Function Of Nutrient Availability Research Articles

Reconciling contrasting effects of nitrogen on host immunity and pathogen transmission using stoichiometric models.

Hosts rely on the availability of nutrients for growth, and for defense against pathogens. At the same time, changes in host nutrition can alter the dynamics of pathogens that rely on their host for reproduction. For primary producer hosts, enhanced nutrient loads may increase host biomass or pathogen reproduction, promoting faster density-dependent pathogen transmission. However, the effect of elevated nutrients may be reduced if hosts allocate a growth-limiting nutrient to pathogen defense. In canonical disease models, transmission is not a function of nutrient availability. Yet, including nutrient availability is necessary to mechanistically understand the response of infection to changes in the environment. Here, we explore the implications of nutrient-mediated pathogen infectivity and host immunity on infection outcomes. We developed a stoichiometric disease model that explicitly integrates the contrasting dependencies of pathogen infectivity and host immunity on nitrogen (N) and parameterized it for an algal-host system. Our findings reveal dynamic shifts in host biomass build-up, pathogen prevalence, and the force of infection along N supply gradients with N-mediated host infectivity and immunity, compared with a model in which the transmission rate was fixed. We show contrasting responses in pathogen performance with increasing N supply between N-mediated infectivity and N-mediated immunity, revealing an optimum for pathogen transmission at intermediate N supply. This was caused by N limitation of the pathogen at a low N supply and by pathogen suppression via enhanced host immunity at a high N supply. By integrating both nutrient-mediated pathogen infectivity and host immunity into a stoichiometric model, we provide a theoretical framework that is a first step in reconciling the contrasting role nutrients can have on host-pathogen dynamics.

CORRELATION OF AVAILABLE NUTRIENTS WITH YIELD OF RICE IN CALCAREOUS SOIL

Soil fertility is the function of nutrient availability in the soil. Soil properties and crop production are liable to change due to continuous cropping with long term fertilization. Correlation study is used for the study of available nutrients of agricultural soil with yield of crops. The objective of this study is to investigate the correlation between soils available nutrients and the yield of rice. The long term effect of fertilizers and manures on response of rice-wheat cropping rotation and changes in physical and chemical properties of sandy loam Typic Calciorthents was stated during rabi 1988-89 in split plot design with three replication. Four levels of chemical fertilizer were taken as main plot treatment and four levels of organic sources on nutrients were taken as sub plot treatments. The results showed that integrated use of compost and crop residue either alone or in combination of inorganic sources of nutrients augmented higher build of soil available nutrients. Soil available N, P, P2O5, K2O and S were positively and significantly correlated and available Zn and B were negatively correlated with yield of rice crop.

ABACO: A New Model of Microalgae-Bacteria Consortia for Biological Treatment of Wastewaters

Microalgae-bacteria consortia have been proposed as alternatives to conventional biological processes to treat different types of wastewaters, including animal slurry. In this work, a microalgae-bacteria consortia (ABACO) model for wastewater treatment is proposed, it being calibrated and validated using pig slurry. The model includes the most relevant features of microalgae, such as light dependence, endogenous respiration, and growth and nutrient consumption as a function of nutrient availability (especially inorganic carbon), in addition to the already reported features of heterotrophic and nitrifying bacteria. The interrelation between the different populations is also included in the model, in addition to the simultaneous release and consumption of the most relevant compounds, such as oxygen and carbon dioxide. The implementation of the model has been performed in MATLAB software; the calibration of model parameters was carried out using genetic algorithms. The ABACO model allows one to simulate the dynamics of different components in the system, and the relative proportions of microalgae, heterotrophic bacteria, and nitrifying bacteria. The percentage of each microbial population obtained with the model was confirmed by respirometric techniques. The proposed model is a powerful tool for the development of microalgae-related wastewater treatment processes, both to maximize the production of microalgal biomass and to optimize the wastewater treatment capacity.

Nutrient sensing and cAMP signaling in yeast: G-protein coupled receptor versus transceptor activation of PKA.

A major signal transduction pathway regulating cell growth and many associated physiological properties as a function of nutrient availability in the yeast Saccharomyces cerevisiae is the protein kinase A (PKA) pathway. Glucose activation of PKA is mediated by G-protein coupled receptor (GPCR) Gpr1, and secondary messenger cAMP. Other nutrients, including nitrogen, phosphate and sulfate, activate PKA in accordingly-starved cells through nutrient transceptors, but apparently without cAMP signaling. We have now used an optimized EPAC-based fluorescence resonance energy transfer (FRET) sensor to precisely monitor in vivo cAMP levels after nutrient addition. We show that GPCR-mediated glucose activation of PKA is correlated with a rapid transient increase in the cAMP level in vivo, whereas nutrient transceptor-mediated activation by nitrogen, phosphate or sulfate, is not associated with any significant increase in cAMP in vivo. We also demonstrate direct physical interaction between the Gap1 amino acid transceptor and the catalytic subunits of PKA, Tpk1, 2 and 3. In addition, we reveal a conserved consensus motif in the nutrient transceptors that is also present in Bcy1, the regulatory subunit of PKA. This suggests that nutrient transceptor activation of PKA may be mediated by direct release of bound PKA catalytic subunits, triggered by the conformational changes occurring during transport of the substrate by the transceptor. Our results support a model in which nutrient transceptors are evolutionary ancestors of GPCRs, employing a more primitive direct signaling mechanism compared to the indirect cAMP second-messenger signaling mechanism used by GPCRs for activation of PKA.

Visualising the concept of metabolic regulation in bacteria: a simple laboratory experiment on polyhydroxybutyrate storage

ABSTRACT Regulation is a key concept for understanding the dynamics of metabolism in bacteria. This report outlines a simple laboratory experiment aimed at studying a key form of regulation in bacterial metabolism, exemplifying how microbes switch the flux of carbon towards alternative metabolic fates as a function of nutrient availability and according to their physiological status. The experiment involves the use of a Sinorhizobium meliloti wild-type strain and its isogenic derivative carrying a null mutation in the gene encoding the synthase that generates the storage polymer polyhydroxybutyrate (PHB). These strains serve to characterise the effects of growth phase and carbon availability at the end of balanced growth on the extent of PHB accumulation by rhizobia. The experimental set-up can be completed in a main 4-h laboratory session, followed by an additional 1-h session after an initial incubation for subsequent bacterial-colony counting (48 h), and requires equipment usually available at any university. The protocol described here is performed by the undergraduates of our biochemistry course. We consider this exercise to be a useful complementary tool for spotlighting the concept of metabolic regulation in bacteria and for promoting scientific thinking along with the development of students’ wet-bench laboratory skills.

Nano pyrite driven root foraging increases production of the heavy feeders, viz., cauliflower, cabbage and tomato in nutrient deficient soil with no fertiliser application

Plant draws nutrition from soil and air, while former contributes minerals and water, the later provides carbon dioxide. Similar to early man, who wandered around, hunting for resources, roots ‘forage’ underneath into the soil for nutrients. Root foraging is a function of nutrient availability. Here, for the first time, we show, root foraging which is quantified by the root architecture, can be modulated by a brief nano pyrite (FeS2) intervention. A 3 h root treatment of plant saplings with a 100 μg ml−1 suspension of nano FeS2, followed by transplantation onto a fallow land with no fertiliser application, influences root architecture and yield of cabbage, cauliflower, and tomato. These ‘heavy feeder’ vegetables drawing significant nutrients from the soil, are grown and consumed globally. This root treatment strategy, if applied for ‘heavy feeders’, can contribute towards sustainable vegetable farming with reduced fertiliser input; thus helping the marginal farmers across the world.

Skeletal Muscle TRIB3 Mediates Glucose Toxicity in Diabetes and High- Fat Diet-Induced Insulin Resistance.

In the current study, we used muscle-specific TRIB3 overexpressing (MOE) and knockout (MKO) mice to determine whether TRIB3 mediates glucose-induced insulin resistance in diabetes and whether alterations in TRIB3 expression as a function of nutrient availability have a regulatory role in metabolism. In streptozotocin diabetic mice, TRIB3 MOE exacerbated, whereas MKO prevented, glucose-induced insulin resistance and impaired glucose oxidation and defects in insulin signal transduction compared with wild-type (WT) mice, indicating that glucose-induced insulin resistance was dependent on TRIB3. In response to a high-fat diet, TRIB3 MOE mice exhibited greater weight gain and worse insulin resistance in vivo compared with WT mice, coupled with decreased AKT phosphorylation, increased inflammation and oxidative stress, and upregulation of lipid metabolic genes coupled with downregulation of glucose metabolic genes in skeletal muscle. These effects were prevented in the TRIB3 MKO mice relative to WT mice. In conclusion, TRIB3 has a pathophysiological role in diabetes and a physiological role in metabolism. Glucose-induced insulin resistance and insulin resistance due to diet-induced obesity both depend on muscle TRIB3. Under physiological conditions, muscle TRIB3 also influences energy expenditure and substrate metabolism, indicating that the decrease and increase in muscle TRIB3 under fasting and nutrient excess, respectively, are critical for metabolic homeostasis.

Marine microalgae growth and carbon partitioning as a function of nutrient availability

To understand in which way the structural differences of three marine microalgae (Nannochloropsis gaditana, Rhodomonas marina and Isochrysis sp.) affect their carbon partitioning, growth and applicability; a stoichiometric imbalance was imposed by steady carbon and other nutrients variation. Towards high nutrients concentrations/low carbon availability a decrease of 12–51% in C/N microalgae ratio was observed and maximum cell densities were achieved. Moreover, linear correlation between the nutrient input and microalgae protein content were observed. The macromolecular ratios pointed that carbohydrate was the main contributor for the C/N decrement. Although lipid content in R. marina remained constant throughout the experiment, a rise of 37–107% in N. gaditana and Isochrysis sp. was verified. Lipid fractions revealed high percentages of glycolipids in all microalgae (57–73% of total lipids). The present study shows an easy way to understand and modulate microalgae carbon partitioning relying on the field of application.

A quantitative and mechanistic model for monoclonal antibody glycosylation as a function of nutrient availability during cell culture

Monoclonal antibodies (mAbs) are currently the highest-selling products of the biopharmaceutical industry, having had global sales of over $45 billion in 2012 [1]. All commercially-available mAbs contain a consensus N-linked glycosylation site on each of the Cγ2 domains of their constant fragment (Fc). The monosaccharide composition and distribution of these N-linked carbohydrates (glycans) has been widely reported to directly impact the safety and efficacy of mAbs when administered to patients. Many studies have also shown that manufacturing bioprocess conditions (e.g. nutrient availability, metabolite accumulation, dissolved oxygen, pH, temperature and stirring speed) directly influence the composition and distribution of N-linked glycans bound to mAbs and other recombinant proteins. Given this tight interconnection between manufacturing process conditions, product quality and ensuing safety and therapeutic efficacy, mAbs and their glycosylation present a clear opportunity where process development can be guided by quality by design (QbD) principles. QbD is a conceptual framework that aims to build quality into drug products at every stage of process development. Specifically, implementation of QbD to pharmaceutical process development requires identifying critical quality attributes (CQAs) that define the drug's safety and therapeutic efficacy. QbD then uses all available information on the mechanisms that quantitatively relate process inputs with product quality to control the manufacturing process so that product CQAs are maintained and end-product quality is ensured. Within the QbD context, composition and distribution of the glycans present on the Fc of mAbs is defined as a CQA, and thus, the processes employed in their manufacture must be controlled so that their glycan distribution ensures the required safety and efficacy profiles. Under this perspective, we have defined a mathematical model that mechanistically and quantitatively describes mAb Fc glycosylation as a function of nutrient availability during cell culture. Such a model aims to be used for bioprocess design, control and optimisation, thus facilitating the manufacture of mAbs with built-in glycosylation-associated quality under the QbD scope.

Floristic patterns, ecological gradients and biodiversity in the composite channels (Central Alps, Italy)

Composite channels in the alpine region are heterogeneous environments resulting from a variety of erosive and depositional processes. They can have different ecological functions: habitats for plant species, conduits, filters, sources and sinks. They can contain sparse, intermittent vegetation cover, and are frequently free of vegetation except along the banks and levees. We hypothesised that this disturbed and fragmented landscape unit encourages biodiversity with characteristic plant species adapted to survive in the channel niches. In this study, which was carried out mostly in the subalpine belt of the Adamello-Presanella Group, we aimed to characterize floristic and biodiversity patterns with respect to the dominant channel gradients by means of a canonical correspondence analysis (CCA) ordination approach and an analysis of diversity indexes. The frequency table and CCA results showed considerable floristic heterogeneity within the composite channels mainly as a function of nutrient availability and altitude. Different gradients of biodiversity (alpha, beta and gamma diversity) depended on the geomorphological disturbances (alpha and gamma) and environmental heterogeneity across the channel subunits. Geomorphological processes seem to play key roles in the dispersal of seeds, spores and propagules and in the colonization, establishment and spread of plants in this complex environment. The composite channels could play an important refuge–habitat function for microthermic species during the widely accepted current trend of global warming.

Systems approach identifies an organic nitrogen-responsive gene network that is regulated by the master clock control gene CCA1.

Understanding how nutrients affect gene expression will help us to understand the mechanisms controlling plant growth and development as a function of nutrient availability. Nitrate has been shown to serve as a signal for the control of gene expression in Arabidopsis. There is also evidence, on a gene-by-gene basis, that downstream products of nitrogen (N) assimilation such as glutamate (Glu) or glutamine (Gln) might serve as signals of organic N status that in turn regulate gene expression. To identify genome-wide responses to such organic N signals, Arabidopsis seedlings were transiently treated with ammonium nitrate in the presence or absence of MSX, an inhibitor of glutamine synthetase, resulting in a block of Glu/Gln synthesis. Genes that responded to organic N were identified as those whose response to ammonium nitrate treatment was blocked in the presence of MSX. We showed that some genes previously identified to be regulated by nitrate are under the control of an organic N-metabolite. Using an integrated network model of molecular interactions, we uncovered a subnetwork regulated by organic N that included CCA1 and target genes involved in N-assimilation. We validated some of the predicted interactions and showed that regulation of the master clock control gene CCA1 by Glu or a Glu-derived metabolite in turn regulates the expression of key N-assimilatory genes. Phase response curve analysis shows that distinct N-metabolites can advance or delay the CCA1 phase. Regulation of CCA1 by organic N signals may represent a novel input mechanism for N-nutrients to affect plant circadian clock function.

Competitive Ability and Adaptation to Fertile and Infertile Soils in Two Eriophorum Species

We investigated the role of competition in adaptation to varying nitrogen (N) levels for two Alaskan species of Eriophorum found naturally in low— vs. high—nutrient soils. In a growth—chamber experiment, seedlings were grown at a range of proportions (0, 0.5, 1.0) of the two species and at a range of densities (n = 1,2, and 4 plants per pot) under low— and high—N treatments. In a field experiment, plants were reciprocally transplanted between low— and high—nutrient sites into both unvegetated (noncompetitive) and vegetated (competitive) plots. The two species responded similarly to density and nitrogen in pure cultures, but in mixtures the species from the high—nutrient site (E. scheuchzeri (showed a greater growth response to N than did the species from the low—nutrient site (E. vaginatum). Analyzed as a replacement series, the experiment showed a reversal in relative competitive ability (as measured by the relative crowding coefficient) of the two species between low— and high—N treatments at high density. Tissue N concentrations were higher and more responsive to N addition for E, scheuchzeri. Nitrogen use efficiency was higher for E. vaginatum in all treatments, while N uptake efficiency was higher for E. scheuchzeri in all treatments. In the field, survival, growth, and flowering responses to reciprocal transplanting suggested local adaptation of the two species to their respective home sites. In noncompetitive plots, the growth response mirrored that seen in the growth chamber. However, after 2 yr there was a clear reversal between sites in relative aboveground masses of the two species. The local species acquired more nitrogen than the alien species at both sites. We conclude that Eriophorum vaginatum and E. scheuchzeri possess traits typical of species adapted to infertile and fertile soils, respectively. The contrasting ecological responses of the two species are due, at least in part, to differences in their nutritional physiology, including differences in nutrient use efficiency, nutrient uptake efficiency, and root: shoot ratio. In the field, these differences result in differential growth, reproduction, and survival, while in the growth chamber, the differences result in differential ability to accumulate biomass and reversal in competitive ability as a function of nutrient availability. This and other studies suggest that adaptations to low, as well as high, resource levels may confer improved competitive ability.