Nitrogen Availability Affects the Metabolic Profile in Cyanobacteria.
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ABSTRACT:
SUBMITTER: Inabe K
PROVIDER: S-EPMC8707274 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Dinitrogen (N2) fixation is a major source of external nitrogen (N) to aquatic ecosystems and therefore exerts control over productivity. Studies have shown that N2 -fixers release freshly fixed N into the environment, but the causes for this N release are largely unclear. Here, we show that the availability of phosphate can directly affect the transfer of freshly fixed N to epibionts in filamentous, diazotrophic cyanobacteria. Stable-isotope incubations coupled to single-cell analyses showed that <1% and ~15% of freshly fixed N was transferred to epibionts of Aphanizomenon and Nodularia, respectively, at phosphate scarcity during a summer bloom in the Baltic Sea. When phosphate was added, the transfer of freshly fixed N to epibionts dropped to about half for Nodularia, whereas the release from Aphanizomenon increased slightly. At the same time, the growth rate of Nodularia roughly doubled, indicating that less freshly fixed N was released and was used for biomass production instead. Phosphate scarcity and the resulting release of freshly fixed N could explain the heavy colonization of Nodularia filaments by microorganisms during summer blooms. As such, the availability of phosphate may directly affect the partitioning of fixed N2 in colonies of diazotrophic cyanobacteria and may impact the interactions with their microbiome.
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Project description:Input of labile carbon may accelerate the decomposition of existing soil organic matter (priming effect), with the priming intensity depending on changes in soil nitrogen availability after permafrost thaw. However, experimental evidence for the linkage between the priming effect and post-thaw nitrogen availability is unavailable. Here we test the hypothesis that elevated nitrogen availability after permafrost collapse inhibits the priming effect by increasing microbial metabolic efficiency based on a combination of thermokarst-induced natural nitrogen gradient and nitrogen addition experiment. We find a negative correlation between the priming intensity and soil total dissolved nitrogen concentration along the thaw sequence. The negative effect is confirmed by the reduced priming effect after nitrogen addition. In contrast to the prevailing view, this nitrogen-regulated priming intensity is independent of extracellular enzyme activities but associated with microbial metabolic efficiency. These findings demonstrate that post-thaw nitrogen availability regulates topsoil carbon dynamics through its modification of microbial metabolic efficiency.
| S-EPMC6160441 | biostudies-literature
Project description:Carbon/nitrogen (C/N) balance sensing is a key requirement for the maintenance of cellular homeostasis. Therefore, cyanobacteria have evolved a sophisticated signal transduction network targeting the metabolite 2-oxoglutarate (2-OG), the carbon skeleton for nitrogen assimilation. It serves as a status reporter for the cellular C/N balance that is sensed by transcription factors NtcA and NdhR and the versatile PII-signaling protein. The PII protein acts as a multitasking signal-integrating regulator, combining the 2-OG signal with the energy state of the cell through adenyl-nucleotide binding. Depending on these integrated signals, PII orchestrates metabolic activities in response to environmental changes through binding to various targets. In addition to 2-OG, other status reporter metabolites have recently been discovered, mainly indicating the carbon status of the cells. One of them is cAMP, which is sensed by the PII-like protein SbtB. The present review focuses, with a main emphasis on unicellular model strains Synechoccus elongatus and Synechocystis sp. PCC 6803, on the physiological framework of these complex regulatory loops, the tight linkage to metabolism and the molecular mechanisms governing the signaling processes.
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Project description:This review summarizes recent aspects of (di)nitrogen fixation and (di)hydrogen metabolism, with emphasis on cyanobacteria. These organisms possess several types of the enzyme complexes catalyzing N(2) fixation and/or H(2) formation or oxidation, namely, two Mo nitrogenases, a V nitrogenase, and two hydrogenases. The two cyanobacterial Ni hydrogenases are differentiated as either uptake or bidirectional hydrogenases. The different forms of both the nitrogenases and hydrogenases are encoded by different sets of genes, and their organization on the chromosome can vary from one cyanobacterium to another. Factors regulating the expression of these genes are emerging from recent studies. New ideas on the potential physiological and ecological roles of nitrogenases and hydrogenases are presented. There is a renewed interest in exploiting cyanobacteria in solar energy conversion programs to generate H(2) as a source of combustible energy. To enhance the rates of H(2) production, the emphasis perhaps needs not to be on more efficient hydrogenases and nitrogenases or on the transfer of foreign enzymes into cyanobacteria. A likely better strategy is to exploit the use of radiant solar energy by the photosynthetic electron transport system to enhance the rates of H(2) formation and so improve the chances of utilizing cyanobacteria as a source for the generation of clean energy.
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Project description:Nearly half of carbon fixation and primary production originates from marine phytoplankton, and much of it occurs in episodic blooms in upwelling regimes. Here, we simulated blooms limited by nitrogen and iron by incubating Monterey Bay surface waters with subnutricline waters and inorganic nutrients and measured the whole-community transcriptomic response during mid- and late-bloom conditions. Cell counts revealed that centric and pennate diatoms (largely Pseudo-nitzschia and Chaetoceros spp.) were the major blooming taxa, but dinoflagellates, prasinophytes, and prymnesiophytes also increased. Viral mRNA significantly increased in late bloom and likely played a role in the bloom's demise. We observed conserved shifts in the genetic similarity of phytoplankton populations to cultivated strains, indicating adaptive population-level changes in community composition. Additionally, the density of single nucleotide variants (SNVs) declined in late-bloom samples for most taxa, indicating a loss of intraspecific diversity as a result of competition and a selective sweep of adaptive alleles. We noted differences between mid- and late-bloom metabolism and differential regulation of light-harvesting complexes (LHCs) under nutrient stress. While most LHCs are diminished under nutrient stress, we showed that diverse taxa upregulated specialized, energy-dissipating LHCs in low iron. We also suggest the relative expression of NRT2 compared to the expression of GSII as a marker of cellular nitrogen status and the relative expression of iron starvation-induced protein genes (ISIP1, ISIP2, and ISIP3) compared to the expression of the thiamine biosynthesis gene (thiC) as a marker of iron status in natural diatom communities. IMPORTANCE Iron and nitrogen are the nutrients that most commonly limit phytoplankton growth in the world's oceans. The utilization of these resources by phytoplankton sets the biomass available to marine systems and is of particular interest in high-nutrient, low-chlorophyll (HNLC) coastal fisheries. Previous research has described the biogeography of phytoplankton in HNLC regions and the transcriptional responses of representative taxa to nutrient limitation. However, the differential transcriptional responses of whole phytoplankton communities to iron and nitrogen limitation has not been previously described, nor has the selective pressure that these competitive bloom environments exert on major players. In addition to describing changes in the physiology of diverse phytoplankton, we suggest practical indicators of cellular nitrogen and iron status for future monitoring.
| S-EPMC9599627 | biostudies-literature
Project description:Genome sequences of two Synechococcus ecotypes inhabiting the Octopus Spring microbial mat in Yellowstone National Park revealed the presence of all genes required for nitrogenase biosynthesis. We demonstrate that nif genes of the Synechococcus ecotypes are expressed in situ in a region of the mat that varies in temperature from 53.5 degrees C to 63.4 degrees C (average 60 degrees C); transcripts are only detected at the end of the day when the mat becomes anoxic. Nitrogenase activity in mat samples was also detected in the evening. Hitherto, N2 fixation in hot spring mats was attributed either to filamentous cyanobacteria (not present at >50 degrees C in these mats) or to heterotrophic bacteria. To explore how energy-generating processes of the Synechococcus ecotypes track natural light and O2 conditions, we evaluated accumulation of transcripts encoding proteins involved in photosynthesis, respiration, and fermentation. Transcripts from photosynthesis (cpcF, cpcE, psaB, and psbB) and respiration (coxA and cydA) genes declined in the evening. In contrast, transcripts encoding enzymes that may participate in fermentation fell into two categories; some (ldh, pdhB, ald, and ackA) decreased in the evening, whereas others (pflB, pflA, adhE, and acs) increased at the end of the day and remained high into the night. Energy required for N2 fixation during the night may be derived from fermentation pathways that become prominent as the mat becomes anoxic. In a broader context, our data suggest that there are critical regulatory switches in situ that are linked to the diel cycle and that these switches alter many metabolic processes within the microbial mat.
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Project description:We used cDNA microarray technology to compare the genome-wide expression profiles of a wild type strain (BY4700) (E02, E04, E06) or the isogenic strain deleted of GLN3 and GAT1 genes (E01, E03, E05) grown in YNB medium with glutamine as nitrogen source (M.Gln) against the wild type strain grown in M.Gln after addition of rapamacyn (20 min) (E01, E02), or M.proline (M.Pro) (E03, E04) or after a two hours shift from M.Gln to M.Pro (E05, E06), all growth conditions known to modify the expression of genes involved in nitrogen utilization. These microarrays allowed to identify the set of genes that were up or down-regulated in response to the quality of the nitrogen source. To evaluate whether the majority of genes responding to the nitrogen source were dependent on Gln3 and Gat1, we compared the expression profiles of the wild type strain and of the isogenic strain deleted of GLN3 and GAT1 genes (03167b: ura3, gln3∆, gat1∆), when both strains were grown on M.Gln + rapamycin (E07), or M.Pro (E08) or after a shift from M.Gln to M.Pro (E09). We also used an independent means of identifying Gln3-Gat1 regulated genes by comparing the expression profiles in wild type and ure2∆ (4709∆URE2) strains on M.Gln medium (E10). Keywords: nitrogen availability, knock-out response
2006-07-06 | GSE2891 | GEO
Project description:The building blocks of a virus derived from de novo biosynthesis during infection and/or catabolism of preexisting host cell biomass, and the relative contribution of these 2 sources has important consequences for understanding viral biogeochemistry. We determined the uptake of extracellular nitrogen (N) and its biosynthetic incorporation into both virus and host proteins using an isotope-labeling proteomics approach in a model marine cyanobacterium Synechococcus WH8102 infected by a lytic cyanophage S-SM1. By supplying dissolved N as 15N postinfection, we found that proteins in progeny phage particles were composed of up to 41% extracellularly derived N, while proteins of the infected host cell showed almost no isotope incorporation, demonstrating that de novo amino acid synthesis continues during infection and contributes specifically and substantially to phage replication. The source of N for phage protein synthesis shifted over the course of infection from mostly host derived in the early stages to more medium derived later on. We show that the photosystem II reaction center proteins D1 and D2, which are auxiliary metabolic genes (AMGs) in the S-SM1 genome, are made de novo during infection in an apparently light-dependent manner. We also identified a small set of host proteins that continue to be produced during infection; the majority are homologs of AMGs in S-SM1 or other viruses, suggesting selective continuation of host protein production during infection. The continued acquisition of nutrients by the infected cell and their utilization for phage replication are significant for both evolution and biogeochemical impact of viruses.
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Project description:We used cDNA microarray technology to compare the genome-wide expression profiles of a wild type strain (BY4700) (E02, E04, E06) or the isogenic strain deleted of GLN3 and GAT1 genes (E01, E03, E05) grown in YNB medium with glutamine as nitrogen source (M.Gln) against the wild type strain grown in M.Gln after addition of rapamacyn (20 min) (E01, E02), or M.proline (M.Pro) (E03, E04) or after a two hours shift from M.Gln to M.Pro (E05, E06), all growth conditions known to modify the expression of genes involved in nitrogen utilization. These microarrays allowed to identify the set of genes that were up or down-regulated in response to the quality of the nitrogen source. To evaluate whether the majority of genes responding to the nitrogen source were dependent on Gln3 and Gat1, we compared the expression profiles of the wild type strain and of the isogenic strain deleted of GLN3 and GAT1 genes (03167b: ura3, gln3â, gat1â), when both strains were grown on M.Gln + rapamycin (E07), or M.Pro (E08) or after a shift from M.Gln to M.Pro (E09). We also used an independent means of identifying Gln3-Gat1 regulated genes by comparing the expression profiles in wild type and ure2â (4709âURE2) strains on M.Gln medium (E10). The hybridization signal was measured using a GSM418 laser scanner. Image analysis for each array was processed using the GenePix Pro 4.0 (Axon Instruments, Inc.) software package, which measures fluorescence intensity pairs for each gene. Following image acquisition, a visual inspection of the individual spots on each microarray (size, signal-to-noise ratio, background level, and spot uniformity) completed the flagging (present/not present, good/bad) of the data. To maximize sensitivity two scans were made, one at high laser power and high PMT (Photo Multiplier Tube) gain to detect the faintest spots, and a second one using low laser power and a PMT gain avoiding saturation. The values for spots presenting ⥠5% saturation in the first scan were calculated based on an extrapolation after linear regression analysis of the intensities from both scans. These data were then imported in the GeneSpring 7.1 (Silicon Genetics) software package, applying a per spot per chip intensity-dependent (Lowess) normalization for further analysis.
2010-07-01 | E-GEOD-2891 | biostudies-arrayexpress
Project description:Oxygen availability, along with the abundance of nutrients (such as glucose, glutamine, lipids and albumin), fluctuates significantly during tumour evolution and the recruitment of blood vessels, leukocytes and reactive fibroblasts to complex tumour microenvironments. As such, hypoxia and concomitant nutrient scarcity affect large gene expression programmes, signalling pathways, diverse metabolic reactions and various stress responses. This Review summarizes our current understanding of how these adaptations are integrated in hypoxic tumour cells and their role in disease progression.
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