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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↗

PubMed1988

The 5S ribosomal RNA sequences of a red algal rhodoplast and a gymnosperm chloroplast. Implications for the evolution of plastids and cyanobacteria.

The 5S ribosomal RNA sequences have been determined for the rhodoplast of the red alga Porphyra umbilicalis and the chloroplast of the conifer Juniperus media. The 5S RNA sequence of the Vicia faba chloroplast is corrected with respect to a previous report. A survey of the known sequences and secondary structures of 5S RNAs from plastids and cyanobacteria shows a close structural similarity between all 5S RNAs from land plant chloroplasts. The algal plastid 5S RNAs on the other hand show much more structural diversity and have certain structural features in common with bacterial 5S RNAs. A dendrogram constructed from the aligned sequences by a clustering algorithm points to a common ancestor for the present-living cyanobacteria and the land plant plastids. However, the algal plastids branch off at an early stage within the plastid-cyanobacteria cluster, before the divergence between cyanobacteria and land plant chloroplasts. This evolutionary picture points to the occurrence of multiple endosymbiotic events, with the ancestors of the present algal plastids already established as photosynthetic endosymbionts at a time when the ancestors of the present land plant chloroplasts were still free-living cells.

Base Sequence↗

PubMed1988

Evolutionary relationships among cyanobacteria and green chloroplasts.

The 16S rRNAs from 29 cyanobacteria and the cyanelle of the phytoflagellate Cyanophora paradoxa were partially sequenced by a dideoxynucleotide-terminated, primer extension method. A least-squares distance matrix analysis was used to infer phylogenetic trees that include green chloroplasts (those of euglenoids, green algae, and higher plants). The results indicate that many diverse forms of cyanobacteria diverged within a short span of evolutionary distance. Evolutionary depth within the surveyed cyanobacteria is substantially less than that separating the major eubacterial taxa, as though cyanobacterial diversification occurred significantly after the appearance of the major eubacterial groups. Three of the five taxonomic sections defined by Rippka et al. (R. Rippka, J. Deruelles, J. B. Waterbury, M. Herdman, and R. Y. Stanier, J. Gen. Microbiol. 111:1-61, 1979) (sections II [pleurocapsalean], IV [heterocystous, filamentous, nonbranching], and V [heterocystous, filamentous, branching]) are phylogenetically coherent. However, the other two sections (I [unicellular] and III [nonheterocystous, filamentous]) are intermixed and hence are not natural groupings. Our results not only support the conclusion of previous workers that the cyanobacteria and green chloroplasts form a coherent phylogenetic group but also suggest that the chloroplast lineage, which includes the cyanelle of C. paradoxa, is not just a sister group to the free-living forms but rather is contained within the cyanobacterial radiation.

Base Sequence↗

PubMed1989

Evolutionary relationship of psbA genes from cyanobacteria, cyanelles and plastids.

The psbA gene is part of the reaction center of photosystem II in cyanobacteria and the plastids of higher plants. Its primary sequence is highly conserved among all species investigated so far and its sequence shows homologies with the L and M subunits of the reaction center of photosynthetic bacteria. We have analyzed the psbA homolog from a eukaryotic alga, Cyanophora paradoxa, where the gene is encoded on cyanelle DNA. These cyanelles are surrounded by a murein sacculus and resemble cyanobacteria in many other characteristics, although they are genuine organelles that functionally replace plastids. Analysis of the gene revealed a psbA protein identical in length (360 codons) with the cyanobacterial counterpart. The overall sequence identity is, however, more pronounced between cyanelle psbA and the shorter (353 amino acids) psbA product found in higher plants. These data strongly support the postulated bridge position of cyanelles between chloroplasts and free-living cyanobacteria.

Amino Acid Sequence↗

PubMed1985

The role of glutathione and ascorbate in hydroperoxide removal in cyanobacteria.

The antioxidative potential of cyanobacteria to scavenge hydroperoxides formed as by-products of photosynthetic activity was investigated in Nostoc muscorum 7119 and Synechococcus 6311. These cells contained a high concentration of glutathione, 2-5 mM, and a low concentration of ascorbate, 20-100 uM. No glutathione peroxidase was detected while the activity of ascorbate peroxidase was high, reacting with hydrogen peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Dehydroascorbate reductase was active in recycling ascorbate and glutathione reductase regenerated glutathione from glutathione disulphide. The activity of these antioxidative enzymes in the cyanobacteria was sufficient to remove between 60-230 nmoles H2O2 .mg protein-1 min-1. It is suggested that in cyanobacteria an effective reaction sequence for removal of hydroperoxides involves ascorbate peroxidase and recycling of glutathione and ascorbate.

Ascorbate Peroxidases↗

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↗

PubMed1990

Purification and properties of glutamine synthetases from the cyanobacteria Synechocystis sp. strain PCC 6803 and Calothrix sp. strain PCC 7601.

Glutamine synthetases (GSs) from two cyanobacteria, one unicellular (Synechocystis sp. strain PCC 6803) and the other filamentous (Calothrix sp. strain PCC 7601 [Fremyella diplosiphon]), were purified to homogeneity. The biosynthetic activities of both enzymes were strongly inhibited by ADP, indicating that the energy charge of the cell might regulate the GS activity. Both cyanobacteria exhibited an ammonium-mediated repression of GS synthesis. In addition, the Synechocystis sp. showed an inactivation of GS promoted by ammonium that had not been demonstrated previously in cyanobacteria.

Adenosine Diphosphate↗

PubMed1992

Oxygen relations of nitrogen fixation in cyanobacteria.

The enigmatic coexistence of O2-sensitive nitrogenase and O2-evolving photosynthesis in diazotrophic cyanobacteria has fascinated researchers for over two decades. Research efforts in the past 10 years have revealed a range of O2 sensitivity of nitrogenase in different strains of cyanobacteria and a variety of adaptations for the protection of nitrogenase from damage by both atmospheric and photosynthetic sources of O2. The most complex and apparently most efficient mechanisms for the protection of nitrogenase are incorporated in the heterocysts, the N2-fixing cells of cyanobacteria. Genetic studies indicate that the controls of heterocyst development and nitrogenase synthesis are closely interrelated and that the expression of N2 fixation (nif) genes is regulated by pO2.

Cyanobacteria↗

PubMed1986

Transformation in cyanobacteria.

The lack of any known transduction or indigenous conjugation systems has left transformation as the major means for genetic manipulations in cyanobacteria. Studies of transformation in cyanobacteria generally have dealt with one of two distinct areas. The first area is genomic transformation where internalized donor DNA recombines with chromosomally located genes. Chromosomal transformation can be a powerful tool for genetic mapping and mutagenesis. The second area is plasmid transformation where internalized plasmid donor DNA becomes established as an independent replicon in the recipient cyanobacterium. This second area has received a great deal of attention because it allows the generation of merodiploids for studies of genetic regulation and control and because it potentially allows the expression of foreign genes in an oxygenic photoautotroph. This article will attempt to describe the development of our current understanding of these two types of genetic transformation in cyanobacteria.

Chromosome Mapping↗

PubMed1986

Toxic peptides from freshwater cyanobacteria (blue-green algae). I. Isolation, purification and characterization of peptides from Microcystis aeruginosa and Anabaena flos-aquae.

Toxic peptides from two European Microcystis aeruginosa and one Canadian Anabaena flos-aquae species of freshwater cyanobacteria (blue-green algae) were purified by high performance liquid chromatography (HPLC) and examined by amino acid analysis and mass spectrometry. A toxic fraction from a butanol/methanol extract of toxic lyophilized cells was separated by G-25 gel filtration and purified by HPLC using a C-18 semi-preparative Column. A toxic peak with the same elution time was detected for each of the three toxic cyanobacteria. The desalted purified toxins (i.p. LD50 in mice, 50 micrograms/kg) caused signs of poisoning identical with previous literature reports of hepatotoxic peptides from Microcystis. On hydrolysis and amino acid analysis all three toxins showed a similar profile, consisting of equimolar amounts of glutamic acid, alanine, arginine and leucine. beta-methyl aspartic acid was identified in all of the toxic peptides. The fast atom bombardment mass spectra of the toxins indicated the molecular weight to be 994 for all the peptides. The absence of sequence ions in their corresponding fast atom bombardment mass spectra indicated the peptides to be cyclic.

Amino Acids↗

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↗

PubMed1990

The psbA-gene from a red alga resembles those from cyanobacteria and cyanelles.

Plastid DNA (ptDNA) from the unicellular red alga Cyanidium caldarium was isolated. A 5.8 kb Eco RI, fragment containing the entire psbA-gene was cloned and the nucleotide sequence of the psbA-gene determined. At the carboxyl terminus the encoded protein (D1) contains the seven amino acid-insertion which was found to be typical of the cyanobacteria and the cyanelles of Cyanophora paradoxa. However, the overall sequence homology does not support a direct relationship between the plastids of Cyanidium, cyanelles and the cyanobacteria. As in other photosynthetic organisms the psbA-gene is transcribed as a monocistronic mRNA. The ribosomal RNA operon was located 4 kb upstream of the psbA-gene.

Amino Acid Sequence↗

PubMed1988

Organization of the nif genes in cyanobacteria in symbiotic association with Azolla and Anthoceros.

The sizes of endonuclease digestion fragments of DNA from cyanobacteria in symbiotic association with Azolla caroliniana or Anthoceros punctatus, or in free-living culture, were compared by Southern hybridization using cloned nitrogenase (nif) genes from Anabaena sp. PCC 7120 as probes. The restriction fragment pattern produced by cyanobacteria isolated from A. caroliniana by culture through symbiotic association with Anthoceros differed from that of the major symbiotic cyanobacterium freshly separated from A. caroliniana. The results indicate that minor cyanobacterial symbionts occur in association with Azolla and that the dominant symbiont was not cultured in the free-living state. Both the absence of hybridization to an xisA gene probe and the mapping of restriction fragments indicated a contiguous nifHDK organization in all cells of the symbiont in association with Azolla. On the other hand, in the cultured isolate from Azolla and in Nostoc sp. 7801, the nifD and nifK genes are nominally separated by an interval of unknown length, compatible with the interruption of the nifHDK operon by a DNA element as observed in Anabaena sp. PCC 7120. In the above cultured strains, restriction fragments consistent with a contiguous nifHDK operon were also present at varying hybridization intensities, especially in Nostoc sp. 7801 grown in association with Anthoceros, presumably due to gene rearrangement in a fraction of the cells.

Autoradiography↗

PubMed1986

Production, by filamentous, nitrogen-fixing cyanobacteria, of a bacteriocin and of other antibiotics that kill related strains.

Colonies of sixty-five filamentous cyanobacteria were screened for the production of temperate phages and/or antibiotics on solid medium. None of them was observed to release phages. However, seven N2-fixing strains were found to produce antibiotics very active against other cyanobacteria. The antibiotic produced by Nostoc sp. 78-11A-E represents a bacteriocin of low molecular weight. Nostoc sp. ATCC 29132 appears to secrete, together with an antibiotic, a protein that inhibits its action.

Anti-Bacterial Agents↗

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↗

PubMed1990

Immunologically cross-reactive and redox-competent cytochrome b6/f-complexes in the chlorophyll-free plasma membrane of cyanobacteria.

Plasma and thylakoid membranes were separated and purified from cell-free extracts of the cyanobacteria Anacystis nidulans, Synechocystis 6714, Anabaena variabilis and Nostoc sp. strain Mac. Immunoblots of the membrane proteins using antisera raised against subunits I-IV of the chloroplast b6/f-complex gave evidence for the presence of a homologous complex in both plasma and thylakoid membranes from the four species of cyanobacteria investigated. Both plasma and thylakoid membranes catalyzed the electron transfer from (exogenous) plastoquinol-9 and NADH to horse heart ferricytochrome c. However, while with plasma membranes these reactions were severely inhibited by low concentrations of antimycin A and rotenone, respectively, the inhibitors were without major effect on thylakoid membranes. The results will be discussed in terms of a possible similarity (analogy and/or homology?) of cyanobacterial plasma membranes to the inner mitochondrial membrane.

Cell Membrane↗

PubMed1989

Toxicity of three herbicides to some nitrogen-fixing cyanobacteria.

The effects of some common rice field herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D), Machete, and Saturn, on the paddy field nitrogen-fixing cyanobacteria Nostoc linckia, Nostoc calcicola, Nostoc sp., and Anabaena doliolum were studied. These cyanobacteria were found to be more tolerant to 2,4-D (lethal doses 1500-2000 micrograms/ml) than to Machete and Saturn (lethal doses 6-8 micrograms/ml). The effects of these three herbicides on some physiological processes of N. linckia were studied. The 2,4-D stimulated the growth and nitrogen fixation up to 100 micrograms/ml concentration (a dose higher than the field dose, i.e., about 40 micrograms/ml), recommended for field application. However, with Machete and Saturn this type of stimulation was not observed even at lower concentrations. Similarly, the uptake of nutrients, such as NO3- and NH+4, was also inhibited by Machete and Saturn. However, 100 micrograms/ml 2,4-D stimulated the uptake of NO3- but not of NH+4; higher doses of 2,4-D inhibited the uptake of both nutrients. Factors such as pH, organic carbon sources (glucose and acetate), and amino acids were found to regulate the toxicity of all three herbicides to N. linckia. Lower pH enhanced the toxicity of all three herbicides, whereas higher pH (up to 9.0) lowered it. Glucose and acetate (each 500 micrograms/ml) protected against the toxicity of 2,4-D and Saturn, but not against Machete. Whereas glutamine, arginine, serine, and tryptophan conferred upon N. linckia a greater protection against the toxicity of all three herbicides, methionine did not do so, and the presence of methionine with herbicide in the culture medium resulted in greater toxicity to N. linckia than that in the presence of the herbicide alone.

2,4-Dichlorophenoxyacetic Acid↗