SEARCH · PubMed Health

Results for “Anabaena”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1992

Regulation of Anabaena sp. strain PCC 7120 glutamine synthetase activity in a Synechocystis sp. strain PCC 6803 derivative strain bearing the Anabaena glnA gene and a mutated host glnA gene.

The glnA gene from Synechocystis sp. strain PCC 6803 was cloned by hybridization with the glnA gene from Anabaena sp. strain PCC 7120, and a deletion-insertion mutation of the Synechocystis gene was generated in vitro. A strain derived from Synechocystis sp. strain PCC 6803 which contained integrated into the chromosome, in addition to its own glnA gene, the Anabaena glnA gene was constructed. From that strain, a Synechocystis sp. glnA mutant could be obtained by transformation with the inactivated Synechocystis glnA gene; this mutant grew by using Anabaena glutamine synthetase and was not a glutamine auxotroph. A Synechocystis sp. glnA mutant could not be obtained, however, from the wild-type Synechocystis sp. The Anabaena glutamine synthetase enzyme was subject to ammonium-promoted inactivation when expressed in the Synechocystis strain but not in the Anabaena strain itself.

Anabaena↗

PubMed1991

Identification and initial utilization of a portion of the smaller plasmid of Anabaena variabilis ATCC 29413 capable of replication in Anabaena sp. strain M-131.

Anabaena variabilis ATCC 29413 contains two cryptic plasmids. Clones of the smaller (41 kb) plasmid, designated pRDS1, in cosmid vectors were used to construct a physical map. A clone bank of pRDS1 constructed by ligating fragments from a XhoII digest of a pRDS1 cosmid clone into a mobilizable plasmid was used to locate an origin of replication of pRDS1. Because we were unable to cure A. variabilis of pRDS1, the clone bank was transferred by conjugation to another strain of Anabaena sp., strain M-131. A 5.3 kb fragment of pRDS1 contained all of the sequences necessary for replication in Anabaena sp. strain M-131 as judged by the ability to rescue the hybrid vector from exconjugants in unchanged from after many generations. Hybrid plasmids derived from pRDS1, one bearing genes for luciferase, were also transferred by conjugation to A. variabilis, where they appeared to recombine with pRDS1.

Chromosome Deletion↗

PubMed1999

Electrostatic forces involved in orienting Anabaena ferredoxin during binding to Anabaena ferredoxin:NADP+ reductase: site-specific mutagenesis, transient kinetic measurements, and electrostatic surface potentials.

Transient absorbance measurements following laser flash photolysis have been used to measure the rate constants for electron transfer (et) from reduced Anabaena ferredoxin (Fd) to wild-type and seven site-specific charge-reversal mutants of Anabaena ferredoxin:NADP+ reductase (FNR). These mutations have been designed to probe the importance of specific positively charged amino acid residues on the surface of the FNR molecule near the exposed edge of the FAD cofactor in the protein-protein interaction during et with Fd. The mutant proteins fall into two groups: overall, the K75E, R16E, and K72E mutants are most severely impaired in et, and the K138E, R264E, K290E, and K294E mutants are impaired to a lesser extent, although the degree of impairment varies with ionic strength. Binding constants for complex formation between the oxidized proteins and for the transient et complexes show that the severity of the alterations in et kinetics for the mutants correlate with decreased stabilities of the protein-protein complexes. Those mutated residues, which show the largest effects, are located in a region of the protein in which positive charge predominates, and charge reversals have large effects on the calculated local surface electrostatic potential. In contrast, K138, R264, K290, and K294 are located within or close to regions of intense negative potential, and therefore the introduction of additional negative charges have considerably smaller effects on the calculated surface potential. We attribute the relative changes in et kinetics and complex binding constants for these mutants to these characteristics of the surface charge distribution in FNR and conclude that the positively charged region of the FNR surface located in the vicinity of K75, R16, and K72 is especially important in the binding and orientation of Fd during electron transfer.

Anabaena↗

PubMed1994

Transfer of a genetic marker from a megaplasmid of Anabaena sp. strain PCC 7120 to a megaplasmid of a different Anabaena strain.

The 410-kb alpha megaplasmid of the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 was found to bear the nucA gene that encodes a sugar-nonspecific nuclease. That gene was mutated by insertion of a cassette that confers resistance to neomycin. The resulting strain, AMP2, was mated with a streptomycin-resistant derivative of Anabaena sp. strain PCC 7118, a strain that does not form heterocysts. Cells resistant to both neomycin and streptomycin that were derived from such matings were found to bear the neomycin resistance cassette of the donor strain in a larger megaplasmid characteristic of the recipient strain and did not form heterocysts. This is the first example of transfer of a genetic marker directly between strains of cyanobacteria in which incontrovertible physical evidence of transfer has been obtained. DNA sequences homologous to the nucA gene were present in 13 heterocyst-forming cyanobacteria that were tested but in none of six diverse unicellular strains that were examined.

Anabaena↗

PubMed2000

Highly nonproductive complexes with Anabaena ferredoxin at low ionic strength are induced by nonconservative amino acid substitutions at Glu139 in Anabaena ferredoxin:NADP+ reductase.

Ferredoxin (Fd) and ferredoxin:NADP(+) reductase (FNR) from Anabaena function in photosynthetic electron transfer (et). The et interaction between the FNR charge-reversal mutant E139K and Fd at 12 mM ionic strength (mu) is extremely impaired relative to the reaction with wt FNR, and the dependency of k(obs) on E139K concentration shows strong upward curvature at protein concentrations > or = 10 microM. However, at values of mu > or = 200 mM, reaction rates approach those of wild-type FNR, and normal saturation kinetics are observed. For the E139Q mutant, which is also significantly impaired in its et interaction with Fd at low FNR concentrations and low mu values, the dependency of k(obs) on E139Q concentration shows a smaller degree of upward curvature at mu = 12 and 100 mM and shows saturation kinetics at higher values of mu. wt FNR and the E139D mutant both show a slight amount of upward curvature at FNR concentrations >30 microM at mu = 12 mM but show the expected saturation kinetics at higher values of mu. These results are explained by a mechanism in which the mutual orientation of the proteins in the complex formed at low ionic strength with the E139K mutant is so far from optimal that it is almost unreactive. At increased E139K concentrations, the added mutant FNR reacts via a collisional interaction with the reduced Fd present in the unreactive complex. The et reactivity of the low ionic strength complexes depends on the particular amino acid substitution, which via electrostatic interactions alters the specific geometry of the interface between the two proteins. The presence of a negative charge at position 139 of FNR allows the most optimal orientations for et at ionic strengths below 200 mM.

Amino Acid Substitution↗

PubMed1989

Isolation, sequence, and expression in Escherichia coli of an unusual thioredoxin gene from the cyanobacterium Anabaena sp. strain PCC 7120.

Two sequences with homology to a thioredoxin oligonucleotide probe were detected by Southern blot analysis of Anabaena sp. strain PCC 7120 genomic DNA. One of the sequences was shown to code for a protein with 37% amino acid identity to thioredoxins from Escherichia coli and Anabaena sp. strain PCC 7119. This is in contrast to the usual 50% homology observed among most procaryotic thioredoxins. One gene was identified in a library and was subcloned into a pUC vector and used to transform E. coli strains lacking functional thioredoxin. The Anabaena strain 7120 thioredoxin gene did not complement the trxA mutation in E. coli. Transformed cells were not able to use methionine sulfoxide as a methionine source or support replication of T7 bacteriophage or the filamentous viruses M13 and f1. Sequence analysis of a 720-base-pair TaqI fragment indicated an open reading frame of 115 amino acids. The Anabaena strain 7120 thioredoxin gene was expressed in E. coli, and the protein was purified by assaying for protein disulfide reductase activity, using insulin as a substrate. The Anabaena strain 7120 thioredoxin exhibited the properties of a conventional thioredoxin. It is a small heat-stable redox protein and an efficient protein disulfide reductase. It is not a substrate for E. coli thioredoxin reductase. Chemically reduced Anabaena strain 7120 thioredoxin was able to serve as reducing agent for both E. coli and Anabaena strain 7119 ribonucleotide reductases, although with less efficiency than the homologous counterparts. The Anabaena strain 7120 thioredoxin cross-reacted with polyclonal antibodies to Anabaena strain 7119 thioredoxin. However, this unusual thioredoxin was not detected in extracts of Anabaena strain 7120, and its physiological function is unknown.

Amino Acid Sequence↗

PubMed2002

Phylogenetic comparison of the cyanobacterial genera Anabaena and Aphanizomenon.

Morphological analysis and sequencing of the 165 rRNA gene, the spacer region of the ribosomal operon (ITS1) and the rbcLX (RubisCO) region was performed on 26 Anabaena strains and 14 Aphanizomenon strains isolated from several lakes in Denmark, Finland and France. Based on their morphology, Anabaena strains differed from strains of Aphanizomenon: the vegetative cells, heterocysts and akinetes were significantly wider in Anabaena than in Aphanizomenon. Phylogenetic trees based on the 16S rDNA, ITS1 and rbcLX regions showed that the planktic Anabaena strains were not distinguishable from Aphanizomenon strains. The results of the clustering of Anabaena and Aphanizomenon strains based on 16S rDNA sequences showed that these two genera are not monophyletic. Sequence analysis of the 16S rDNA, ITS1-S and rbcLX regions of the planktic Anabaena strains showed that this genus is heterogeneous. In all methods, Anabaena strains that produced different toxic compounds (e.g. anatoxin-a, microcystin and an unknown neurotoxin) were clustered separately from each other but were grouped either with non-toxic Anabaena and/or Aphanizomenon strains. Our data suggest that the planktic Anabaena and Aphanizomenon isolates belong to the same genus, regardless of their morphological differences. Thus, a taxonomic revision of the two genera is required.

Anabaena↗

PubMed1982

Regulation of glutamine synthetase activity and synthesis in free-living and symbiotic Anabaena spp.

Regulation of the synthesis and activity of glutamine synthetase (GS) in the cyanobacterium Anabaena sp. strain 7120 was studied by determining GS transferase activity and GS antigen concentration under a variety of conditions. Extracts prepared from cells growing exponentially on a medium supplemented with combined nitrogen had a GS activity of 17 mumol of gamma-glutamyl transferase activity per min per mg of protein at 37 degrees C. This activity doubled in 12 h after transfer of cells to a nitrogen-free medium, corresponding to the time required for heterocyst differentiation and the start of nitrogen fixation. Addition of NH3 to a culture 11 h after an inducing transfer immediately blocked the increase in GS activity. In the Enterobacteriaceae, addition of NH3 after induction results in the covalent modification of GS by adenylylation. The GS of Anabaena is not adenylylated by such a protocol, as shown by the resistance of the transferase activity of the enzyme to inhibition by Mg2+ and by the failure of the enzyme to incorporate 32P after NH3 upshift. Methionine sulfoximine inhibited Anabaena GS activity rapidly and irreversibly in vivo. After the addition of methionine sulfoximine to Anabaena, the level of GS antigen neither increased nor decreased, indicating that Glutamine cannot be the only small molecule capable of regulating GS synthesis. Methionine sulfoximine permitted heterocyst differentiation and nitrogenase induction to escape repression by NH3. Nitrogen-fixing cultures treated with methionine sulfoximine excreted NH3. The fern Azolla caroliniana contains an Anabaena species living in symbiotic association. The Anabaena species carries out nitrogen fixation sufficient to satisfy all of the combined nitrogen requirements of the host fern. Experiments by other workers have shown that the activity of GS in the symbiont is significantly lower than the activity of GS in free-living Anabaena. Using a sensitive radioimmune assay and a normalization procedure based on the content of diaminopimelic acid, a component unique to the symbiont, we found that the level of GS antigen in the symbiont was about 5% of the level in free-living Anabaena cells. Thus, the host fern appears to repress synthesis of Anabaena GS in the symbiotic association.

Cyanobacteria↗

PubMed1995

Two heterocyst-specific DNA rearrangements of nif operons in Anabaena cylindrica and Nostoc sp. strain Mac.

Two site-specific DNA rearrangements occur during heterocyst differentiation in the cyanobacterium Anabaena sp. strain PCC 7120: the deletion of an 11 kb element from within the nifD gene and the deletion of a 55 kb element from within the fdxN gene. Three Nostoc and six Anabaena strains were screened for the presence of the nifD and fdxN elements by Southern hybridization with Anabaena PCC 7120 DNA probes. Eight of the nine strains contained DNA sequences that were similar to the nifD element. Three strains, Nostoc sp. strain Mac, Anabaena cylindrica and Anabaena sp. strain M131, also showed significant similarity to portions of the 55 kb fdxN element. Anabaena sp. strain CA lacked both the nifD and fdxN elements. Southern analysis of vegetative cell and heterocyst DNA from A. cylindrica and a Fox+ revertant of Nostoc Mac (isolate R2) showed rearrangement of the nifD and fdxN elements in heterocysts. We found no RFLPs between Anabaena M131 and Anabaena PCC 7120 suggesting that strain M131 is a Het- derivative of strain PCC 7120.

Anabaena↗

PubMed1997

Identification and characterization of the nifV-nifZ-nifT gene region from the filamentous cyanobacterium Anabaena sp. strain PCC 7120.

The nifV and leuA genes, which encode homocitrate synthase and alpha-isopropylmalate synthase, respectively, were cloned from the filamentous cyanobacterium Anabaena sp. strain PCC 7120 by a PCR-based strategy. Since the N-terminal parts of NifV and LeuA from other bacteria are highly similar to each other, a single pair of PCR primers was used to amplify internal fragments of both Anabaena strain 7120 genes. Sequence analysis of cloned PCR products confirmed the presence of two different nifV-like DNA fragments, which were subsequently used as nifV- and leuA-specific probes, respectively, to clone XbaI fragments of 2.1 kbp (pOST4) and 2.6 kbp (pOST2). Plasmid pOST4 carried the Anabaena strain 7120 nifV-nifZ-nifT genes, whereas pOST2 contained the leuA and dapF genes. The nifVZT genes were not located in close proximity to the main nif gene cluster in Anabaena strain 7120, and therefore nifVZT forms a second nif gene cluster in this strain. Overlaps between the nifV and nifZ genes and between the nifZ and nifT genes and the presence of a 1.8-kb transcript indicated that nifVZT might form one transcriptional unit. Transcripts of nifV were induced not only in a nitrogen-depleted culture but also by iron depletion irrespective of the nitrogen status. The nifV gene in Anabaena strain 7120 was interrupted by an interposon insertion (mutant strain BMB105) and by a plasmid integration via a single crossover with a nifV internal fragment as a site for recombination (mutant strain BMB106). Both mutant strains were capable of diazotrophic growth, and their growth rates were only slightly impaired compared to that of the wild type. Heterologous complementation of the Rhodobacter capsulatus nifV mutant R229I by the Anabaena strain 7120 nifV gene corroborated the assumption that Anabaena strain 7120 nifV also encodes a homocitrate synthase. In contrast, the Anabaena strain 7120 leuA gene did not complement the nifV mutation of R229I efficiently.

2-Isopropylmalate Synthase↗

PubMed1988

Characterization of Escherichia coli-Anabaena sp. hybrid thioredoxins.

Thioredoxin is a small redox protein with an active-site disulfide/dithiol. The protein from Escherichia coli has been well characterized. The genes encoding thioredoxin in E. coli and in the filamentous cyanobacterium Anabaena PCC 7119 have been cloned and sequenced. Anabaena thioredoxin exhibits 50% amino acid identity with the E. coli protein and interacts with E. coli enzymes. The genes encoding Anabaena and E. coli thioredoxin were fused via a common restriction site in the nucleotide sequence coding for the active site of the proteins to generate hybrid genes, coding for two chimeric thioredoxins. These proteins are designated Anabaena-E. coli (A-E) thioredoxin for the construct with the Anabaena sequence from the N-terminus to the middle of the active site and the E. coli sequence to the C-terminus, and E. coli-Anabaena (E-A) for the opposite construct. The gene encoding the A-E thioredoxin complements all phenotypes of an E. coli thioredoxin-deficient strain, whereas the gene encoding E-A thioredoxin is only partially effective. Purified E-A thioredoxin exhibits a much lower catalytic efficiency with E. coli thioredoxin reductase and ribonucleotide reductase than either E. coli or Anabaena thioredoxin. In contrast, the A-E thioredoxin has a higher catalytic efficiency in these reactions than either parental protein. Reaction with antibodies to E. coli and Anabaena thioredoxins shows that the antigenic determinants for thioredoxin are located in the C-terminal part of the molecule and retain the native conformation in the hybrid proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1989

Excision of an 11-kilobase-pair DNA element from within the nifD gene in anabaena variabilis heterocysts.

The 3' region of the Anabaena variabilis nifD gene contains an 11-kilobase-pair element which is excised from the chromosome during heterocyst differentiation. We have sequenced the recombination sites which border the element in vegetative cells and the rearranged heterocyst sequences. In vegetative cells, the element was flanked by 11-base-pair direct repeats which were identical to the repeats present at the ends of the nifD element in Anabaena sp. strain PCC 7120 (Anabaena strain 7120). Although Anabaena strain 7120 and A. variabilis are quite distinct in many ways, the overall sequence similarity between the two strains for the regions sequenced was 96%. Like the Anabaena strain 7120 element, the A. variabilis element was excised in heterocysts to produce a functional nifD gene and a free circularized element which was neither amplified nor degraded. The Anabaena strain 7120 xisA gene is located at the nifK-proximal end of the nifD element and is required for excision of the element in heterocysts. The A. variabilis element also contained an xisA gene which could complement a defective Anabaena strain 7120 xisA gene. A. variabilis did not contain the equivalent of the Anabaena strain 7120 fdxN 55-kilobase-pair element.

Amino Acid Sequence↗

PubMed1993

DNA amplification fingerprinting of the Azolla-Anabaena symbiosis.

The Azolla-Anabaena symbiosis has been used for centuries as a nitrogen biofertilizer in rice paddies. Genetic improvement of the symbiosis has been limited by the difficulty in identifying Azolla-Anabaena accessions and Anabaena azollae strains. The recently developed technique of DNA amplification fingerprinting (DAF) was applied to this problem. DAF uses single, short, oligonucleotide primers of arbitrary sequence to direct amplification of a characteristic set of DNA products by a thermostable DNA polymerase in a thermocycling reaction. The products are separated in polyacrylamide gels and detected by silver staining. DAF could easily distinguish and positively identify accessions of Azolla-Anabaena with DNA extracted from the intact symbiosis. The contribution of prokaryotic Anabaena sequences to the fingerprint of the intact symbiosis, however, ranged from 0 to 77%, depending on the primer sequence. Therefore, DNA extracted from the intact symbiosis would not be suitable for Azolla taxonomy studies. The fingerprints of Anabaena strains isolated by sucrose gradient centrifugation from different species of Azolla could be easily distinguished, and DAF patterns were used to confirm the maternal pattern of transmission of Anabaena in a sexual hybrid. Template DNA extracted from roots was used to produce fingerprints for Azolla without interference from the microsymbiont. Comparison of the patterns from the parents and a hybrid gave strong evidence confirming sexual hybridization.

Anabaena↗

PubMed2003

Biotransformation of an organochlorine insecticide, endosulfan, by Anabaena species.

This study assesses the role of the blue-green algal species present in the soil in the dissipation of endosulfan and its metabolites in the soil environment. Two Anabaena species, Anabaena sp. PCC 7120 and Anabaena flos-aquae, were used in this study. Anabaena sp. PCC 7120 produced three principal biotransformation compounds, chiefly endosulfan diol (endodiol), and minor amounts of endosulfan hydroxyether and endosulfan lactone. Trace amounts of endosulfan sulfate were detected. In comparison, the biotransformation of endosulfan by Anabaena flos-aquae yielded mainly endodiol with minor amounts of endosulfan sulfate. An unknown compound was produced up to 70% from endosulfan spiked in the medium inoculated by A. flos-aquae after 8 days of incubation. Therefore, the endosulfan fate was dependent on the species. Within 1 day of incubation, two Anabaena species produced low amounts of beta-endosulfan after application of alpha-endosulfan. These results suggest the presence of isomerase in the Anabaena species. Further studies using a fermentor to control the medium pH at 7.2 to minimize chemical hydrolysis of endosulfan revealed a major production of endodiol with minor amounts of endosulfan sulfate and the unknown compound. These results showed that the production of the unknown compound might be dependent on the alkaline pH in the medium and that the production of endodiol by A. flos-aquae might be biologically controlled. This study showed that two algal species could contribute in the detoxification pathways of endosulfan in the soil environment.

Anabaena↗

PubMed1994

NADP(+)-isocitrate dehydrogenase from the cyanobacterium Anabaena sp. strain PCC 7120: purification and characterization of the enzyme and cloning, sequencing, and disruption of the icd gene.

NADP(+)-isocitrate dehydrogenase (NADP(+)-IDH) from the dinitrogen-fixing filamentous cyanobacterium Anabaena sp. strain PCC 7120 was purified to homogeneity. The native enzyme is composed of two identical subunits (M(r), 57,000) and cross-reacts with antibodies obtained against the previously purified NADP(+)-IDH from the unicellular cyanobacterium Synechocystis sp. strain PCC 6803. Anabaena NADP(+)-IDH resembles in its physicochemical and kinetic parameters the typical dimeric IDHs from prokaryotes. The gene encoding Anabaena NADP(+)-IDH was cloned by complementation of an Escherichia coli icd mutant with an Anabaena genomic library. The complementing DNA was located on a 6-kb fragment. It encodes an NADP(+)-IDH that has the same mobility as that of Anabaena NADP(+)-IDH on nondenaturing polyacrylamide gels. The icd gene was subcloned and sequenced. Translation of the nucleotide sequence gave a polypeptide of 473 amino acids that showed high sequence similarity to the E. coli enzyme (59% identity) and with IDH1 and IDH2, the two subunits of the heteromultimeric NAD(+)-IDH from Saccharomyces cerevisiae (30 to 35% identity); however, a low level of similarity to NADP(+)-IDHs of eukaryotic origin was found (23% identity). Furthermore, Anabaena NADP(+)-IDH contains a 44-residue amino acid sequence in its central region that is absent in the other IDHs so far sequenced. Attempts to generate icd mutants by insertional mutagenesis were unsuccessful, suggesting an essential role of IDH in Anabaena sp. strain PCC 7120.

Amino Acid Sequence↗

PubMed1988

Identification of the region of cyanobacterial plasmid pDU1 necessary for replication in Anabaena sp. strain M-131.

Shuttle vectors based on plasmid pDU1 from Nostoc sp. strain PCC7524 are able to replicate both in Escherichia coli and in strains of Anabaena and Nostoc spp. Derivatives partially deleted in the pDU1 portion were tested for their ability to replicate in Anabaena sp. strain M-131. Plasmid pRL6HE containing a 1.75-kb HindIII-ScaI fragment of pDU1 replicated stably in that cyanobacterium and also in Anabaena sp. strain PCC7120. Plasmid pRL6HC, containing an even smaller HpaI-ScaI fragment (1.3 kb) replicated in Anabaena sp. strain M-131 but not in Anabaena sp. strain PCC7120. Similarly, when the 1.75-kb fragment of pDU1 was transferred from pRL6HE to another vector (pRL40 delta), the resulting plasmids replicated in Anabaena sp. strain M-131 but not in Anabaena sp. strain PCC7120.

Cyanobacteria↗

PubMed1987

Nitrogen starvation mediated by DL-7-azatryptophan in the cyanobacterium Anabaena sp. strain CA.

The addition of DL-7-azatryptophan (AZAT), a tryptophan analog, to continuous cultures of Anabaena sp. strain CA grown with 10 mM nitrate as the nitrogen source resulted in the differentiation of heterocysts. Analysis of the intracellular amino acid pools of Anabaena sp. strain CA after the addition of AZAT showed a marked decline in the intracellular glutamate pool and a slight increase in the levels of glutamine. The in vitro activity of glutamate synthase, the second enzyme involved in primary ammonia assimilation in Anabaena spp., was partially inhibited by the presence of AZAT at concentrations which are effective in triggering heterocyst formation (15% inhibition at 10 microM AZAT and up to 85% inhibition at 1.0 mM AZAT). Azaserine, a glutamine analog and potent glutamate synthase inhibitor, had no effect on the triggering of heterocyst development from undifferentiated batch and continuous cultures of Anabaena sp. strain CA. However, the presence of 1.0 microM azaserine significantly decreased the intracellular glutamate pool and increased the glutamine pool. The addition of AZAT also caused a decrease in the C-phycocyanin content of Anabaena sp. strain CA as a result of its proteolytic degradation. AZAT also had an inhibitory effect on the nitrogenase activity of Anabaena sp. strain CA. All these results suggest that AZAT causes a general nitrogen starvation of Anabaena sp. strain CA filaments, triggering heterocyst synthesis.

Acetylene↗

PubMed1978

Paracrystalline inclusions in various isolates of the blue-green bacteria Nostoc and Anabaena.

A number of different crystalline inclusions were observed in various isolates of Anabaena and Nostoc. Membrane-limited crystalline bodies were observed in 7 of 20 isolates of Anabaena and 19 of 29 isolates of Nostoc. These are spherical, single membrane-limited bodies from 0.6 to 0.1 micron in diameter. In most of the isolates they contained needle-like crystals 20 A in thickness and up to 80 nm in length. In 9 of the isolates the inclusions contained granular and fibrillar material. The number of bodies per cell varied in the different isolates from only a few, observed in many sections, up to 5 in a single section of A. subtropica (B1618). Crystalloids were observed in the cytoplasm of Anabaena sp. (1551), N. calcicola (B382), Nostoc sp. (588), and N. punctiforme (1629). In Anabaena sp. (1551) the roughly cuboidal inclusions 0.6 micron in diameter were composed of 100 A thick osmiophilic striations spaced to produce a 150 A periodicity. In Nostoc sp. (588) the elongate, 0.1 micron by 2.5 micron, crystalloids were composed of 100 A thick osmiophilic striations spaced to produce a 200 A periodicity. N. punctiforme (1629) and N. calciola (B382) contained intrathylakoidal crystalloids which consisted of short curved segments with 100 A thick osmiophilic striations producing a 200 A periodicity. Granular areas were observed in 2 isolates of Anabaena and 5 of Nostoc. These bodies found in various locations in the cells, were interpreted to be elongate structures 0.2 micron thick, 1.2 micron long and about 5 micron in depth. These inclusions were composed of 15 nm diameter granules which in some section planes appeared in rows spaced 20 nm apart. Spherical bodies up to 0.7 micron in diameter and of medium electron density were observed in 4 isolates of Anabaena and 2 of Nostoc. Convoluted inclusions were found in N. calcicola (B382) and Anabaena sp. (1551). These roughly spherical bodies up to 0.8 micron in diameter contain lighter swirled areas.

Crystallization↗