Uniform step-by-step observer for aerobic bioreactor based on super-twisting algorithm

This paper describes a fixed-time convergent step-by-step high order sliding mode observer for a certain type of aerobic bioreactor system. The observer was developed using a hierarchical structure based on a modified super-twisting algorithm. The modification included nonlinear gains of the output error that were used to prove uniform convergence of the estimation error. An energetic function similar to a Lyapunov one was used for proving the convergence between the observer and the bioreactor variables. A nonsmooth analysis was proposed to prove the fixed-time convergence of the observer states to the bioreactor variables. The observer was tested to solve the state estimation problem of an aerobic bioreactor described by the time evolution of biomass, substrate and dissolved oxygen. This last variable was used as the output information because it is feasible to measure it online by regular sensors. Numerical simulations showed the superior behavior of this observer compared to the one having linear output error injection terms (high-gain type) and one having an output injection obtaining first-order sliding mode structure. A set of numerical simulations was developed to demonstrate how the proposed observer served to estimate real information obtained from a real aerobic process with substrate inhibition.     

Endocytic SNAREs are involved in optimal Coxiella burnetii vacuole development

Coxiella burnetii is a Gram‐negative intracellular bacterium. As previously described, both the endocytic and the autophagic pathways contribute to the maturation of Coxiella replicative vacuoles (CRVs). The large CRVs share the properties of both phagolysosomal and autophagolysosomal compartments. Vamp3, Vamp7 and Vamp8 are v‐SNAREs involved in the endocytic pathway which participate mainly in the fusion between endosomes and lysosomes. In the present study we observed that Vamp7 interacts with C. burnetii at different infection times (1 h–48 h p.i.). We have determined that a truncated mutant of Vamp7 (Vamp7 NT) and a siRNA against this SNARE protein affects the optimal development of CRVs, suggesting that Vamp7 mediates fusion events that are required for the biogenesis of CRVs. Indeed, we have observed that overexpression of Vamp7 NT inhibited the heterotypic fusion with lysosomes and the homotypic fusion between individual Coxiella phagosomes and CRVs. Moreover, we have detected in the vacuole membrane, at different infection times, the Vamp7 partners (Vti1a and Vti1b). Interestingly, treatment with chloramphenicol reduced the colocalization between C. burnetii and Vamp7, Vti1a or Vti1b, indicating that the recruitment of these SNAREs proteins is a bacteria‐driven process that favours the CRV biogenesis, likely by facilitating the interaction with the endolysosomal compartment.     

Domain Organization,Catalysis and Regulation of Eukaryotic Cystathionine Beta-Synthases

Cystathionine beta-synthase (CBS) is a key regulator of sulfur amino acid metabolism diverting homocysteine, a toxic intermediate of the methionine cycle, via the transsulfuration pathway to the biosynthesis of cysteine. Although the pathway itself is well conserved among eukaryotes, properties of eukaryotic CBS enzymes vary greatly. Here we present a side-by-side biochemical and biophysical comparison of human (hCBS), fruit fly (dCBS) and yeast (yCBS) enzymes. Preparation and characterization of the full-length and truncated enzymes, lacking the regulatory domains, suggested that eukaryotic CBS exists in one of at least two significantly different conformations impacting the enzyme’s catalytic activity, oligomeric status and regulation. Truncation of hCBS and yCBS, but not dCBS, resulted in enzyme activation and formation of dimers compared to native tetramers. The dCBS and yCBS are not regulated by the allosteric activator of hCBS, S-adenosylmethionine (AdoMet); however, they have significantly higher specific activities in the canonical as well as alternative reactions compared to hCBS. Unlike yCBS, the heme-containing dCBS and hCBS showed increased thermal stability and retention of the enzyme’s catalytic activity. The mass-spectrometry analysis and isothermal titration calorimetry showed clear presence and binding of AdoMet to yCBS and hCBS, but not dCBS. However, the role of AdoMet binding to yCBS remains unclear, unlike its role in hCBS. This study provides valuable information for understanding the complexity of the domain organization, catalytic specificity and regulation among eukaryotic CBS enzymes.     

Quantitative trait loci for foliar terpenes in a global eucalypt species

Terpenes are a diverse group of plant secondary metabolites that mediate a plethora of ecological interactions in many plant species. Despite increasing research into the genetic control of important adaptive traits in some plant species, the genetic control of terpenes in forest tree species is still relatively poorly studied. In this study, we use quantitative genetic and quantitative trait loci (QTL) analysis to investigate the genetic control of foliar terpenes in an ecologically and commercially important eucalypt species, Eucalyptus globulus. We show a moderate to high within-family broad-sense heritability and significant genetic basis to the variation in 14 of the 16 terpenes assayed. This is the first report of QTL for terpenes in this species. Eleven QTL influenced the terpenes overall. One QTL on linkage group 6 affected six of the seven different sesquiterpenes assayed (plus one monoterpene), which, in combination with highly significant correlations between these compounds, argues that their variation is influenced by a QTL with pleiotropic effect early in the biosynthetic pathway. We examine the homology of these QTL to those found in a closely related eucalypt, Eucalyptus nitens, and provide evidence that both common and unique QTL influence terpene levels.     

Effect of norepinephrine and vasopressin on renal kallikrein excretion in rats

The purpose of this study was to investigate the effect of norepinephrine and vasopressin on urinary kallikrein excretion in the rat. Two studies were undertaken: (a) acute experiments in which the rats were infused with 30% dextrose in water with the addition of norepinephrine or vasopressin, (b) chronic experiments in which the drugs were infused during seven days through an osmotic minipump. In acute experiments, urinary kallikrein excretion increased without modification in urinary flow and glomerular filtration rate. In chronic experiments, urinary kallikrein excretion was not modified in norepinephrine-treated rats and decreased in vasopressin-infused animals. This decrease followed the modifications of the urine flow. In chronic experiments the dextrose infusion increased urinary kallikrein excretion. In all the groups studied a positive correlation between urine flow and urinary kallikrein excretion was observed. It is concluded that norepinephrine and vasopressin are important stimulators of the urinary kallikrein excretion only in those circumstances where it is necessary to eliminate an excess of water.     

Drought tolerance increases with seed size in a semiarid grassland from southern Mexico

Plant Ecology - Due to increased reserves available to face adverse conditions, drought tolerance should increase with seed size. This has been confirmed in the laboratory, but under field...     

Circulating adiposity-related microRNAs as predictors of the response to a low-fat diet in subjects with obesity

Recent studies have revealed the critical role of several microRNAs (miRNAs) in energy homeostasis and metabolic processes and suggest that circulating miRNAs can be used as early predictors of weight loss in the design of precision nutrition. Thus, the aim of this study was to investigate circulating adiposity-related miRNAs as biomarkers of the response to two specific weight loss dietary treatments. The expression of 86 miRNAs was investigated in plasma of 78 subjects with obesity randomized to two different diets [moderately high-protein diet (n = 38) and low-fat diet (n = 40)] and in 25 eutrophic controls (BMI ≤ 25 kg/m²). Bioinformatic analyses were performed to explore the target genes and biological pathways regulated by the dysregulated miRNAs. As results, 26 miRNAs were found differently expressed in eutrophic and volunteers with obesity. Moreover, 7 miRNAs (miR-130a-3p, miR-142-5p, miR-144-5p, miR-15a-5p, miR-22-3p, miR-221-3p and miR-29c-3p) were differentially expressed between responders and non-responders to a low-fat diet. Furthermore, after adjustment for basal glucose levels, 1-SD increase in miR-22-3p expression was associated with reduction in the risk of non-response to low-fat diet [OR = 0.181, 95% CI (0.084-0.947), P = .043]. Bioinformatic analyses evidenced that these 7 miRNAs regulate the expression of genes participating in important metabolic pathways. Conclusively, 7 circulating miRNAs related to adiposity could be used for predicting the response to a low-fat diet intervention prescribed to lose weight.     

Extreme storms cause rapid but short-lived shifts in nearshore subtropical bacterial communities

Climate change scenarios predict tropical cyclones will increase in both frequency and intensity, which will escalate the amount of terrestrial run-off and mechanical disruption affecting coastal ecosystems. Bacteria are key contributors to ecosystem functioning, but relatively little is known about how they respond to extreme storm events, particularly in nearshore subtropical regions. In this study, we combine field observations and mesocosm experiments to assess bacterial community dynamics and changes in physicochemical properties during early- and late-season tropical cyclones affecting Okinawa, Japan. Storms caused large and fast influxes of freshwater and terrestrial sediment – locally known as red soil pollution – and caused moderate increases of macronutrients, especially SiO₂ and PO₄³⁻, with up to 25 and 0.5 μM respectively. We detected shifts in relative abundances of marine and terrestrially derived bacteria, including putative coral and human pathogens, during storm events. Soil input alone did not substantially affect marine bacterial communities in mesocosms, indicating that other components of run-off or other storm effects likely exert a larger influence on bacterial communities. The storm effects were short-lived and bacterial communities quickly recovered following both storm events. The early- and late-season storms caused different physicochemical and bacterial community changes, demonstrating the context-dependency of extreme storm responses in a subtropical coastal ecosystem.