Mode Of Energy Metabolism Research Articles

Microbial metabolic flexibility guarantees function resilience in response to starvation disturbance

Starvation disturbance due to nutrient limitation is a common problem in bioreactors. However, an understanding of how microbial systems respond to starvation remains in its infancy. Here the metabolic response mechanism of a biofilm community to starvation was investigated using a well-controlled gaseous toluene treatment biofilter through interruption of its operation. It was found that metabolic characteristics showed significant differences before and after starvation. The dominant carbon source utilization type shifted from amino acids and carboxylic acids to esters and carbohydrates after starvation, which is more conducive to improving energy production. Metagenomic sequencing analysis supported that the changes in the dominant metabolic substrate, enhanced metabolic stability, and flexibility in the mode of energy metabolism could be the main ways to guarantee functional resilience in ecosystems after starvation. The results highlight the microbial metabolic response to starvation, which would be beneficial to the understanding of functional resilience and bioreactor stability.

Global diversity and inferred ecophysiology of microorganisms with the potential for dissimilatory sulfate/sulfite reduction.

Sulfate/sulfite-reducing microorganisms (SRM) are ubiquitous in nature, driving the global sulfur cycle. A hallmark of SRM is the dissimilatory sulfite reductase encoded by the genes dsrAB. Based on analysis of 950 mainly metagenome-derived dsrAB-carrying genomes, we redefine the global diversity of microorganisms with the potential for dissimilatory sulfate/sulfite reduction and uncover genetic repertoires that challenge earlier generalizations regarding their mode of energy metabolism. We show: (i) 19 out of 23 bacterial and 2 out of 4 archaeal phyla harbor uncharacterized SRM, (ii) four phyla including the Desulfobacterota harbor microorganisms with the genetic potential to switch between sulfate/sulfite reduction and sulfur oxidation, and (iii) the combination as well as presence/absence of different dsrAB-types, dsrL-types and dsrD provides guidance on the inferred direction of dissimilatory sulfur metabolism. We further provide an updated dsrAB database including>60% taxonomically resolved, uncultured family-level lineages and recommendations on existing dsrAB-targeted primers for environmental surveys. Our work summarizes insights into the inferred ecophysiology of newly discovered SRM, puts SRM diversity into context of the major recent changes in bacterial and archaeal taxonomy, and provides an up-to-date framework to study SRM in a global context.

Knockdown of PFKFB2 Alleviates Oxidative Stress and Inflammation in LPS-Induced Alveolar Epithelial Cells by Reducing Glycolysis

Glycolysis is the most important mode of energy metabolism in endothelial cells and has been shown to be involved in the pathological processes of acute and chronic inflammatory diseases. Phosphofructokinase 2/fructose-2, 6-bisphosphatase 2 (PFKFB2) exerts an important regulatory factor in the process of glycolysis by catalyzing the synthesis and degradation of fructose 2,6-bisphosphate. There is still unclear however, whether PFKFB2 can play a role in sepsis-related acute lung injury by regulating glycolysis. This research examines the role and mechanism of PFKFB2 in LPS-induced alveolar epithelial cells. In this study, the detection of mRNA expressions of PFKFB2, glycolysis and inflammation-related proteins employed quantitative real-time PCR (RTqPCR). Western blot was applied to examine the expressions of all proteins. The viability of A549 cells was assessed with the use of cell counting kit (CCK)-8. The expressions of related factors were quantified by commercial assay kits, respectively. The experimental results showed that the expression of PFKFB2 was increased in sepsis. Knockdown of PFKFB2 alleviated glycolysis in LPS-induced A549 cells. Additionally, knockdown of PFKFB2 reduced LPS-induced oxidative stress and inflammation through glycolysis. Knockdown of PFKFB2 also mitigated LPS-induced oxidative stress and inflammation in alveolar epithelial cells by reducing glycolysis. Hence, PFKFB2 may be served as an effective target for the treatment of sepsis-related acute lung injury.

Effects of Flow Velocity on the Growth and Survival of Haliotis discus hannai Larvae in the Recirculating Upflow System From the Point of Energy Metabolism

For the abalone Haliotis discus hannai, attachment and metamorphosis are crucial stages in the transition from planktonic to benthic life. Increasing the larval metamorphosis rate by artificially controlling the external environment and simulating natural seawater flow is vital to enhance the hatchery efficiency of H. discus hannai. Thus, in the current study, an upflow recirculating aquaculture unit was designed for the rearing of larval abalone, and the larval hatching rate, survival rate, mode of energy metabolism, and expression levels of metamorphosis-related genes at different flow velocities (0, 5, 10, 20, and 40 L/h) were compared and analyzed. At flow velocities less than 20 L/h, no significant differences occurred in larval hatching, survival, and metamorphosis rates, whereas significant differences were recorded at flow rates of 20 and 40 L/h. Differences were also observed in the activity of enzymes, such as hexokinase (HK), pyruvate kinase (PK), lactate dehydrogenase (LDH), succinate dehydrogenase (SDH), and malate dehydrogenase (MDH), as well as glycogen levels, at the higher flow rates. These results suggested that velocity in excess of a certain limit leads to a higher glycolysis rate and transition of energy utilization from aerobic to anaerobic metabolism for the abalone larvae. Compared with conventional still-water aquacultural systems, the flow velocity at 5–10 L/h could maintain the water environment stability, and avoid both fertilized eggs from being densely deposited before hatching and the consumption of energy needed to resist high flow velocities. Thus, these results are useful references to enhance the hatchery efficiency, and to conduct large-scale rearing, of abalone larvae.

Oxidoreductase Activities in Oxyphilic Tissues of the Black Sea Ruff Scorpaena porcus under Short-term Hydrogen Sulfide Loading

Hydrogen sulfide can both exert a toxic effect and function as a signaling molecule in various physiological processes. Under conditions of experimental short-term hydrogen sulfide loading (HSL), activities of oxidoreductases (enzymes of energy metabolism and antioxidant defense)—malate dehydrogenase (MDH, 1.1.1.37), lactate dehydrogenase (LDH, 1.1.1.27) and catalase (1.11.1.6) were analyzed in oxyphilic tissues (brain, heart, gills) of the Black Sea sea ruff Scorpaena porcus Linnaeus, 1758. Two groups of fish were exposed for 5 min to different concentrations of sodium sulfide (37 and 75 µM Na2S) used as a hydrogen sulfide donor. High MDH and LDH activities were simultaneously detected in the brain structures and heart chambers, reflecting a similar potential of energy metabolism in these tissues, while enhanced LDH activity in the brain indicated anaerobization of the energy metabolism pathways. Differences in oxydoreductase activities were found between the first and fourth branchial arches, heart atrium and ventricle, as well as between different brain compartments. Under HSL, the gills exhibited some signs of hypoxemia (increasing darkening of the lamellae as the Na2S concentration moved upward) and metabolic depression. At a low Na2S concentration, HSL did not cause significant changes in oxidoreductase activities in the brain and heart, while upon a 2-fold increase in the Na2S concentration these changes became more pronounced. In the key oxyphilic structures (anterior brain compartments, heart ventricle) intense HSL led to a simultaneous increase in LDH and MDH activities, which was due to the ability of MDH to participate in anaerobic processes. The less O2-sensitive structures (medulla oblongata and heart atrium) exhibited almost no changes in MDH and LDH activities even in response to high-intensity HSL, suggesting a different mode of energy metabolism in these tissues. Under intense HSL, the oxidoreductases in the heart ventricles and anterior brain compartments demonstrated responses, which were similar to those under hypoxia/anoxia.

Insights into the regulation of molecular mechanisms involved in energy shortage in detached citrus fruit

Harvested fruit undergo carbon and energy deprivation. However, the events underlying this energy-related stress in detached fruit and their involvement in cell damage have not yet been elucidated. We showed that supplementing detached sweet oranges with additional carbon or energy sources reduced peel damage, while inhibitors of energy metabolism increased it. We investigated the effect of an exogenous source of carbon (glycerol), energy (ATP), and an inhibitor of energy metabolism 2-deoxy-D-glucose (DeOGlc) + sodium iodoacetate (IAc), on the transcriptome of harvested fruit flavedo (outer peel part). ATP and Gly induced common, but also specific, alternative modes of energy metabolism by reducing the stress caused by energy shortage. They also induced shifts in energy metabolism that led to the production of the intermediates required for plant defense secondary metabolites to form. ATP and Gly triggered changes in the expression of the genes involved in cell lesion containment through a defined pathway involving hormones and redox-mediated signaling. DeOGlc + IAc had a contrasting effect on some of these mechanisms. These chemicals altered the biological processes related to membrane integrity and molecular mechanisms involving reactive oxygen species (ROS) production, and lipid and protein degradation.

АКТИВНОСТЬ ОКСИДОРЕДУКТАЗ В ОКСИФИЛЬНЫХ ТКАНЯХ МОРСКОГО ЕРША SCORPAENA PORCUS LINNAEUS, 1758 ПРИ КРАТКОСРОЧНОЙ СЕРОВОДОРОДНОЙ НАГРУЗКЕ

Hydrogen sulfide can exert a toxic effect and also function as a signaling molecule in various physiological processes. Under conditions of short-term experimental hydrogen sulfide loading (HSL), activities of oxidoreductases (enzymes of energy metabolism and antioxidant defense) - malate dehydrogenase (MDH, 1.1.1.37), lactate dehydrogenase (LDH, 1.1.1.27), catalase (1.11.1.6) – were analyzed in oxyphilic tissues (brain, heart, gills) of the Black Sea scorpionfish Scorpaena porcus Linnaeus, 1758. Two groups of fish were exposed for 5 min to different concentrations of sodium sulfide (37 and 75 μM Na2S) used as a hydrogen sulfide donor. High MDH and LDH activities were detected in the brain structures and heart chambers, reflecting a similar potential of energy metabolism in these tissues, while enhanced LDH activity in the brain indicated anaerobization of the energy metabolism pathways. Differences in oxydoreductase activities were found between the first and fourth branchialarches, heart atrium and ventricle, as well as between different brain compartments. Under HSL, the gills exhibited some signs of hypoxemia (increasing darkening of the lamellae as the Na2S concentration moved upward) and metabolic depression. At a low Na2S concentration, HSL did not cause significant changes in oxidoreductase activities in the brain and heart, while upon a 2-fold increase in the concentration these changes became more pronounced. In the key oxyphilic structures (anterior brain compartments, heart ventricle) intense HSL led to a simultaneous increase in LDH and MDH activities, which was due to the ability of MDH to participate in anaerobic processes. The less O2-sensitive structures (medulla oblongata and heart atrium) exhibited almost no changes in MDH and LDH activities even in response to high-intensity HSL, suggesting a different mode of energy metabolism in these tissues. Under intense HSL, the oxidoreductases in the heart ventricles and anterior brain compartments demonstrated responses, which were similar to those under hypoxia/anoxia.

Long-chain vitamin K2 production in Lactococcus lactis is influenced by temperature, carbon source, aeration and mode of energy metabolism

BackgroundVitamin K2 (menaquinone, MK-n) is a lipid-soluble vitamin that functions as a carboxylase co-factor for maturation of proteins involved in many vital physiological processes in humans. Notably, long-chain vitamin K2 is produced by bacteria, including some species and strains belonging to the group of lactic acid bacteria (LAB) that play important roles in food fermentation processes. This study was performed to gain insights into the natural long-chain vitamin K2 production capacity of LAB and the factors influencing vitamin K2 production during cultivation, providing a basis for biotechnological production of vitamin K2 and in situ fortification of this vitamin in food products.ResultsWe observed that six selected Lactococcus lactis strains produced MK-5 to MK-10, with MK-8 and MK-9 as the major MK variant. Significant diversities between strains were observed in terms of specific concentrations and titres of vitamin K2. L. lactis ssp. cremoris MG1363 was selected for more detailed studies of the impact of selected carbon sources tested under different growth conditions [i.e. static fermentation (oxygen absent, heme absent); aerobic fermentation (oxygen present, heme absent) and aerobic respiration (oxygen present, heme present)] on vitamin K2 production in M17 media. Aerobic fermentation with fructose as a carbon source resulted in the highest specific concentration of vitamin K2: 3.7-fold increase compared to static fermentation with glucose, whereas aerobic respiration with trehalose resulted in the highest titre: 5.2-fold increase compared to static fermentation with glucose. When the same strain was applied to quark fermentation, we consistently observed that altered carbon source (fructose) and aerobic cultivation of the pre-culture resulted in efficient vitamin K2 fortification in the quark product.ConclusionsWith this study we demonstrate that certain LAB strains can be employed for efficient production of long-chain vitamin K2. Strain selection and optimisation of growth conditions offer a viable strategy towards natural vitamin K2 enrichment of fermented foods, and to improved biotechnological vitamin K2 production processes.

De novo DNA methylation during monkey pre-implantation embryogenesis

Critical epigenetic regulation of primate embryogenesis entails DNA methylome changes. Here we report genome-wide composition, patterning, and stage-specific dynamics of DNA methylation in pre-implantation rhesus monkey embryos as well as male and female gametes studied using an optimized tagmentation-based whole-genome bisulfite sequencing method. We show that upon fertilization, both paternal and maternal genomes undergo active DNA demethylation, and genome-wide de novo DNA methylation is also initiated in the same period. By the 8-cell stage, remethylation becomes more pronounced than demethylation, resulting in an increase in global DNA methylation. Promoters of genes associated with oxidative phosphorylation are preferentially remethylated at the 8-cell stage, suggesting that this mode of energy metabolism may not be favored. Unlike in rodents, X chromosome inactivation is not observed during monkey pre-implantation development. Our study provides the first comprehensive illustration of the 'wax and wane' phases of DNA methylation dynamics. Most importantly, our DNA methyltransferase loss-of-function analysis indicates that DNA methylation influences early monkey embryogenesis.

Abstract 4933: Novel insight into hallmark switch in cancer metabolism using the Interrogative Biology™ discovery platform

Abstract Cancer metabolism is an intergrative ensemble of disrupted enzyme kinetics and dysregulated metabolite utilization leading to loss of normal cellular function that is the result of a multi-factorial yet coordinated breakdown in vascular, immune, cell cycle, apoptotic, and ECM components. In actively metabolizing cancer, the switch from mitochondrial OXPHOS to anaerobic glycolysis is very well characterized and understood. Global cellular changes in response to metabolic switch have either been overlooked or not been primary interest or relevance to cancer metabolism. We describe a novel systems biology/engineering approach encompassing cell models that are conditioned under various oncogenic perturbations or environments and then coupled with functional bioenergetic read out such as employing the XF24 Seahorse Bioscience analyzer, ATP assays, and ROS production. The OCR and ECAR measurements generated by XF24 analyzer enabled quantifying the switch from aerobic to the anerobic mode of energy metabolism. Cellular profiles were captured in the form of multi-omic (proteomic, genomic, proteomic) signatures using high-throughput mass spectrometry based protocols. Analyses were performed on oncogenic breast, prostate, liver, pancreatic, skin (melanoma, squamous cell carcinoma) and were compared to normal fibroblasts, keratinocytes, hepatocytes, kidney cells, adipocytes, and human aortic and endothelial cells. High throughput data cascades from various cancer states were integrated with the metabolic data from the XF24 analyzer using an AI-based data mining platform to generate causal network based on bayesian models (REFS™ model). The output enables the understanding of differential mechanisms that drive glycolysis and mitochondrial OXPHOS in a cancer versus normal environment. Further validation of prominent hub of activity as they partake as key drivers of metabolic end points by siRNA knockdown experiments followed by measurement using the XF24 analyzer confirmed the relevance of these hubs in cancer metabolism and their relevance as potential therapeutic targets and biomarkers for diagnostics development. The data output presented herein strongly suggest that the Interrogative Biology® platform is a key tool in deciphering differential network analysis pertinent to disease pathophysiology and bioenergetics. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4933. doi:1538-7445.AM2012-4933

Two putative histidine kinases are required for cyst formation in Rhodospirillum Centenum

The photosynthetic bacterium, Rhodospirillum centenum, has a flexible life cycle that permits it to survive starvation as dormant cyst cells. Previous studies have identified some of the key regulators for encystment and demonstrated that the control of development is intricate. This complexity may arise from the need to integrate several environmental signals to mediate a switch from one mode of energy metabolism to another and to ensure that a transition to dormancy is initiated only when necessary. We searched for additional regulators of development by screening for encystment deficient strains after subjecting wild type R. centenum to mini-Tn5 mutagenesis. Analysis of "hypo-cyst" strains led to the identification of two genes that encode putative hybrid histidine kinases (cyd1 and cyd2). Cells with deletions of either gene fail to form cysts under conditions that normally induce development. Furthermore, the deletion strains exhibit altered swarming behavior suggesting that Cyd1 and Cyd2 affect behaviors utilized when the organism is attached to a substrate.

Temperature induced anaerobiosis in two populations of the polychaete worm Arenicola marina (L.)

Temperature dependent changes in the mode of energy metabolism and in acid-base status were studied in the range from )1.7 to 26 oC in two populations of Are- nicola marina collected in summer as well as in winter from intertidal flats of the North Sea (boreal) and the White Sea (subpolar). Extreme temperatures led to an accumulation of anaerobic end products, indicating the existence of both a low and a high critical temperature, beyond which anaerobic metabolism becomes involved in energy production. In summer animals from the North Sea the high critical temperature was found at tempera- tures above 20 oC, and the low critical temperature below 5 oC. Latitudinal or seasonal cold adaptation lead to a more or less parallel shift of both high and low critical temperature values to lower values. Between critical temperatures intracellular pH declined with rising tem- perature. Slopes varied between )0.012 and )0.022 pH- units/oC. In summer animals from the North Sea, the slope was slightly less than in White Sea animals, but dierences appeared independent of the season. However, slopes were no longer linear beyond critical temperatures. A drop in intracellular pH at low temperatures coincided with the accumulation of volatile fatty acids in the body wall tissue of North Sea animals. A failure of active pHi adjustment is held responsible for the reduced ΔpHi/Δ Ta t temperatures above the high critical temperature. Extra- cellular pH was kept constant over the whole temperature range investigated. The ability of North Sea animals to adapt to temperatures beyond the critical temperature is poor compared to White Sea specimens. The larger range of temperature fluctuations at the White Sea is seen as a reason for the higher adaptational capacity of the sub- polar animals. A hypothesis is proposed that among other mechanisms critical temperature values are set by an adjustment of mitochondrial density and thus, aerobic capacity.

The energy metabolism of the leech Hirudo medicinalis in anoxia and muscular work

AbstractThe medical leech Hirudo medicinalis has only small reserves of glycogen (˜ 40 μmol/g fresh weight), but malate is present in comparatively high concentrations (8 to 10 μmol/gm fresh weight) in the tissues and in the blood. Leeches are able to survive several days of anoxia at 20°C. From the onset of anoxia the level of malate drops rapidly and concomitantly the concentration of succinate rises in converse manner. After the initial phase, both metabolites do not change significantly. Then large quantities of propionate accumulate which, in part, are also excreted into the surrounding water. In contrast, continuous swimming causes the concentration of lactate to rise steeply and lactate is the dominant end product. There is only a modest decrease in the concentration of malate whereas succinate does not change. These distinct patterns of metabolite concentrations arising in anoxia and in muscular activity seem to indicate that different modes of energy metabolism are used in both situations.

Proton motive force in growing Streptococcus lactis and Staphylococcus aureus cells under aerobic and anaerobic conditions.

Measurements of the electrochemical gradient of hydrogen ions, which gives rise to the proton motive force (PMF), were carried out with growing Streptococcus lactis and Staphylococcus aureus cells. The facultative anaerobe was chosen in order to compare the PMF of cells growing aerobically and anaerobically. It was expected that during aerobic growth the cells would have a higher PMF than during anaerobic growth, because the H+-translocating ATPase (BF0F1) operates in the direction of H+ influx and ATP synthesis during respiration, whereas under anaerobic conditions the BF0F1 hydrolyzes glycolytically generated ATP and establishes the proton gradient by extruding H+. The electrical component of the PMF, delta psi, and the chemical gradient of H+, delta pH, were measured with radiolabeled tetraphenylphosphonium and benzoate ions. In both S. lactis and S. aureus cells, the PMF was constant during the exponential phase of batch growth and decreased in the stationary phase. In both species of bacteria, the exponential-phase PMF was not affected by varying the growth rate by adding different sugars to the medium. The relative contributions of delta psi and delta pH to the PMF, however, depended on the pH of the medium. The internal pH of S. aureus was constant at pH 7.4 to 7.6 under all conditions of growth tested. Under aerobic conditions, the delta psi of exponential phase S. aureus remained fairly constant at 160 to 170 mV. Thus, the PMF was 250 to 270 mV in cells growing aerobically in media at pH 6 and progressively lower in media of higher pH, reaching 195 to 205 mV at pH 7. Under anaerobic conditions, the delta psi ranged from 100 to 120 mV in cells at pH 6.3 to 7, resulting in a PMF of 150 to 140 mV. Thus, the mode of energy metabolism (i.e., respiration versus fermentation) and the pH of the medium are the two important factors influencing the PMF of these gram-positive cells during growth.