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At least 19 recordsLinked to original sources

PubMed1992

Conjugative gene transfer in marine cyanobacteria: Synechococcus sp., Synechocystis sp. and Pseudanabaena sp.

Versatility of gene transfer by transconjugation in marine cyanobacteria was demonstrated. In this study, seven different marine cyanobacteria were used as recipient cells. First, transconjugation was carried out using the mobilizable transposon (Tn5) carrying plasmid pSUP1021. Transconjugates were observed in all marine cyanobacteria tested. Second, the broad-host-range vector pKT0230 (IncQ) was tested for transconjugation. pKT230 has been successfully transferred in a marine cyanobacterium Synechococcus sp. NKBG15041C, and replicated as an autonomous replicon without alteration in the restriction enzyme pattern. A maximum transfer efficiency of 5.2 x 10(-4) transconjugants/recipient cell was observed, when mating was performed on agar plates containing low salinity (0.015 M NaCl) medium. This is the first study to demonstrate gene transfer in marine cyanobacteria via transconjugation.

Biotechnology↗

PubMed1978

Pathways of assimilation of [13N]N2 and 13NH4+ by cyanobacteria with and without heterocysts.

The principal initial product of metabolism of [13N]N2 and 13NH4+ by five diverse cyanobacteria is glutamine. Methionine sulfoximine inhibits formation of [13N]glutamine except in the case of Gloeothece sp., an organism with a thick sheath through which the inhibitor may not penetrate. Thus, glutamine synthetase appears to catalyze the initial step in the assimilation of N2-derived or exogenous NH4+ by these organisms. [13N]Glutamate is, in all cases, the second major product of assimilation of 13N-labeled N2 and NH4+. In all of the N2-fixing cyanobacteria studied, the fraction of 13N in glutamine declines and that in glutamate increases with increasing times of assimilation of [13N]N2 and 13NH4+, and (Gloeothece again excepted) methionine sulfoximine reduces incorporation of 13N into glutamate as well as into glutamine. Glutamate synthase therefore appears to catalyze the formation of glutamate in a wide range of N2-fixing cyanobacteria. However, the major fraction of [13N]glutamate formed by Anacystis nidulans incubated with 13NH4+ may be formed by glutamic acid dehydrogenase. The formation of [13N]alanine from 13NH4+ appears to be catalyzed principally either by alanine dehydrogenase (as in Cylindrospermum licheniforme) or by a transaminase (as in Anabaena variabilis).

Alanine↗

PubMed1978

Survey of extrachromosomal DNA found in the filamentous cyanobacteria.

Cleared lysates of 13 species of filamentous cyanobacteria were examined for the presence of extrachromosomal DNA by using agarose gel electrophoresis and ethidium bromide staining. Seven of the 13 species contained extrachromosomal covalently closed circular DNA, and all but 1 species contained multiple elements. There was no correlation between the presence of extrachomosomal DNA and either the range of metabolic activities found in the cyanobacteria or the differentiated cell types or structures elaborated by the morphologically complex filamentous cyanobacteria.

Cyanobacteria↗

PubMed1992

Identification of anatoxin-A in benthic cyanobacteria (blue-green algae) and in associated dog poisonings at Loch Insh, Scotland.

Dog deaths occurred in 1990 and 1991 after the animals drank water containing blooms of benthic cyanobacteria along the shoreline of Loch Insh, Scotland. Signs of poisoning in the affected animals and the high neurotoxicity of bloom extracts in laboratory bioassays indicated acute poisoning due to cyanobacterial neurotoxin(s). The neurotoxic blooms consisted largely of benthic Oscillatoria species which were also observed in the stomach contents of the poisoned dogs. Stomach contents were also neurotoxic in bioassays with the same signs of poisoning as the Oscillatoria blooms. The cyanobacterial alkaloid neurotoxin anatoxin-a was identified in bloom extracts and poisoned dog stomach contents by high-performance liquid chromatography and gas chromatography-mass spectrometry. A species of benthic Oscillatoria has been isolated from the neurotoxic bloom material and shown to produce anatoxin-a in laboratory culture. These findings are the first to associate anatoxin-a toxicoses with benthic, rather than planktonic, cyanobacteria. Procedures for anatoxin-a extraction and identification from the blooms and animal material are also detailed.

Animals↗

PubMed1979

Sulfide inhibition of photosystem II in cyanobacteria (blue-green algae) and tobacco chloroplasts.

The present study shows that in the presence of 600 nm light, sulfide acts as a specific inhibitor of photosynthetic electron transport between water and Photosystem II in the cyanobacteria Aphanothece halophytica and Synechococcus 6311 as well as in tobacco chloroplasts. In the presence of 600 nm light sulfied affects the fast fluorescence transients as does a low concentration (10 mM) of hydroxylamine; the fluorescence yield decreases in the presence of either chemical and can be restored by the addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. In chloroplasts, however, NH2OH, an electron donor at high concentrations (40 mM), relieves the sulfide effect. In the dark, sulfide affects the cyanobacterial fluorescence transients through decrease of oxygen tension. The fluorescence yield increases in a similar pattern to that observed under nitrogen flushing. Upon omission of sulfide in A. halophytica, the characteristic aerobic fluorescence transients return, consistent with the ease of alternation between oxygenic and sulfide-dependent anoxygenic photosynthesis in many cyanobacteria.

Aerobiosis↗

PubMed2026

Green genes from blue greens: challenges and solutions to unlocking the potential of cyanobacteria in drug discovery.

Cyanobacteria are prolific producers of biologically active compounds that are important in influencing ecology, behavior of interacting organisms, and as leads in drug discovery efforts. Here we discuss the challenges faced by all natural product researchers, especially those that focus on cyanobacteria, and then describe progress that has been made in these areas. We also propose some solutions, paths forward, and thoughts for consideration on these challenges.

Biological Products↗

PubMed1977

Occurrence of facultative anoxygenic photosynthesis among filamentous and unicellular cyanobacteria.

Eleven of 21 cyanobacteria strains examined are capable of facultative anoxygenic photosynthesis, as shown by their ability to photoassimilate CO2 in the presence of Na2S, 3-(3,4-dichlorophenyl)-1,1-dimethylurea and 703-nm light. These include different cyanobacterial types (filamentous and unicellular) of different growth histories (aerobic, anaerobic, and marine and freshwater). Oscillatoria limnetica, Aphanothece halophytica (7418), and Lyngbya (7104) have different optimal concentrations of Na2S permitting CO2 photoassimilation, above which the rate decreases: 3.5, 0.7, and 0.1 mM, respectively. In A. halophytica, for each CO2 molecule photoassimilated two sulfide molecules are oxidized to elemental sulfur, which is excreted from the cells. The ecological and evolutionary significance of anoxygenic photosynthesis in the cyanobacteria is discussed.

Aerobiosis↗

PubMed1979

Control of heterocyst and nitrogenase synthesis in cyanobacteria.

The development of the heterocyst by filamentous nitrogen-fixing cyanobacteria provides an attractive model system for studying cellular differentiation. Heterocyst synthesis is repressed by the presence of exogenous combined nitrogen. In this report, it is shown that the tryptophan analog, D,L-7-azatryptophan (Aza-T), is capable of relieving the repressive effect of exogenous NH4NO3 on heterocyst and nitrogenase synthesis. In nitrogen-fixing cultures, the presence of 20 micron Aza-T increases the heterocyst frequency twofold. The glutamate analog, L-methionine-D,L-sulfoximine (MSX), has also been shown to cause a derepression in the synthesis of heterocysts and nitrogenase. However, unlike MSX, Aza-T does not appear to exert its effects by inhibiting the activity of glutamine synthetase. Therefore, glutamine synthetase may not be the sole key to the derepression of heterocyst and nitrogenase development in the cyanobacteria. It is hoped that a study of Aza-T action may lead to the elucidation of a novel control mechanism.

Cyanobacteria↗

PubMed1978

Adsorption of cyanophage AS-1 to unicellular cyanobacteria and isolation of receptor material from Anacystis nidulans.

Cells of unicellular cyanobacteria of typological group Ia, containing approximately 50 mol% guanine + cytosine (G+C) in their DNA (R. Y. Stanier, R. Kunisawa, M. Mandel, and G. Cohen-Bazire, Bacteriol. Rev. 35:171-205, 1971), were susceptible to infection by the cyanophage AS-1. Cyanobacteria of the same typological group, containing approximately 65 mol% G+C in their DNA, did not adsorb the cyanophage AS-1 or adsorbed it at a low rate. AS-1 was not propagated by any of the investigated strains with a high G+C content in their DNA. However, cells of strains 6907 and 6911 were lysed by cyanophage AS-1. A comparison of the host range of this phage with the lipopolysaccharide composition of host and non-host cell walls suggests that lipopolysaccharides are involved in the adsorption process. About 8 microgram of lipopolysaccharide per ml from host strains inactivated 50% of the particles of a solution containing 100 PFU/ml after 60 min of incubation at 30 degrees C. Material with receptor activity was extracted from the host strain Anacystis nidulans KM. The extract was purified of glycolipids and pigments, and a fraction showing receptor activity was isolated. This fraction contained three polypeptides of molecular weights between 54,000 and 64,000. Heat and protease treatment of whole cells and of isolated receptor material decreased the receptor activity. The fluorescence intensity of A. nidulans cells labeled with 1-anilino-8-naphthalene sulfonate was increased when AS-1 was adsorbed to these cells. The participation of lipopolysaccharides and proteins in the formation of the receptor complex is discussed.

Adsorption↗

PubMedDate not supplied

[Blooming and destruction of cyanobacteria in the drainage bassin of the hydrogen sulfide spring of Staraya Matsesty].

The growth of cyanobacteria belonging to the genera Oscillatoria and Anabaena (up to 2.1 x 10(7) filaments per 1 g of wet sample) was found in a water reservoir with a high content of sulfides (up to 9 mM) in Staraya Matsesta throughout the year. The spots of Oscillatoria are located in the spring in more illuminated areas as compared to Anabaena. In the spring, not only spots of actively growing cells were detected, but also accumulations of Oscillatoria cells being destroyed (blue spots). Water-bloom spots in which Oscillatoria prevailed can transform into the spots of Anabaena. The main accompanying forms in the spots of Anabaena are long thin filaments of the flexibacterial type while short rods are found in the spots where Oscillatoria predominates. Heterotrophic enteric bacteria (48 x 10(4) cells per 1 g), Bacillus, Pseudomonas, and coryneform bacteria were also detected. Green bacteria (Chlorobium) and nonsulfur purple bacteria (Rhodomicrobium) were present in small quantities (16 x 10(3) cells per 1 g) as well as sulfate-reducing bacteria (5--15 x 10(2) cells per 1 g) and thiobacilli (40--60 cells per 1 g). In the spring, stones were covered with pink spots of spherical motile purple bacteria and with yellow-green spots of filamentous green bacteria. The cyanobacteria from the spots are capable of oxygenated photosynthesis. Fixation of CO2 by them in situ is 0.08 mcg per 1 g of dry sample per hour or 0.06 mcg per 10(6) cells per hour, and is inhibited by 10(-5) M DCMU by 70%.

Cyanobacteria↗

PubMed1979

Influence of pesticides on the growth of cyanobacteria.

Two unicellular and two filamentous cyanobacteria (blue-green algae) were exposed under conditions optimal for photoautotrophic growth to eleven pesticides. Low concentrations (0.01 to 5 ppm) of diuron, atrazine, and paraquat inhibited growth. With MCPA, MCPP, 2,4-D, milstem and ethrel, marked inhibitory effects were achieved only at concentrations above 100 ppm. Growth was inhibited by glyphosate, DDT, and thiram at intermediate concentrations. In some cases, the effective concentration of the pesticide varied considerably with the organism tested.

Cyanobacteria↗

PubMed1978

Hydrogen metabolism in the facultative anoxygenic cyanobacteria (blue-green algae) Oscillatoria limnetica and Aphanothece halophytica.

Two facultative anoxygenic photoautotrophic cyanobacteria, Oscillatoria limnetica and Aphanothece halophytica were found capable of CO2 photoassimilation using molecular hydrogen as electron donor in a photosystem I driven reaction. A. halophytica was also capable of evolving hydrogen from Na-dithionite reduced methylviologen in a light independent reaction.

Anaerobiosis↗

PubMed1975

Lactate dehydrogenases in cyanobacteria.

NAD-linked lactate dehydrogenases specific for the D- and L-lactate have been demonstrated in a number of strains of unicellular cyanobacteria. The D-lactate dehydrogenase of one strain (Synechococcus 6716) was partially purified and its properties were studied. The enzyme has a molecular weight of ca. 115000-120000, is highly specific, autooxidizable, and susceptible to inhibition by iodoacetamide, oxamate and ATP. The possible physiological functions of the enzyme in the metabolism of the organism were investigated. D-lactate carbon was incorporated in cell material during photosynthetic growth with CO2, but lactate was not used as sole source for carbon for photosynthetic or chemosynthetic development. D-lactate and pyruvate were oxidized aerobically in the dark by resting cell suspensions with the assimilation mainly of the C2 and the C3 carbon atoms. In the oxidation of lactate, acetate was excreted into the medium. No fermentation of glucose was found, but a small amount of D-lactate was detected as a product of endogenous dark metabolism of the cell. All enzymes required for the production of lactate from glucose and from glycogen were found in exponentially growing cells, but the activity of some key enzymes was low or undetectable in old cultures.

Acetates↗

PubMed1978

Calcium and photosynthetic oxygen evolution in cyanobacteria.

Calcium activation of oxygen evolution from French-press preparations of Phormidium luridum is largely reversible upon removal of added Ca(2+). Activation occurs via a first-order binding with a dissociation constant of 2.8 mM. An 8-fold increase in oxygen evolution rate observed upon Ca(2+) addition is accounted for by a 4-fold increase in the number of active photosynthetic units, and a doubling of turnover rate. While both Ca(2+) and Mg(2+) stimulate turnover, unit activation is Ca(2+) specific. Under optimal conditions, 30% of the units functioning in the intact cell can be recovered in the Ca(2+) -activated preparation. The Ca(2+) requirement of P. luridum preparations is not relieved by proton-carrying uncouplers, or by rate-saturating concentrations of the Hill acceptor, ferricyanide. Taken together with the reported stimulation by Ca(2+) of oxygen evolution in the presence of DCMU (Piccioni, R.G. and Mauzerall, D.C. (1976) Biochim. Biophys. Acta 423, 605--609) these observations strongly suggest a site of Ca(2+) action within Photosystem II. The pronounced specificity of the Ca(2+) requirement appears in preparations of other cyanobacteria (Anabaena flos-aquae and Anacystis nidulans) but not in the eucaryote Chlorella vulgaris. While milder cell-disruption methods bring about some Ca(2+) dependence in P. luridum, French-press treatment is required for maximal expression of Ca(2+) -specific effects. French-press breakage causes a release of endogenous Ca(2+) from cells, supporting the view that added Ca(2+) restores oxygen evolution by satisfying a physiological requirement for the cation.

Binding Sites↗

PubMed1979

EPR spectra of photosystem I and other iron protein components in intact cells of cyanobacteria.

Electron paramagnetic resonance (EPR) spectra were recorded of whole filaments of the cyanobacteria Nostoc muscorum and Anabaena cylindrica. Signals due to manganese were removed by freezing and thawing the cells in EDTA. EPR spectra were assigned on the basis of their g values, linewidths, temperature dependence and response to dithionite and light treatments. The principal components identified were: (i) rhombic Fe3+ (signal at g = 4.3), probably a soluble storage form of iron; (ii) iron-sulfur centers A and B of Photosystem I; (iii) the photochemical electron acceptor 'X' of Photosystem I; this component was also observed for the first time in isolated heterocysts; (iv) soluble ferredoxin which was present at a concentration of 1 molecule per 140 +/- 20 chlorophyll molecules; (v) a membrane-bound iron-sulfur protein (g = 1.92). A signal g = 6 in the oxidized state was probably due to an unidentified heme compound. During deprivation of iron the rhombic Fe3+, centers A, B and X of Photosystem I, and soluble ferredoxin were all observed to decrease.

Cyanobacteria↗

PubMed1979

Isolation of photosynthetic catalysts from cyanobacteria.

Methods are described for the isolation of ferredoxins I and II, cytochrome c-553, cytochrome f, cytochrome c-550 and plastocyanin from large quantities of various cyanobacteria. The amino acid composition of cytochrome c-550 is reported. There is a variation in the relative amounts of these proteins in different batches of cells which may relate to the nutritional status of the organisms.

Amino Acids↗

PubMed1992

Large ATP synthase operon of the red alga Antithamnion sp. resembles the corresponding operon in cyanobacteria.

The large plastid ATP synthase operon of the multicellular red alga Antithamnion sp. was cloned and the sequence of six ATPase genes determined. The operon resembles more the one from cyanobacteria than the ATP synthase operon of the chloroplast genome. The gene order is atpI, H, G, F, D and A, coding for the ATPase subunits a, c, b', b, delta and alpha, respectively. In green plants, the genes atpG and atpD are located in the nucleus. Unlike the situation in three published cyanobacterial ATP synthase operons, atpC, coding for the gamma subunit, is not a part of the rhodoplast operon. A single 4.5 kb transcript was detected with atpG, F, D and A gene probes that could span the whole operon, but no transcript could be detected with atpI and atpH probes. The end of an open reading frame preceding the atp genes shows remarkable homology to elongation factor TS from Escherichia coli. Behind the ATPase cluster, two open reading frames were detected that are not homologous to any known chloroplast gene. One of them may code for a transport protein of unknown specificity. Gene arrangement and sequence comparisons support the hypothesis of a polyphyletic origin of rhodoplasts and chloroplasts.

Amino Acid Sequence↗

PubMed1992

Pressure and low temperature effects on the fluorescence emission spectra and lifetimes of the photosynthetic components of cyanobacteria.

The effects of hydrostatic pressure on the excited state reactions of the photosynthetic system of cyanobacteria were studied with the use of stationary and dynamic fluorescence spectroscopy. When the cells were excited with blue light (442 nm), hydrostatic pressure promoted a large increase in the fluorescence emission of the phycobilisomes (PBS). When PBS were excited at 565 nm, the shoulder originating from photosystem II (PSII) emission (F685) disappeared under 2.4 kbar compression, suggesting suppression of the energy transfer from PBS to PSII. At atmospheric pressure, the excited state decay was complex due to energy transfer processes, and the best fit to the data consisted of a broad Lorentzian distribution of short lifetimes. At 2.4 kbar, the decay data changed to a narrower distribution of longer lifetimes, confirming the pressure-induced suppression of the energy transfer between the PBS and PSII. When the cells were excited with blue light, the decay at atmospheric pressure was even more complex and the best fit to the data consisted of a two-component Lorentzian distribution of short lifetimes. Under compression, the broad distribution of lifetimes spanning the region 100-1,000 ps disappeared and gave rise to the appearance of a narrow distribution characteristic of the PBS centered at 1.2 ns. The emission of photosystem I underwent 2.2-fold increase at 2.4 kbar and room temperature. A decrease in temperature from 20 to -10 degrees C at 2.4 kbar promoted a further increase in the fluorescence emission from photosystem I to a level comparable with that obtained at temperatures below 120 degrees K and atmospheric pressure. On the other hand, when the temperature was decreased under pressure, the PBS emission diminished to very low value at blue or green excitation, suggesting the disassembly into the phycobiliprotein subunits.

Biophysical Phenomena↗