.

Thylakoids of Oscillatoria chalybea are able to split water. The Hill reaction of these thylakoids is sensitive to DCMU. Diphenylcarbazide can substitute for water as the electron donor to photosystem II with these fully functioning thylakoids. However, the diphenylcarbazide photooxidation is completely insensitive to 3-(3,4-dichlorophenyl)-N-N'-dimethyl urea (DCMU) at high diphenylcarbazide concentrations. In with Tris-treated Oscillatoria thylakoids the water splitting capacity is lost and diphenylcarbazide restores electron transport through photosystem II as occurs with higher plant chloroplasts. However, also these photoreactions are insensitive to DCMU. If diphenylcarbazide acts in Oscillatoria as an electron donor to photosystem II the result suggests that diphenylcarbazide feeds in its electrons behind the DCMU inhibition site. This in turn indicates that in Oscillatoria the site of inhibition of DCMU is on the donor side of photosystem II.

Chloroplasts↗
PubMed1976

Accumulation, mobilization and turn-over of glycogen in the blue-green bacterium Anacystis nidulans.

1. Accumulation of glycogen up to a constant amount per cell was observed during the postexponential phase of growth, in the presence of an excess of a utilizable carbon source. Cell multiplication was reproducibly controlled by growth of the organism in a nitrogen-limiting medium under photoautotrophic conditions (presence of light, air plus CO2). 2. Temporary starvation, i.e. by removal of light or by the addition to an illuminated culture of DCMU, 3-(3',4'-dichlorophenyl)-1,1'-dimethylurea, a specific inhibitor of photosystem II, lead to a mobilization of glycogen in the cell. Furthermore, Anacystis nidulans, having accumulated glycogen by virtue of preculture under nitrogen-limiting conditions, will resume cell division when the culture medium is complemented with a nitrogen source. The ability of the organism to use glycogen as an endogenous carbon source for growth was observed by addition of a nitrogen source to nitrogen-starving cells and simultaneous removal of CO2. 3. During the period of constant amount of glycogen per cell the reserve polysaccharide was subject to turnover as demonstrated with a pulse chase-labelling technique. The demonstration of a turnover--for the first time with a bacterial species--indicated a strict balance in the relative rate of synthesis and degradation.

Cell Division↗
PubMed1975

Sulphate uptake and metabolism in the chrysomonad, monochrysis lutheri.

The intracellular concentration of inorganic 35SO4 in Monochrysis lutheri cells exposed to 0.513 mM Na235SO4 for up to 6-hr remained constant at about 0.038 mM. The exchange rate of this 35SO4 with the external unlabelled sulphate was negligible compared to the rate of influx across the plasmalemma (0.032 mu moles/g cells/hr). The flux of free 35SO4 to organic 35S was 0.029 mu moles/g cells/hr. Assuming an internal electrical potential in the cells of -70 mV, this intracellular concentration of inorganic 35SO4 was well in excess of that obtainable by passive diffusion as calculated from the Nernst equation. These results indicate that sulphate is accumulated by an active mechanism rather than by facilitated diffusion. Sulphate uptake appears to occur via a carrier-mediated membrane transport system which conforms to Michaelis-Menten type saturation kinetics with a Km of 3.2 X 10(-5) M and Vmax of 7.9 X 10(-5) mu moles sulphate/hr/10(5) cells. Uptake was dependent on a source of energy since the metabolic inhibitor CCCP almost completely inhibited uptake under both light and dark conditions and DCMU caused a 50% decrease in uptake under light conditions. Under dark conditions, uptake remained at about 80% of that observed under light conditions and was little affected by DCMU, indicating that the energy for uptake could be supplied by either photosynthesis or respiration. A charge and size recognition site in the cell is implied by the finding that sulphate uptake was inhibited by chromate and selenate but not by tungstate, molybdate, nitrate or phosphate. Chromate did not inhibit photosynthesis. Cysteine and methionine added to the culture medium were apparently capable of exerting inhibition of sulphate uptake in both unstarved and sulphate-starved cells. Cycloheximide slightly inhibited sulphate uptake over an 8-hr period indicating, either a slow rate of entry of the inhibitor into the cells or a slow turnover of the protein(s) associated with sulphate transport.

Biological Transport, Active↗
PubMed1976

ATP pools and transientss in the blue-green alga, Anabaena cylindrica.

Anabaena cylindrica grown in steady state continuous culture has an extractable ATP pool, measured on the basis of the luciferin-luciferase assay of 165 +/- 35 nmoles ATP mg chla-1. This pool is maintained by a dynamic balance between the rate of ATP synthesis and the rate of ATP utilization. Phosphorylating mechanisms which can maitain the pool in the short term are total photophosphorylation, cyclic photophosphorylation and oxidative phosphorylation. The alga can maintain its ATP pool by switching rapidly from one of these phosphorylating mechanisms to another depending on the environmental conditions. At each switch-over there is a transient drop in the ATP pool for a few seconds. On switching to conditions where only substrate level phosphorylation operates, the ATP pool falls immediately, but takes several hours to recover. The apparent rates of ATP synthesis by total photophosphorylation and by cyclic photophosphorylation are both much higher (210 +/- 30 and 250 +/- 13 mumoles ATP mg chla-1 h-1 respectively) than the apparent rate of ATP synthesis by oxidative phosphorylation (22 +/- 3 mumoles ATP mg chla-1 h-1). In long term experiments the ATP pool is maintained when total photophosphorylation is operating. It cannot be maintained in the long term by cyclic photophosphorylation alone in the absence of photosystem II activity in endogenous carbon compounds, or by oxidative phosphorylation in the absence of endogenous carbon compounds. Measurements of ATP, ADP and AMP show that the total pool of adenylates is similar in the light and in the dark in the short term. There is only limited production of ATP under dark anaerobic conditions when glycolysis and substrate phosphorylation can operate which suggests that these processes are of limited significance in providing ATP in Anabaena cylindrica.

Adenosine Triphosphate↗
PubMed1991

Biochemical studies carried out on different groups of Candida parapsilosis and Candida rhagii strains by comparing some cellular and mitochondrial activities.

A comparative biochemical study was performed on some strains of Candida rhagii and on strains belonging to different subgroups of Candida parapsilosis. Measurements of alcohol dehydrogenase activity, resistance to drugs and occurrence of an alternative pathway enabled us to confirm the classification between several subgroups within the C. parapsilosis species.

1-Propanol↗
PubMed1975

Possibilities of using insectistatics and pheromones in pest control.

Agents that can decimate insect populations by suppressing growth and reproduction rather than by causing rapid mortality are called insectistatics. Their activity includes interruption of cuticle formation, induction of hormonal imbalance by extrinsic juvenoids or ecdysoids, developmental disturbances due to nutrient antagonists, symbioticides, or accelerators of metabolism. Disruption of mating may be accomplished by pheromone trapping and disorientation or by prevention of sex attraction. The possible contribution of such biotechnical procedures to the control of storage pests is discussed.

Animals↗
PubMed1985

Characterization of the photosynthetic electron transport chain in normal and photobleached Anabaena cylindrica by flash spectroscopy.

Electron transport of normal and photobleached Anabaena cylindrica was studied using spectral and kinetic analyses of absorbance transients induced by single turnover flashes. Between 500 and 600 nm two positive bands (approximately 540 and approximately 566 nm) and two negative bands (approximately 515 and approximately 554 nm) were found. Absorbance changes at 515 and 540 nm were partly characterized. None of these absorbance changes represent an electrochromic shift. Absorbance changes at 554 and 566 nm correspond to the oxidation of cytochrome f and the reduction of cytochrome b563, respectively. We found a very slight 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) sensitivity of cytochrome f in normal cells, while DCMU was completely ineffective for cytochrome f reduction in photobleached cells. The absorbance change of cytochrome b563 increased, while the absorbance change of cytochrome f was smaller than in normal cells. The increased O2 evolution in photobleached cells and the negligible electron transport via cytochrome f suggest the participation of other electron acceptor(s) in the electron-transport chain of photobleached Anabaena cylindrica.

Cyanobacteria↗
PubMed1981

Interaction between ubiquinone and ATPase in mitochondrial membranes.

The extraction of ubiquinone from mitochondrial membranes produces alterations of ATPase activity including a reversible loss of oligomycin sensitivity which is restored by long-chain Q-homologs, Short-chain ubiquinones like Q3 produce a loss of oligomycin and dicyclohexyl carbodiimide (DCCD) sensitivity in submitochondrial particles. The effect shows uncompetitive or noncompetitive Kinetics with respect to oligomycin or DCCD respectively. Long-chain ubiquinones have a competitive effect with Q3, thus restoring oligomycin sensitivity; they behave, however, in about the same way as Q3 in lowering the DCCD sensitivity in submitochondrial particles. On the basis of these observations we suggest that ubiquinone may be a physiological modulator of ATPase activity in the mitochondrial membrane.

Adenosine Triphosphatases↗
PubMed1986

Application of chlorophyll fluorescence in ecophysiology.

In vivo chlorophyll fluorescence measurements have become a valuable tool in ecophysiology. Fluorescence emission spectra are influenced by the reabsorption of the tissue and indicate the composition of the antenna system and are influenced by the chlorophyll content per leaf area. The fluorescence induction kinetics ("Kautsky effect") can be used to study photosynthetic activity. These rapid, non-destructive methods can be applied for ecophysiological field research to check the vitality of plants and to document stress effects on the photosynthetic apparatus. The Rfd-values (Rfd = fd/fs), the ratio of the fluorescence decrease (fd) to the steady state fluorescence (fs), can be taken as a rapid vitality index of the leaves and trees. We here describe fundamental chlorophyll fluorescence results of leaves which are needed for the interpretation of in vivo fluorescence signatures in stress physiology and in the forest dieback research.

Chlorophyll↗