Activity of cytochrome c oxidase and lactate dehydrogenase in muscle tissue of slow growing (lower modal group) and fast growing (upper modal group) Atlantic salmon

Fast growing Atlantic salmon (upper modal group) exhibit a higher activity of muscle cytochrome c oxidase (CCO) and lactate dehydrogenase (LDH) than the slow growing salmon (lower modal group). The ratios of CCO/LDH activity, indicate a higher aerobic/anaerobic metabolic potential of the axial muscle in the upper modal group.     

Ethanol-dependent oxygen consumption and acetaldehyde formation during vanadyl oxidation by H2O2

Sequential addition of vanadyl sulfate to a phosphate-buffered solution of H₂O₂ released oxygen only after the second batch of vanadyl. Ethanol added to such reaction mixtures progressively decreased oxygen release and increased oxygen consumption during oxidation of vanadyl by H₂O₂. Inclusion of ethanol after any of the three batches of vanadyl resulted in varying amounts of oxygen consumption, a property also shared by other alcohols (methanol, propanol and octanol). On increasing the concentration of ethanol, vanadyl sulfate or H₂O₂, both oxygen consumption and acetaldehyde formation increased progressively. Formation of acetaldehyde decreased with increase in the ratio of vanadyl:H₂O₂ above 2:1 and was undetectable with ethanol at 0.1 mM. The reaction mixture which was acidic in the absence of phosphate buffer (pH 7.0), released oxygen immediately after the first addition of vanadyl and also in presence of ethanol soon after initial rapid consumption of oxygen, with no accompanying acetaldehyde formation. The results underscore the importance of some vanadium complexes formed during vanadyl oxidation in the accompanying oxygen-transfer reactions.     

Oxidative damage to sarcoplasmic reticulum Ca2+-pump induced by Fe2+/H2O2/ascorbate is not mediated by lipid peroxidation or thiol oxidation and leads to protein fragmentation

The major protein in the sarcoplasmic reticulum (SR) membrane is the Ca²⁺ transporting ATPase which carries out active Ca²⁺ pumping at the expense of ATP hydrolysis. The aim of this work was to elucidate the mechanisms by which oxidative stress induced by Fenton's reaction (Fe²⁺ + H₂O₂ HO· + OH^–+ Fe³⁺) alters the function of SR. ATP hydrolysis by both SR vesicles (SRV) and purified ATPase was inhibited in a dose-dependent manner in the presence of 0–1.5 MM H₂O₂ plus 50 M Fe²⁺ and 6 mM ascorbate. Ca²⁺ uptake carried out by the Ca²⁺-ATPase in SRV was also inhibited in parallel. The inhibition of hydrolysis and Ca²⁺ uptake was not prevented by butylhydroxytoluene (BHT) at concentrations which significantly blocked formation of thiobarbituric acid-reactive substances (TBARS), suggesting that inhibition of the ATPase was not due to lipid peroxidation of the SR membrane. In addition, dithiothreitol (DTT) did not prevent inhibition of either ATPase activity or Ca²⁺ uptake, suggesting that inhibition was not related to oxidation of ATPase thiols. The passive efflux of ⁴⁵Ca²⁺ from pre-loaded SR vesicles was greatly increased by oxidative stress and this effect could be only partially prevented (ca 20%) by addition of BHT or DTT. Trifluoperazine (which specifically binds to the Ca²⁺-ATPase, causing conformational changes in the enzyme) fully protected the ATPase activity against oxidative damage. These results suggest that the alterations in function observed upon oxidation of SRV are mainly due to direct effects on the Ca²⁺-ATPase. Electrophoretic analysis of oxidized Ca²⁺-ATPase revealed a decrease in intensity of the silver-stained 110 kDa Ca²⁺-ATPase band and the appearance of low molecular weight peptides (MW < 100 kDa) and high molecular weight protein aggregates. Presence of DTT during oxidation prevented the appearance of protein aggregates and caused a simultaneous increase in the amount of low molecular weight peptides. We propose that impairment of function of the Ca²⁺-pump may be related to aminoacid oxidation and fragmentation of the protein.Abbreviations AcP acetylphosphate - BHT butylhydroxytoluene - DTT dithiothreitol - Hepes 4-(2-hydroxyethyl)-1-piperazine-ethanesulfonic acid - SDS sodium dodecyl sulfate - SDS-PAGE polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate - SR sarcoplasmic reticulum - SRV sarcoplasmic reticulum vesicles - TBA thiobarbituric acid - TBARS thiobarbituric acid-reactive substances - TFP trifluoperazine     

The effect of a propionic acid bacterial inoculant applied at ensiling on the aerobic stability of wheat and sorghum silages

The effect of a new strain ofPropionibacterium shermanii (PAB), applied at ensiling, on the aerobic stability of wheat and sorghum silages was studied in several experiments under laboratory conditions. In the one experiment with wheat and in those with sorghum a lactic acid bacteria (LAB) inoculant (Lactobacillus plantarum andPediococcus cerevisiae) was also included. After treatment, the chopped forages were ensiled in 1.5-L anaerobic jars which were sampled in triplicate on predetermined dates to follow fermentation dynamics. At the end of the experiments, the silages were subjected to an aerobic stability test. The PAB inoculant improved the aerobic stability only in one experiment with wheat, in which the decrease in pH was very slow; the final pH remained relatively high (4.5). The PAB-treated silages contained 19.5±2.0 g of propionic acid per kg of dry matter. In the experiments with sorghum, the control and PAB-inoculated silages were stable, whereas LAB-inoculated silages deteriorated. The results suggest that PAB can survive in and improve the aerobic stability of only slow-fermenting silages which are prone to aerobic deterioration.     

Inhibition of the catalase reaction of Photosystem II by anions

A new binding site for anions which inhibit the water oxidizing complex (WOC) of Photosystem II in spinach has been identified. Anions which bind to this site inhibit the flash-induced S₂/S₀ catalase reaction (2H₂O₂2H₂O+O₂) of the WOC by displacing hydrogen peroxide. Using a mass spectrometer and gas permeable membrane to detect the ³²O₂ product, the yield and lifetime of the active state of the flash-induced catalase (to be referred to simply as flash-catalase) reaction were measured after forming the S₂ or S₀-states by a short flash. The increase in flash-catalase activity with H₂O₂ concentration exhibits a K_m=10–20 mM, and originates from an increase in the lifetime by 20-fold of the active state. The increased lifetime in the presence of peroxide is ascribed to formation of the long-lived S₀-state at the expense of the unstable S₂-state. The anion inhibition site differs from the chloride site involved in stimulating the photolytic water oxidation reaction (2H₂OO₂+4e^-+4H⁺). Whereas water oxidation requires Cl^- and is inhibited with increasing effectiveness by F^-CN^-N₃ ^-, the flash-catalase reaction is weakly inhibited by Cl^-, and with increasing effectiveness by F^-CN^-, N₃ ^-. Unlike water oxidation, chloride is unable to suppress or reverse inhibition of the flash-catalase reaction caused by these anions. The inhibitor effectiveness correlates with the pK_a of the conjugate acid, suggesting that the protonated species may be the active inhibitor. The reduced activity arises from a shortening of the lifetime of the flash-induced catalase active state by 3–10 fold owing to stronger anion binding in the flash-induced states, S₂ and S₀, than in the dark S-states, S₁ and S_-1. To account for the paradoxical result that higher anion concentrations are required to inhibit at lower H₂O₂ concentrations, where S₂ forms initially after the flash, than at higher H₂O₂ concentrations, where S₀ forms initially after the flash, stronger anion binding to the S₀-state than to the S₂-state is proposed. A kinetic model is given which accounts for these equilibria with anions and H₂O₂. The rate constant for the formation/release of O₂ by reduction of S₂ in the WOC is <0.4 s^-1.Abbreviations ADRY acceleration of the deactivation reactions of the water splitting enzyme system Y - BTP bis [tris(hydroxymethyl)methylamino]-propane - CCCP carbonylcyanide m-chlorophenylhyrazone - DCBQ 2,5-dichlorobenzoquinone - DMBQ 2,3-dimethylbenzoquinone - WOC water oxidizing complex     

Decreasing glycolysis increases sensitivity to mitochondrial inhibition in primary cultures of renal proximal tubule cells

Summary We have previously shown that shaking the culture plates (SHAKE) of rabbit renal proximal tubule cells (RPTC) to maintain adequate aeration increased aerobic metabolism and decreased the induction of glycolysis compared to RPTC cultured under standard conditions (STILL). However, glycolysis in SHAKE RPTC remained elevated compared to glycolysis in proximal tubules in vivo. In the present study the contribution of culture medium sugar composition and concentration to glycolytic metabolism was assessed in RPTC. SHAKE and STILL RPTC cultured in 5 mM glucose contained lactate levels equivalent to the respective SHAKE and STILL RPTC cultured in standard culture medium which contains 17.5 mM glucose. Similarly, the activity of lactate dehydrogenase was unchanged by lowering the medium glucose concentration. Substituting 5 mM galactose for 5 mM glucose in the culture medium significantly reduced the lactate content of both SHAKE and STILL RPTC but had no effect on lactate dehydrogenase activity. Cell growth was equivalent under all culture conditions. Sensitivity to mitochondrial inhibition was determined for each culture condition by measuring cell death after exposure to the respiratory inhibitor antimycin A. The results showed a hierarchy of sensitivity to antimycin A (5 mM galactose SHAKE >5 mM glucose SHAKE >17.5 mM glucose SHAKE = 17.5 mM glucose STILL), which was generally inversely correlated with the level of glycolysis as measured by lactate content (17.5 mM glucose STILL >17.5 mM glucose SHAKE = 5 mM glucose SHAKE >5 mM galactose SHAKE).     

Ozonolysis of Thymidine: Isolation and Identification of the Main Oxidation Products

The ozone-mediated oxidation of thymidine was investigated on the basis of final product identification. The oxidation reaction gave rise to five major modified nucleosides which were isolated and characterised from extensive H NMR and mass spectrometry studies. The comparison with the current knowledge of the hydroxyl radical-mediated oxidation reactions of thymidine in aerated aqueous solution indicates that the formation of ozone oxidation products may be mostly explained in terms of initial generation of an ozonide. Indeed, the identified products obtained by ozonolysis of thymidine resulted from the opening of the pyrimidine C5-C5 bond.     

Complete ammonia oxidization in agricultural soils: High ammonia fertilizer loss but low N2O production

The contribution of agriculture to the sustainable development goals requires climate-smart and profitable farm innovations. Increasing the ammonia fertilizer applications to meet the global food demands results in high agricultural costs, environmental quality deterioration, and global warming, without a significant increase in crop yield. Here, we reported that a third microbial ammonia oxidation process, complete ammonia oxidation (comammox), is contributing to a significant ammonia fertilizer loss (41.9 ± 4.8%) at the rate of 3.53 ± 0.55 mg N kg⁻¹ day⁻¹ in agricultural soils around the world. The contribution of comammox to ammonia fertilizer loss, occurring mainly in surface agricultural soil profiles (0–0.2 m), was equivalent to that of bacterial ammonia oxidation (48.6 ± 4.5%); both processes were significantly more important than archaeal ammonia oxidation (9.5 ± 3.6%). In contrast, comammox produced less N₂O (0.98 ± 0.44 μg N kg⁻¹ day⁻¹, 11.7 ± 3.1%), comparable to that produced by archaeal ammonia oxidation (16.4 ± 4.4%) but significantly lower than that of bacterial ammonia oxidation (72.0 ± 5.1%). The efficiency of ammonia conversion to N₂O by comammox (0.02 ± 0.01%) was evidently lower than that of bacterial (0.24 ± 0.06%) and archaeal (0.16 ± 0.04%) ammonia oxidation. The comammox rate increased with increasing soil pH values, which is the only physicochemical characteristic that significantly influenced both comammox bacterial abundance and rates. Ammonia fertilizer loss, dominated by comammox and bacterial ammonia oxidation, was more intense in soils with pH >6.5 than in soils with pH <6.5. Our results revealed that comammox plays a vital role in ammonia fertilizer loss and sustainable development in agroecosystems that have been previously overlooked for a long term.     

好氧反硝化细菌及其在微污染水源水修复中的应用研究进展

相比于氨氮,天然水体中的硝酸盐氮通常更稳定,导致更难将其从水中去除。由于好氧反硝化可以在有氧环境下进行反硝化作用去除硝酸盐氮,该过程对含有较高溶解氧的天然水体中硝酸盐氮处理有重要作用。本文综述了好氧反硝化菌的分离纯化现状、微生物代谢机制和环境影响因子,并介绍了功能菌群在微污染饮用水源水生物修复的应用研究进展。与一般的厌氧反硝化类似,好氧反硝化菌的种属分布较广,常见的如假单胞菌属(Pseudomoas)、产碱杆菌属(Alcaligenes)、副球菌属(Paracoccus)和芽孢杆菌属(Bacillus)等所属部分微生物均有好氧反硝化能力。大部分好氧反硝化菌株在最佳生长条件下(25–37℃、溶解氧浓度为3–5mg/L、pH为7–8、碳氮比为5–10)具有高效的脱氮效率。但目前好氧反硝化作用在微污染饮用水源水的生物修复方面的应用仍有着脱氮性能不稳定、菌剂流失等不足。此外,目前较少相关中试及实际工程应用的研究,需要进一步的深入探究。