Ammonium assimilation in cyanobacteria

Muro‐Pastor, M. Isabel; Reyes, José Carlos Castañeda; Florencio, Francisco J.

doi:10.1007/s11120-004-2082-7

Cited by 239 publications

(192 citation statements)

References 93 publications

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“…These observations gave rise to the hypothesis that high 2OG levels are used as an indicator for N limitation (Muro-Pastor et al, 2001. In conclusion, the unexpected increase of the 2OG pool after shifts from high to low CO 2 , which is accompanied by a relative increase in the N-C ratio, found here in Synechococcus 7942 and previously in Synechocystis 6803 (Eisenhut et al, 2008a), is in contrast to previous reports of the major role of 2OG as an indicator for N limitation (Muro-Pastor et al, 2005;Forchhammer, 2008). Whereas the metabolites of the 2OG branch of the incomplete TCA cycle responded consistently in Synechococcus 7942 and Synechocystis 6803, major differences were observed in the C4 branch of the TCA cycle: namely, succinate increased whereas malate and fumarate decreased in Synechococcus 7942 when shifted from HC to LC (Fig.…”

Section: Changes In the Metabolome Of Wild-type Cells After Shifts Frcontrasting

confidence: 99%

Metabolic and Transcriptomic Phenotyping of Inorganic Carbon Acclimation in the Cyanobacterium Synechococcus elongatus PCC 7942

et al. 2011

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The amount of inorganic carbon is one of the main limiting environmental factors for photosynthetic organisms such as cyanobacteria. Using Synechococcus elongatus PCC 7942, we characterized metabolic and transcriptomic changes in cells that had been shifted from high to low CO 2 levels. Metabolic phenotyping indicated an activation of glycolysis, the oxidative pentose phosphate cycle, and glycolate metabolism at lowered CO 2 levels. The metabolic changes coincided with a general reprogramming of gene expression, which included not only increased transcription of inorganic carbon transporter genes but also genes for enzymes involved in glycolytic and photorespiratory metabolism. In contrast, the mRNA content for genes from nitrogen assimilatory pathways decreased. These observations indicated that cyanobacteria control the homeostasis of the carbon-nitrogen ratio. Therefore, results obtained from the wild type were compared with the MP2 mutant of Synechococcus 7942, which is defective for the carbon-nitrogen ratio-regulating PII protein. Metabolites and genes linked to nitrogen assimilation were differentially regulated, whereas the changes in metabolite concentrations and gene expression for processes related to central carbon metabolism were mostly similar in mutant and wild-type cells after shifts to low-CO 2 conditions. The PII signaling appears to down-regulate the nitrogen metabolism at lowered CO 2 , whereas the specific shortage of inorganic carbon is recognized by different mechanisms.

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Section: Changes In the Metabolome Of Wild-type Cells After Shifts Frcontrasting

confidence: 99%

Metabolic and Transcriptomic Phenotyping of Inorganic Carbon Acclimation in the Cyanobacterium Synechococcus elongatus PCC 7942

et al. 2011

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“…6) seems an important clue to understanding the nature of the growth inhibition in the mutant. Ammonium is incorporated into carbon skeletons of cyanobacteria mainly by the combined action of Gln synthetase and Glu synthase (GS-GOGAT cycle; Muro-Pastor et al, 2005). GS catalyzes the ATP-dependent amidation of Glu to yield Gln.…”

Section: Cause Of Growth Inhibition Of the Dcyabrb2 Mutant Under Photmentioning

confidence: 99%

Deletion of the Transcriptional Regulator cyAbrB2 Deregulates Primary Carbon Metabolism in Synechocystis sp. PCC 6803

Kaniya¹,

Kizawa²,

Miyagi

et al. 2013

Plant Physiology

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cyAbrB is a transcriptional regulator unique to and highly conserved among cyanobacterial species. A gene-disrupted mutant of cyabrB2 (sll0822) in Synechocystis sp. PCC 6803 exhibited severe growth inhibition and abnormal accumulation of glycogen granules within cells under photomixotrophic conditions. Within 6 h after the shift to photomixotrophic conditions, sodium bicarbonate-dependent oxygen evolution activity markedly declined in the DcyabrB2 mutant, but the decrease in methyl viologen-dependent electron transport activity was much smaller, indicating inhibition in carbon dioxide fixation. Decreases in the transcript levels of several genes related to sugar catabolism, carbon dioxide fixation, and nitrogen metabolism were also observed within 6 h. Metabolome analysis by capillary electrophoresis mass spectrometry revealed that several metabolites accumulated differently in the wild-type and mutant strains. For example, the amounts of pyruvate and 2-oxoglutarate (2OG) were significantly lower in the mutant than in the wild type, irrespective of trophic conditions. The growth rate of the DcyabrB2 mutant was restored to a level comparable to that under photoautotrophic conditions by addition of 2OG to the growth medium under photomixotrophic conditions. Activities of various metabolic processes, including carbon dioxide fixation, respiration, and nitrogen assimilation, seemed to be enhanced by 2OG addition. These observations suggest that cyAbrB2 is essential for the active transcription of genes related to carbon and nitrogen metabolism upon a shift to photomixotrophic conditions. Deletion of cyAbrB2 is likely to deregulate the partition of carbon between storage forms and soluble forms used for biosynthetic purposes. This disorder may cause inactivation of cellular metabolism, excess accumulation of reducing equivalents, and subsequent loss of viability under photomixotrophic conditions.

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“…Nitrate, ammonium and some amino acids inhibit nitrogenase activity and thus fully prohibit aerobic hydrogen production by cyanobacteria (Rawson, 1985). Furthermore, NH z 4 is a direct nitrogen source (nitrate is reduced to NH z 4 ) that can be incorporated into biomass via glutamine/glutamate synthase (Muro-Pastor et al, 2005). Cyanothece 51142, however, only grows at low concentrations of NH z 4 (below 1 mM) because of an inhibition effect (Galmozzi et al, 2007;Rawson, 1985).…”

Section: Nitrogen Utilization and Nitrogenase-dependent Hydrogen Prodmentioning

confidence: 99%

Mixotrophic and photoheterotrophic metabolism in Cyanothece sp. ATCC 51142 under continuous light

et al. 2010

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The unicellular diazotrophic cyanobacterium Cyanothece sp. ATCC 51142 (Cyanothece 51142) is able to grow aerobically under nitrogen-fixing conditions with alternating light-dark cycles or continuous illumination. This study investigated the effects of carbon and nitrogen sources on Cyanothece 51142 metabolism via 13 C-assisted metabolite analysis and biochemical measurements. Under continuous light (50 mmol photons m "2 s "1 ) and nitrogen-fixing conditions, we found that glycerol addition promoted aerobic biomass growth (by twofold) and nitrogenasedependent hydrogen production [up to 25 mmol H 2 (mg chlorophyll) "1 h "1 ], but strongly reduced phototrophic CO 2 utilization. Under nitrogen-sufficient conditions, Cyanothece 51142 was able to metabolize glycerol photoheterotrophically, and the activity of light-dependent reactions (e.g. oxygen evolution) was not significantly reduced. In contrast, Synechocystis sp. PCC 6803 showed apparent mixotrophic metabolism under similar growth conditions. Isotopomer analysis also detected that Cyanothece 51142 was able to fix CO 2 via anaplerotic pathways, and to take up glucose and pyruvate for mixotrophic biomass synthesis. INTRODUCTIONRising concerns about global warming due to the greenhouse effect have renewed research focused on the biological capture of CO 2 . Cyanobacteria have versatile metabolic capabilities, which allow them to grow under autotrophic, heterotrophic and mixotrophic conditions (Bottomley & Van Baalen, 1978;Eiler, 2006;Yang et al., 2002). More importantly, some cyanobacteria can capture solar energy to fix nitrogen and generate H 2 , thereby serving as a source of biofertilizer and biofuel, while simultaneously consuming atmospheric CO 2 (Bernat et al., 2009;Dutta et al., 2005;Fay, 1992;Madamwar et al., 2000;Tamagnini et al., 2007;Tuli et al., 1996). Cyanothece sp. ATCC 51142 (Cyanothece 51142), a unicellular diazotrophic cyanobacterium, is able to grow aerobically under nitrogen-fixing conditions and has been recognized as contributing to the marine nitrogen cycle. The recent sequencing of the Cyanothece 51142 genome and its transcriptional analysis have uncovered the diurnally oscillatory metabolism of the bacterium in alternating light-dark cycles (photosynthesis during the day and nitrogen fixation at night) (Stöckel et al., 2008;Toepel et al., 2008;Welsh et al., 2008). In general, cyanobacteria use spatial or temporal separation of oxygen-sensitive nitrogen fixation and oxygen-evolving photosynthesis as a strategy for diazotrophic growth (Benemann & Weare, 1974;Fay, 1992). Interestingly, Cyanothece 51142 demonstrates simultaneous N 2 fixation and O 2 evolution under continuous-light conditions, though it appears to be unicellular (Colon-Lopez et al., 1997;Huang & Chow, 1986). For example, a recent study of the transcriptional and translational regulation of continuously illuminated Cyanothece has revealed a strong synthesis capability for nitrogenase and circadian expression of 10 % of its genes (Toepel et al., 2008). Furthermore, Cyanothece str...

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Ammonium assimilation in cyanobacteria

Cited by 239 publications

References 93 publications

Metabolic and Transcriptomic Phenotyping of Inorganic Carbon Acclimation in the Cyanobacterium Synechococcus elongatus PCC 7942

Metabolic and Transcriptomic Phenotyping of Inorganic Carbon Acclimation in the Cyanobacterium Synechococcus elongatus PCC 7942

Deletion of the Transcriptional Regulator cyAbrB2 Deregulates Primary Carbon Metabolism in Synechocystis sp. PCC 6803

Mixotrophic and photoheterotrophic metabolism in Cyanothece sp. ATCC 51142 under continuous light

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