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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Poly-beta-hydroxybutyrate (PHB) accumulation in the unicellular cyanobacterium, Synechocystis sp. PCC 6803, was studied under various cultural and nutritional conditions. Under controlled condition, cells harvested at the stationary phase of growth depicted maximum accumulation of PHB, i.e., 4.5% (w/w of dry cells) as compared to lag (1.8%) or logarithmic (2.9%) phases of cultures. A temperature range of 28-32 degrees C and pH between 7.5 and 8.5 were preferred for PHB accumulation. Cells cultivated under regular light-dark cycles accumulated more PHB (4.5%) than those grown under continuous illumination (2.4%). Nitrogen and phosphorus starvation stimulated PHB accumulation up to the tune of 9.5 and 11% (w/w of dry cells), respectively. Synechocystis cells pre-grown in glucose (0.1%)-supplemented BG-11 medium when subjected to P-deficiency in presence of acetate (0.4%), PHB accumulation was boosted up to 29% (w/w of dry cells), the value almost 6-fold higher with respect to photoautotrophic condition. Fishpond discharges were found as suitable media for PHB accumulation in the test cyanobacterium.
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PMID:Optimization of cultural and nutritional conditions for accumulation of poly-beta-hydroxybutyrate in Synechocystis sp. PCC 6803. 1604 19

Cells of the psbH deletion mutant IC7 of the cyanobacterium Synechocystis PCC 6803 grown in the absence of glucose contain strongly reduced levels of chlorophyll when compared with cells grown in the presence of glucose, or compared with wild-type (WT) cells. Low-temperature fluorescence emission spectra revealed decreased content of both active PS II (Photosystem II) and PS I (Photosystem I) complexes. Analysis of thylakoid membrane complexes of IC7 by native electrophoresis showed a similar set of chlorophyll-proteins, namely a PS II core complex and trimeric and monomeric PS II complexes, as in WT. However, in contrast to WT, the (35)S-methionine protein labeling pattern of the mutant exhibited no preferential labeling of the D1 protein in the PS II core complexes, and the labeled D1 and D2 proteins accumulated predominantly in the PS II reaction center lacking CP47. The results show that in autotrophically grown cells of the psbH deletion mutant, selective D1 turnover is inhibited and synthesis of CP47 becomes a limiting step in the PS II assembly.
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PMID:Autotrophic cells of the Synechocystis psbH deletion mutant are deficient in synthesis of CP47 and accumulate inactive PS II core complexes. 1607 17

The PII signaling protein plays a pivotal role in the coordination of carbon and nitrogen metabolism in a wide variety of bacteria, Archaea, and plant chloroplasts. By using a yeast two-hybrid screening system, we identified a transmembrane protein, designated PamA (encoded by sll0985), as a PII-binding protein in Synechocystis sp. PCC 6803. The interaction between PII and PamA was confirmed in vitro, and the interaction was inhibited in the presence of ATP and 2-oxoglutarate, whereas the interaction was not influenced by the phosphorylation status of PII. Northern blot analyses revealed that the transcripts of a set of nitrogen-related genes, including nblA, nrtABCD, and ureG, were decreased in a pamA deletion mutant. The mRNA and protein levels of a group 2 sigma factor SigE were also reduced by the pamA mutation, and transcripts for sugar catabolic genes, such as gap1, zwf, and gnd that are under the control of SigE, were consequently decreased in the pamA mutant. In addition, the pamA mutant was found to be unable to grow in glucose-containing media. These results indicate that PamA has a role in the transcript control of genes for nitrogen and sugar metabolism in Synechocystis sp. PCC 6803.
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PMID:Identification of PamA as a PII-binding membrane protein important in nitrogen-related and sugar-catabolic gene expression in Synechocystis sp. PCC 6803. 1610 9

A catalase-negative mutant of the yeast Hansenula polymorpha consumed methanol in the presence of glucose when the organism was grown in carbon-limited chemostat cultures. The organism was apparently able to decompose the H(2)O(2) generated in the oxidation of methanol by alcohol oxidase. Not only H(2)O(2) generated intracellularly but also H(2)O(2) added extracellularly was effectively destroyed by the catalase-negative mutant. From the rate of H(2)O(2) consumption during growth in chemostat cultures on mixtures of glucose and H(2)O(2), it appeared that the mutant was capable of decomposing H(2)O(2) at a rate as high as 8 mmol . g of cells . h. Glutathione peroxidase (EC 1.11.1.9) was absent under all growth conditions. However, cytochrome c peroxidase (CCP; EC 1.11.1.5) increased to very high levels in cells which decomposed H(2)O(2). When wild-type H. polymorpha was grown on mixtures of glucose and methanol, the CCP level was independent of the rate of methanol utilization, whereas the level of catalase increased with increasing amounts of methanol in the substrate feed. Also, the wild type decomposed H(2)O(2) at a high rate when cells were grown on mixtures of glucose and H(2)O(2). In this case, an increase of both CCP and catalase was observed. When Saccharomyces cerevisiae was grown on mixtures of glucose and H(2)O(2), the level of catalase remained low, but CCP increased with increasing rates of H(2)O(2) utilization. From these observations and an analysis of cell yields under the various conditions, two conclusions can be drawn. (i) CCP is a key enzyme of H(2)O(2) detoxification in yeasts. (ii) Catalase can effectively compete with mitochondrial CCP for hydrogen peroxide only if hydrogen peroxide is generated at the site where catalase is located, namely in the peroxisomes.
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PMID:Hydrogen peroxide metabolism in yeasts. 1634 19

Quantitative relationships were studied between the indicators (common coliform bacteria (CCP), glucose-positive bacteria (GPB), thermoduric bacteria (TDB), coliform bacteria, enterococci, clostridia, coliphages) and the opportunistic (Pseudomonas aeruginosa, Proteus, Klebsiella) and pathogenetic (Salmonella and intestinal viruses) microorganisms at the stages of effluent purification and decontamination, in processes of self-purification in the water reservoirs and of water preparation at water-supplying stations, as well as in the association with the incidence of acute intestinal infections of bacterial and viral genesis in different climatic zones of the country. Salmonella and the opportunistic bacteria of the Enterobacteriaceae family and Pseudomonas aeruginosa were found to be highly resistant to detoxifying agents and environmental factors, adaptable, able to reproduce in pure water, to long survive in underground waters, and to accumulate when water is desalinated at the erections. The cases of intestinal infections were found in the population using the portable water of the standard quality in terms of E. coli, TDB, CCB, and enterococci. In this case only the wider integral index of GPB, which includes the indices of E. coli, TDB, CCB, as well as lactose-negative pathogenic and opportunistic species retains its sanitary significance in terms of all signs and is a reliable indicator of the potential epidemic hazard of drinking water use. Long-term studies have provided evidence for the sanitary value of coliphages as indicators of viral drinking water contamination.
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PMID:[Problems of epidemic safety of drinking water use by the population of Russia]. 1640 75

Kinetics of the redox reactions in the reaction center (P700) of photosystem I (PSI) of the cyanobacterium Synechocystis sp. PCC 6803 have been studied by EPR spectroscopy. The redox kinetics were recorded based on accumulation of the EPRI signal when the final signal was the sum of individual signals produced in response to illumination of the cells. After prolonged (more than 3 sec) dark intervals between illuminations, the kinetic curve of the EPR signal from P700+ was multiphasic. After a sharp increase in the signal amplitude at the beginning of illumination (phase I), the amplitude rapidly (for 0.1-0.2 sec) decreased (phase II). Then the signal amplitude gradually increased (phase III) until the steady rate of electron transfer was established. With short-term (1 sec) dark intervals between the flashes and also in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), the kinetics of the light-induced increase in the EPR signal from P700+ were monophasic. Inhibition with iodoacetamide of electron transport on the acceptor side of PSI under anaerobic conditions or an increase in the amount of respiration substrates on addition of glucose into a suspension of DCMU-treated wild-type cells increased the level of P700 reduction in phase III. The findings suggest that the kinetic curve of the EPR signal from P700+ is determined by both the electron entrance onto P700+ on the donor side of PSI and activity of electron acceptors of PSI.
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PMID:Effects of dark adaptation on light-induced electron transport through photosystem I in the cyanobacterium Synechocystis sp. PCC 6803. 1641 63

Chemotaxis may be important when forming cyanobacterial symbioses. However, knowledge of cyanobacterial attraction towards plants and factors affecting chemotaxis is limited. Chemo-attraction was observed in Nostoc strains 8964:3 and PCC 73102 towards exudate or crushed extract of the natural hosts Gunnera manicata, Cycas revoluta and Blasia pusilla, and the nonhost plants Trifolium repens, Arabidopsis thaliana and Oryza sativa. As all tested plant extracts generated chemotaxis, the possibility to attract cyanobacteria may be widespread in plants. Chemotaxis was reduced by increased temperature and darkness and was stimulated by phosphorous and iron starvation and elevated salt concentration. Sugars (arabinose, galactose, and glucose) had a positive effect on chemotaxis, whereas flavonoids (chrysin and naringenin) and amino acids (methionine, glycine, serine, phenylalanine, glutamine, and lysine) had no effect.
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PMID:Cyanobacterial chemotaxis to extracts of host and nonhost plants. 1646 77

The reason(s) for glucose sensitivity in certain cyanobacterial strains is poorly understood. Inactivation of genes encoding the putative sensor kinase Hik31 in Synechocystis sp. strain PCC 6803 resulted in a mutant unable to grow in the presence of D-glucose. Sensitivities to D-glucose, its analogue 2-deoxy-D-glucose, and fructose, were alleviated in mutants in which glcP, encoding the glucose transporter, was inactivated. These data indicate that permeation of these substrates is required to inflict cell death. The mutant Deltahik31, and the glucose-sensitive strain of Synechocystis, do not possess glucokinase activity, although a transcript originating from glk, encoding glucokinase, is present. Inactivation of glk led to severe sensitivity to glucose, indicating that the presence of glucose itself, within the cells, inflicted this sensitivity. On the other hand, sensitivity to 2-deoxy-D-glucose was lower in Deltaglk, thus distinguishing between the effect of glucose itself and that of its analogue, which, in the absence of glucokinase activity, may not be phosphorylated. Addition of glucose led to a small rise in glucose-6-phosphate dehydrogenase activity in the wild type, but constitutive activity was observed in the Deltahik31 mutant regardless of the presence of glucose. Microarray analyses showed only small changes in the abundance of global transcripts in Synechocystis following glucose addition, but the transcription levels of several genes, including icfG, but not glk, were strongly affected by inactivation of hik31. The mechanism(s) whereby Hik31 is involved in glucose sensing and response is discussed.
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PMID:A putative sensor kinase, Hik31, is involved in the response of Synechocystis sp. strain PCC 6803 to the presence of glucose. 1651 45

alpha-Tocopherol is synthesized exclusively in oxygenic phototrophs and is known to function as a lipid-soluble antioxidant. Here, we report that alpha-tocopherol also has a novel function independent of its antioxidant properties in the cyanobacterium Synechocystis sp. PCC 6803. The photoautotrophic growth rates of wild type and mutants impaired in alpha-tocopherol biosynthesis are identical, but the mutants exhibit elevated photosynthetic activities and glycogen levels. When grown photomixotrophically with glucose (Glc), however, these mutants cease growth within 24 h and exhibit a global macronutrient starvation response associated with nitrogen, sulfur, and carbon, as shown by decreased phycobiliprotein content (35% of the wild-type level) and accumulation of the nblA1-nblA2, sbpA, sigB, sigE, and sigH transcripts. Photosystem II activity and carboxysome synthesis are lost in the tocopherol mutants within 24 h of photomixotrophic growth, and the abundance of carboxysome gene (rbcL, ccmK1, ccmL) and ndhF4 transcripts decreases to undetectable levels. These results suggest that alpha-tocopherol plays an important role in optimizing photosynthetic activity and macronutrient homeostasis in Synechocystis sp. PCC 6803. Several lines of evidence indicate that increased oxidative stress in the tocopherol mutants is unlikely to be the underlying cause of photosystem II inactivation and Glc-induced lethality. Interestingly, insertional inactivation of the pmgA gene, which encodes a putative serine-threonine kinase similar to RsbW and RsbT in Bacillus subtilis, results in a similar increase in glycogen and Glc-induced lethality. Based on these results, we propose that alpha-tocopherol plays a nonantioxidant regulatory role in photosynthesis and macronutrient homeostasis through a signal transduction pathway that also involves PmgA.
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PMID:alpha-Tocopherol plays a role in photosynthesis and macronutrient homeostasis of the cyanobacterium Synechocystis sp. PCC 6803 that is independent of its antioxidant function. 1656 98

The hemolysin-like protein (HLP) Sll1951, characterized by the GGXGXDXUX nonapeptide motif implicated in Ca(2+) binding, was purified from the glucose-tolerant strain (GT) of Synechocystis sp. strain PCC 6803. HLP was eluted at 560 kDa after gel filtration chromatography. Atomic absorption spectroscopy indicated that the protein bound calcium. The bound Ca(2+) was not chelated with EGTA; however, it was released after being heated at 100 degrees C for 1 min, and it rebound to the Ca(2+)-depleted protein at room temperature. The apparent HLP molecular mass increased to 1,000 kDa and reverted to 560 kDa during the release and rebinding of Ca(2+), respectively. The monomers of the respective forms appeared at 90 and 200 kDa after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. HLP showed no apparent hemolytic activity against sheep erythrocytes; however, a slight hemolytic activity was detected during the conformational change caused by the rebinding of Ca(2+). Immunoelectron microscopy using polyclonal antibodies against the 200-kDa monomer revealed that HLP is located in the cell surface layer. The localization and Ca(2+)-induced reversible conformational change suggest that HLP is a member of the repeat in toxin (RTX) protein family despite its latent and low toxicity. In some other cyanobacteria, RTX proteins are reported to be necessary for cell motility. However, the GT was immotile. Moreover, the motile wild-type strain did not express any HLP, suggesting that HLP is one of the factors involved in the elimination of motility in the GT. We concluded that the involvement of RTX protein in cyanobacterial cell motility is not a general feature.
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PMID:Purification and characterization of a hemolysin-like protein, Sll1951, a nontoxic member of the RTX protein family from the Cyanobacterium Synechocystis sp. strain PCC 6803. 1667 8


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