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Abstract At a given exercise intensity, blood flow restriction (BFR) reduces the volume of exercise required to impair post‐exercise neuromuscular function. Compared to traditional exercise, the time course of recovery is less clear. After strenuous exercise, force output assessed with electrical muscle stimulation is impaired to a greater extent at low versus high stimulation frequencies, a condition known as prolonged low‐frequency force depression (PLFFD). It is unclear if BFR increases PLFFD after exercise. This study tested if BFR during exercise increases PLFFD and slows recovery of neuromuscular function compared to regular exercise. Fifteen physically active participants performed six low‐load sets of knee‐extensions across four conditions: resistance exercise to task failure (RETF), resistance exercise to task failure with BFR applied continuously (BFRCONT) or intermittently (BFRINT), and resistance exercise matched to the lowest exercise volume condition (REVM). Maximal voluntary contraction (MVC) force output, voluntary activation and a force–frequency (1–100 Hz) curve were measured before and 0, 1, 2, 3, 4 and 24 h after exercise. Exercise to task failure caused similar reductions at 0 h for voluntary activation (RETF = 81.0 ± 14.2%, BFRINT = 80.9 ± 12.4% and BFRCONT = 78.6 ± 10.7%) and MVC force output (RETF = 482 ± 168 N, BFRINT = 432 ± 174 N, and BFRCONT = 443 ± 196 N), which recovered to baseline values between 4 and 24 h. PLFFD occurred only after RETF at 1 h supported by a higher frequency to evoke 50% of the force production at 100 Hz (1 h: 17.5 ± 4.4 vs. baseline: 15 ± 4.1 Hz, P = 0.0023), BFRINT (15.5 ± 4.0 Hz; P = 0.03), and REVM (14.9 ± 3.1 Hz; P = 0.002), with a trend versus BFRCONT (15.7 ± 3.5 Hz; P = 0.063). These findings indicate that, in physically active individuals, using BFR during exercise does not impair the recovery of neuromuscular function by 24 h post‐exercise.

At a given exercise intensity, blood flow restriction (BFR) reduces the volume of exercise required to impair post‐exercise neuromuscular function. Compared to traditional exercise, the time course of recovery is less clear. After strenuous exercise, force output assessed with electrical muscle stimulation is impaired to a greater extent at low versus high stimulation frequencies, a condition known as prolonged low‐frequency force depression (PLFFD). It is unclear if BFR increases PLFFD after exercise. This study tested if BFR during exercise increases PLFFD and slows recovery of neuromuscular function compared to regular exercise. Fifteen physically active participants performed six low‐load sets of knee‐extensions across four conditions: resistance exercise to task failure (RETF), resistance exercise to task failure with BFR applied continuously (BFRCONT) or intermittently (BFRINT), and resistance exercise matched to the lowest exercise volume condition (REVM). Maximal voluntary contraction (MVC) force output, voluntary activation and a force–frequency (1–100 Hz) curve were measured before and 0, 1, 2, 3, 4 and 24 h after exercise. Exercise to task failure caused similar reductions at 0 h for voluntary activation (RETF = 81.0 ± 14.2%, BFRINT = 80.9 ± 12.4% and BFRCONT = 78.6 ± 10.7%) and MVC force output (RETF = 482 ± 168 N, BFRINT = 432 ± 174 N, and BFRCONT = 443 ± 196 N), which recovered to baseline values between 4 and 24 h. PLFFD occurred only after RETF at 1 h supported by a higher frequency to evoke 50% of the force production at 100 Hz (1 h: 17.5 ± 4.4 vs. baseline: 15 ± 4.1 Hz, P = 0.0023), BFRINT (15.5 ± 4.0 Hz; P = 0.03), and REVM (14.9 ± 3.1 Hz; P = 0.002), with a trend versus BFRCONT (15.7 ± 3.5 Hz; P = 0.063). These findings indicate that, in physically active individuals, using BFR during exercise does not impair the recovery of neuromuscular function by 24 h post‐exercise. What is the central question of this study?Does the addition of blood flow restriction (BFR) during resistance exercise impaired recovery of neuromuscular function in physically active individuals?What is the main finding and its importance?While BFR during exercise increased fatiguability compared to exercise without BFR, it did not further impair the 24‐h recovery in neuromuscular function compared to exercise without BFR. These findings are relevant for applying BFR exercise in the training and/or rehabilitation of physically active populations such that it does not appear to further exacerbate muscle contractile function compared to regular strenuous exercise. [ABSTRACT FROM AUTHOR]

Simple Summary: This study establishes how trout's swimming energy changes under various oxygen levels and temperatures, leading to the development of a model that predicts oxygen conditions inside the cages. A case study using the model reveals that a 10 °C rise in temperature causes oxygen concentration to drop threefold, necessitating a 3.7-fold increase in water flow to maintain optimal oxygen levels. To ensure optimal feed intake, growth, and general fish health in aquaculture sea cages, interactions between drivers that affect oxygen conditions need to be understood. The main drivers are oxygen consumption and water exchange, caused by flow through the cage. Swimming energetics in rainbow trout (Oncorhynchus mykiss) in normoxia and hypoxia at 10, 15, and 20 °C were determined. Using the determinations, a conceptual model of oxygen conditions within sea cages was created. By applying the model to a case study, results show that with a temperature increase of 10 °C, oxygen concentration will decrease three times faster. To maintain optimal oxygen concentration within the cage, the flow velocity must be increased by a factor of 3.7. The model is highly relevant for current farms since the model predictions can explain why and when suboptimal conditions occur within the cages. Using the same method, the model can be used to estimate the suitability of potential new aquaculture sites. [ABSTRACT FROM AUTHOR]

The study combined the use of biometric, behavioral, physiological and external tissue damage scoring systems to better understand how high stocking densities drive schooling behavior and other adaptive features during the finishing growing phase of farmed gilthead sea bream in the Western Mediterranean. Fish were grown at three different final stocking densities (LD, 8.5 kg/m3; MD, 17 kg/m3; HD, 25 kg/m3). Water oxygen concentration varied between 5 and 6 ppm in LD fish to 3-4 ppm in HD fish with the summer rise of water temperature from 19°C to 26°C (May-July). HD fish showed a reduction of feed intake and growth rates, but they also showed a reinforced social cohesion with a well-defined endogenous swimming activity rhythm with feeding time as a main synchronization factor. The monitored decrease of the breathing/swimming activity ratio by means of the AEFishBIT data-logger also indicated a decreased energy partitioning for growth in the HD environment with a limited oxygen availability. Plasma glucose and cortisol levels increased with the rise of stocking density, and the close association of glycaemia with the expression level of antioxidant enzymes (mn-sod, gpx4, prdx5) in liver and molecular chaperones (grp170, grp75) in skeletal muscle highlighted the involvement of glucose in redox processes via rerouting in the pentosephosphate-pathway. Other adaptive features included the depletion of oxidative metabolism that favored lipid storage rather than fatty acid oxidation to decrease the oxygen demand as last electron acceptor in the mitochondrial respiratory chain. This was coincident with the metabolic readjustment of the Gh/Igf endocrine-growth cascade that promoted the regulation of muscle growth at the local level rather than a systemic action via the liver Gh/Igf axis. Moreover, correlation analyses within HD fish displayed negative correlations of hepatic transcripts of igf1 and igf2 with the data-logger measurements of activity and respiration, whereas the opposite was found for muscle igf2, ghr1 and ghr2. This was indicative of a growth-regulatory transition that supported a proactive instead of a reactive behavior in HD fish, which was considered adaptive to preserve an active and synchronized feeding behavior with a minimized risk of oxidative stress and epidermal skin damage. [ABSTRACT FROM AUTHOR]

The study combined the use of biometric, behavioral, physiological and external tissue damage scoring systems to better understand how high stocking densities drive schooling behavior and other adaptive features during the finishing growing phase of farmed gilthead sea bream in the Western Mediterranean. Fish were grown at three different final stocking densities (LD, 8.5 kg/m3; MD, 17 kg/m3; HD, 25 kg/m3). Water oxygen concentration varied between 5 and 6 ppm in LD fish to 3–4 ppm in HD fish with the summer rise of water temperature from 19°C to 26°C (May–July). HD fish showed a reduction of feed intake and growth rates, but they also showed a reinforced social cohesion with a well-defined endogenous swimming activity rhythm with feeding time as a main synchronization factor. The monitored decrease of the breathing/swimming activity ratio by means of the AEFishBIT data-logger also indicated a decreased energy partitioning for growth in the HD environment with a limited oxygen availability. Plasma glucose and cortisol levels increased with the rise of stocking density, and the close association of glycaemia with the expression level of antioxidant enzymes (mn-sod, gpx4, prdx5) in liver and molecular chaperones (grp170, grp75) in skeletal muscle highlighted the involvement of glucose in redox processes via rerouting in the pentose-phosphate-pathway. Other adaptive features included the depletion of oxidative metabolism that favored lipid storage rather than fatty acid oxidation to decrease the oxygen demand as last electron acceptor in the mitochondrial respiratory chain. This was coincident with the metabolic readjustment of the Gh/Igf endocrine-growth cascade that promoted the regulation of muscle growth at the local level rather than a systemic action via the liver Gh/Igf axis. Moreover, correlation analyses within HD fish displayed negative correlations of hepatic transcripts of igf1 and igf2 with the data-logger measurements of activity and respiration, whereas the opposite was found for muscle igf2, ghr1 and ghr2. This was indicative of a growth-regulatory transition that supported a proactive instead of a reactive behavior in HD fish, which was considered adaptive to preserve an active and synchronized feeding behavior with a minimized risk of oxidative stress and epidermal skin damage.

To ensure optimal feed intake, growth, and general fish health in aquaculture sea cages, interactions between drivers that affect oxygen conditions need to be understood. The main drivers are oxygen consumption and water exchange, caused by flow through the cage. Swimming energetics in rainbow trout (Oncorhynchus mykiss) in normoxia and hypoxia at 10, 15, and 20 °C were determined. Using the determinations, a conceptual model of oxygen conditions within sea cages was created. By applying the model to a case study, results show that with a temperature increase of 10 °C, oxygen concentration will decrease three times faster. To maintain optimal oxygen concentration within the cage, the flow velocity must be increased by a factor of 3.7. The model is highly relevant for current farms since the model predictions can explain why and when suboptimal conditions occur within the cages. Using the same method, the model can be used to estimate the suitability of potential new aquaculture sites.

An advanced model is developed to elucidate relationship between availability of oxygen and active corrosion, considering the equilibrium between gaseous and dissolved oxygen, as well as the equilibrium of oxygen diffusion and consumption. This research notably incorporates self-regulation mechanisms of cathodes and anodes in both macrocell and microcell corrosion. Accelerated corrosion experiments were performed under simulated marine environment, monitoring variations in corrosive medium concentration and electrochemical corrosion processes. Results indicate significant reduction in oxygen concentration following the activation of rebar. Potential inaccuracies in predicting corrosion rate arise from the adoption of a static cathodic to anodic area ratio was highlighted. • Availability of oxygen in cathodic areas throughout the steel corrosion process. • Self-regulation mechanisms of cathodes and anodes in both macrocell and microcell corrosion configurations. • Accelerated corrosion experiments under simulated marine environment. • Significant reduction in oxygen concentration following the activation of rebar. • Oxygen concentration ultimately achieving a steady state of equilibrium between influx and consumption. [ABSTRACT FROM AUTHOR]

Animals, including insects, need oxygen for aerobic respiration and eventually asphyxiate without it. Aerobic respiration, however, produces reactive oxygen species (ROS), which contribute to dysfunction and aging. Animals appear to balance risks of asphyxiation and ROS by regulating internal oxygen relatively low and stable, but sufficient levels. How much do levels vary among species, and how does variation depend on environment and life history? We predicted that lower internal oxygen levels occur in insects with either limited access to environmental oxygen (i.e., insects dependent on aquatic respiration, where low internal levels facilitate diffusive oxygen uptake, and reduce asphyxiation risks) or consistently low metabolic rates (i.e., inactive insects, requiring limited internal oxygen stores). Alternatively, we predicted insects with long life-stage durations would have internal oxygen levels > 1 kPa (preventing high ROS levels that are believed to occur under tissue hypoxia). We tested these predictions by measuring partial pressures of oxygen (PO 2 ) in tissues from juvenile and adult stages across 15 species comprising nine insect orders. Tissue PO 2 varied greatly (from 0 to 18.8 kPa) and variation across species and life stages was significantly related to differences in habitat, activity level, and life stage duration. Individuals with aquatic respiration sustained remarkably low PO 2 (mean = 0.88 kPa) across all species from Ephemeroptera (mayflies), Plecoptera (stoneflies), Trichoptera (caddisflies), and Diptera (true flies), possibly reflecting a widespread, but hitherto unknown, adaptation for extracting sufficient oxygen from water. For Odonata (dragonflies), aquatic juveniles had higher PO 2 levels (mean = 6.12 kPa), but these were still lower compared to terrestrial adults (mean = 13.3 kPa). Follow-up tests in juvenile stoneflies showed that tissue PO 2 remained low even when exposed to hyperoxia, suggesting that levels were down-regulated. This was further corroborated since levels could be modulated by ambient oxygen levels in dead individuals. In addition, tissue PO 2 was positively related to activity levels of insect life stages across all species and was highest in stages with short durations. Combined, our results support the idea that internal PO 2 is an evolutionarily labile trait that reflects the balance between oxygen supply and demand within the context of the environment and life-history of an insect., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors. Published by Elsevier B.V.)

Green turtle (Chelonia mydas) embryos are in an arrested state of development when the eggs are laid, but in the presence of oxygen, arrest is broken and development resumes within 12–16 h. However, the precise oxygen level at which embryos break arrest and continue development is not known. To better understand the impact of oxygen concentration on breaking of arrest and early embryonic development, we incubated freshly laid eggs of the green sea turtle for three days at each of six different oxygen concentrations (less than or equal to 1%, 3%, 5%, 7%, 9% and 21%) and monitored the appearance and growth of white spots on the shell, indicative of embryonic development. As reported previously, white spots did not develop on eggs incubated in anoxia (less than or equal to 1% oxygen). For all other treatments, mean time to white spot detection and white spot growth rate varied inversely with oxygen concentration. In nearly all cases the difference between eggs at different oxygen levels was statistically significant (p ≤ 0.05). This suggests that sea turtle embryonic development may respond to oxygen in a dose-dependent manner. Our results indicate that the development of green turtle embryos may be slowed if they are exposed to the most hypoxic conditions reported in mature natural nests.

In this study, Baltic Sea sediments, as a source of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), ammonium (NH4+), and phosphates (PO43−), were investigated based on samples obtained in 2017 and 2018, shortly after a sequence of inflows from the North Sea that occurred between 2014 and 2017. Two different data sets (I and II) were used to assess benthic diffusive fluxes and thus elucidate both the temporal conditions at the time of sampling (data set I) and the diffusion potential of the sediments (data set II). The estimated fluxes were characterized by a high spatial variability within the whole Baltic Sea and ranged between −0.01 and 3.33 mmol m−2 d−1 for DIC, −0.02 and 0.44 mmol m−2 d−1 for DOC, −40.5 and 1370.1 µmol m−2 d−1 for NH4+, and −5.9 and 60.9 µmol m−2 d−1 for PO43−. The estimated benthic diffusive fluxes indicated a high potential for DIC, DOC, NH4+, and PO43− release from Baltic Sea sediments. The high O2 concentrations in the water column of the Gulf of Bothnia together with major Baltic inflows (MBIs) bringing oxygenated seawater to the Baltic Proper and to some extent the Eastern Gotland Basin regulate the amounts of chemicals released from the sediment. Our study showed that a sequence of inflows has greater impact on the diminution of diffusive fluxes than does a single MBI and that the sediments of the Baltic Proper, even under the influence of inflows, are an important source of C, N, and P (159 kt yr−1 for DIC+DOC, 6.3 kt yr−1 for N-NH4+ and 3.7 kt yr−1 for P-PO43−) that should be considered in regional budget estimations.

Abstract Background Production of 2,3-butanediol from renewable resources is a promising measure to decrease the consumption of fossil resources in the chemical industry. One of the most influential parameters on biotechnological 2,3-butanediol production is the oxygen availability during the cultivation. As 2,3-butanediol is produced under microaerobic process conditions, a well-controlled oxygen supply is the key parameter to control biomass formation and 2,3-butanediol production. As biomass is on the one hand not the final product, but on the other hand the essential biocatalyst, the optimal compromise between biomass formation and 2,3-butanediol production has to be defined. Results A shake flask methodology is presented to evaluate the effects of oxygen availability on 2,3-butanediol production with Bacillus licheniformis DSM 8785 by variation of the filling volume. A defined two-stage cultivation strategy was developed to investigate the metabolic response to different defined maximum oxygen transfer capacities at equal initial growth conditions. The respiratory quotient was measured online to determine the point of glucose depletion, as 2,3-butanediol is consumed afterwards. Based on this strategy, comparable results to stirred tank reactors were achieved. The highest space–time yield (1.3 g/L/h) and a 2,3-butanediol concentration of 68 g/L combined with low acetoin concentrations and avoided glycerol formation were achieved at a maximum oxygen transfer capacity of 13 mmol/L/h. The highest overall 2,3-butanediol concentration of 78 g/L was observed at a maximum oxygen transfer capacity of 4 mmol/L/h. Conclusions The presented shake flask approach reduces the experimental effort and costs providing a fast and reliable methodology to investigate the effects of oxygen availability. This can be applied especially on product and by-product formation under microaerobic conditions. Utilization of the maximum oxygen transfer capacity as measure for the oxygen availability allows for an easy adaption to other bioreactor setups and scales.

Next generation biofuels including longer-chain alcohols such as butanol are attractive as renewable, high-energy fuels. A barrier to microbial production of butanols is the increased toxicity compared to ethanol; however, the cellular targets and microbial defense mechanisms remain poorly understood, especially under anaerobic conditions used frequently in industry. Here we took a comparative approach to understand the response of Saccharomyces cerevisiae to 1-butanol, isobutanol, or ethanol, across three genetic backgrounds of varying tolerance in aerobic and anaerobic conditions. We find that strains have different growth properties and alcohol tolerances with and without oxygen availability, as well as unique and common responses to each of the three alcohols. Our results provide evidence for strain-by-alcohol-by-oxygen interactions that moderate how cells respond to alcohol stress.

Abstract Background Rapamycin is a potent inhibitor of the highly conserved TOR kinase, the nutrient-sensitive controller of growth and aging. It has been utilised as a chemotherapeutic agent due to its anti-proliferative properties and as an immunosuppressive drug, and is also known to extend lifespan in a range of eukaryotes from yeast to mammals. However, the mechanisms through which eukaryotic cells adapt to sustained exposure to rapamycin have not yet been thoroughly investigated. Methods Here, S. cerevisiae response to long-term rapamycin exposure was investigated by identifying the physiological, transcriptomic and metabolic differences observed for yeast populations inoculated into low-dose rapamycin-containing environment. The effect of oxygen availability and acidity of extracellular environment on this response was further deliberated by controlling or monitoring the dissolved oxygen level and pH of the culture. Results Yeast populations grown in the presence of rapamycin reached higher cell densities complemented by an increase in their chronological lifespan, and these physiological adaptations were associated with a rewiring of the amino acid metabolism, particularly that of arginine. The ability to synthesise amino acids emerges as the key factor leading to the major mechanistic differences between mammalian and microbial TOR signalling pathways in relation to nutrient recognition. Conclusion Oxygen levels and extracellular acidity of the culture were observed to conjointly affect yeast populations, virtually acting as coupled physiological effectors; cells were best adapted when maximal oxygenation of the culture was maintained in slightly acidic pH, any deviation necessitated more extensive readjustment to additional stress factors.

Exercise intensity variations throughout a cycling time trial (TT) might be influenced by subject's functional state. Purpose: The current study characterized the performance fatigability etiology, immediately after exercise cessation, and its relation to the dynamic changes in muscle O2 saturation (SmO2) at different TT phases. Methods: Twelve males performed three separated TT of different distances, in a crossover counterbalanced design, until the end of the fast-start (FS, 827 ± 135 m), even-pace (EP, 3590 ± 66 m), or end-spurt (ES, 4000 m) TT phases. Performance fatigability was characterized by using isometric maximal voluntary contractions (IMVC), whereas the maximal voluntary activation (VA) and contractile function of knee extensors (e.g., peak torque of potentiated twitches [TwPt]) were evaluated using electrically evoked contractions performed before and immediately after each exercise bouts. SmO2, power output (PO), and EMG were also recorded. Results: Immediately after the FS phase, there were lower values for IMVC (−23%), VA (−8%), and TwPt (−43%) (all P < 0.001), but no further changes were measured after EP (IMVC, −28%; VA, −8%; TwPt, −38%). After the ES phase, IMVC (−34%) and TwPt (−59%) further decreased compared with the previous phases (P < 0.05). There were lower SmO2 and higher EMG/PO values during FS and ES compared with EP phase. Conclusion: FS and EP phases had similar performance fatigability etiology, but ES showed further impairments in contractile function. This later finding might be due to the abrupt changes in SmO2 and EMG/PO because of the high exercise intensity during the ES, which elicited maximal decline in contractile function at the finish line. [ABSTRACT FROM AUTHOR]

Oxygen deprivation within tumors is one of the most prevalent causes of resilient cancer cell survival and increased immune evasion in breast cancer (BCa). Current in vitro models do not adequately mimic physiological oxygen levels relevant to breast tissue and its tumor-immune interactions. In this study, we propose an approach to engineer a three-dimensional (3D) model (named 3D engineered oxygen, 3D-O) that supports the growth of BCa cells and generates physio- and pathophysiological oxygen levels to understand the role of oxygen availability in tumor-immune interactions. BCa cells (MDA-MB-231 and MCF-7) were embedded into plasma-derived 3D-O scaffolds that reflected physio- and pathophysiological oxygen levels relevant to the healthy and cancerous breast tissue. BCa cells grown within 3D-O scaffolds were analyzed by flow cytometry, confocal imaging, immunohistochemistry/immunofluorescence for cell proliferation, extracellular matrix protein expression, and alterations in immune evasive outcomes. Exosome secretion from 3D-O scaffolds were evaluated using the NanoSight particle analyzer. Peripheral blood mononuclear cells were incorporated on the top of 3D-O scaffolds and the difference in tumor-infiltrating capabilities as a result of different oxygen content were assessed by flow cytometry and confocal imaging. Lastly, hypoxia and Programmed death-ligand 1 (PD-L1) inhibition were validated as targets to sensitize BCa cells in order to overcome immune evasion. Low oxygen-induced adaptations within 3D-O scaffolds validated known tumor hypoxia characteristics such as reduced BCa cell proliferation, increased extracellular matrix protein expression, increased extracellular vesicle secretion and enhanced immune surface marker expression on BCa cells. We further demonstrated that low oxygen in 3D-O scaffolds significantly influence immune infiltration. CD8+ T cell infiltration was impaired under pathophysiological oxygen levels and we were also able to establish that hypoxia and PD-L1 inhibition re-sensitized BCa cells to cytotoxic CD8+ T cells. Bioengineering the oxygen-deprived BCa tumor microenvironment in our engineered 3D-O physiological and tumorous scaffolds supported known intra-tumoral hypoxia characteristics allowing the study of the role of oxygen availability in tumor-immune interactions. The 3D-O model could serve as a promising platform for the evaluation of immunological events and as a drug-screening platform tool to overcome hypoxia-driven immune evasion.

Abstract Background Azotobacter vinelandii is a bacterium that produces alginate and polyhydroxybutyrate (P3HB); however, the role of NAD(P)H/NAD(P)+ ratios on the metabolic fluxes through biosynthesis pathways of these biopolymers remains unknown. The aim of this study was to evaluate the NAD(P)H/NAD(P) + ratios and the metabolic fluxes involved in alginate and P3HB biosynthesis, under oxygen-limiting and non-limiting oxygen conditions. Results The results reveal that changes in the oxygen availability have an important effect on the metabolic fluxes and intracellular NADPH/NADP+ ratio, showing that at the lowest OTR (2.4 mmol L−1 h−1), the flux through the tricarboxylic acid (TCA) cycle decreased 27.6-fold, but the flux through the P3HB biosynthesis increased 6.6-fold in contrast to the cultures without oxygen limitation (OTR = 14.6 mmol L−1 h−1). This was consistent with the increase in the level of transcription of phbB and the P3HB biosynthesis. In addition, under conditions without oxygen limitation, there was an increase in the carbon uptake rate (twofold), as well as in the flux through the pentose phosphate (PP) pathway (4.8-fold), compared to the condition of 2.4 mmol L−1 h−1. At the highest OTR condition, a decrease in the NADPH/NADP+ ratio of threefold was observed, probably as a response to the high respiration rate induced by the respiratory protection of the nitrogenase under diazotrophic conditions, correlating with a high expression of the uncoupled respiratory chain genes (ndhII and cydA) and induction of the expression of the genes encoding the nitrogenase complex (nifH). Conclusions We have demonstrated that changes in oxygen availability affect the internal redox state of the cell and carbon metabolic fluxes. This also has a strong impact on the TCA cycle and PP pathway as well as on alginate and P3HB biosynthetic fluxes.

Abstract Background Understanding the effects of oxygen levels on yeast xylose metabolism would benefit ethanol production. In this work, xylose fermentative capacity of Scheffersomyces stipitis, Spathaspora passalidarum, Spathaspora arborariae and Candida tenuis was systematically compared under aerobic, oxygen-limited and anaerobic conditions. Results Fermentative performances of the four yeasts were greatly influenced by oxygen availability. S. stipitis and S. passalidarum showed the highest ethanol yields (above 0.44 g g−1) under oxygen limitation. However, S. passalidarum produced 1.5 times more ethanol than S. stipitis under anaerobiosis. While C. tenuis showed the lowest xylose consumption rate and incapacity to produce ethanol, S. arborariae showed an intermediate fermentative performance among the yeasts. NAD(P)H xylose reductase (XR) activity in crude cell extracts correlated with xylose consumption rates and ethanol production. Conclusions Overall, the present work demonstrates that the availability of oxygen influences the production of ethanol by yeasts and indicates that the NADH-dependent XR activity is a limiting step on the xylose metabolism. S. stipitis and S. passalidarum have the greatest potential for ethanol production from xylose. Both yeasts showed similar ethanol yields near theoretical under oxygen-limited condition. Besides that, S. passalidarum showed the best xylose consumption and ethanol production under anaerobiosis.

Abstract Background Riboflavin, an intermediate of primary metabolism, is one kind of important food additive with high economic value. The microbial cell factory Bacillus subtilis has already been proven to possess significant importance for the food industry and have become one of the most widely used riboflavin-producing strains. In the practical fermentation processes, a sharp decrease in riboflavin production is encountered along with a decrease in the dissolved oxygen (DO) tension. Influence of this oxygen availability on riboflavin biosynthesis through carbon central metabolic pathways in B. subtilis is unknown so far. Therefore the unveiled effective metabolic pathways were still an unaccomplished task till present research work. Results In this paper, the microscopic regulation mechanisms of B. subtilis grown under different dissolved oxygen tensions were studied by integrating 13C metabolic flux analysis, metabolomics and transcriptomics. It was revealed that the glucose metabolic flux through pentose phosphate (PP) pathway was lower as being confirmed by smaller pool sizes of metabolites in PP pathway and lower expression amount of ykgB at transcriptional level. The latter encodes 6-phosphogluconolactonase (6-PGL) under low DO tension. In response to low DO tension in broth, the glucose metabolic flux through Embden–Meyerhof–Parnas (EMP) pathway was higher and the gene, alsS, encoding for acetolactate synthase was significantly activated that may result due to lower ATP concentration and higher NADH/NAD+ ratio. Moreover, ResE, a membrane-anchored protein that is capable of oxygen regulated phosphorylase activity, and ResD, a regulatory protein that can be phosphorylated and dephosphorylated by ResE, were considered as DO tension sensor and transcriptional regulator respectively. Conclusions This study shows that integration of transcriptomics, 13C metabolic flux analysis and metabolomics analysis provides a comprehensive understanding of biosynthesized riboflavin’s regulatory mechanisms in B. subtilis grown under different dissolved oxygen tension conditions. The two-component system, ResD–ResE, was considered as the signal receiver of DO tension and gene regulator that led to differences between biomass and riboflavin production after triggering the shifts in gene expression, metabolic flux distributions and metabolite pool sizes.

Forced aeration is one of the major energy consumption factors of the bioleaching process of run-of-mine ore. The effect of aeration in the microbial community has scarcely been studied at industrial level. Leptospirillum ferriphilum is one of the most representative species of the Fe3+ producing population in this kind of systems. We analyzed the effect of oxygen availability on L. ferriphilum by growth activity and transcriptional dynamics of its two terminal oxidases (cbb3 and bd complexes) under different experimental test: culture reactor, bioleaching column, and industrial heap tests. Relatively low O2 availability triggered important changes in the microbial community composition, cell growth, microbial activity and cydAB genes transcription in all cases of study. We assessed the potential role of the terminal oxidases on the adaptation to variable aeration conditions in different lifestyles of L. ferriphilum and identified transcriptional markers associated to oxygen metabolism in an industrial system. An interesting hypothesis about the possible role of the cbb3 complex in the response to oxidative stress as well as their role as a high oxygen-affinity oxidase in L. ferriphilum is proposed and discussed. This study successfully proves the function of the cydAB genes as valid genetic markers for low-grade copper industrial bioleaching systems.

Forced aeration is one of the major energy consumption factors of the bioleaching process of run-of-mine ore. The effect of aeration in the microbial community has scarcely been studied at industrial level. Leptospirillum ferriphilum is one of the most representative species of the Fe3+ producing population in this kind of systems. We analyzed the effect of oxygen availability on L. ferriphilum by growth activity and transcriptional dynamics of its two terminal oxidases (cbb3 and bd complexes) under different experimental test: culture reactor, bioleaching column, and industrial heap tests. Relatively low O2 availability triggered important changes in the microbial community composition, cell growth, microbial activity and cydAB genes transcription in all cases of study. We assessed the potential role of the terminal oxidases on the adaptation to variable aeration conditions in different lifestyles of L. ferriphilum and identified transcriptional markers associated to oxygen metabolism in an industrial system. An interesting hypothesis about the possible role of the cbb3 complex in the response to oxidative stress as well as their role as a high oxygen-affinity oxidase in L. ferriphilum is proposed and discussed. This study successfully proves the function of the cydAB genes as valid genetic markers for low-grade copper industrial bioleaching systems. [ABSTRACT FROM AUTHOR]

Next generation biofuels including longer-chain alcohols such as butanol are attractive as renewable, high-energy fuels. A barrier to microbial production of butanols is the increased toxicity compared to ethanol; however, the cellular targets and microbial defense mechanisms remain poorly understood, especially under anaerobic conditions used frequently in industry. Here we took a comparative approach to understand the response of Saccharomyces cerevisiae to 1-butanol, isobutanol, or ethanol, across three genetic backgrounds of varying tolerance in aerobic and anaerobic conditions. We find that strains have different growth properties and alcohol tolerances with and without oxygen availability, as well as unique and common responses to each of the three alcohols. Our results provide evidence for strain-byalcohol- by-oxygen interactions that moderate how cells respond to alcohol stress. [ABSTRACT FROM AUTHOR]

The Gh/Prl/Sl family has evolved differentially through evolution, resulting in varying relationships between the somatotropic axis and growth rates within and across fish species. This is due to a wide range of endogenous and exogenous factors that make this association variable throughout season and life cycle, and the present minireview aims to better define the nutritional and environmental regulation of the endocrine growth cascade over precisely defined groups of fishes, focusing on Mediterranean farmed fishes. As a result, circulating Gh and Igf-i are revitalized as reliable growth markers, with a close association with growth rates of gilthead sea bream juveniles with deficiency signs in both macro- or micro-nutrients. This, together with other regulated responses, promotes the use of Gh and Igf-i as key performance indicators of growth, aerobic scope, and nutritional condition in gilthead sea bream. Moreover, the sirtuin-energy sensors might modulate the growth-promoting action of somatotropic axis. In this scenario, transcripts of igf-i and gh receptors mirror changes in plasma Gh and Igf-i levels, with the ghr-i/ghr-ii expression ratio mostly unaltered over season. However, this ratio is nutritionally regulated, and enriched plant-based diets or diets with specific nutrient deficiencies downregulate hepatic ghr-i , decreasing the ghr-i / ghr-ii ratio. The same trend, due to a ghr-ii increase, is found in skeletal muscle, whereas impaired growth during overwintering is related to increase in the ghr-i / ghr-ii and igf-ii / igf-i ratios in liver and skeletal muscle, respectively. Overall, expression of insulin receptors and igf receptors is less regulated, though the expression quotient is especially high in the liver and muscle of sea bream. Nutritional and environmental regulation of the full Igf binding protein 1–6 repertoire remains to be understood. However, tissue-specific expression profiling highlights an enhanced and nutritionally regulated expression of the igfbp-1/-2/-4 clade in liver, whereas the igfbp-3/-5/-6 clade is overexpressed and regulated in skeletal muscle. The somatotropic axis is, therefore, highly informative of a wide-range of growth-disturbing and stressful stimuli, and multivariate analysis supports its use as a reliable toolset for the assessment of growth potentiality and nutrient deficiencies and requirements, especially in combination with selected panels of other nutritionally regulated metabolic biomarkers. [ABSTRACT FROM AUTHOR]

Abstract The kinetics of astaxanthin degradation and lipid oxidation in shrimp oil from hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) as affected by storage temperature were studied. When shrimp oil was incubated at different temperatures (4, 30, 45 and 60 °C) for 16 h, the rate constants (k) of astaxanthin degradation and lipid oxidation in shrimp oil increased with increasing temperatures (p

This study assessed the feasibility of using bleached cellulose pulp from Eucalyptus wood as a feedstock for the production of itaconic acid by fermentation. Additionally, different process strategies were tested with the aim of selecting suitable conditions for an efficient production of itaconic acid by the fungus Aspergillus terreus. The feasibility of using cellulose pulp was demonstrated through assays that revealed the preference of the strain in using glucose as carbon source instead of xylose, mannose, sucrose or glycerol. Additionally, the cellulose pulp was easily digested by enzymes without requiring a previous step of pretreatment, producing a glucose-rich hydrolysate with a very low level of inhibitor compounds, suitable for use as a fermentation medium. Fermentation assays revealed that the technique used for sterilization of the hydrolysate (membrane filtration or autoclaving) had an important effect in its composition, especially on the nitrogen content, consequently affecting the fermentation performance. The carbon-to-nitrogen ratio (C:N ratio), initial glucose concentration and oxygen availability, were also important variables affecting the performance of the strain to produce itaconic acid from cellulose pulp hydrolysate. By selecting appropriate process conditions (sterilization by membrane filtration, medium supplementation with 3 g/L (NH4)2SO4, 60 g/L of initial glucose concentration, and oxygen availability of 7.33 (volume of air/volume of medium)), the production of itaconic acid was maximized resulting in a yield of 0.62 g/g glucose consumed, and productivity of 0.52 g/L·h.

Background: Azotobacter vinelandii is a bacterium that produces alginate and polyhydroxybutyrate (P3HB); however, the role of NAD(P)H/NAD(P)+ ratios on the metabolic fluxes through biosynthesis pathways of these biopolymers remains unknown. The aim of this study was to evaluate the NAD(P)H/NAD(P)+ ratios and the metabolic fluxes involved in alginate and P3HB biosynthesis, under oxygen-limiting and non-limiting oxygen conditions. Results: The results reveal that changes in the oxygen availability have an important effect on the metabolic fluxes and intracellular NADPH/NADP+ ratio, showing that at the lowest OTR (2.4 mmol L-1 h-1), the flux through the tricarboxylic acid (TCA) cycle decreased 27.6-fold, but the flux through the P3HB biosynthesis increased 6.6-fold in contrast to the cultures without oxygen limitation (OTR = 14.6 mmol L-1 h-1). This was consistent with the increase in the level of transcription of phbB and the P3HB biosynthesis. In addition, under conditions without oxygen limitation, there was an increase in the carbon uptake rate (twofold), as well as in the flux through the pentose phosphate (PP) pathway (4.8-fold), compared to the condition of 2.4 mmol L-1 h-1. At the highest OTR condition, a decrease in the NADPH/NADP+ ratio of threefold was observed, probably as a response to the high respiration rate induced by the respiratory protection of the nitrogenase under diazotrophic conditions, correlating with a high expression of the uncoupled respiratory chain genes (ndhII and cydA) and induction of the expression of the genes encoding the nitrogenase complex (nifH). Conclusions: We have demonstrated that changes in oxygen availability affect the internal redox state of the cell and carbon metabolic fluxes. This also has a strong impact on the TCA cycle and PP pathway as well as on alginate and P3HB biosynthetic fluxes. [ABSTRACT FROM AUTHOR]

Oxygen availability is a critical factor in regulating cell viability that ultimately contributes to the normal morphogenesis and functionality of human tissues. Among various cell culture platforms, construction of 3D multicellular spheroids based on microwell arrays has been extensively applied to reconstitute in vitro human tissue models due to its precise control of tissue culture conditions as well as simple fabrication processes. However, an adequate supply of oxygen into the spheroidal cellular aggregation still remains one of the main challenges to producing healthy in vitro spheroidal tissue models. Here, we present a novel design for controlling the oxygen distribution in concave microwell arrays. We show that oxygen permeability into the microwell is tightly regulated by varying the poly-dimethylsiloxane (PDMS) bottom thickness of the concave microwells. Moreover, we validate the enhanced performance of the engineered microwell arrays by culturing non-proliferated primary rat pancreatic islet spheroids on varying bottom thickness from 10 μm to 1050 μm. Morphological and functional analyses performed on the pancreatic islet spheroids grown for 14 days prove the long-term stability, enhanced viability, and increased hormone secretion under the sufficient oxygen delivery conditions. We expect our results could provide knowledge on oxygen distribution in 3-dimensional spheroidal cell structures and critical design concept for tissue engineering applications. Statement of Significance In this study, we present a noble design to control the oxygen distribution in concave microwell arrays for the formation of highly functional pancreatic islet spheroids by engineering the bottom of the microwells. Our new platform significantly enhanced oxygen permeability that turned out to improve cell viability and spheroidal functionality compared to the conventional thick-bottomed 3-D culture system. Therefore, we believe that this could be a promising medical biotechnology platform to further develop high-throughput tissue screening system as well as in vivo -mimicking customised 3-D tissue culture systems. [ABSTRACT FROM AUTHOR]

A series of Ag/CeO 2 catalysts was synthesized by the incipient wetness method. Compared with Ag/Al 2 O 3 and CeO 2 catalysts, Ag/CeO 2 catalysts are more promising candidates for naphthalene oxidation, in which Ce x + act as the main active sites and are efficiently promoted by Ag species. By characterizing the solid properties and the redox ability, the mechanism of ceria catalysis by the Ag-modified catalysts was investigated. It was found that Ag species can work as an oxygen pump to enhance the oxygen availability in the ceria bulk. They also promote the oxygen regeneration capacity by the oxygen spillover effect. However, such an effect would also decrease the ability for active oxygen regeneration at higher Ag loading, which arises from the lower surface oxygen vacancy concentration. Because of the balance between these two factors, the Ag/CeO 2 catalyst with 1 wt.% Ag shows the best performance for isothermal catalytic oxidation of naphthalene. [ABSTRACT FROM AUTHOR]

Nearly half of US lakes are impaired, primarily resulting from excessive nutrients and resultant eutrophication. The stability and recycling of sediment P results in differing degrees of internal P loading, which can alter lake water quality. In this study, we asked: (1) What are the underlying mechanisms controlling internal loading (net release) and retention of P? and (2) How does trophic state, specifically a hypereutrophic condition, affect internal P loading in agricultural reservoirs? We show that shifts in internal P loading are related to trophic-level indicators, including total P (TP) and chl- a concentrations. All study reservoirs were classified as hypereutrophic, and we grouped them as 'less eutrophic' or 'more eutrophic' based on TP and chl- a concentrations. In less eutrophic lakes, chemical variables (for example, oxygen) and sediment iron-bound P primarily controlled internal P loading under anaerobic conditions. However, in the more eutrophic lakes, biological variables, including phytoplankton biomass (as indicated by chl- a concentrations) and extracellular enzyme activity, drove internal P loading or reduced P retention under aerobic conditions. Biologically controlled aerobic internal P cycling was related to higher sediment organic P pools being broken down by enzymatic hydrolysis. Therefore, we theorize that as lakes become hypereutrophic, biological mechanisms begin to amplify internal P release by acting under both anaerobic and aerobic conditions, thus creating a perpetual cycle of internal P loading. Thus, the role of biological processes and oxygen availability should be considered in water quality management strategies aimed at alleviating eutrophication in lakes. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes is a Gram positive foodborne pathogen that can colonize the gastrointestinal tract of a number of hosts, including humans. These environments contain numerous stressors such as bile, low oxygen and acidic pH, which may impact the level of colonization and persistence of this organism within the GI tract. The ability of L. monocytogenes to establish infections and colonize the gastrointestinal tract is directly related to its ability to overcome these stressors, which is mediated by the efficient expression of several stress response mechanisms during its passage. This review will focus upon how and when this occurs and how this impacts the outcome of foodborne disease.

Background: Understanding the effects of oxygen levels on yeast xylose metabolism would benefit ethanol production. In this work, xylose fermentative capacity of Schefersomyces stipitis, Spathaspora passalidarum, Spathaspora arborariae and Candida tenuis was systematically compared under aerobic, oxygen-limited and anaerobic conditions. Results: Fermentative performances of the four yeasts were greatly influenced by oxygen availability. S. stipitis and S. passalidarum showed the highest ethanol yields (above 0.44 g g-1) under oxygen limitation. However, S. passalidarum produced 1.5 times more ethanol than S. stipitis under anaerobiosis. While C. tenuis showed the lowest xylose consumption rate and incapacity to produce ethanol, S. arborariae showed an intermediate fermentative performance among the yeasts. NAD(P)H xylose reductase (XR) activity in crude cell extracts correlated with xylose consumption rates and ethanol production. Conclusions: Overall, the present work demonstrates that the availability of oxygen influences the production of ethanol by yeasts and indicates that the NADH-dependent XR activity is a limiting step on the xylose metabolism. S. stipitis and S. passalidarum have the greatest potential for ethanol production from xylose. Both yeasts showed similar ethanol yields near theoretical under oxygen-limited condition. Besides that, S. passalidarum showed the best xylose consumption and ethanol production under anaerobiosis. [ABSTRACT FROM AUTHOR]

A modified 3D numerical model on the energy conversion process in the anode side of a Direct Methanol Fuel Cell (DMFC) system was constructed and validated to published experimental results. Systematic simulations were performed to investigate the underlying mechanisms of the energy conversion process, and the combined effects of inlet flow rate and input methanol concentration were summarized systematically. The increase of flow rate was found to be an effective strategy to accelerate the internal flow fields, while the diffusion layer was proposed to be a critical component in the design of high-performance DMFC. The frontier for optimal conditions of DMFC's output was also determined, which can be helpful to improve the energy conversion performance of DMFC in practical applications. [ABSTRACT FROM AUTHOR]

Seagrass ecosystems are significant carbon sinks, and their resident microbial communities ultimately determine the quantity and quality of carbon sequestered. However, environmental perturbations have been predicted to affect microbial-driven seagrass decomposition and subsequent carbon sequestration. Utilizing techniques including 16S-rDNA sequencing, solid-state NMR and microsensor profiling, we tested the hypothesis that elevated seawater temperatures and eutrophication enhance the microbial decomposition of seagrass leaf detritus and rhizome/root tissues. Nutrient additions had a negligible effect on seagrass decomposition, indicating an absence of nutrient limitation. Elevated temperatures caused a 19% higher biomass loss for aerobically decaying leaf detritus, coinciding with changes in bacterial community structure and enhanced lignocellulose degradation. Although, community shifts and lignocellulose degradation were also observed for rhizome/root decomposition, anaerobic decay was unaffected by temperature. These observations suggest that oxygen availability constrains the stimulatory effects of temperature increases on bacterial carbon remineralization, possibly through differential temperature effects on bacterial functional groups, including putative aerobic heterotrophs (e.g. Erythrobacteraceae, Hyphomicrobiaceae) and sulfate reducers (e.g. Desulfobacteraceae). Consequently, under elevated seawater temperatures, carbon accumulation rates may diminish due to higher remineralization rates at the sediment surface. Nonetheless, the anoxic conditions ubiquitous to seagrass sediments can provide a degree of carbon protection under warming seawater temperatures. [ABSTRACT FROM AUTHOR]

Multimodal neuromonitoring in neurocritical care increasingly includes electrocorticography to measure epileptic events and spreading depolarizations. Spreading depolarization causes spreading depression of activity (=isoelectricity) in electrically active tissue. If the depression is long-lasting, further spreading depolarizations occur in still isoelectric tissue where no activity can be suppressed. Such spreading depolarizations are termed isoelectric and are assumed to indicate energy compromise. However, experimental and clinical recordings suggest that long-lasting spreading depolarizationinduced depression and isoelectric spreading depolarizations are often recorded outside of the actual ischemic zones, allowing the remote diagnosis of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage. Here, we analyzed simultaneous electrocorticography and tissue partial pressure of oxygen recording in 33 aneurysmal subarachnoid hemorrhage patients. Multiple regression showed that both peak total depression duration per recording day and mean baseline tissue partial pressure of oxygen were independent predictors of outcome. Moreover, tissue partial pressure of oxygen preceding spreading depolarization was similar and differences in tissue partial pressure of oxygen responses to spreading depolarization were only subtle between isoelectric spreading depolarizations and spreading depressions. This further supports that, similar to clustering of spreading depolarizations, long spreading depolarizationinduced periods of isoelectricity are useful to detect energy compromise remotely, which is valuable because the exact location of future developing pathology is unknown at the time when the neurosurgeon implants recording devices. [ABSTRACT FROM AUTHOR]

Previous research supports that low-load resistance exercise with blood flow restriction (LL-BFR) acutely increases physiological responses and muscle mass accrual compared with low-load resistance exercise (LL-RE) alone. However, most studies have work-matched LL-BFR and LL-RE. Completing sets to similar perceived efforts, thereby allowing for a variable amount of work, may provide a more ecologically valid approach to compare LL-BFR and LL-RE. This study aimed to examine acute signaling and training responses following LL-RE or LL-BFR performed to task failure. Ten participants had each leg randomly assigned to perform LL-RE or LL-BFR. Muscle biopsies were obtained before and 2-h after the first exercise bout and after 6-wk of training for Western blot and immunohistochemistry analyses. Repeated measure ANOVA and intraclass coefficients (ICCs) were used to compare responses of each condition. After exercise, AKT (T308) phosphorylation increased after LL-RE and LL-BFR (both ∼145% of baseline, P < 0.05) and trended for p70 S6K (T389) (LL-RE: ∼158% and LL-BFR: ∼137%, P = 0.06). BFR did not alter these responses, resulting in fair-excellent ICCs for signaling proteins involved in anabolism (ICC AKT(T308) = 0.889, P = 0.001; ICC AKT(S473) = 0.519, P = 0.074; ICC p70 S6K(T389) = 0.514, P = 0.105). After training, muscle fiber cross-sectional area and vastus lateralis whole muscle thickness were similar between conditions (ICC ≥ 0.637, P ≤ 0.031). Similar acute and chronic responses between conditions and high ICC values between legs suggest that both LL-BFR and LL-RE performed by the same person result in similar adaptations. These data support the concept that sufficient muscular exertion is a key factor for training-induced muscle hypertrophy with low-load resistance exercise independent of total work and blood flow. NEW & NOTEWORTHY The addition of blood flow restriction during low-load resistance exercise is considered to increase the signaling events and muscle growth responses to a greater extent than low-load resistance exercise alone. It remains unclear whether blood flow restriction accelerates or increases these adaptive responses, as most studies have each condition perform the same amount of work. Despite different amounts of work performed, we show similar signaling and muscle growth responses occur after low-load resistance exercise with and without blood flow restriction. Our work supports that blood flow restriction accelerates fatigue but does not increase the signaling events and muscle growth responses during low-load resistance exercise.

The physiology of B. subtilis R14 was investigated in minimal medium under excess-oxygen and oxygen-limited conditions. Growth and efficient sporulation could be achieved in excess-oxygen culture on medium with readily metabolizable carbon and nitrogen sources, which allowed high growth rate and high biomass yield. A short transition phase between the exponential growth and sporulation could be attained by formulating a medium with a well-balanced C/N ratio. Under oxygen-limitation, but in the presence of essential nutrients (i.e. excess-nutrient cultivation), B. subtilis R14 produced bioactive compounds, which showed activity against several phytopathogenic bacteria. Under anaerobic condition, the organism did not grow neither through fermentation nor anaerobic respiration. However, addition of pyruvate to the medium allowed its growth through fermentation and anaerobic respiration. The knowledge acquired in this work could be relevant both for the design of a production process as well as for the formulation of an effective commercial biocontrol product.A fisiologia de B. subtilis R14 foi investigada em meio mínimo em condições de excesso e limitação de oxigênio. Crescimento e esporulação eficientes foram obtidas em culturas com excesso de oxigênio em meio contendo fontes de carbono e nitrogênio de fácil assimilação, que permitiram alta taxa de crescimento e alto rendimento em biomassa. Uma fase de transição curta, entre o crescimento exponencial e a esporulação, pode ser obtida pela formulação de um meio com razão C/N balanceada. Sob limitação de oxigênio, mas em presença de nutrientes essenciais, B. subtilis R14 produziu compostos bioativos. Os compostos apresentaram atividade contra várias bactérias fitopatogênicas. Sob condição de anaerobiose, o microrganismo não cresceu, nem através de fermentação nem de respiração anaeróbica. A adição de piruvato ao meio permitiu o crescimento, tanto através de fermentação como de respiração anaeróbica. O conhecimento adquirido neste trabalho é relevante tanto para o projeto do processo de produção quanto para a formulação de um produto comercial eficiente para biocontrole.

This study aims at investigating decomposition processes in wetlands that are daily or seasonally exposed to intermittent oxic and anoxic conditions. We hypothesized that in wetland ecosystems where anoxia regularly establishes, decomposition rates are not affected by oxygen shortage, especially when nitrates are available. Monitoring and experiments were performed from December 2003 to January 2005 in one of the widest (81 ha) freshwater wetlands in the Po river floodplain (Natural Reserve Paludi del Busatello, Italy). Intact sediment cores were sampled on a seasonal basis. Sediment-water fluxes of oxygen, dissolved inorganic carbon, methane, and inorganic nitrogen were determined under oxic and anoxic conditions. Oxic-anoxic transitions always resulted in enhanced ammonium, dissolved inorganic carbon, and methane effluxes. At high temperatures, the methane release from sediments was inversely related to both nitrate concentrations and uptake. Likely, nitrate can compensate for the oxygen deficiency while maintaining an oxidative metabolism, either supporting microbial decomposition as an electron acceptor or stimulating the oxidation of the byproducts of the anaerobic metabolism, e.g., methane. This is a key point as the number of temperate wetlands with concurrent nitrate pollution and oxygen shortage is increasing throughout the world. [ABSTRACT FROM AUTHOR]

The kinetics of astaxanthin degradation and lipid oxidation in shrimp oil from hepatopancreas of Pacific white shrimp ( Litopenaeus vannamei) as affected by storage temperature were studied. When shrimp oil was incubated at different temperatures (4, 30, 45 and 60 °C) for 16 h, the rate constants ( k) of astaxanthin degradation and lipid oxidation in shrimp oil increased with increasing temperatures ( p < 0.05). Thus, astaxanthin degradation and lipid oxidation in shrimp oil were augmented at high temperature. When shrimp oils with different storage conditions (illumination, oxygen availability and temperature) were stored for up to 40 days, astaxanthin contents in all samples decreased throughout storage ( p < 0.05). All factors were able to enhance astaxanthin degradation during 40 days of storage. With increasing storage time, the progressive formation of primary and secondary oxidation products were found in all samples as evidenced by the increases in both peroxide values (PV) and thiobarbituric acid reactive substances (TBARS) ( p < 0.05). Light, air and temperatures therefore had the marked effect on astaxanthin degradation and lipid oxidation in shrimp oils during the extended storage. [ABSTRACT FROM AUTHOR]

How complex physiological systems evolve is one of the major questions in evolutionary physiology. For example, how traits interact at the physiological and genetic level, what are the roles of development and plasticity in Darwinian evolution, and eventually how physiological traits will evolve, remains poorly understood. In this article we summarize the current frame of work evolutionary physiologists are employing to study the evolution of physiological adaptations, as well as the role of developmental and reversible phenotypic plasticity in this context. We also highlight representative examples of how the integration of evolutionary and developmental physiology, concomitantly with the mechanistic understanding of physiological systems, can provide a deeper insight on how endothermic vertebrates could cope with reduced ambient temperatures and oxygen availability characteristic of high altitude environments. In this context, high altitude offers a unique system to study the evolution of physiological traits, and we believe much can be gained by integrating theoretical and empirical knowledge from evolutionary biology, such as life-history theory or the comparative method, with the mechanistic understanding of physiological processesUna de las preguntas más importantes en fisiología evolutiva es como evolucionan los sistemas fisiológicos complejos. Por ejemplo, actualmente sabemos poco sobre la interacción entre varios rasgos a niveles genéticos y fisiológicos, sobre el papel de la plasticidad fenotípica durante distintas etapas del desarrollo y madurez para la evolución fisiológica dentro de un linaje. En este trabajo explicamos el marco conceptual ocupado por fisiólogos evolutivos en la actualidad para estudiar adaptaciones fisiológicas a nivel evolutivo y el papel de la plasticidad dentro de la evolución Darviniana. Citamos ejemplos de como la integración de la fisiología evolutiva y del desarrollo nos permitió un mayor entendimiento de como vertebrados endotérmicos pueden "adaptarse" a altas altitudes. Los organismos de alta altitud ofrecen un excelente sistema para estudiar la evolución de rasgos fisiológicos, y hay mucho por aprender en ese contexto al integrarse el conocimiento teórico y empírico de la biología evolutiva, tales como teoría de historia de vida o el método comparativo, con el conocimiento mecanicista de los procesos fisiológicos

Two major intraspecific patterns of adult size variation are plastic temperature-size (T-S) responses and latitude-size (L-S) clines. Yet, the degree to which these co-vary and share explanatory mechanisms has not been systematically evaluated. We present the largest quantitative comparison of these gradients to date, and find that their direction and magnitude co-vary among 12 arthropod orders ( r2 = 0.72). Body size in aquatic species generally reduces with both warming and decreasing latitude, whereas terrestrial species have much reduced and even opposite gradients. These patterns support the prediction that oxygen limitation is a major controlling factor in water, but not in air. Furthermore, voltinism explains much of the variation in T-S and L-S patterns in terrestrial but not aquatic species. While body size decreases with warming and with decreasing latitude in multivoltine terrestrial arthropods, size increases on average in univoltine species, consistent with predictions from size vs. season-length trade-offs. [ABSTRACT FROM AUTHOR]

We investigated how oxygen availability, substrate amount, and quality affect the temperature dependency of enzymatic processes involved in the production of carbon dioxide (CO) and nitrous oxide (NO). Three substrates differing in microbial degradability (glucose with potassium nitrate, glycine, and phenylalanine) were added to a mountain grassland soil at a range of concentrations. Soils were incubated at 21 and 1 % of O content and at 10 and 20 °C. Oxygen availability was a main factor controlling the reaction rates and temperature sensitivity of CO and NO production. The temperature sensitivity of CO production was higher under aerobic versus oxygen-limited conditions, and the opposite dependency was observed for the NO production. Substrate availability was a second factor affecting the temperature sensitivity of the processes leading to the production of these gases. The temperature response was reduced under substrate limitation. Apparent activation energy for aerobic CO production was similar ( E ~ 30 kJ mol) for tested substrates, while E for anaerobic NO production increased in the order phenylalanine < glycine < glucose + NO having values 45, 75, and 106 kJ mol, respectively. Commonly, the temperature sensitivity of NO production (2 < Q < 4.5) was much higher than that for CO ( Q ≤ 1.5). [ABSTRACT FROM AUTHOR]