End Products Of Anaerobic Metabolism Research Articles

Membrane engineering of Escherichia coli based on “Building bridges” and “Digging tunnels” to improve electro-fermentation of succinate

Succinate is the end product of anaerobic metabolism of Escherichia coli, and its over-production needs abundant reducing force. Electro-fermentation (EF) is a novel biotechnology to steer and control fermentative processes by supplying extra electrons. However, E.coli is a non-electroactive strain which needs the support of electron shuttle in EF. Here, membrane engineering strategies of “Building bridges” via screening direct electron transport pathway and “Digging tunnels” via screening membrane porins were developed to improve the transmembrane transport of electron during the cathodic electro-fermentation (CEF). As a result, the total electron quantity during electro-fermentation was increased from 1.21 mmol to 7.90 mmol, and succinate yield was increased by 23.3% when these strategies simultaneously were applied to the succinate candidate E. coli Suc260. Hence, this study provides a reference mode for designing and constructing non-electroactive bacteria for electro-fermentation of reductive metabolites.

Treatment of Refractory Lactic Acidosis With Thiamine Administration in a Non-alcoholic Patient

Lactate, or lactic acid, is an end-product of anaerobic metabolism. The build-up of lactate in the body is commonly due to type A lactic acidosis, resulting from an inability to meet the body’s oxygen delivery demands. When lactic acidosis persists, other causes need to be ruled out. Here, we describe the case of a 63-year-old female who initially presented with hypoglycemia and was found to have significant lactic acidosis. Her blood sugar levels improved with dextrose supplementation; however, lactic acidosis persisted despite fluid hydration and empiric antibiotics. After excluding other causes of lactic acidosis, she was started on intravenous thiamine due to suspicion of thiamine deficiency secondary to poor nutrition. Lactic acid levels improved drastically after starting thiamine supplementation. Thiamine is a water-soluble vitamin that plays an essential role as a cofactor in several biochemical reactions. Thiamine deficiency is a rare, underdiagnosed cause of type B lactic acidosis, with early diagnosis and intervention playing crucial roles in preventing severe cardiac and neurological impairment.

Effects of Continuous Albuterol Inhalation on Serum Metabolome in Healthy Subjects: More Than Just Lactic Acid.

Treatment with β2-agonists may cause elevated lactic acid, the end product of anaerobic metabolism of glucose. It has been proposed that lactic acidosis associated with β2-agonists is caused by changes to direct biochemical impacts on glycolysis, gluconeogenesis, pyruvate metabolism, and free fatty acid production. However, much remains unknown, and there is a paucity of evidence regarding the underlying chemical changes associated with this lactic acidosis. The goal of our study was to investigate the impact of 1 hour of continuous albuterol on the untargeted serum metabolome of healthy subjects. Twenty-four healthy participants received 7.5 mg of continuous albuterol for 1 hour. Baseline, 1-hour, and 2-hour lactic acid levels were drawn. Samples obtained at baseline and 1 hour were sent for untargeted metabolomic profiling. Participants had a baseline lactic acid of 1.45 ± 0.46 mmol/L. On average, lactate levels increased 0.33 ± 0.67 mmol/L after 1 hour (P = .02) and remained elevated at 2 hours (0.32 ± 0.72 mmol/L, P = .02), although there was overlap in lactate levels across times. For metabolomic analysis, fatty acids, organic acids, and sugars were elevated, and amino acids were reduced. Lactic acid and pyruvic acid metabolites, however, did not significantly change (after false discovery rate adjustment). In healthy participants, continuous albuterol alters the serum metabolome, but this change may not be clinically significant. The data support recent hypotheses that β2-receptor activation stimulates lactic acid production, altering aerobic glycolysis, gluconeogenesis, and free fatty acid production.

Resistance training and exercise tolerance during high-intensity exercise: moving beyond just running economy and muscle strength.

Resistance training and exercise tolerance during high-intensity exercise: moving beyond just running economy and muscle strength.

Acidosis Is Not a Significant Cause of Skeletal Muscle Fatigue.

Acute skeletal muscle fatigue develops in situations with high energy demand and large dependency on anaerobic metabolism. When fatigued, muscles become weaker and slower, and two end products of anaerobic metabolism, H+ and inorganic phosphate ions (Pi), have received most attention as causes of th

Utilidad del lactato en el paciente críticamente enfermo

Lactate is the end product of anaerobic metabolism and a valuable diagnostic tool for interpretation, stratification and understanding of different pathological processes of the critically ill patient. Thanks to the technological advances that have led to a steady growth in laboratory techniques, lactate measurement is widely used in clinical practice, providing a more objective criterion to establish risk, diagnoses, prognoses and guide treatments aimed at improving perfusion. Like all diagnostic tests, interpretation of lactate requires a knowledge of pathophysiological processes and the confounding variables to help in making the proper clinical decision for the benefit for the patient. In this review, a comprehensive search of the literature was performed in order to clarify the role of lactate as a biomarker of homeostasis. A description is presented of the origin, metabolism, clearance and usefulness of lactate measurements, showing the most important variables that may affect its value and interpretation as a para-clinical test. A guide to its interpretation is provided, as well as how it correlates with other biomarkers available for the treatment of the critically ill patient.

Paradoxical anaerobism in desert pupfish.

In order to estimate metabolic demands of desert pupfish for conservation purposes, we measured oxygen consumption in fish acclimated to the ecologically relevant temperatures of 28 or 33°C. For these experiments, we used fish derived from a refuge population of Devils Hole pupfish (Cyprinodon diabolis). Measurement of routine oxygen consumption (V̇O2,routine) revealed some 33°C-acclimated fish (10% of 295 assayed fish) periodically exhibited periods of no measurable oxygen consumption despite available ambient oxygen tensions that were above the critical PO2. We call this phenomenon paradoxical anaerobism. The longest observed continuous bout with no oxygen consumption was 149 min, although typical bouts were much shorter. Fish maintained normal posture and ventilation rate (>230 ventilations per minute) during paradoxical anaerobism. Fish rarely demonstrated a compensatory increase in oxygen use following a period of paradoxical anaerobism. In contrast, only one out of 262 sampled fish acclimated at 28°C spontaneously demonstrated paradoxical anaerobism. Muscle lactate concentration was not elevated during periods of paradoxical anaerobism. However, the amount of ethanol released by the 33°C-acclimated fish was 7.3 times greater than that released by the 28°C acclimation group, suggesting ethanol may be used as an alternative end product of anaerobic metabolism. Exposure to exogenous ethanol, in concentrations as low as 0.1%, produced periods of paradoxical anaerobism even in 28°C-acclimated fish.

The squat lobster Pleuroncodes monodon tolerates anoxic “dead zone” conditions off Peru

The squat lobster Pleuroncodes monodon is a key species of the highly productive, but oxygen-poor upwelling system of the Eastern Tropical South Pacific. Observations of P. monodon in the water column off Peru have led to the hypothesis that anoxic conditions force this otherwise primarily benthic species to adopt a pelagic lifestyle. Here we show that off Peru, P. monodon can be found in the oxygenated surface water, but also on the anoxic seafloor. Our physiological experiments demonstrate that juvenile and adult specimens have a very low critical respiratory pO2 of 0.5 kPa and that adults survive anoxia for 30.5–70.5 h. Anoxic conditions at the seafloor should therefore force P. monodon to regularly migrate to the oxic surface layer in order to restore energy reserves and recycle metabolic end products of anaerobic metabolism. It was recently estimated that the ammonium supply mediated by diel vertical migrations (DVMs) of zooplankton and nekton considerably fuels bacterial anaerobic ammonium oxidation—a major loss process for fixed nitrogen in the ocean. These estimates were based on the implicit assumption that anoxia does not result in a down-regulation of ammonium excretion. We here show that exposure to anoxia elicits a fourfold reduction in ammonium excretion from 2.1 ± 0.6 µmol h−1 g dry weight−1 under normoxic to 0.5 ± 0.6 µmol h−1 g DW−1 under anoxic conditions in P. monodon. Estimates of ammonium supply to the anoxic core of oxygen minimum zones via DVM therefore are likely too high.

Paradoxical Anaerobism in Desert Pupfish

Oxidation of glucose through aerobic pathways is ~15X more efficient than is anaerobic metabolism. Pupfish of the genus Cyprinodon experience variable periods of up to nearly 5h of virtually no oxygen consumption. This paradoxical anaerobism occurs in the presence of oxygen. The longest continuous bout was 149 min although more typical bouts are only a few minutes in length. Fish randomly cycle between periods of paradoxical anaerobism and stable oxygen consumption patterns suggesting no long‐term damage or alternations to mitochondria. There is no evidence for compensatory oxygen use. Fish produce ethanol as an apparent alternate end product of anaerobic metabolism. Exposure to exogenous ethanol induces rapid onset of paradoxical anaerobism.

Mitochondrial lactate metabolism is involved in antioxidative defense in human astrocytoma cells

Although lactate has traditionally been known to be an end product of anaerobic metabolism, recent studies have revealed its disparate biological functions. Oxidative energy production and cell signaling are two important roles assigned to this monocarboxylic acid. Here we demonstrate that mitochondrial lactate metabolism to pyruvate mediated by lactate dehydrogenase (LDH) in a human astrocytic cell line is involved in antioxidative defense. The pooling of this α-ketoacid helps to detoxify reactive oxygen species, with the concomitant formation of acetate. In-gel activity assays following blue native PAGE electrophoresis were utilized to demonstrate the increase in mitochondrial LDH activity coupled to the decrease in pyruvate dehydrogenase activity in the cells challenged by oxidative stress. The enhanced production of pyruvate with the concomitant formation of acetate in astrocytoma cells was monitored by high-performance liquid chromatography. The ability of pyruvate to fend off oxidative stress was visualized by fluorescence microscopy with the aid of the dye 2',7'-dichlorodihydrofluorescein diacetate. Immunoblotting helped confirm the presence of elevated levels of LDH in cells exposed to oxidative stress, and recovery experiments were performed with pyruvate to diminish the oxidative burden on the astrocytoma. The acetate, generated as a consequence of the antioxidative attribute of pyruvate, was subsequently channeled toward the production of lipids, a process facilitated by the upregulation in activity of acetyl-CoA synthetase and acetyl-CoA carboxylase, as demonstrated by in-gel activity assays. The mitochondrial lactate metabolism mediated by LDH appears to play an important role in antioxidative defence in this astrocytic system.

Physiological and biochemical responses to cold and drought in the rock-dwelling pulmonate snail, Chondrina avenacea

The pulmonate snail Chondrina avenacea lives on exposed rock walls where it experiences drastic daily and seasonal fluctuations of abiotic conditions and food availability. We found that tolerance to dry conditions was maintained at a very high level throughout the year and was mainly based on the snails' ability to promptly enter into estivation (quiescence) whenever they experienced drying out of their environment. Snails rapidly suppressed their metabolism and minimized their water loss using discontinuous gas exchange pattern. The metabolic suppression probably included periods of tissue hypoxia and anaerobism as indicated by accumulation of typical end products of anaerobic metabolism: lactate, alanine and succinate. Though the drought-induced metabolic suppression was sufficient to stimulate moderate increase of supercooling capacity, the seasonally highest levels of supercooling capacity and the highest tolerance to subzero temperatures were tightly linked to hibernation (diapause). Hibernating snails did not survive freezing of their body fluids and instead relied on supercooling strategy which allowed them to survive when air temperatures dropped to as low as -21°C. No accumulation of low-molecular weight compounds (potential cryoprotectants) was detected in hibernating snails except for small amounts of the end products of anaerobic metabolism.

Melatonin-mitochondria Interplay in Health and Disease

Although two main hypotheses of mitochondrial origin have been proposed, i.e., the autogenous and the endosymbiotic, only the second is being seriously considered currently. The 'hydrogen hypothesis' invokes metabolic symbiosis as the driving force for a symbiotic association between an anaerobic, strictly hydrogen-dependent (the host) and an eubacterium (the symbiont) that was able to respire, but which generated molecular hydrogen as an end product of anaerobic metabolism. The resulting proto-eukaryotic cell would have acquired the essentials of eukaryotic energy metabolism, evolving not only aerobic respiration, but also the physiological cost of the oxygen consumption, i.e., generation of reactive oxygen species (ROS) and the associated oxidative damage. This is not the only price to pay for respiring oxygen: mitochondria possess nitric oxide (NO·) for regulatory purposes but, in some instances it may react with superoxide anion radical to produce the toxic reactive nitrogen species (RNS), i.e. peroxynitrite anion, and the subsequent nitrosative damage. New mitochondria contain their own genome with a modified genetic code that is highly conserved among mammals. The transcription of certain mitochondrial genes may depend on the redox potential of the mitochondrial membrane. Mitochondria are related to the life and death of cells. They are involved in energy production and conservation, having an uncoupling mechanism to produce heat instead of ATP, but they are also involved in programmed cell death. Increasing evidence suggest the participation of mitochondria in neurodegenerative and neuromuscular diseases involving alterations in both nuclear (nDNA) and mitochondrial (mtDNA) DNA. Melatonin is a known powerful antioxidant and anti-inflammatory and increasing experimental and clinical evidence shows its beneficial effects against oxidative/nitrosative stress status, including that involving mitochondrial dysfunction. This review summarizes the data and mechanisms of action of melatonin in relation to mitochondrial pathologies.

SERUM LACTATE AS A PREDICTOR OF MORTALITY IN ACUTE INTESTINAL INFARCTION

PURPOSE: Lactate has been evaluated as a prognostic tool utilized in early goal directed therapy. An end product of anaerobic metabolism, it is associated with mortality in shock states. Accordingly, the objective of this study was to determine if increased serum lactate levels portend a worse outcome in acute intestinal infarction.

Uncoupling of acetate degradation from methane formation in Alaskan wetlands: Connections to vegetation distribution

Laboratory incubations, gas and solute analyses, and stable isotope methods were used to investigate the pathway of methanogenesis in 25 wetland peats of varying vegetation composition along a latitudinal gradient in Alaska. Sites were divided into gross vegetation classes indicative of tropic status: mostly Sphagnum (class 1); Sphagnum plus vascular plants (i.e., Carex) (class 2); mostly vascular plants, but still containing Sphagnum (class 3), and; sites dominated by vascular plants with no visible Sphagnum species (class 4). The magnitude of CO2, acetate and CH4 as end products of anaerobic metabolism varied greatly, but ratios of end product formation indicative of differences in the pathway of C flow and methanogenesis corresponded with vegetation classes, especially at the extremes, e.g., acetate‐C accounted for 67% of total C production in Sphagnum‐rich sites (class 1) decreasing to 13% in sites devoid of sphagna (class 4). Conversely, CH4 comprised only 0.4% of products in class 1 sites, but increased to 14% in class 4. Total respiration rates (sum of all three products) varied by only a factor of ∼2 among vegetation classes (200–440 nmol ml−1 day−1), but rates differed greatly if acetate formation was not included suggesting that belowground C cycling can be much more rapid than previously thought. Apparent fractionation factors (α = δ13CDIC + 1000/δ13CCH4 + 1000) that estimate methanogenic pathway, i.e., the relative contribution of CO2 reduction or acetate as precursors of methane, varied from ∼1.030 to ∼1.080 and agreed with incubation end product ratios, underscoring the importance of the presence or absence of vascular plants and Sphagnum mosses in affecting the pathway of anaerobic C flow. We contend that methanogenesis in general, including CO2 reduction, is impeded in northern wetlands compared to the production of other C compounds and that its importance decreases with oligotrophy. The connection with vegetation suggests that climate change scenarios leading to increases in vascular plant cover in northern wetlands may shift methanogenic pathways toward increased acetotrophy and increased methane formation, which is a positive feedback on warming.

KILLIFISH: CHAMPION ANOXIA SURVIVORS

The annual killifish Austrofundulus limnaeus lives life on the edge. The Venezuelan ponds where it lives rapidly evaporate in the dry season,killing off the adults and exposing their mud-buried embryos to extended periods of drought. Not that drought is the first of the embryo's problems:microbes living in the soil use up all the oxygen. `Not only are they coping with life without water, but also with life without oxygen,' says Jason Podrabsky from Portland State University, who has investigated with his colleagues the root of the embryos' extreme anoxia tolerance(p. 2253).The key to the embryos' survival is that they go into periods of dormancy,or diapause, twice during their development, even if conditions are ideal.`Their environment is very harsh and unpredictable, so diapause occurs as a part of their natural developmental program,' says Podrabsky. Unlike most annual killifish, A. limnaeus embryos skip diapause I at four days of development, but enter diapause II at around 24 days old and diapause III near the end of development. During diapause the metabolism slows down greatly, so could this be the key to surviving anoxia?To assess anoxia tolerance during development, the team collected fertilised embryos from 4 to 32 days old and put them in embryo medium at 25°C before sealing the jars and bubbling nitrogen through them to remove all the oxygen. They then kept a close eye on the developing embryos, opening the jars when they started dying and counting how many of them were still alive. They found that the later embryos were exposed to anoxia, the longer they survived: 4-day-old embryos suffered 50% mortality after 20 days of anoxia, while 32-day-old embryos, in diapause II, suffered 50% mortality after more than 60 days anoxia. This is the longest anoxia survival of any vertebrate at 25°C.The team knew from the brine shrimp, another anoxia tolerant animal that enters diapause, that there is a window of opportunity after diapause where the animal can shut down again even if it has restarted its development. To find out if this window existed in the killifish embryos, they collected embryos just out of diapause II and tested their anoxia tolerance. They found that embryos exposed to anoxia 4 days after the end of diapause were still very tolerant, but lost this tolerance when they were tested 8 days after,showing that post-diapause safety cushion in the killifish is about 4 days.But what about changes in metabolism? The team took embryos of different developmental stages and flash froze them to preserve their metabolites. After mashing them up and extracting their metabolites, which they analysed using chromatrography and mass spectrometry, they found that anoxic embryos produced lactate, succinate and the amino acid alanine, which are end-products of anaerobic metabolism. This suggests that the embryos survive by relying on glycogen stores and reducing their metabolic rate, but that they haven't developed an alternative strategy for dealing with anoxia. Embryos that accumulated lactate at the slowest rate also survived the longest.They also found that anoxic embryos produced lots of the neurotransmitter GABA, which is known to protect neurons in other anoxia tolerant species, such as turtles and the crucian carp. Podrabsky explains that it's possible that GABA is protecting the traditionally anoxia-sensitive brain and heart tissue in diapause II embryos. For now, the killifish embryo can elbow its way onto the roll-call of champion vertebrate anoxia survivors.

Flexibility in energy metabolism supports hypoxia tolerance inDrosophilaflight muscle: metabolomic and computational systems analysis

The fruitfly Drosophila melanogaster offers promise as a genetically tractable model for studying adaptation to hypoxia at the cellular level, but the metabolic basis for extreme hypoxia tolerance in flies is not well known. Using 1H NMR spectroscopy, metabolomic profiles were collected under hypoxia. Accumulation of lactate, alanine, and acetate suggested that these are the major end products of anaerobic metabolism in the fly. A constraint-based model of ATP-producing pathways was built using the annotated genome, existing models, and the literature. Multiple redundant pathways for producing acetate and alanine were added and simulations were run in order to find a single optimal strategy for producing each end product. System-wide adaptation to hypoxia was then investigated in silico using the refined model. Simulations supported the hypothesis that the ability to flexibly convert pyruvate to these three by-products might convey hypoxia tolerance by improving the ATP/H+ ratio and efficiency of glucose utilization.

Lactic acid, pyruvic acid and lactate/pyruvate ratio in the Anoplocephalid tapeworm Stilesia globipunctata infecting sheep ( Ovis aries)

Lactic acid content was found to vary among the different proglottid types of the parasite. This higher amount of lactic acid might be considered as the end product of anaerobic metabolism. The pyruvic acid level of the parasitic proglottides remained lower than lactate level. The intermediary carbohydrate metabolites, viz. lactate, pyruvate and the lactate/pyruvate ratio being indicators of high rate metabolism, their levels may notably infer the metabolic status of the parasite and also the interaction between the parasite species Stilesia globipunctata and the sheep host.

Effect of Temperature on Anaerobic Ethanol Oxidation and Methanogenesis in Acidic Peat from a Northern Wetland

The effects of temperature on rates and pathways of CH4 production and on the abundance and structure of the archaeal community were investigated in acidic peat from a mire in northern Scandinavia (68 degrees N). We monitored the production of CH4 and CO2 over time and measured the turnover of Fe(II), ethanol, and organic acids. All experiments were performed with and without specific inhibitors (2-bromoethanesulfonate [BES] for methanogenesis and CH3F for acetoclastic methanogenesis). The optimum temperature for methanogenesis was 25 degrees C (2.3 micromol CH4.g [dry weight](-1) . day(-1)), but the activity was relatively high even at 4 degrees C (0.25 micromol CH4. g [dry weight](-1) . day(-1)). The theoretical lower limit for methanogenesis was calculated to be at -5 degrees C. The optimum temperature for growth as revealed by real-time PCR was 25 degrees C for both archaea and bacteria. The population structure of archaea was studied by terminal restriction fragment length polymorphism analysis and remained constant over a wide temperature range. Hydrogenotrophic methanogenesis accounted for about 80% of the total methanogenesis. Most 16S rRNA gene sequences that were affiliated with methanogens and all McrA sequences clustered with the exclusively hydrogenotrophic order Methanobacteriales, correlating with the prevalence of hydrogenotrophic methanogenesis. Fe reduction occurred parallel to methanogenesis and was inhibited by BES, suggesting that methanogens were involved in Fe reduction. Based upon the observed balance of substrates and thermodynamic calculations, we concluded that the ethanol pool was oxidized to acetate by the following two processes: syntrophic oxidation with methanogenesis (i) as an H2 sink and (ii) as a reductant for Fe(III). Acetate accumulated, but a considerable fraction was converted to butyrate, making volatile fatty acids important end products of anaerobic metabolism.

Facultative Methanotrophs Revisited

Facultative Methanotrophs Revisited

Brain lesions with elevated lactic acid peaks on magnetic resonance spectroscopy

Magnetic resonance (MR) spectroscopy is a noninvasive imaging tool that provides information on various metabolite concentrations within brain lesions. The biochemical information obtained with MR spectroscopy, along with the morphologic appearance of a lesion on MR imaging, allows for better characterization and improved diagnostic ability. Lactic acid is an end product of anaerobic metabolism. Under conditions of anaerobic metabolism or inflammation, lactate levels become elevated and a characteristic peak at 1.3 ppm is detected on MR spectroscopy. This review will discuss the significance of lactate as a metabolite and will describe various brain lesions and disease conditions in which elevated lactate levels are detected.