Major Metabolic Shift Research Articles

Induced responses to the wheat pathogen: Tan Spot—(Pyrenophora tritici-repentis) in wheat (Triticum aestivum) focus on changes in defence associated and sugar metabolism

IntroductionTan Spot (TS) disease of wheat is caused by Pyrenophora tritici-repentis (Ptr), where most of the yield loss is linked to diseased flag leaves. As there are no fully resistant cultivars available, elucidating the responses of wheat to Ptr could inform the derivation of new resistant genotypes.ObjectivesThe study aimed to characterise the flag-leaf metabolomes of two spring wheat cultivars (Triticum aestivum L. cv. PF 080719 [PF] and cv. Fundacep Horizonte [FH]) following challenge with Ptr to gain insights into TS disease development.MethodsPF and FH plants were inoculated with a Ptr strain that produces the necrotrophic toxin ToxA. The metabolic changes in flag leaves following challenge (24, 48, 72, and 96 h post-inoculation [hpi]) with Ptr were investigated using untargeted flow infusion ionisation-high resolution mass spectroscopy (FIE-HRMS).ResultsBoth cultivars were susceptible to Ptr at the flag-leaf stage. Comparisons of Ptr- and mock-inoculated plants indicated that a major metabolic shift occurred at 24 hpi in FH, and at 48 hpi in PF. Although most altered metabolites were genotype specific, they were linked to common pathways; phenylpropanoid and flavonoid metabolism. Alterations in sugar metabolism as well as in glycolysis and glucogenesis pathways were also observed. Pathway enrichment analysis suggested that Ptr-triggered alterations in chloroplast and photosynthetic machinery in both cultivars, especially in FH at 96 hpi. In a wheat-Ptr interactome in integrative network analysis, “flavone and flavonol biosynthesis” and “starch and sucrose metabolism” were targeted as the key metabolic processes underlying PF–FH–Ptr interactions.ConclusionThese observations suggest the potential importance of flavone and flavonol biosynthesis as well as bioenergetic shifts in susceptibility to Ptr. This work highlights the value of metabolomic approaches to provide novel insights into wheat pathosystems.

Combined metabolomic and proteomic analyses reveal the aerobic and respirative life-style of Lactobacillus plantarum SXC48

O2 is considered one of the main factors affecting the survival of lactic acid bacteria used in the production of a variety of fermented foods and biotechnology industries. The aim of this study was to systematically investigate the differences of Lactobacillus plantarum SXC48 under aerobic, respiratory (aerobic condition with respiratory cofactors-heme and menaquinone supplementation) and anaerobic conditions through quantitative proteomic and metabonomic analyses. Results showed that the growth of SXC48 under respiratory condition was better. O2 impaired the carbohydrate metabolism, especially the citrate cycle pathway. A major metabolic shift was observed after supplementing respiratory cofactors, leading to increased expression of proteins mediating cellular oxidant detoxification and antioxidant activity as well as the production of more nucleotides and less l-lactate. The findings confirmed that respiration reduced the detrimental effect of O2 through the regulation of central carbohydrate, which may be useful for the development of competitive starter or probiotic cultures.

The multi-level regulation of clownfish metamorphosis by thyroid hormones

Most marine organisms have a biphasic life cycle during which pelagic larvae transform into radically different juveniles. In vertebrates, the role of thyroid hormones (THs) in triggering this transition is well known, but how the morphological and physiological changes are integrated in a coherent way with the ecological transition remains poorly explored. To gain insight into this question, we performed an integrated analysis of metamorphosis of a marine teleost, the false clownfish (Amphiprion ocellaris). We show how THs coordinate a change in color vision as well as a major metabolic shift in energy production, highlighting how it orchestrates this transformation. By manipulating the activity of liver X regulator (LXR), a major regulator of metabolism, we also identify a tight link between metabolic changes and metamorphosis progression. Strikingly, we observed that these regulations are at play in the wild, explaining how hormones coordinate energy needs with available resources during the life cycle.

Extracellular succinate induces spatially organized biofilm formation in Clostridioides difficile

Clostridioides difficile infection associated to gut microbiome dysbiosis is the leading cause for nosocomial diarrhea. The ability of C. difficile to form biofilms has been progressively linked to its pathogenesis as well as its persistence in the gut. Although C. difficile has been reported to form biofilms in an increasing number of conditions, little is known about how these biofilms are formed in the gut and what factors may trigger their formation. Here we report that succinate, a metabolite abundantly produced by the dysbiotic gut microbiota, induces in vitro biofilm formation of C. difficile strains. We characterized the morphology and spatial composition of succinate-induced biofilms, and compared to non-induced or deoxycholate (DCA) induced biofilms. Biofilms induced by succinate are significantly thicker, structurally more complex, and poorer in proteins and exopolysaccharides (EPS). We then applied transcriptomics and genetics to characterize the early stages of succinate-induced biofilm formation and we showed that succinate-induced biofilm results from major metabolic shifts and cell-wall composition changes. Similar to DCA-induced biofilms, biofilms induced by succinate depend on the presence of a rapidly metabolized sugar. Finally, although succinate can be consumed by the bacteria, we found that the extracellular succinate is in fact responsible for the induction of biofilm formation through complex regulation involving global metabolic regulators and the osmotic stress response. Thus, our work suggests that as a gut signal, succinate may drive biofilm formation and help persistence of C. difficile in the gut, increasing the risk of relapse.

LAL deficiency induced myeloid-derived suppressor cells as targets and biomarkers for lung cancer

BackgroundMyeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells in tumor microenvironment, which suppress antitumor immunity. Expansion of various MDSC subpopulations is closely associated with poor clinical outcomes in...

Phytogenic Blend Improves Intestinal Health and Reduces Obesity, Diabetes, Cholesterol and Cancers: A Path toward Customised Supplementation.

Poultry production is among the most challenging industries for pathogen control. High animal density and abundance of faecal material demand strict biosecurity measures and continual vigilance in monitoring animal health parameters. Despite this vigilance, dealing with disease outbreaks is a part of farmers’ routines. Phytogenic feed additives comprised of herbs, spices, essential oils, and oleoresins have potent antimicrobial and anti-inflammatory actions. Related studies are gaining substantial interest in human and animal health worldwide. In this study, a commercial blend phytogenic feed additive was supplemented to layers in an industrial free-range production system with 20,000 birds in both control and treatment groups. At the end of the trial, the ileum tissue was sampled for RNAseq transcriptomic analysis to study the host reaction to the supplement. Phytogenic supplement significantly inhibited four cholesterol-related pathways and reduced the Arteriosclerosis disease category towards improved cardiovascular health. The supplemented birds exhibited reduced disease susceptibility for 26 cancer categories with p-values in the range from 5.23 × 10−4 to 1.02 × 10−25. Major metabolic shifts in Lipid metabolism in combination with Carbohydrate metabolism have resulted in a decrease in the Obesity category, altering the ratio of fat and carbohydrate metabolism toward lower fat storage.

Regulation of autoimmune disease progression by Pik3ip1 through metabolic reprogramming in T cells and therapeutic implications.

Metabolic alterations could profoundly affect immune functions and influence the progression and outcome of autoimmune diseases. However, the detailed mechanisms and their therapeutic potential remain to be defined. Here, we show that phosphatidylinositide 3-kinase interacting protein 1 (Pik3ip1), a newly identified negative immune regulator, is notably down-regulated in several major autoimmune diseases through a previously unidentified mechanism mediated by interleukin-21/p38 mitogen-activated protein kinase/a disintegrin and metalloprotease-17 (ADAM17) pathway. Down-regulation of Pik3ip1 in T cells causes a major metabolic shift from oxidative phosphorylation toward aerobic glycolysis, leading to their overactivation and aggressive disease progression in experimental autoimmune encephalomyelitis (EAE) mouse model. Suppression of hypoxia-inducible factor 1α (Hif1α) or pharmacologic inhibition of glycolysis could reverse these phenotypes and largely mitigate EAE severity. Our study reveals a previously unrecognized role of Pik3ip1 in metabolic regulation that substantially affects the inflammatory loop in the autoimmune setting and identifies the Pik3ip1/Hif1α/glycolysis axis as a potential therapeutic target for treatment of autoimmune diseases.

Lysosomal acid lipase, CSF1R, and PD-L1 determine functions of CD11c+ myeloid-derived suppressor cells.

Lysosomal acid lipase (LAL) is a key enzyme in the metabolic pathway of neutral lipids. In the blood of LAL-deficient (Lal–/–) mice, increased CD11c+ cells were accompanied by upregulated programmed cell death ligand 1 (PD-L1) expression. Single-cell RNA sequencing of Lal–/– CD11c+ cells identified 2 distinctive clusters with a major metabolic shift toward glucose utilization and reactive oxygen species overproduction. Pharmacologically blocking pyruvate dehydrogenase in glycolysis not only reduced CD11c+ cells and their PD-L1 expression but also reversed their capabilities of T cell suppression and tumor growth stimulation. Colony-stimulating factor 1 receptor (CSF1R) played an essential role in controlling Lal–/– CD11c+ cell homeostasis and function and PD-L1 expression. Pharmacological inhibition of LAL activity increased CD11c, PD-L1, and CSF1R levels in both normal murine myeloid cells and human blood cells. Tumor-bearing mice and human patients with non–small cell lung cancer also showed CD11c+ cell expansion with PD-L1 and CSF1R upregulation and immunosuppression. There were positive correlations among CD11c, PD-L1, and CSF1R expression and negative correlations with LAL expression in patients with lung cancer or melanoma using The Cancer Genome Atlas database and patient samples. Therefore, CD11c+ cells switched their functions to immune suppression and tumor growth stimulation through CSF1R/PD-L1 upregulation and metabolic reprogramming.

Warburg Effect and Cancer Survival

Warburg effect is a major metabolic shift of glycolysis in cancer cells towards anaerobic fermentation. Key reaction here overproduces lactate from pyruvate catalyzed by lactate dehydrogenase-A (LDHA). Augmented Warburg effect and oncometabolism may contribute to cancer progression worsening patients’ survival. Expressions of various key enzymes were used as surrogates to validate the clinical influence of metabolic alterations in cancers. Expression and Kaplan-Meier survival data were extracted from the R2 Genomics Analysis and Visualization Platform (R2) and Human Protein Atlas (HPA). Expression of LDHA gene was 2-4 times higher than normal tissues in certain cancers including breast, colon, genitourinary and B-cell lymphomas. No cancer specificity or strong associations were observed between RNA and protein expressions of LDHA. However, higher LDHA gene expression correlated with poorer survival in renal, liver, lung, pancreatic, cervical and breast cancers. These cancers moderately or strongly stained for LDHA protein. Per HPA, gliomas had low LDHA without survival correlation. Nevertheless, this correlation was observed in the largest glioblastoma database (R2). Furthermore, 3 of 4 medulloblastoma subtypes showed poor survival with higher LDHA. Contrarily, in B-cell lymphomas and colon cancer high LDHA was a favorable prognostic marker. Poor survival correlated with high expression of other enzymes for glycolysis and amino acid metabolism (PFK-isoenzymes, GFPT2 and BCAT1). Warburg effect may not be universally dominant for all cancers, but most cancers have high LDHA and/or associated poor survival, confirming importance of this metabolic derangement in cancers. Heterogeneity of metabolic alterations can serve to diversify anti-metabolic strategies for targeted anti-cancer therapies.

The Metabolic Response to Infection With Wolbachia Implicates the Insulin/Insulin-Like-Growth Factor and Hypoxia Signaling Pathways in Drosophila melanogaster

The endosymbiotic bacteria, Wolbachia, are best known for their ability to manipulate insect-host reproduction systems that enhance their vertical transmission within host populations. Increasingly, Wolbachia have been shown to depend on their hosts' metabolism for survival and in turn provision metabolites to their host. Wolbachia depends completely on the host for iron and as such iron has been speculated to be a fundamental aspect of Wolbachia-host interplay. However, the mechanisms by which dietary iron levels, Wolbachia, and its host interact remain to be elucidated. To understand the metabolic dependence of Wolbachia on its host, the possibility of metabolic provisioning and extraction, and the interplay with available dietary iron, we have used NMR-based metabolomics and compared metabolite profiles of Wolbachia-infected and uninfected Drosophila melanogaster flies raised on varying levels of dietary iron. We observed marked metabolite differences in the affected metabolite pathways between Wolbachia-infected and uninfected Drosophila, which were dependent on the dietary iron levels. Excess iron led to lipid accumulation, whereas iron deficiency led to changes in carbohydrate levels. This represents a major metabolic shift triggered by alterations in iron levels. Lipids, some amino acids, carboxylic acids, and nucleosides were the major metabolites altered by infection. The metabolic response to infection showed a reprogramming of the mitochondrial metabolism in the host. Based on these observations, we developed a physiological model which postulates that the host's insulin/insulin-like-growth factor pathway is depressed and the hypoxia signaling pathway is activated upon Wolbachia infection. This reprogramming leads to predominantly non-oxidative metabolism in the host, whereas Wolbachia maintains oxidative metabolism. Our data also support earlier predictions of the extraction of alanine from the host while provisioning riboflavin and ATP to the host.

A metabolic switch regulates the transition between growth and diapause in C. elegans

BackgroundMetabolic activity alternates between high and low states during different stages of an organism’s life cycle. During the transition from growth to quiescence, a major metabolic shift often occurs from oxidative phosphorylation to glycolysis and gluconeogenesis. We use the entry of Caenorhabditis elegans into the dauer larval stage, a developmentally arrested stage formed in response to harsh environmental conditions, as a model to study the global metabolic changes and underlying molecular mechanisms associated with growth to quiescence transition.ResultsHere, we show that the metabolic switch involves the concerted activity of several regulatory pathways. Whereas the steroid hormone receptor DAF-12 controls dauer morphogenesis, the insulin pathway maintains low energy expenditure through DAF-16/FoxO, which also requires AAK-2/AMPKα. DAF-12 and AAK-2 separately promote a shift in the molar ratios between competing enzymes at two key branch points within the central carbon metabolic pathway diverting carbon atoms from the TCA cycle and directing them to gluconeogenesis. When both AAK-2 and DAF-12 are suppressed, the TCA cycle is active and the developmental arrest is bypassed.ConclusionsThe metabolic status of each developmental stage is defined by stoichiometric ratios within the constellation of metabolic enzymes driving metabolic flux and controls the transition between growth and quiescence.

Abstract 1473: Role of acetyltransferases CBP and p300 in de novo fatty acid synthesis in colorectal cancer

Abstract CBP/p300 are two paralogous lysine acetyltransferases that acetylate protein substrates including histones, and serve as transcriptional co-activators for numerous signaling pathways involved in tumorigenesis and cancer progression. Recently, evidence has emerged that p300 regulates the transcription of genes involved in lipogenesis in cancers. Dysregulated lipogenesis and increased de novo production of fatty acids (FA) represent a major metabolic shift in cancer. De novo FA synthesis in cancer is suggested to be a source of lipids for membrane biogenesis, a reservoir of energy, and a source of pro-survival signaling molecules. Therefore, de novo FA synthesis has been linked to survival and increased proliferation of cancer cells, representing a potential area for therapeutic intervention. While emerging evidence indicates CBP/p300 may play a key role in regulating lipogenesis, little is known about the mechanism of how these proteins control lipid production in different cancers. Colorectal cancer (CRC) is a commonly diagnosed human cancer and is a major cause of cancer-related mortality. Key regulators for de novo FA synthesis, such as FASN, have been reported to be elevated in colorectal cancer. We analyzed publically available data sets and report that in colon adenocarcinoma, the mRNA levels of CBP/p300 positively correlate with the expression of genes involved in lipogenesis, such as FASN, SREBP1 and SREBP2. Furthermore, our analysis shows that EP300 expression is negatively correlated with patient survival. Strikingly, our preliminary data suggests that HDAC inhibitors may regulate p300 activity and could serve as a therapeutic approach for suppressing lipogenesis. We are currently utilizing small molecule inhibitors, genetic manipulation of the CREBBP/EP300 genes, and biochemical experiments to investigate the role of CBP/p300 in de novo FA synthesis in colorectal cancer. We hypothesize that inhibition of CBP/p300 could be an attractive therapeutic option for inhibiting tumor growth through downregulating de novo FA synthesis in colorectal cancer. (Supported by grants from James and Esther King Biomedical Research Program and Bankhead-Coly Cancer Research Program, Florida Department of Health.) Citation Format: Aaron Waddell, Iqbal Mahmud, Daiqing Liao. Role of acetyltransferases CBP and p300 in de novo fatty acid synthesis in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1473.

TGF-b1 or hypoxia enhance glucose metabolism and lactate production via HIF1A signaling in tendon cells

ABSTRACTPurpose/Aim of the study: Healthy tendons are maintained in homeostasis through controlled usage of glucose for energy and redox equilibrium. Tendon cell stress imposed by overuse injury or vascular insufficiency is accompanied by activation of wound healing pathways which facilitate an adaptive response and the restoration of homeostasis. To understand this response at the gene expression level we have studied the in vivo effects of injected TGF-β1 in a murine model of tendinopathy, as well as treatment of murine tendon explants with either TGF-β1 or hypoxia in vitro.Methods and Results: We provide evidence (from expression patterns and immunohistochemistry) that both in vivo and in vitro, the stress response in tendon cells may be metabolically controlled in part by glycolytic reprogramming. A major feature of the response to TGF-β1 or hypoxia is activation of the Warburg pathway which generates lactate from glucose under normoxia and thereby inhibits mitochondrial energy production.Conclusions: We discuss the likely outcome of this major metabolic shift in terms of the potential benefits and damage to tendon and suggest how incorporation of this metabolic response into our understanding of initiation and progression of tendinopathies may offer new opportunities for diagnosis and the monitoring of therapies.

Pyrimidine tract-binding protein 1 mediates pyruvate kinase M2-dependent phosphorylation of signal transducer and activator of transcription 3 and oncogenesis in anaplastic large cell lymphoma

PKM2 (pyruvate kinase M2), a critical regulator of glycolysis, is phosphorylated by numerous growth factor receptors and oncogenic tyrosine kinases including NPM-ALK which is expressed in a subset of aggressive T-cell non-Hodgkin lymphomas known as anaplastic large cell lymphoma, ALK-positive. Our previous work demonstrated that phosphorylation of Y105-PKM2 by NPM-ALK regulates a major metabolic shift to promote lymphomagenesis. In addition to its role in metabolism, recent studies have shown that PKM2 promotes oncogenesis by phosphorylating nuclear STAT3 (signal transducer and activator of transcription 3) and regulating transcription of genes involved in cell survival and proliferation. We hypothesized that identification of novel PKM2 interactors could provide additional insights into its expanding functional role in cancer. To this end, immunocomplexes of FLAG-tagged PKM2 were isolated from NPM-ALK-positive ALCL (anaplastic large cell lymphoma) cells and subjected to liquid chromatography tandem mass spectrometry (LC–MS/MS) which led to the identification of polypyrimidine tract-binding protein (PTBP1) as a novel interactor of PKM2. The interaction between PTBP1 and PKM2 was restricted to the nucleus and was dependent on NPM-ALK mediated Y105 phosphorylation of PKM2. Stable shRNA-mediated silencing of PTBP1 resulted in a marked decrease in pY105-PKM2 and pY705-STAT3 which led to decreased ALCL cell proliferation and colony formation. Overall, our data demonstrate that PTBP1 interacts with PKM2 and promotes ALCL oncogenesis by facilitating PKM2-dependent activation of STAT3 within the nucleus.

Genome-Wide Investigation of Biofilm Formation in Bacillus cereus.

Bacillus cereus is a soil-dwelling Gram-positive bacterium capable of forming structured multicellular communities, or biofilms. However, the regulatory pathways controlling biofilm formation are less well understood in B. cereus In this work, we developed a method to study B. cereus biofilms formed at the air-liquid interface. We applied two genome-wide approaches, random transposon insertion mutagenesis to identify genes that are potentially important for biofilm formation, and transcriptome analyses by RNA sequencing (RNA-seq) to characterize genes that are differentially expressed in B. cereus when cells were grown in a biofilm-inducing medium. For the first approach, we identified 23 genes whose disruption by transposon insertion led to altered biofilm phenotypes. Based on the predicted function, they included genes involved in processes such as nucleotide biosynthesis, iron salvage, and antibiotic production, as well as genes encoding an ATP-dependent protease and transcription regulators. Transcriptome analyses identified about 500 genes that were differentially expressed in cells grown under biofilm-inducing conditions. One particular set of those genes may contribute to major metabolic shifts, leading to elevated production of small volatile molecules. Selected volatile molecules were shown to stimulate robust biofilm formation in B. cereus Our studies represent a genome-wide investigation of B. cereus biofilm formation.IMPORTANCE In this work, we established a robust method for B. cereus biofilm studies and applied two genome-wide approaches, transposon insertion mutagenesis and transcriptome analyses by RNA-seq, to identify genes and pathways that are potentially important for biofilm formation in B. cereus We discovered dozens of genes and two major metabolic shifts that seem to be important for biofilm formation in B. cereus Our study represents a genome-wide investigation on B. cereus biofilm formation.

Metabonomics-based analysis of Brachyspira pilosicoli's response to tiamulin reveals metabolic activity despite significant growth inhibition

Pathogenic anaerobes Brachyspira spp. are responsible for an increasing number of Intestinal Spirochaetosis (IS) cases in livestock against which few approved treatments are available. Tiamulin is used to treat swine dysentery caused by Brachyspira spp. and recently has been used to handle avian intestinal spirochaetosis (AIS). The therapeutic dose used in chickens requires further evaluation since cases of bacterial resistance to tiamulin have been reported. In this study, we evaluated the impact of tiamulin at varying concentrations on the metabolism of B. pilosicoli using a 1H-NMR-based metabonomics approach allowing the capture of the overall bacterial metabolic response to antibiotic treatment. Based on growth curve studies, tiamulin impacted bacterial growth even at very low concentration (0.008 μg/mL) although its metabolic activity was barely affected 72 h post exposure to antibiotic treatment. Only the highest dose of tiamulin tested (0.250 μg/mL) caused a major metabolic shift. Results showed that below this concentration, bacteria could maintain a normal metabolic trajectory despite significant growth inhibition by the antibiotic, which may contribute to disease reemergence post antibiotic treatment. Indeed, we confirmed that B. pilosicoli remained viable even after exposition to the highest antibiotic dose. This paper stresses the need to ensure new evaluation of bacterial viability post bacteriostatic exposure such as tiamulin to guarantee treatment efficacy and decrease antibiotic resistance development.

α/β-Hydrolase Domain 6 in the Ventromedial Hypothalamus Controls Energy Metabolism Flexibility

α/β-Hydrolase domain 6 (ABHD6) is a monoacylglycerol hydrolase that degrades the endocannabinoid 2-arachidonoylglycerol (2-AG). Although complete or peripheral ABHD6 loss of function is protective against diet-induced obesity and insulin resistance, the role of ABHD6 in the central control of energy balance is unknown. Using a viral-mediated knockout approach, targeted endocannabinoid measures, and pharmacology, we discovered that mice lacking ABHD6 from neurons of the ventromedial hypothalamus (VMHKO) have higher VMH 2-AG levels in conditions of endocannabinoid recruitment and fail to physiologically adapt to key metabolic challenges. VMHKO mice exhibited blunted fasting-induced feeding and reduced food intake, energy expenditure, and adaptive thermogenesis in response to cold exposure, high-fat feeding, and dieting (transition to a low-fat diet). Our findings identify ABHD6 as a regulator of the counter-regulatory responses to major metabolic shifts, including fasting, nutrient excess, cold, and dieting, thereby highlighting the importance of ABHD6 in the VMH in mediating energy metabolism flexibility.

Viral serine palmitoyltransferase induces metabolic switch in sphingolipid biosynthesis and is required for infection of a marine alga

Marine viruses are the most abundant biological entities in the oceans shaping community structure and nutrient cycling. The interaction between the bloom-forming alga Emiliania huxleyi and its specific large dsDNA virus (EhV) is a major factor determining the fate of carbon in the ocean, thus serving as a key host-pathogen model system. The EhV genome encodes for a set of genes involved in the de novo sphingolipid biosynthesis, not reported in any viral genome to date. We combined detailed lipidomic and biochemical analyses to characterize the functional role of this virus-encoded pathway during lytic viral infection. We identified a major metabolic shift, mediated by differential substrate specificity of virus-encoded serine palmitoyltransferase, a key enzyme of sphingolipid biosynthesis. Consequently, unique viral glycosphingolipids, composed of unusual hydroxylated C17 sphingoid bases (t17:0) were highly enriched in the infected cells, and their synthesis was found to be essential for viral assembly. These findings uncover the biochemical bases of the virus-induced metabolic rewiring of the host sphingolipid biosynthesis during the chemical "arms race" in the ocean.

Aluminum stress inhibits root growth and alters physiological and metabolic responses in chickpea (Cicer arietinum L.)

Chickpea (Cicer arietinum L.) roots were treated with aluminum (Al3+) in calcium chloride (CaCl2) solution (pH 4.7) and growth responses along with physiological and metabolic changes were investigated. Al3+ treatment for 7d resulted in a dose dependent decline of seed germination and inhibition of root growth. A significant (p ≤ 0.05) decline in fresh and dry biomass were observed after 7d of Al3+ stress. The root growth (length) was inhibited after 24 and 48 h of stress imposition. The hydrogen peroxide (H2O2) levels increased significantly (p ≤ 0.05) with respect to control in Al3+ treated roots. The hematoxylin and Evans blue assay indicated significant (p ≤ 0.05) accumulation of Al3+ in the roots and loss of plasmamembrane integrity respectively. The time-course evaluation of lipid peroxidation showed increase in malondialdehyde (MDA) after 12, 24 and 48 h of stress imposition. Al3+ treatment did not alter the MDA levels after 2 or 4 h of stress, however, a minor increase was observed after 6 and 10 h of treatment. The proton (1H) nuclear magnetic resonance (NMR) spectrum of the perchloric acid extracts showed variation in the abundance of metabolites and suggested a major metabolic shift in chickpea root during Al3+ stress. The key differences that were observed include changes in energy metabolites. Accumulation of phenolic compounds suggested its possible role in Al3+ exclusion in roots during stress. The results suggested that Al3+ alters growth pattern in chickpea and induces reactive oxygen species (ROS) production that causes physiological and metabolic changes.

Biochemical, genetic, and metabolic engineering strategies to enhance coproduction of 1-propanol and ethanol in engineered Escherichia coli

We recently reported the heterologous production of 1-propanol in Escherichia coli via extended dissimilation of succinate under anaerobic conditions through expression of the endogenous sleeping beauty mutase (Sbm) operon. In the present work, we demonstrate high-level coproduction of 1-propanol and ethanol by developing novel engineered E. coli strains with effective cultivation strategies. Various biochemical, genetic, metabolic, and physiological factors affecting relative levels of acidogenesis and solventogenesis during anaerobic fermentation were investigated. In particular, CPC-PrOH3, a plasmid-free propanogenic E. coli strain derived by activating the Sbm operon on the genome, showed high levels of solventogenesis accounting for up to 85 % of dissimilated carbon. Anaerobic fed-batch cultivation of CPC-PrOH3 with glycerol as the major carbon source produced high titers of nearly 7 g/L 1-propanol and 31 g/L ethanol, implying its potential industrial applicability. The activated Sbm pathway served as an ancillary channel for consuming reducing equivalents upon anaerobic dissimilation of glycerol, resulting in an enhanced glycerol dissimilation and a major metabolic shift from acidogenesis to solventogenesis.