Blue-green Alga Anabaena Cylindrica Research Articles

Demonstration and possible role of a ferredoxin- dependent pyruvate decarboxylation in the nitrogen- fixing blue-green alga Anabaena cylindrica

Using crude extracts from the nitrogen-fixing blue-green alga, Anabaena cylindrica, a decarboxylation reaction can be demonstrated, which is dependent on pyruvate and ferredoxin and which is stimulated by coenzyme A, a SH-protecting compound and ATP. The activity of the pyruvate decarboxylation in Anabaena grown with ammonia is lower than one-fifth of that in cells grown with molecular nitrogen or nitrate as the nitrogen source. From this it is suggested that a physiological role of the reaction is to generate reduced ferredoxin which serves as the reductant in the assimilation of nitrogen to ammonia.

Pathways of glycollate metabolism in the blue-green alga Anabaena cylindrica.

1. Exogenous glycollate was assimilated by the blue-green alga Anabaena cylindrica. 2. About 50% of the C-1 carbon of 14C-1-glycollate (i.e.25% of the total carbon) was released as 14CO2 in the dark and also in the light in the presence of DCMU. Most of the 14CO2 released in the light in the absence of DCMU was refixed. 3. Assimilation was almost completely inhibited by α-hydroxy-2-pyridinemethane sulphonic acid, an inhibitor of enzymic glycollate oxidation. Cell extracts catalyzed the oxidation of glycollate to glyoxylate at rates sufficient to account for the in vivo assimilation. 4. Isonicotinylhydrazide, an inhibitor of the conversion of glycine to serine in higher plant/green algae glycollate metabolism, did not significantly affect glycollate metabolism in A. cylindrica. Short-term labelling experiments with 14C-1-glycollate in the light and dark did not show a significant metabolism of 14C via glycine and serine. However, the enzymes for the metabolism of glyoxylate via glycine, serine and hydroxypyruvate to glycerate were demonstrated in cell extracts, although the activity of the enzyme catalyzing the metabolism of serine to hydroxypyruvate was not sufficient to account for the in vivo rate of glycollate assimilation. 5. Cell extracts catalyzed the enzymic condensative decarboxylation of glyoxylate to tartronic semialdehyde and also the enzymic reduction of tartronic semialdehyde to glycerate. The activities in extracts were sufficient to account for the total in vivo photoassimilation of glycollate. The specific activity of malate synthase was insufficient to account for the total photometabolism of glycollate but exceeded the in vivo rate in the dark. 6. On the basis of the inhibitor and kinetic experiments and in terms of the enzymes detected, it appears that in the light glycollate is metabolized mainly via glyoxylate → tatronic semialdehyde → glycerate → 3-phosphoglycerate → (glycolytic pathway) → pyruvate → alanine plus tricarboxylic acid cycle and related compounds. The bulk of the CO2 released in the light is probably refixed via the Calvin cycle. In the dark, the glyoxylate, produced from exogenous glycollate, appears to be metabolized mainly by malate synthase directly to malate.

The effect of chloramphenicol on the production of cyanophycin granule polypeptide in the blue green alga Anabaena cylindrica.

The cyanophycin or structured granule of the blue-green algae is composed of polypeptides which are copolymers of aspartic acid and arginine. The addition of chloramphenicol to an exponentially growing culture of the blue-green alga Anabaena cylindrica at concentrations which completely inhibit protein synthesis results both in the inhibition of growth and in the accumulation of the cyanophycin granule polypeptide (CGP). The chloramphenicol induced increase in CGP content is energy dependent. Removal of the chloramphenicol results in resumption of growth and the hydrolysis of the stored CGP. The data presented indicate that CGP is synthesized via a non-ribosomal system and are consistent with the idea that CGP serves as a cellular nitrogen reserve.

Effect of far red light and inhibitors on nitrogen fixation and photosynthesis in the blue-green alga Anabaena cylindrica

Experiments on the relationship between nitrogen fixation and photosynthesis in intact Anabaena cylindrica are reported.

Correspondence of cyanophycin granules with structured granules in Anabaena cylindrica

Granules isolated from the blue-green alga Anabaena cylindrica and composed of copolymers of arginine and aspartic acid have the electron microscopic aspects of structured granules and the solubility and certain of the staining properties of cyanophycin granules. Material which accumulates at the poles of heterocysts may have a similar composition.

Absence of Photosystem 2 in heterocysts of the blue-green alga Anabaena

Heterocysts of the filamentous blue-green alga Anabaena cylindrica have a high concentration of the System 1 reaction center P700 and are able to photooxidize a cytochrome. They have a low yield of chlorophyll a fluorescence, do not show light-induced changes in fluorescence yield, show a very low intensity of delayed light emission and do not show Hill-reaction activity. It is concluded that heterocysts contain Photosystem 1 only.

Characteristics of the nitrogenase system of the blue-green alga Anabaena cylindrica.

The requirements for activity of blue-green algal nitrogenase have been studied. The optimal concentration ranges for ATP and Na2S2O4 are 2-3 mM and 4-10 mM respectively. A magnesium requirement has been confirmed but the enzyme is not specific for Mg2+, Co2+ and Mn2+ will also support activity but Ca2+, Cu2+ and Zn2+ will not. The partially purified enzyme is soluble and specific activities of 50–100 nmoles C2H4/mg protein/min have been obtained. The biochemical characteristics of the enzyme, as determined in studies using enzyme inhibitors, are similar to those of bacterial and legume nitrogenases in that the enzyme is a metallo-protein containing iron and reduced thiol groups and the redox capacity of the enzyme involves a possible valency change in the iron. The transfer of electrons from H2 via a bacterial hydrogenase has been shown to be mediated, at least in part, by ferredoxin. The role of ferredoxin and the interrelationships between photosynthesis, reductant pool and hydrogen metabolism are discussed in the light of recent results obtained by ourselves and other workers.

Physiological electron donor systems to the nitrogenase of the blue-green alga Anabaena cylindrica

Reduced ferredoxin was found to function as electron donor to nitrogenase present in extracts prepared from the blue-green alga Anabaena cylindrica. Two physiological mechanisms of reducing ferredoxin were identified. The major physiological mechanism of reducing ferredoxin was a process linked to the photosynthetic electron transport chain which was dependent on light. An alternative source of reducing potential was NADP + reduced in dark reaction by substrates such as isocitrate or pyruvate. Transfer of electrons from NADPH to nitrogenase was dependent on ferredoxin-NADP + reductase and ferredoxin.

Incorporation of amino sugars into walls during heterocyst differentiation

During exponential growth of the blue-green alga Anabaena cylindrica, a small fraction of the vegetative cells differentiates into heterocysts. The incorporation of amino sugars during formation of the thick wall of the heterocyst was studied by pulse-labeling exponentially growing filaments with 14CO 3 2− and by isolating the walls of mature heterocysts at various times thereafter. The time course of labeling of hexosamine in isolated heterocyst walls indicated a rapid incorporation early in the process of heterocyst differentiation. The pattern of labeling of muramic acid in isolated heterocyst walls was consistent with the idea that the glycopeptide from vegetative cells is largely retained during differentiation of heterocysts. Preliminary observations indicating equivalent amounts of muramic acid in heterocysts and vegetative cells support this interpretation.

Absence of histone in the blue-green alga Anabaena cylindrica.

THE finding that more histones are associated with the chromosomal DNA of higher organisms than with that of lower organisms1–4 is consistent with the suggestion5 that histones act as suppressors in the regulation of gene expression in cellular differentiation. Thus histones must have been acquired at some stage in the evolution of differentiated eukaryotic organisms from the primitive prokaryon.

Photostimulation of nitrogen fixation in Anabaena cylindrica

Photostimulation of N 2 fixation in the blue-green alga Anabaena cylindrica was investigated using monochromatic light and by comparing action spectra of C 2H 2 reduction with that of photosynthetic O 2 evolution. Maximum nitrogenase activity per unit energy was measured at a wavelength which corresponds to the maximum light absorption of chlorophyll a. The action spectrum of C 2H 2 reduction indicates a primary involvement of Photosystem I in N 2 fixation by blue-green algae.

Soluble nitrogenase from vegetative cells of the blue-green alga Anabaena cylindrica.

REPORTS of nitrogen fixation by blue–green algal species have, in the main, been restricted to members of the orders Nostocales and Stigonematales1. Unless they are grown in the presence of large concentrations of free ammonium ions, all the species produce characteristic types of cells called heterocysts. The correlation between the ability of a species to fix nitrogen and the possession of heterocysts has led to the suggestion that the heterocyst is the site of nitrogen fixation in blue–green algae2.

Photochemically active chromoprotein isolated from the blue-green alga Anabaena cylindrica.

WHILE carrying out a biochemical study of the photosynthetic system of Anabaena cylindrica, we have found that a chromoprotein isolated from the algal cells is active in the photo-oxidation of ascorbate. We report here the methods for isolation of the active chromoprotein, and some of its characteristics.

Metabolic activities of isolated heterocysts of the blue-green alga Anabaena cylindrica.

KNOWLEDGE of the nature of the heterocysts of blue-green algae has been limited by the lack of suitable techniques for investigation of the physiology and biochemistry of these puzzling structures. The association of the presence of heterocysts with the ability to fix free nitrogen and the findings1,2 that ammonia suppresses both nitrogen fixation and heterocyst formation have led to the suspicion that these cells might be involved in the nitrogen-fixation process. In this communication we report a successful technique of ‘differential cell disruption’ for the isolation of heterocysts of Anabaena cylindrica. We also present the first results concerning the metabolic activities of isolated heterocysts.

Control of sporulation in a blue-green alga

Sporulation of the blue-green alga Anabaena cylindrica Lemm. generally ensues adjacent to heterocysts, in strings of from one to several cells. As a preliminary to an attempt to test whether heterocysts help to initiate sporulation of cells adjacent to them, environmental conditions conducive to rapid, sure sporulation adjacent to heterocysts were established. These conditions included the absence of phosphate from the medium, presence of alanyl-glycine or alanyl-alanine as a buffer, inclusion of sodium acetate and of a relatively high concentration of calcium ion, exposure to an optimal light intensity, and use of an adequate amount of inoculum. Evidence is presented in support of the hypothesis that sporulation of a vegetative cell near a heterocyst is dependent upon two processes: (1) abatement of a sporulation-inhibiting influence which acts on the vegetative cell, and (2) a sequential process commencing adjacent to the heterocyst.

NITROGEN FIXATION AND PHOTOSYNTHESIS IN A SUBCELLULAR FRACTION OF THE BLUE-GREEN ALGA ANABAENA CYLINDRICA.

NITROGEN FIXATION AND PHOTOSYNTHESIS IN A SUBCELLULAR FRACTION OF THE BLUE-GREEN ALGA ANABAENA CYLINDRICA.

The fine structure of the nuclear material of a blue-green alga, Anabaena cylindrica Lemm.

The chromatinic material of the blue-green alga Anabaena cylindrica has complex configurations in the central regions of the cells. The distribution of the chromatin within the cells varies in different filaments, probably in response to variations in the disposition of other cellular components. In electron micrographs of thin sections of organisms fixed by the method of Kellenberger, Ryter, and Séchaud (1958) the centroplasm contains fibrillar and possibly granular components which can be identified as the nuclear material by comparison with stained preparations viewed in the light microscope. The fibrils in the nuclear regions have diameters in the range of 5 to 7 mmicro and are embedded in a matrix of lower density. The nuclear regions are not greatly different from the cytoplasm in their electron density. Reducing the calcium content of the fixative results in coagulation of the fibrils to form coarser structures. The significance of the observations is discussed in relation to observations on the fine structure of other classes of algae and of bacteria.

Photochemical reduction of elementary nitrogen in the blue-green alga Anabaena cylindrica

Photochemical reduction of elementary nitrogen in the blue-green alga Anabaena cylindrica

Sodium as an Essential Micronutrient Element for Atriplex vesicaria, Heward

SODIUM has been recorded as an essential nutrient element only for the blue-green alga Anabaena cylindrica Lemm.1. It has, however, been shown that increase in dry weight occurs following application of sodium salts to various higher plants growing in low-potassium culture solution and also to members of the Chenopodiaceae growing in solutions containing adequate potassium; views have been expressed that sodium may partially replace the function of potassium or may prevent toxic accumulations of other elements2. The object of this communication is to record sodium as an essential micro-nutrient element for the bladder saltbush (Atriplex vesicaria, Heward), to describe the visual deficiency symptoms when plants were grown in solutions carefully freed from sodium and the recovery of such deficient plants on addition of sodium salts.