Glucose Assimilation Research Articles

The Influence of Exogenous CdS Nanoparticles on the Growth and Carbon Assimilation Efficiency of Escherichia coli.

This study investigated the impact of CdS nanoparticles (NPs) on Escherichia coli growth and metabolism under varying conditions. Under illumination, CdS NPs significantly enhanced bacterial growth, glucose assimilation, and biomass accumulation. Key metabolic and stress response genes showed increased expression, indicating improved ATP synthesis and oxidative stress resistance. Additionally, CdS NPs enhanced the electrochemical properties of E. coli, promoting efficient electron transfer. No significant changes were observed in the dark. These findings suggest that light-activated CdS NPs promote E. coli growth and metabolic efficiency by upregulating crucial genes involved in growth and oxidative stress management.

Deciphering the Sertoli Cell Signaling Pathway with Protein-Protein Interaction, Single-Cell Sequencing, and Gene Ontology.

Spermatogenesis constitutes a complex and intricate cascade of differentiation, indispensable for the male reproductive competence. The intercellular communication conduits of Sertoli cells (SCs) are pivotal in orchestrating this cascade ensuring sustenance and development of germ cells. Single cells and bioinformatics recently demonstrated articles are used for the regulatory modalities through which SCs modulate spermatogenesis, specifically via androgen receptors (ARs), the transforming growth factor-beta/Smad axis, mitogen-activated protein kinases, cAMP/protein kinase A (PKA), phosphatidylinositol 4,5-bisphosphate 3-kinase (PI3k)/AKT serine threonine kinase (Akt), AMP-activated protein kinase, and AR pathways. Within this framework, homeostasis of gap junction dynamics, cryptic sites and the activities at tight junctions and adherens junctions, with the integrity of the testicular barrier, glucose assimilation, lactate distribution, being governed also along with SC maturation. Disruptions in activities or abnormal concentration in derangements in AR, cAMP/PKA, and PI3k/Akt pathways, and as well as the molecules that comprise them, would present male infertility.

Efficient Fermentative Production of β-Alanine from Glucose through Multidimensional Engineering of Escherichia coli.

β-Alanine, a valuable β-type amino acid, is experiencing increased demand due to its multifaceted applications in food flavoring, nutritional supplements, pharmaceuticals, and the chemical industry. Nevertheless, the sustainable biosynthesis of β-alanine currently faces challenges due to the scarcity of robust strains, attributed to the complexities of modulating multiple genes and the inherent physiological constraints. Here, systems metabolic engineering was implemented in Escherichia coli to overcome these limitations. First, an efficient l-aspartate-α-decarboxylase (ADC) was recruited for β-alanine biosynthesis. To conserve phosphoenolpyruvate flux, we subsequently modified the endogenous glucose assimilation system by inactivating the phosphotransferase system (PTS) and introducing an alternative non-PTS system, which increased β-alanine production to 1.70 g/L. The supply of key precursors, oxaloacetate and l-aspartate, was synergistically improved through comprehensive modulation, including strengthening main flux and blocking bypass metabolism, which significantly increased the β-alanine titer to 3.43 g/L. Next, the expression of ADC was optimized by promoter and untranslated region (UTR) engineering. Further transport engineering, which involved disrupting β-alanine importer CycA and heterologously expressing β-alanine exporter NCgI0580, improved β-alanine production to 8.48 g/L. Additionally, corn steep liquor was used to develop a cost-effective medium. The final strain produced 74.03 g/L β-alanine with a yield of 0.57 mol/mol glucose during fed-batch fermentation.

Efficient Fermentative Production of d-Alanine and Other d-Amino Acids by Metabolically Engineered Corynebacterium glutamicum.

d-Amino acids (d-AAs) have wide applications in industries such as pharmaceutical, food, and cosmetics due to their unique properties. Currently, the production of d-AAs has relied on chemical synthesis or enzyme catalysts, and it is challenging to produce d-AAs via direct fermentation from glucose. We observed that Corynebacterium glutamicum exhibits a remarkable tolerance to high concentrations of d-Ala, a crucial characteristic for establishing a successful fermentation process. By optimizing meso-diaminopilmelate dehydrogenases in different C. glutamicum strains and successively deleting l-Ala biosynthetic pathways, we developed an efficient d-Ala fermentation system. The d-Ala titer was enhanced through systems metabolic engineering, which involved strengthening glucose assimilation and pyruvate supply, reducing the formation of organic acid byproducts, and attenuating the TCA cycle. During fermentation in a 5-L bioreactor, a significant accumulation of l-Ala was observed in the broth, which was subsequently diminished by introducing an l-amino acid deaminase. Ultimately, the engineered strain DA-11 produced 85 g/L d-Ala with a yield of 0.30 g/g glucose, accompanied by an optical purity exceeding 99%. The fermentation platform has the potential to be extended for the synthesis of other d-AAs, as demonstrated by the production of d-Val and d-Glu.

Ageing and mating status affect food utilization efficiencies and assimilation of macronutrients in adults of Parthenium beetle, Zygogramma bicolorata Pallister

AbstractInvestigations of age‐based food conversion and utilization efficiencies in phytophagous insects are very few. Studies examining the effects of age, sex and mating status on biochemical assimilation of macronutrients by phytophagous insects are scarce as well. Hence, we designed the present study to evaluate the combined effect of age, sex and mating status on food consumption and utilization efficiencies, and the assimilation of macronutrients by the Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae), on the invasive weed, Parthenium hysterophorus Linnaeus (Asterales: Asteraceae). We hypothesized that mated adults would consume and utilize more food than unmated adults, that assimilation of nutrients by old adults would be lower than young adults and that females would consume and utilize food more efficiently than males. However, our results revealed that as adults aged, their food consumption and utilization efficiencies decreased, and they assimilated less proteins and glucose in their body. Despite that, their mean body biomass and assimilation of triglycerides increased. While mated adults had higher food utilization efficiencies and increased assimilation of triglycerides and glucose, unmated adults assimilated more proteins. Females had higher food consumption rates and increased assimilation of nutrients, whereas males had higher food conversion efficiencies and growth rates. Furthermore, middle‐aged adults had higher food utilization efficiencies and they assimilated more nutrients than young and old adults. Our results therefore suggest compensatory feeding in adults of Z. bicolorata with ageing. We also recommend the release of more numbers of mated middle‐aged females to control P. hysterophorus in agro‐ecosystems.

Real-time Analysis of Gut-brain Neural Communication: Cortex wide Calcium Dynamics in Response to Intestinal Glucose Stimulation.

Communication between the gastrointestinal tract and the brain after nutrient absorption plays an essential role in food preference, metabolism, and feeding behaviors. Particularly concerning specific nutrients, many studies have elucidated that the assimilation of glucose within gut epithelial cells instigates the activation of many signaling molecules. Hormones such as glucagon-like peptide-1 are renowned as quintessential signaling mediators. Since hormones predominantly influence the brain through circulatory pathways, they slowly modulate brain activity. However, recent studies have shown two expeditious gut-brain pathways facilitated by the autonomic nervous system. One operates via the spinal afferent neural pathway, while the vagus nerve mediates the other. Consequently, brain responses following glucose assimilation in the gastrointestinal tract are complicated. Moreover, as intestinal stimulation finally induces diverse cortical activities, including sensory, nociceptive, reward, and motor responses, it is necessary to employ methodologies that facilitate the visualization of localized brain circuits and pan-cortical activities to comprehend gut-brain neural transmission fully. Some studies have indicated precipitous alterations in calcium ion (Ca2+) concentrations within the hypothalamus and ventral tegmental area independently through different pathways after intestinal stimulation. However, whether there are changes in cerebral cortex activity has not been known. To observe cerebral cortex activity after intragastric glucose injection, we developed an imaging technique for real-time visualization of cortex wide Ca2+ dynamics through a fully intact skull, using transgenic mice expressing genetically encoded Ca2+ indicators. This study presents a comprehensive protocol for a technique designed to monitor intestinal stimulation-induced transcranial cortex wide Ca2+ imaging following intragastric glucose injection via an implanted catheter. The preliminary data suggest that administering glucose solution into the gut activates the frontal cortex, which remains unresponsive to water administration.

Characterization of a new HUP+ Phaeodactylum tricornutum strain having improved production of eicosapentaenoic acid

AbstractBACKGROUNDEicosapentaenoic acid (EPA, 20:5) is an essential fatty acid of the omega‐3 family and its importance for prevention and treatment of several disorders has been documented. Phaeodactylum tricornutum is a prominent candidate as an EPA producer. In several microalgal species the mixotrophic growth allows improvement of cell growth and EPA production, although P. tricornutum does not have glucose transporter proteins, limiting glucose assimilation. In the present study, the growth and EPA production of P. tricornutum UTEX 646 and its transformant T‐HUP*(8), in which the glucose transporter hup1 gene was expressed, was evaluated under mixotrophic cultivation using glucose as carbon source.RESULTSInsertion of the gene hup1 in the T‐HUP*(8) strain allowed an increase in the glucose uptake of 4.4‐fold compared to the glucose consumption observed in the wild type strain. In T‐HUP*(8) the lipid content and productivity were 42% and 63% higher than in the wild type; these differences were reflected in the EPA concentration, which was enhanced up to twofold in cultivation of T‐HUP*(8) strain. The improvement observed in lipid and EPA production in the strain T‐HUP*(8) can be explained by increases of 2.97‐, 5.71‐, and 9.44‐fold in the relative expression of the genes acc1, me1, and ptd5, respectively.CONCLUSIONIncrease in glucose consumption in cultivation of the P. tricornutum T‐HUP*(8) strain caused metabolic changes that increased the lipid content and EPA specific concentration, making this strain a good candidate for improved EPA production. © 2023 Society of Chemical Industry (SCI)

Fermentation of Murta (Ugni molinae) Juice: Effect on Antioxidant Activity and Control of Enzymes Associated with Glucose Assimilation.

Berries are rich in bioactive compounds, including antioxidants and especially polyphenols, known inhibitors of starch metabolism enzymes. Lactic acid fermentation of fruits has received considerable attention due to its ability to enhance bioactivity. This study investigated the effect of fermentation with L. mesenteroides of juice from the Chilean berry murta on antioxidant activity, release of polyphenols, and inhibitory activity against α-amylase and α-glucosidase enzymes. Three types of juices (natural fruit, freeze-dried, and commercial) were fermented. Total polyphenol content (Folin-Ciocalteu), antioxidant activity (DPPH and ORAC), and the ability to inhibit α-amylase and α-glucosidase enzymes were determined. Fermented murta juices exhibited increased antioxidant activity, as evidenced by higher levels of polyphenols released during fermentation. Inhibition of α-glucosidase was observed in the three fermented juices, although no inhibition of α-amylase was observed; the juice from freeze-dried murta stood out. These findings highlight the potential health benefits of fermented murta juice, particularly its antioxidant properties and the ability to modulate sugar assimilation by inhibiting α-glucosidase.

Comparative effect of resveratrol, carnosic acid and hernandulcin on target enzymes and biochemical markers linked to carbohydrate and lipid metabolism in mice

Resveratrol (RV), carnosic acid (CA) and hernandulcin (HE; a non-caloric sweetener) are envisioned as promising nutraceuticals to designnew functional foods for improving lipid and carbohydrate metabolism. This study aimed to investigate the in vitro inhibitory effectof these molecules on specific enzyme targets and their capacity to improve distinctive markers associated to carbohydrate and lipidmetabolism in murine model. The enzymes explored were alpha-amylase, alpha-glucosidase, and pancreatic lipase whereas ICR malemice were used for in vivo testing. Saturation curves (10-200 µM mL-1) and Lineweaver-Burk regressions suggested that RV, CA andHE exerts non-competitive inhibition on pancreatic lipase, alpha-glucosidase and alpha-amylase but, CA produced a strong competitiveactivity on alpha-amylase. RV was more effective to inhibit alpha-glucosidase (IC50, 22.1 µM) whereas CA was the most effective toinhibit both alpha-amylase (IC50, 11.7 µM) and pancreatic lipase (IC50, 31.5 µM). The effects of the oral administration of RV (300 mg/kg) HE (100 mg/kg) and CA (100 mg/kg) as well as the simultaneous administration of the three compounds at the same concentration was also explored in normoglycemic and diabetic mice. In addition, the prolonged administration of these substances combined with hypercaloric/atherogenic diet for 30 days was performed. Our results revealed a clear modulatory activity in both postprandial glucose and triglyceride levels as well an improvement in biochemical markers of mice treated with hypercaloric/atherogenic diet. The administration of HE produced a notable change (p < 0.01) in postprandial glucose assimilation at 60 min post-treatment in diabetic mice, whereas the other two compounds exerted a stronger depletion of glucose levels from 30 to 120 min post-treatment. A similar trend was recorded by RV and CA in postprandial triglyceride content, however, the latter compound was more effective (p < 0.05) at lower doses than RV. The simultaneous administration of the three compounds produced a significant improvement (p < 0.01) in biochemical parameters associated to carbohydrate (insulin and glucose) and lipid metabolism (total cholesterol, LDL-c, HDL-c, triglycerides, leptin, and adiponectin).Outstandingly, the mixture of the three compounds was more effective (p < 0.01) than the administration of sole compounds to amelioratethe side effects of the hypercaloric/atherogenic diet. Finally, the body weight of treated mice significantly decreased (from 5 to 20%; p < 0.05) in comparison with mice only fed with hypercaloric/atherogenic diet. Our results suggest that mixtures of RV, HE and CA may work better than their sole administration in mice and part of their biological activity could be associated with their inhibitory properties on the enzyme targets evaluated in this investigation.
 Keywords: Carnosic acid; Hernandulcin; Resveratrol; Hypoglycemic; Hypolipidemic; Murine model; Target enzymes

Bioprocess engineering to produce essential polyunsaturated fatty acids from Thraustochytrium sp.

In recent studies, thraustochytrid has emerged as a sustainable substitute to fish oil or polyunsaturated fatty acid (PUFA) sources: docosapentaenoic acid (DPA) eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Due to growing health concerns, there is increasing demand for food and health applications of PUFA for several diseases, aquaculture feeds, and dietary products. Thraustochytrium sp. found a sustainable source for considerable PUFA and SFA production and to meet omega PUFA demand globally. This study aims to increase PUFA yield by the maximum possible glucose carbon with an appropriate nitrogen ratio (10:1). The maximum biomass and lipid obtained from 40 g/L glucose, were 7.47 ± 0.3 g/L and 4.63 g/L (60.84 ± 1.4%), respectively. However, maximum relative lipid, DHA and DPA yields were from 30 g/L glucose i.e, 67.6 ± 1.9 % and 963.58 ± 24 and 693.10 ± 24 mg/L respectively with complete glucose assimilation. Thus, this could be a potential source of commercial DPA and DHA producers under the biorefinery scheme.

Studies on the co-metabolism of glucose and glycerol in the fungus Umbelopsis isabellina

Over the past few years, it is observed an increased interest for oleaginous microorganisms in the perspective to produce microbial oils of great commercial interest through the consumption of low/zero cost substrates. In this paper, the physiology of the fungus Umbelopsis isabellina growing on blends of glycerol and glucose was investigated. In all experiments the fungus completely consumed glucose and produced satisfactory quantities of biomass containing reserve lipids in high percentages. However, glycerol concentration in the growth medium was negatively correlated to glucose assimilation rate, mainly during the balanced-growth phase. Nevertheless, at high initial concentrations, glycerol was partially consumed and seemed to contribute positively to the suppression of lipid degradation. Following the discovery of this complex regulatory mechanism regarding glucose and glycerol co-assimilation, the activity of three key-enzymes namely aldolase, glycerol kinase and glycerol dehydrogenase, which are implicated in glycerol and glucose assimilation, was investigated. The experiments revealed a clear preference of the fungus for glucose over glycerol. On the other hand, storage polysaccharides are degraded instead of storage lipid at the late oleaginous phase for maintenance purpose. These new biochemical features will enable the design of appropriate growth media for the co-fermentation of these two substrates by U. isabellina with the aim to maximize lipid accumulation.

Glucose assimilation rate determines the partition of flux at pyruvate between lactic acid and ethanol in Saccharomyces cerevisiae.

Engineered Saccharomyces cerevisiae expressing a lactic acid dehydrogenase can metabolize pyruvate into lactic acid. However, three pyruvate decarboxylase (PDC) isozymes drive most carbon flux toward ethanol rather than lactic acid. Deletion of endogenous PDCs will eliminate ethanol production, but the resulting strain suffers from C2 auxotrophy and struggles to complete a fermentation. Engineered yeast assimilating xylose or cellobiose produce lactic acid rather than ethanol as a major product without the deletion of any PDC genes. We report here that sugar flux, but not sensing, contributes to the partition of flux at the pyruvate branch point in S. cerevisiae expressing the Rhizopus oryzae lactic acid dehydrogenase (LdhA). While the membrane glucose sensors Snf3 and Rgt2 did not play any direct role in the option of predominant product, the sugar assimilation rate was strongly correlated to the partition of flux at pyruvate: fast sugar assimilation favors ethanol production while slow sugar assimilation favors lactic acid. Applying this knowledge, we created an engineered yeast capable of simultaneously converting glucose and xylose into lactic acid, increasing lactic acid production to approximately 17gL-1 from the 12gL-1 observed during sequential consumption of sugars. This work elucidates the carbon source-dependent effects on product selection in engineered yeast.

Integrated Proteomic and Metabolomic Analyses Show Differential Effects of Glucose Availability in Marine Synechococcus and Prochlorococcus.

We compared changes induced by the addition of 100 nM and 5 mM glucose on the proteome and metabolome complements in Synechococcus sp. strains WH8102, WH7803, and BL107 and Prochlorococcus sp. strains MED4, SS120, and MIT9313, grown either under standard light conditions or in darkness. Our results suggested that glucose is metabolized by these cyanobacteria, using primarily the oxidative pentoses and Calvin pathways, while no proof was found for the involvement of the Entner-Doudoroff pathway in this process. We observed differences in the effects of glucose availability, both between genera and between Prochlorococcus MED4 and SS120 strains, which might be related to their specific adaptations to the environment. We found evidence for fermentation in Prochlorococcus sp. strain SS120 and Synechococcus sp. strain WH8102 after 5 mM glucose addition. Our results additionally suggested that marine cyanobacteria can detect nanomolar glucose concentrations in the environment and that glucose might be used to sustain metabolism under darkness. Furthermore, the KaiB and KaiC proteins were also affected in Synechococcus sp. WH8102, pointing to a direct link between glucose assimilation and circadian rhythms in marine cyanobacteria. In conclusion, our study provides a wide overview on the metabolic effects induced by glucose availability in representative strains of the diverse marine picocyanobacteria, providing further evidence for the importance of mixotrophy in marine picocyanobacteria. IMPORTANCE Glucose uptake by marine picocyanobacteria has been previously described and strongly suggests they are mixotrophic organisms (capable of using energy from the sun to make organic matter, but also to directly use organic matter from the environment when available). However, a detailed analysis of the effects of glucose addition on the proteome and metabolome of these microorganisms had not been carried out. Here, we analyzed three Prochlorococcus sp. and three Synechococcus sp. strains which were representative of several marine picocyanobacterial clades. We observed differential features in the effects of glucose availability, depending on both the genus and strain; our study illuminated the strategies utilized by these organisms to metabolize glucose and showed unexpected links to other pathways, such as circadian regulation. Furthermore, we found glucose addition had profound effects in the microbiome, favoring the growth of coexisting heterotrophic bacteria.

Putative metabolism of Ca. Accumulibacter via the utilization of glucose

Ca. Accumulibacter was the predominant microorganism (relative FISH bio-abundance of 67 ± 5%) in a lab-scale sequential batch reactor that accomplished enhanced biological phosphorus removal (EBPR) while using glucose and acetate as the carbon sources (1:1 COD-based ratio). Both organic compounds were completely anaerobically consumed. The reactor's performance in terms of P/C ratio, phosphorous release and uptake, and overall kinetic and stoichiometric parameters were on the high end of the reported spectrum for EBPR systems (100:9.3 net mg phosphate removal per mg COD consumed when using glucose and acetate in a 1:1 ratio). The batch tests showed that, to the best of our knowledge, this is the first time a reactor enriched with Ca. Accumulibacter can putatively utilize glucose as the sole carbon source to biologically remove phosphate (COD:P (mg/mg) removal ratio of 100:6.3 when using only glucose). Thus, this research proposes that Ca. Accumulibacter directly anaerobically stored the fed glucose primarily as glycogen by utilizing the ATP provided via the hydrolysis of poly-P and secondarily as PHA by balancing its ATP utilization (glycogen generation) and formation (PHA storage). Alternative hypotheses are also discussed. The reported findings could challenge the conventional theories of glucose assimilation by Ca. Accumulibacter, and can be of significance for the biological removal of phosphorus from wastewaters with high contents of fermentable compounds or low VFAs.

Differential Timing for Glucose Assimilation in Prochlorococcus and Coexistent Microbial Populations in the North Pacific Subtropical Gyre.

ABSTRACTThe marine cyanobacterium Prochlorococcus can utilize glucose as a source of carbon. However, the relative importance of inorganic and organic carbon assimilation and the timing of glucose assimilation are still poorly understood in these numerically dominant cyanobacteria. Here, we investigated whole microbial community and group-specific primary production and glucose assimilation using incubations with radioisotopes combined with flow cytometry cell sorting. We also studied changes in the microbial community structure in response to glucose enrichments and analyzed the transcription of Prochlorocccus genes involved in carbon metabolism and photosynthesis. Our results showed a diel variation for glucose assimilation in Prochlorococcus, with maximum assimilation at midday and minimum at midnight (~2-fold change), which was different from that of the total microbial community. This suggests that the timing in glucose assimilation in Prochlorococcus is coupled to photosynthetic light reactions producing energy, it being more convenient for Prochlorococcus to show maximum glucose uptake precisely when the rest of microbial populations have their minimum glucose uptake. Many transcriptional responses to glucose enrichment occurred after 12- and 24-h periods, but community composition did not change. High-light Prochlorococcus strains were the most impacted by glucose addition, with transcript-level increases observed for genes in pathways for glucose metabolism, such as the pentose phosphate pathway, the Entner-Doudoroff pathway, glycolysis, respiration, and glucose transport. While Prochlorococcus C assimilation from glucose represented less than 0.1% of the bacterium’s photosynthetic C fixation, increased assimilation during the day and glcH gene upregulation upon glucose enrichment indicate an important role of mixotrophic C assimilation by natural populations of Prochlorococcus.IMPORTANCE Several studies have demonstrated that Prochlorococcus, the most abundant photosynthetic organism on Earth, can assimilate organic molecules, such as amino acids, amino sugars, ATP, phosphonates, and dimethylsulfoniopropionate. This autotroph can also assimilate small amounts of glucose, supporting the hypothesis that Prochlorococcus is mixotrophic. Our results show, for the first time, a diel variability in glucose assimilation by natural populations of Prochlorococcus with maximum assimilation during midday. Based on our previous results, this indicates that Prochlorococcus could maximize glucose uptake by using ATP made during the light reactions of photosynthesis. Furthermore, Prochlorococcus showed a different timing of glucose assimilation from the total population, which may offer considerable fitness advantages over competitors “temporal niches.” Finally, we observed transcriptional changes in some of the genes involved in carbon metabolism, suggesting that Prochlorococcus can use both pathways previously proposed in cyanobacteria to metabolize glucose.

Food web and metabolic interactions of the lung inhabitants Streptococcus pneumoniae and Pseudomonas aeruginosa.

Bacteria that successfully adapt to different substrates and environmental niches within the lung and overcome the immune defence can cause serious lung infections. Such infections are generally complex, and recognized as polymicrobial in nature. Both Pseudomonas aeruginosa and Streptococcus pneumoniae can cause chronic lung infections and were both detected in cystic fibrosis (CF) lung at different stages. In this study, single and dual species cultures of Pseudomonas aeruginosa and Streptococcus pneumoniae were studied under well-controlled planktonic growth conditions. Under pH-controlled conditions, both species apparently benefited from the presence of the other. In co-culture with P. aeruginosa, S. pneumoniae grew efficiently under aerobic conditions, whereas in pure S. pneumoniae culture, growth inhibition occurred in bioreactors with dissolved oxygen concentrations above the microaerobic range. Lactic acid and acetoin that are produced by S. pneumoniae were efficiently utilized by P. aeruginosa. In pH-uncontrolled co-cultures, the low pH triggered by S. pneumoniae assimilation of glucose and lactic acid production negatively affected the growth of both strains. Nevertheless, ammonia production improved significantly, and P. aeruginosa growth dominated at later growth stages. This study revealed unreported metabolic interactions of two important pathogenic microorganisms and shed new lights into pathophysiology of bacterial lung infection.

Carbon Assimilation by the Picoplanktonic Community Inhabiting the Secondary Chlorophyll Maximum of the Anoxic Marine Zones of the Eastern Tropical North and South Pacific

Anoxic marine zones (AMZs) constitute pelagic systems distinguished from the oxygen minimum zones (OMZs) by the complete absence of detectable oxygen and the accumulation of nitrite in mid-waters. At the top of the oxygen-depleted layer and below the oxycline, nutrients are abundant; light intensity is very much reduced (<1% of incident light) and a secondary chlorophyll maximum (SCM) is developed. The shoaling of the oxygen-depleted layer, product of the AMZ expansion, could enhance this SCM, which has little-known biogeochemical effects. Here, we show that the SCM is contributing a measurable signal in the particulate organic carbon (POC), enough to alter the δ13CPOC in the top of the oxygen-depleted layer. This data showed significant differences among stations with and without the development of a SCM, being 3.0‰ heavier when a SCM is developed, and indicating photosynthetic activity and/or remineralization in the top of the AMZ. More depleted δ13CPOC values were also found when no SCM was present indicating stronger chemoautotrophic activity, potentially driven by anammox and sulfur-oxidizing bacteria activity. Assimilation rate data show that when sufficient light and Prochlorococcus are present, photosynthesis exceeds chemoautotrophic carbon fixation, and can exceed heterotrophic assimilation of glucose or acetate. However, in the majority of the stations, assimilation rates of both glucose and acetate exceeded carbon fixation rates under light stimulation, suggesting that often the SCM is still a net heterotrophic system.

The Optimal Maturation of Subcutaneous Pouch Can Improve Pancreatic Islets Engraftment in Rat Model.

Transplantation of pancreatic islets into subcutaneous cavities in diabetic rats may be as or even more effective than transplantation into the portal vein. Identifying the optimal timing of the individual steps in this procedure is critical. Macroporous scaffolds were placed in the subcutaneous tissue of diabetic male Lewis rats for 7 or 28 d and the healing of the tissue inside the scaffolds was monitored. A marginal syngeneic graft comprising 4 islets/g of recipient body weight was transplanted at the best timing focusing mainly on vascularization. Recipients were monitored for blood glucose levels and tolerance tests. Histological examination was performed in all implanted scaffolds. The presence of individual endocrine cells was analyzed in detail. Blood glucose levels remained within the physiological range in all recipients until the end of experiment as well as body weight increase. Coefficients of glucose assimilation were normal or slightly reduced with no statistically significant differences between the groups 40 and 80 d after transplantation. Histological analysis revealed round viable islets in the liver similar to those in pancreas, but alpha cells practically disappeared, whereas islets in the scaffolds formed clusters of cells surrounded by rich vascular network and the alpha cells remained partially preserved. Subcutaneous transplantation of pancreatic islets is considerably less invasive but comparably efficient as commonly used islet transplantation into the portal vein. In consideration of alpha and beta cell ratio, the artificial subcutaneous cavities represent a promising site for future islet transplantation therapy.

Microbial carbon use efficiency and priming of soil organic matter mineralization by glucose additions in boreal forest soils with different C:N ratios

During the last decade it has been increasingly acknowledged that carbon (C) contained in root exudates can accelerate decomposition of soil organic matter (SOM), a phenomenon known as rhizosphere priming effect (RPE). However, the controlling factors and the role of different soil microorganisms in RPE are not yet well understood. There are some indications that the response of the soil microbial decomposers to labile C input in the rhizosphere depends on microbial demand of nutrients for growth and maintenance, especially that of C and nitrogen (N). To test this hypothesis, we assessed SOM decomposition induced by 13C-glucose additions during one week in forest soils with different C:N ratios (11.5–22.2). We estimated SOM respiration, the potential activity (concentration) of a range of extracellular enzymes, and incorporation of 13C and deuterium (D) in microbial phospholipid fatty acids (PLFAs).Glucose additions induced positive priming (a 12–52% increase in SOM respiration) in all soil types, but there was no linear relationship between priming and the soil C:N ratio. Instead, priming of SOM respiration was positively linked to the C:N imbalance, where a higher C:N imbalance implies stronger microbial N limitation. The total oxidative enzyme activity and the ratio between the activities of C and N acquiring enzymes were lower in soil with higher C:N ratios, but these findings could not be quantitatively linked to the observed priming rates. It appears as if glucose addition resulted in priming by stimulating the activity rather than the concentration of oxidative enzymes. Microbial incorporation of D and 13C into in PLFAs demonstrated that glucose additions stimulated both fungal and bacterial growth. The increased growth was mainly supported by glucose assimilation in fungi, while the increase in bacterial growth partly was a result of increased availability of C or N released from SOM. Taken together, the findings suggest that the soil C:N ratio is a poor predictor of priming and that priming is more dependent on the C:N imbalance, which reflects both microbial nutrient demand and nutrient provision.

Identification of genes related to hydrolysis and assimilation of Agave fructans in Candida apicola NRRL Y-50540 and Torulaspora delbrueckii NRRL Y-50541 by denovo transcriptome analysis.

Fructans are the main sugar in agave pine used by yeasts during mezcal fermentation processes, from which Candida apicola NRRL Y-50540 and Torulaspora delbrueckii NRRL Y-50541 were isolated. De novo transcriptome analysis was carried out to identify genes involved in the hydrolysis and assimilation of Agave fructans (AF). We identified a transcript annotated as SUC2, which is related to β-fructofuranosidase activity, and several differential expressed genes involved in the transcriptional regulation of SUC2 such as: MIG1, MTH1, SNF1, SNF5, REG1, SSN6, SIP1, SIP2, SIP5, GPR1, RAS2, and PKA. Some of these genes were specifically expressed in some of the yeasts according to their fructans assimilation metabolism. Different hexose transporters that could be related to the assimilation of fructose and glucose were found in both the transcriptomes. Our findings provide a better understanding of AF assimilation in these yeasts and provide resources for further metabolic engineering and biotechnology applications.