Dataset Information

Inorganic Carbon Limitation in Cells of the Wild Type and Photorespiratory Mutants of the Cyanobacterium Synechocystis sp. Strain PCC 6803

ABSTRACT: The amount of inorganic carbon represents one of the main environmental factors determining productivity of photoautotrophic organisms. Using the model cyanobacterium Synechocystis sp. PCC 6803, we performed a first metabolome study with cyanobacterial cells shifted from high CO2 (5% in air) into conditions of low CO2 (LC; ambient air with 0.035% CO2). Using gas chromatography-mass spectrometry, 74 metabolites were reproducibly identified under different growth conditions. Shifting wild-type cells into LC conditions resulted in a global metabolic reprogramming and involved increases of, for example, 2-oxoglutarate (2OG) and phosphoenolpyruvate, and reductions of, for example, sucrose and fructose-1,6-bisphosphate. A decrease in Calvin-Benson cycle activity and increased usage of associated carbon cycling routes, including photorespiratory metabolism, was indicated by synergistic accumulation of the fumarate, malate, and 2-phosphoglycolate pools and a transient increase of 3-phosphoglycerate. The unexpected accumulation of 2OG with a concomitant decrease of glutamine pointed toward reduced nitrogen availability when cells are confronted with LC. Despite the increase in 2OG and low amino acid pools, we found a complete dephosphorylation of the PII regulatory protein at LC characteristic for nitrogen-replete conditions. Moreover, mutants with defined blocks in the photorespiratory metabolism leading to the accumulation of glycolate and glycine, respectively, exhibited features of LC-treated wild-type cells such as the changed 2OG to glutamine ratio and PII phosphorylation state already under high CO2 conditions. Thus, metabolome profiling demonstrated that acclimation to LC involves coordinated changes of carbon and interacting nitrogen metabolism. We hypothesize that Synechocystis has a temporal lag of acclimating carbon versus nitrogen metabolism with carbon leading.

INSTRUMENT(S): GC-MS

SUBMITTER: Joachim Kopka

PROVIDER: MTBLS5 | MetaboLights | 2015-09-14

REPOSITORIES: MetaboLights

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Publications

Metabolome phenotyping of inorganic carbon limitation in cells of the wild type and photorespiratory mutants of the cyanobacterium Synechocystis sp. strain PCC 6803.

Eisenhut Marion M Huege Jan J Schwarz Doreen D Bauwe Hermann H Kopka Joachim J Hagemann Martin M

Plant physiology 20081022 4

The amount of inorganic carbon represents one of the main environmental factors determining productivity of photoautotrophic organisms. Using the model cyanobacterium Synechocystis sp. PCC 6803, we performed a first metabolome study with cyanobacterial cells shifted from high CO(2) (5% in air) into conditions of low CO(2) (LC; ambient air with 0.035% CO(2)). Using gas chromatography-mass spectrometry, 74 metabolites were reproducibly identified under different growth conditions. Shifting wild-ty ...[more]

PMID: 18945936

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Project description:The trophic condition related proteomes of an oxygenic photosynthetic cyanobacterium Synechocystis sp. PCC 6803 (glucose tolerant strain) were analyzed to get further insights into the metabolic traits governing the early exponential growth under photoautotrophic, mixotrophic and heterotrophic conditions. The cells were grown under constant light autotrophically (AT) in low (air-level) CO2 (ATLC) and in high CO2 (ATHC), mixotrophically (MT) in low (air-level) CO2 in the presence of glucose (MTLC) and heterotrophically in low (air-level) CO2 in the presence of glucose and only 10 min exposure to light every 24 hours (Light-Activated Heterotrophic Growth; LAHGLC). The proteomes of ATHC, MTLC and LAHGLC differed substantially from that of ATLC, particularly by downregulation of the inducible carbon concentrating mechanisms (CCM) and photorespiration related enzymes. On the contrary, under carbon-rich conditions (ATHC, MTLC, LAHGLC) the cells accumulated respiratory NAD(P)H dehydrogenase I complexes in the thylakoid membrane. In glucose supplemented cultures (MTLC, LAHGLC) a distinct NDH-2 protein, NdbA, additionally accumulated in the thylakoid membrane whilst the plasma membrane localized NdbC and ARTO decreased in abundance. The light-harvesting proteins together with the photosystem I and II subunits were uniquely depleted under LAHGLC condition, accumulated under ATHC and in MTLC remained at the level of the reference ATLC condition. The accumulation of P-transporters was unique, revealing only minor differences between ATLC and ATHC but strong up-regulation in MTLC and down-regulation in LAHGLC. This likely implies that MTLC stores energy surplus in the highly energetic bonds of polyphosphate polymer that can be used under unfavorable growth conditions. It is concluded that the rigor of cell growth in MTLC condition results to a great extent from high intracellular inorganic carbon conditions created upon glucose breakdown and release of CO2, beside the direct utilization of glucose-derived carbon skeletons for growth. This combination provides the MTLC cultures with excellent conditions for growth that often exceeds that of the mere photoautotrophic growth at high CO2.

Project description:Unlike all other bacteria, the physiology of cyanobacteria is based on the assimilation of organic matter from inorganic carbon driven by oxygenic photosynthesis. This setting poses special regulatory challenges, particularly in integrating carbon and nitrogen metabolism. Several regulatory factors control the primary nitrogen metabolism, such as the PII protein and proteins interacting with it (PirA, PirC or PipX), or the inactivating factors IF7 and IF17 impacting glutamine synthetase activity. However, regulatory proteins of other enzymes in the nitrogen assimilation pathway have not been described thus far. Here, we show that the 81 amino acids regulatory protein NirP1 in the cyanobacterium Synechocystis sp. PCC 6803 functions as an inhibitor of nitrite reductase, a central enzyme in the assimilation of ammonia from nitrate/nitrite. Ectopic overexpression of the nirP1 gene under standard growth conditions led to a pigmentation phenotype and delayed growth, which was correlated by the excretion of nitrite and dramatic changes in metabolite pools. We show that nitrite excretion occurs in Synechocystis wild type cells upon the shift from high CO2 (HC) to low CO2 (LC) conditions when NirP1 expression becomes activated. The expression of nirP1 is controlled by two transcription factors, NtcA, which binds to a recognition site in a repressive position above the transcription start site (TSS), and an activator, which probably binds to an element 60 to 43 nt upstream of the TSS. Therefore, the joint activity of NtcA and this activator leads to the observed induction of NirP1 under LC conditions, whereas it is repressed by shifts to nitrogen starvation. The data demonstrate that NirP1 plays a crucial role in the coordination of C and N primary metabolism in cyanobacteria by targeting the activity of one of the central enzymes. In natural environments, the excreted nitrite will be utilized by other microorganisms; therefore, NirP1 will ultimately impact the activities and composition of the surrounding microbiome.

Dataset Information

Inorganic Carbon Limitation in Cells of the Wild Type and Photorespiratory Mutants of the Cyanobacterium Synechocystis sp. Strain PCC 6803

Publications

Metabolome phenotyping of inorganic carbon limitation in cells of the wild type and photorespiratory mutants of the cyanobacterium Synechocystis sp. strain PCC 6803.

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