Utilization of Nitrogen and Carbon Sources of Sunflower Leaves Under Different Light Conditions and Nitrogen Availability

The CbrA/B system in pseudomonads is involved in the utilization of carbon sources and carbon catabolite repression (CCR) through the activation of the small RNAs crcZ in Pseudomonas aeruginosa, and crcZ and crcY in Pseudomonas putida. Interestingly, previous works reported that the CbrA/B system activity in P. aeruginosa PAO1 and P. putida KT2442 responded differently to the presence of different carbon sources, thus raising the question of the exact nature of the signal(s) detected by CbrA. Here, we demonstrated that the CbrA/B/CrcZ(Y) signal transduction pathway is similarly activated in the two Pseudomonas species. We show that the CbrA sensor kinase is fully interchangeable between the two species and, moreover, responds similarly to the presence of different carbon sources. In addition, a metabolomics analysis supported the hypothesis that CCR responds to the internal energy status of the cell, as the internal carbon/nitrogen ratio seems to determine CCR and non-CCR conditions. The strong difference found in the 2-oxoglutarate/glutamine ratio between CCR and non-CCR conditions points to the close relationship between carbon and nitrogen availability, or the relationship between the CbrA/B and NtrB/C systems, suggesting that both regulatory systems sense the same sort or interrelated signal.

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Glucosamine-6P and glucosamine-1P, respectively an activator and a substrate of rhodococcal ADP-glucose pyrophosphorylases, show a hint to ascertain (actino)bacterial glucosamine metabolism

10.1101/2020.04.11.018549 ◽

2020 ◽

Author(s):

AE Cereijo ◽

HM Alvarez ◽

AA Iglesias ◽

MD Asencion Diez

Keyword(s):

Carbon Storage ◽

Nitrogen Availability ◽

Carbon Sources ◽

Catalytic Performance ◽

Biofuel Production ◽

Enzyme Promiscuity ◽

Evolutionary Mechanisms ◽

Intermediary Metabolite ◽

Main Regulator ◽

Temporary Carbon Storage

AbstractRhodococcus spp. are important microorganisms for biotechnological purposes, such as bioremediation and biofuel production. The latter, founded on the oleaginous characteristic (high lipid accumulation) exhibited by many Rhodococcus species when grown in certain carbon sources under low nitrogen availability. These bacteria accumulate glycogen during exponential growth, and the glucan plays a role as an intermediary metabolite for temporary carbon storage related to lipid metabolism. The kinetic and regulatory properties of the ADP-glucose pyrophosphorylase (ADP-GlcPPase) from Rhodococcus jostii supports this hypothesis. The enzyme was found able to use glucosamine-1P as an alternative substrate. Curiously, the activity with glucosamine-1P was sensitive to glucose-6P, the main activator of actinobacterial ADP-GlcPPases. Herein, we report the study of glucosamine-1P related to the activity and regulation of ADP-GlcPPases from R. jostii and R. fascians, with the finding that glucosamine-6P is also a significant activator. Glucosamine-6P, belonging to a node between carbon and nitrogen metabolism, was identified as a main regulator in Actinobacteria. Thus, its effect on rhodococcal ADP-GlcPPases reinforces the function proposed for glycogen as temporary carbon storage. Results indicate that the activity of the studied enzymes using glucosamine-1P as a substrate responds to the activation by several metabolites that improve their catalytic performance, which strongly suggest metabolic feasibility. Then, studying the allosteric regulation exerted on an alternative activity would open two scenarios for consideration: (i) the existence of new molecules/metabolites yet undescribed, and (ii) evolutionary mechanisms underlying enzyme promiscuity that give rise new metabolic features in bacteria.

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Untargeted Metabolomics Unveil Changes in Autotrophic and Mixotrophic Galdieria sulphuraria Exposed to High-Light Intensity

International Journal of Molecular Sciences ◽

10.3390/ijms22031247 ◽

2021 ◽

Vol 22 (3) ◽

pp. 1247

Author(s):

Lu Liu ◽

Carlos Sanchez-Arcos ◽

Georg Pohnert ◽

Dong Wei

Keyword(s):

Light Exposure ◽

Carbon Sources ◽

High Light Intensity ◽

High Light ◽

Untargeted Metabolomics ◽

Membrane Thickness ◽

Light Conditions ◽

High Concentration ◽

Galdieria Sulphuraria ◽

Low Light

The thermoacidophilic red alga Galdieria sulphuraria has been optimizing a photosynthetic system for low-light conditions over billions of years, thriving in hot and acidic endolithic habitats. The growth of G. sulphuraria in the laboratory is very much dependent on light and substrate supply. Here, higher cell densities in G. sulphuraria under high-light conditions were obtained, although reductions in photosynthetic pigments were observed, which indicated this alga might be able to relieve the effects caused by photoinhibition. We further describe an extensive untargeted metabolomics study to reveal metabolic changes in autotrophic and mixotrophic G. sulphuraria grown under high and low light intensities. The up-modulation of bilayer lipids, that help generate better-ordered lipid domains (e.g., ergosterol) and keep optimal membrane thickness and fluidity, were observed under high-light exposure. Moreover, high-light conditions induced changes in amino acids, amines, and amide metabolism. Compared with the autotrophic algae, higher accumulations of osmoprotectant sugars and sugar alcohols were recorded in the mixotrophic G. sulphuraria. This response can be interpreted as a measure to cope with stress due to the high concentration of organic carbon sources. Our results indicate how G. sulphuraria can modulate its metabolome to maintain energetic balance and minimize harmful effects under changing environments.

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Nitrogen regulator GlnR controls uptake and utilization of non-phosphotransferase-system carbon sources in actinomycetes

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1508465112 ◽

2015 ◽

Vol 112 (51) ◽

pp. 15630-15635 ◽

Cited By ~ 40

Author(s):

Cheng-Heng Liao ◽

Lili Yao ◽

Ya Xu ◽

Wei-Bing Liu ◽

Ying Zhou ◽

...

Keyword(s):

Nitrogen Metabolism ◽

Carbon Metabolism ◽

Nitrogen Availability ◽

Carbon Sources ◽

Culture Conditions ◽

Saccharopolyspora Erythraea ◽

Phosphotransferase System ◽

Potential Applications ◽

Regulation Of Transport ◽

Severe Growth

The regulatory mechanisms underlying the uptake and utilization of multiple types of carbohydrates in actinomycetes remain poorly understood. In this study, we show that GlnR (central regulator of nitrogen metabolism) serves as a universal regulator of nitrogen metabolism and plays an important, previously unknown role in controlling the transport of non-phosphotransferase-system (PTS) carbon sources in actinomycetes. It was observed that GlnR can directly interact with the promoters of most (13 of 20) carbohydrate ATP-binding cassette (ABC) transporter loci and can activate the transcription of these genes in response to nitrogen availability in industrial, erythromycin-producing Saccharopolyspora erythraea. Deletion of the glnR gene resulted in severe growth retardation under the culture conditions used, with select ABC-transported carbohydrates (maltose, sorbitol, mannitol, cellobiose, trehalose, or mannose) used as the sole carbon source. Furthermore, we found that GlnR-mediated regulation of carbohydrate transport was highly conserved in actinomycetes. These results demonstrate that GlnR serves a role beyond nitrogen metabolism, mediating critical functions in carbon metabolism and crosstalk of nitrogen- and carbon-metabolism pathways in response to the nutritional states of cells. These findings provide insights into the molecular regulation of transport and metabolism of non-PTS carbohydrates and reveal potential applications for the cofermentation of biomass-derived sugars in the production of biofuels and bio-based chemicals.

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Production and Activity of Cristazarin in the Lichen-Forming Fungus Cladonia metacorallifera

Journal of Fungi ◽

10.3390/jof7080601 ◽

2021 ◽

Vol 7 (8) ◽

pp. 601

Author(s):

Min-Hye Jeong ◽

Chan-Ho Park ◽

Jung A Kim ◽

Eu Ddeum Choi ◽

Soonok Kim ◽

...

Keyword(s):

High Performance ◽

Polyketide Synthase ◽

Carbon Sources ◽

Bioactive Compound ◽

White Collar ◽

Light Conditions ◽

Red Pigments ◽

Preparative Scale ◽

Ic50 Values ◽

White Collar Genes

Lichens are a natural source of bioactive compounds. Cladonia metacorallifera var. reagens KoLRI002260 is a rare lichen known to produce phenolic compounds, such as rhodocladonic, thamnolic, and didymic acids. However, these metabolites have not been detected in isolated mycobionts. We investigated the effects of six carbon sources on metabolite biosynthesis in the C. metacorallifera mycobiont. Red pigments appeared only in Lilly and Barnett’s media with fructose at 15 °C after 3 weeks of culture and decreased after 6 weeks. We purified these red pigments using preparative-scale high performance liquid chromatography and analyzed them via nuclear magnetic resonance. Results indicated that 1% fructose-induced cristazarin and 6-methylcristazarin production under light conditions. In total, 27 out of 30 putative polyketide synthase genes were differentially expressed after 3 weeks of culture, implying that these genes may be required for cristazarin production in C. metacorallifera. Moreover, the white collar genes Cmwc-1 and Cmwc-2 were highly upregulated at all times under light conditions, indicating a possible correlation between cristazarin production and gene expression. The cancer cell lines AGS, CT26, and B16F1 were sensitive to cristazarin, with IC50 values of 18.2, 26.1, and 30.9 μg/mL, respectively, which highlights the value of cristazarin. Overall, our results suggest that 1% fructose under light conditions is required for cristazarin production by C. metacorallifera mycobionts, and cristazarin could be a good bioactive compound.

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