Hydrogen metabolism in isolated heterocysts of Anabaena 7120

Isolated heterocysts of Anabaena 7120 evolve H₂ in an ATP-dependent nitrogenase-catalyzed process that is inhibited by N₂ and C₂H₂. Heterocysts have an active uptake hydrogenase that only requires an electron acceptor of positive redox potential, e.g., methylene blue, dichlorophenolindophenol or potassium ferricyanide. O₂ supplied at low partial pressures is a very effective physiological oxidant for H₂ uptake. High concentrations of O₂ are inhibitory to H₂ uptake. The oxyhydrogen reaction in heterocysts appears to be mediated by a cytochrome-cytochrome oxidase system, and it supports ATP synthesis via oxidative phosphorylation. Attempts to demonstrate acetylene reduction in isolated heterocysts employing H₂ as an electron donor were unsuccessful. It is suggested that the uptake hydrogenase functions to conserve reductant that otherwise would be dissipated via nitrogenase-catalyzed H₂ evolution.     

Die-offs of the blue-green alga,Anabaena variabilis,in fish ponds

Dense populations of the blue-green alga, Anabaena variabilis, frequently develop in fish ponds at Auburn, Alabama, during windy weather in March and early April. Massive die-offs of this alga can be expected when it forms surface scums during prolonged periods of calm, clear, warm weather between mid April and mid May. Dissolved oxygen concentrations decline following die-offs and fish kills may result.     

Cortical microtubules and cortical microfilaments in the green alga,Micrasterias pinnatifida

Summary Cortical microtubules and cortical microfilaments were visualized in cells ofMicrasterias pinnatifida treated by freeze-substitution, and the pattern of their distribution was reconstructed from serial sections. Most cortical microtubules accompanied the long microfilaments that ran parallel to the microtubules. Cortical microfilaments not accompanied by the microtubules were also found. They were short and slightly curved. Both types of cortical microfilament were not grouped into bundles, and were 6–7 nm in diameter, a value that corresponds to the diameter of filaments of F-actin.     

Isolation and characterization of rapidly-growing,marine, nitrogen-fixing strains of blue-green algae

Five strains of heterocystous blue-green algae capable of high rates of growth and nitrogenase activity were isolated from shallow coastal environments. Growth of the organisms was characterized with respect to temperature, NaCl concentration in the medium, and nitrogen source. The temperature optima ranged from 35–42°C, and all but one of the strains displayed a requirement for added NaCl. The generation times under N₂-fixing conditions were 5.1–5.9 h, and were as low as 3.4 h for growth on NH₄Cl. Nitrogenase activity (C₂H₂ reduction) was high throughout the logarithmic growth phase of each strain. The maximum value observed for one strain was 65.5 nmoles C₂H₄ produced/mg protein x min, and the average values for the five strains ranged from 24.5–46.7 nmoles C₂H₄/mg protein x min. The organisms all belong to the genusAnabaena. The growth and nitrogenase activity of these strains are much higher than those of the heterocystous blue-green algae commonly used for investigation of nitrogen metabolism, and they thus should prove to be useful physiological tools. Their prevalence, as judged by the ease of their enrichment and isolation, in bay and estuarine environments suggests that they are important contributors of combined nitrogen.     

The fine structure of Micrococcus radiophilus and Micrococcus radioproteolyticus

The radiation resistant bacteria Micrococcus radiophilus and M. radioproteolyticus were studied by thin sectioning and freeze-etching techniques and the two species were found to be similar in the fine structure. The only significant difference was in the appearance of the surfaces of the cell walls in freeze-etched preparations.Since the two species, together with M. radiodurans, possess a unique cell wall structure and a cell wall peptidoglycan, which is different from that of other micrococci and Gram-positive cocci, it is recommended that they be reclassified into a new genus.     

Cellular localization of cytochrome c 553 in the N2-fixing cyanobacterium Anabaena variabilis

The in situ location of the electron carrier protein cytochrome C ₅₅₃ (cyt c ₅₅₃) has been investigated in both vegetative cells and heterocysts of the cyanobacterium Anabaena variabilis ATCC 29413 using the antibody-gold technique, carried out as a post-ernbedding immunoelectron microscopy procedure. When using a rabbit polyclonal anti-cyt c ₅₅₃ specific antiserum an intense labelling, associated mainly with the cell periphery (cytoplasmic membrane and periplasmic area), was seen in both heterocysts and vegetative cells. The selective release of most of the cellular cyt c ₅₅₃ during a Tris-EDTA treatment confirms a periplasmic localization of this protein in A. variabilis. The results indicate that most of cyt c ₅₅₃ is located in the periplasmic space. The roles ascribed to this protein in both respiration and photosynthesis in cyanobacteria are discussed.Abbreviations Cyt c ₅₅₃ cytochrome c ₅₅₃ - PBS phosphate buffered saline (20 mM sodium phosphate, 0.9% NaCl, pH 7.4) - PMSF phenylmethylsulfonyl fluoride Recipient of a Research Fellowship of the Alexander von Humboldt Foundation (Bonn, FRG) for a leave to the University of Konstanz.     

Glutamine synthetase specific activity and protein concentration in symbiotic Anabaena associated with Azolla caroliniana

Glutamine synthetase (GS) is the primary NH₄ ⁺ assimilating enzyme of cyanobacteria. The specific activities and cellular protein concentration of GS in symbiotic cyanobacteria associated with the water fern Azolla caroliniana were determined and compared to free-living cultures of Nostoc sp. strain 7801, a strain originally isolated from symbiotic association with the bryophyte Anthoceros punctatus. Both the in vitro specific activity and concentration of GS in symbiotic cyanobacteria separated from A. caroliniana were approximately 3-fold lower than the free-living Nostoc sp. strain 7801 culture. These results imply depressed synthesis of GS by the symbiont associated with A. caroliniana.     

Structural aspects of akinete germination in the cyanobacterium Anabaena variabilis

Electronmicroscopical investigations of light activated akinetes in different phases before outgrowth of the germinating cell showed two alterations in the akinete envelope, obviously in connection with the germination process. After induction of germination the akinetes show formation of an expanding more or less electron dense layer between the outer cell wall layer (outer membrane, L_IV) and the condensed part of the akinete coat (the transformed sheath of the vegetative cell). Between this new formed layer and the mentioned part of the akinete coat thick laminar layers are deposited which contain alternately electron dense and electron transparent strata. The expanding layer is assumed to be a mucous layer which acts as swelling body causing, after bursting of the layered shell, the expulsion of the germinating cell in the manner characteristic for Anabaena variabilis.     

The fine structure of Crithidia fasciculata with special reference to the organelles involved in the ingestion and digestion of protein

Summary As in other trypanosomatids, the cell membrane of Crithidia fasciculata overlies a single layer of microtubules. Each microtubule possesses a large number of periodically arranged drumstick-like appendages and adjacent microtubules are joined by fibrillar connectives. Anteriorly, the microtubules gradually taper to terminate just before or just after entering the reservoir. An attempt is made to correlate microtubule tapering with maintenance of form of the truncated anterior end of the cell. Smooth and coated vesicles are proliferated from the Golgi saccules and the prominent contractile vacuole lies nearby. The single mitochondrion is extensive and expanded at one point to form a capsule for the kinetoplast. The cristae are predominantly plate-like but other configurations do occur. The cytostome, a shallow invagination of the reservoir membrane, is found between two constrictions in the reservoir wall. Supporting the cytostome are several microtubules which penetrate deeply into the cytoplasm. Ingestion of ferritin occurs by pinocytosis from the cytostome and by coated vesicle formation from the reservoir membrane. Digestion probably occurs in multivesicular bodies which contain acid phosphatase activity.     

The length and disposition of cortical microtubules in plant cells fixed in glutaraldehyde—Osmium tetroxide

Serial sectioning has been used to show that the majority of circumferential microtubules lying in the cortex of root tip cells are much shorter than the cell circumference. The significance of this observation is briefly discussed.     

Taxonomic studies of planktic species of Anabaena based on morphological characteristics in cultured strains

Fifty (50) strains of planktic species of Anabaena (cyanobacteria), including collections from Japan and China and from different culture collections, were induced to form akinetes at low temperature (15 °C). Their morphologies were then observed and described. Fourty seven strains successfully formed akinetes and these were classified into 20 species comprising seven with straight trichomes and 13 with coiled trichomes. Three strains, which did not form akinetes, were separated into two taxonomic groups, but could not be identified to any described species. In addition, a key to the planktic species of Anabaena described in the study is presented.     

Inhibition of nitrate uptake by ammonia in a blue-green alga,Anabaena cylindrica

Ammonia at concentrations above 1×10^-5 M inhibits uptake of nitrate in the nitrogen-fixing blue-green alga, Anabaena cylindrica. This inhibition takes place both in the light and in the dark. The rate of nitrate uptake is stimulated by light. Addition of relatively high concentrations of nitrate (1–10 mM) reversibly inhibits ammonia uptake. FCCP, an uncoupler of phosphorylation, inhibits both nitrate and ammonia uptake. Ammonia may inhibit nitrate uptake by reducing the supply of energy (ATP) for active nitrate transport.Abbreviations FCCP carbonyl cyanide p-trifluoromethoxy-phenylhydrazone - CCCP carbonyl cyanide m-chlorophenyl-hydrazone     

The fine structure of the drum muscles of the Tigerfish,Therapon jarbua,as compared with the trunk musculature

Summary The fibers of drum and trunk muscles of the Tigerfish, Therapon jarbua, differ greatly in diameter. The myofibrils of the trunk muscles are irregularly oriented, while those of the drum muscles are rolled into spiral or concentric bands. Both muscle types possess the sarcomere structure typical of cross-striated musculature. However, the myofibrils of the drum muscles differ greatly in sarcomere length and width from those in the trunk musculature. The trunk muscles contain few mitochondria, whereas in the drum muscles mitochondria are abundant. The sarcoplasmic reticulum (SR) of the drum muscles takes the form of elongated tubes in both the A and the I region; that of the trunk musculature consists of small vesicles. Of the two muscle types, the drum muscle contains more SR. With respect to the form of the T system, the trunk musculature is of the Z type and the drum muscles of the A-I type. The drum muscle displays a considerably greater number of motor endplates; these lack typical junctional folds and have mitochondria with very few cristae. No fat could be demonstrated in either the drum or the trunk muscles. However, the concentration of glycogen is higher in the drum muscle than in the musculature of the trunk.This work was accomplished with support from the Deutsche Forschungsgemeinschaft and is gratefully dedicated to Prof. R. Danneel on the occasion of his 75th birthday.     

The fine structure of the antennal sensilla of the pine saw flyNeodiprion sertifer (Insecta: Hymenoptera)

Summary There is a considerable sexual dimorphism as regards the development of the antenna inNeodiprion sertifer. In the male this is manifested in a larger antennal surface area and the possession of a great number of long single-walled sensilla (SW 1), which are located on the antennal branches. In the female the antennal branches are vestigial, and the single-walled sensilla, of a second type (SW 2), are shorter and present in lower numbers. Both sexes have in addition four types of sensilla in common:viz. a third type of single-walled sensilla (SW 3), terminal pore sensilla, double-walled sensilla, and poreless sensilla. These four sensillar types are characterized not only by their external appearance but also by their internal morphology. Especially the cells enveloping the sensory cells vary in number and appearance.Supported by joint grants from the Swedish Council for Planning and Coordination of Research, the Swedish Natural Science Research Council, and the Swedish Council for Forestry and Agricultural Research.     

The fine structure of the thymus of the fetal and neonatal monkey (Macaca mulatta)

Summary The morphologic features of the fetal and neonatal thymus were investigated by light and electron microscopy to determine developmental changes. Primitive epithelial cells differentiate into reticular epithelial cells, medullary epithelial cells, elongated epithelial cells, Hassall's corpuscles and cysts. Thymocytes first appear at 50 days fetal age and the number of thymocytes is amplified from 75–150 days fetal age. Minor differences between the fetal thymus of the monkey and that of other species were observed. Possible functions for the various cellular components of the fetal monkey thymus are discussed.This research was supported in part by grants 5-F3-CA-28, 793-02 and FR-0167 from the National Institutes of Health.     

Isolation and characterization of a temperate cyanophage for a tropical Anabaena strain

In this paper we describe the isolation and characterization of a temperate cyanophage N(S)1 of the genus cyanopodovirus which produces turbid plaques on the host Anabaena 77S15 isolated from tropical soil. Its properties have been compared to those of other well-characterized cyanophages. In addition, two strains of Anabaena 77S15 lysogenic for N(S)1 were isolated. N(S)1 seems to be integrated into the chromosome of the two lysogens, and a 2 kb plasmid present at a low copy number in the non-lysogenic strain is amplified significantly.     

Investigations on the phototactic orientation of Anabaena variabilis

Phototaxis of the blue-green alga Anabaena variabilis was studied using both population method and observation of single trichomes by microscope. The trichomes react positively at low and negatively at high illuminance. The inversion point lies at about 1000 1x. The action spectrum of positive phototaxis indicates that the photosynthetic pigments chlorophyll a, C-phycocyanin and allo-phycocyanin are involved in the absorption of the active light. The same range of wavelengths is active in negative phototaxis, but in addition, wavelengths between 500 and 560 nm and between 700 and 750 nm are also effective. Obviously pigments of unknown chemical nature are sharing in light absorption. Two alternatives are discussed. Since inhibitors of photosynthesis such as DCMU and DBMIB do not affect phototactic orientation, a direct coupling of phototaxis with photosynthesis can be excluded.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DBMIB Dibromothymoquinone (2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone) Presented in part at the International Symposium on Photosynthetic Prokaryotes: August 22–28, 1976, Dundee, Scotland     

Growth,cell volume,and fine structure of Porphyra umbilicalis in relation to osmotic tolerance

Porphyra umbilicalis, a marine red alga occurring in the intertidal zone of the cold North Sea, tolerates a wide range of osmotic conditions from 0.2 x to 6 x artificial seawater medium ASP₁₂. In cells osmotically adapted for two weeks, photosynthesis and respiration are progressively inhibited in media more concentrated than 2 x. In both hypo- and hyperosmotic stress ranges, the most striking fine structural change is the development of vacuoles. In comparison to 1 x medium, where vacuoles are virtually lacking, the vacuolar part of the protoplasm increases 6-fold in 0.2 x and 10-fold in 3.5 x medium, respectively. However, at extreme hyperosmotic stress (6 x medium) the vacuolar part is extremely small. The largest cell volumes are found in 0.2 x and 3.5 x media, the smallest one in 6 x medium. In the osmotically regulated range (0.2–3.5 x medium), the regulated parameter is the volume of the protoplasm without the vacuolar system. It is suggested that at hyperosmotic stress the vacuoles may serve as osmotically active compartment, probably by accumulation of inorganic ions. The intracellular content of Floridean starch granules decreases with increasing osmotic pressure, possibly indicating the significance of soluble organic constituents as osmotically active solutes.Member of the Arbeitsgemeinschaft für Elektronenmikroskople un der Ticrärztlichen Hochschule Hannover     

Immuno-gold localization of glutamine synthetase in a nitrogen-fixing cyanobacterium (Anabaena cylindrica)

Localization of glutamine synthetase in thin sections of nitrogen-fixing Anabaena cylindrica was performed using immuno-gold/transmission electronmicroscopy. The enzyme was present in all of the three cell types possible; vegetative cells, heterocysts and akinetes. The specific gold label was always more pronounced in heterocysts compared with vegetative cells, and showed a uniform distribution in all three types. No specific label was associated with subcellular inclusions such as carboxysomes, cyanophycin granules and polyphosphate granules. When anti-glutamine synthetase antiserum was omitted, no label was observed.Abbreviation GS glutamine synthetase     

Inhibition of the growth of two blue-green algae species (Microsystis aruginosa and Anabaena spiroides) by acidification treatments using carbon dioxide

The effect of pH adjusted by aeration with carbon dioxide (CO₂) on the growth of two species of blue-green algae, Microcystis aeruginosa and Anabaena spiroides, was investigated. Three conditions (pH 5.5, 6.0 and 6.5) were found to have significant inhibitory effects on the growth of the two algae species when acidification treatment was conducted during the logarithmic phase. Differences in the inhibition effect of acidification existed between the two species algae. The tolerance of M. aeruginosa to these conditions was also investigated. The results indicated that M. aeruginosa was inhibited significantly, but not dead at pH 6.5, whereas death occurred at pH 5.5 and 6.0. The greatest inhibitory effect of acidification treatment conducted during the stable breeding phase of M. aeruginosa occurred at pH 5.5, while no inhibitory effect was found at pH 6.5.