Proton Imbalance Research Articles

Effects and molecular mechanism of flagellar gene flgK on the motility, adhesion/invasion, and desiccation resistance of Cronobacter sakazakii

Cronobacter sakazakii (C. sakazakii), a food-borne pathogen, can infect neonates, elderly and immunocompromised populations with a high infection and mortality rate. However, the specific molecular mechanism of its motility, biofilm formation, cell adhesion, and desiccation resistance remains unclear, and flagellum hook associated protein (FlgK), a main component of the flagellar complex, may be an important determinant of its virulence and desiccation resistance. In this study, the flgK mutant strain (ΔflgK) was constructed using the homologous recombination method, and the cpflgK complementary strain was obtained by gene complementation, followed by analysis of the difference between the wild type (WT), mutant, and complementary strains in mobility, biofilm formation, cell adhesion, and desiccation resistance. Results indicated that flgK gene played a positive role in motility and invasion, with no significant effect on biofilm formation. Interestingly, flagellar assembly gene deletion showed increased resistance of C. sakazakii to dehydration. The mechanism underlying the negative correlation of flgK gene with dehydration resistance was further investigated by using the high-throughput sequencing technology to compare the gene expression between WT and ΔflgK strains after drying. The results revealed up-regulation in the expression of 54 genes, including genes involved in osmosis and formate dehydrogenase, while down-regulation in the expression of 50 genes, including genes involved in flagellum hook and nitrate reductase. qRT-PCR analysis of the RNA-seq data further indicated that the flgK gene played an important role in the environmental stress resistance of C. sakazakii by up-regulating the formate dehydrogenase, betaine synthesis, and arginine deiminase pathways, due to dynamic proton imbalance caused by lack of flagella. This study facilitates our understanding of the roles of flgK in motion-related functions and the molecular mechanism of desiccation resistance in C. sakazakii.

Improved anaerobic digestion under ammonia stress by regulating microbiome and enzyme to enhance VFAs bioconversion: The new role of glutathione

Several methods, such as dilution, ion exchange, and bioaugmentation, have been tried to improve anaerobic digestion (AD) process performance under ammonia stress. Herein, a new strategy for improving AD under ammonia pressure by regulating microbiome and enzyme to enhance volatile fatty acids (VFAs) bioconversion was reported. Under ammonia stress, the methane yield was raised by 41.7% with glutathione addition (5 mg/g VS) during long-term AD of food waste. This glutathione-induced improvement was found not due to the mitigation of proton imbalance and potassium depletion or the elimination of excessive reactive oxygen species. Interestingly, the ammonia-stressed bioconversions of propionate and butyrate → acetate → methane and the cell viability were remarkably enhanced in the presence of glutathione. Further integrated metagenomic and metaproteomic analyses revealed that the key microbiota (i.e., syntrophic acetogenic taxa and their assistant bacteria and acetotrophic methanogens) related to the above biotransformations were enriched. Meanwhile, the expressions of vital proteins (such as RNA polymerase subunit α, ribosomal protein L25, and iron adenosine triphosphate binding cassette transporter substrate-binding protein) involved in enzyme synthesis and catalyzing the bioconversions above were significantly upregulated. The reported new role of glutathione on regulating functional microbiome and enzyme offered an alternative strategy for improving AD performance under high ammonia condition.

Inhibition Effects of Free Ammonia (FA) on the Rates of Growth, Photosynthesis and Respiration of Chlorella vulgaris

The potential use of microalgae in advanced biological wastewater treatment processes has been actively studied due to their excellent nitrogen and phosphorus removal capabilities. This study investigated the inhibitory effects of free ammonia (FA) on microalgae under autotrophic, heterotrophic, and mixotrophic growth conditions, since the inhibitory effects in heterotrophic and mixotrophic modes has not been reported yet. Chlorella vulgaris were exposed to 3–20 mg-N L−1 of FA in the autotrophic, heterotrophic, and mixotrophic modes and the effects on growth, photosynthesis, and respiration were studied. The microalgal growth rate was 2–3 times greater in the mixotrophic mode than the other modes. Microalgal growth in the autotrophic mode was most vulnerable to FA and the growth inhibition was observed at FA concentration of ≥ 9 mg-N L−1. Similarly, the photosynthesis and respiration of C. vulgaris were inhibited at FA concentrations higher than 12 mg-N LT−1. The removal of carbon and ammonia was greater in the mixotrophic mode than the other modes. The ammonia removal by microalgae increased in proportion to the FA concentration unlike the carbon removal. This was attributed to the ammonium accumulation in microalgae due to the proton imbalance and differences in intracellular and external pH conditions, which were caused by the presence of excess FA in water. Overall, the results show that the mixotrophic microalgae have greater tolerance to FA, and hence, greater potential for use in treatment of wastewaters having high FA concentrations.

Do nutrients and other bioactive molecules from foods have anything to say in the treatment against COVID-19?

The repositioning of therapeutic agents already approved by the regulatory agencies for the use of drugs is very interesting due to the immediacy of their use; similarly, the possibility of using molecules derived from foods, whether nutrients or not, is of great importance, also because of their immediate therapeutic applicability. Candidates for these natural therapies against COVID-19 should show certain effects, such as restoring mitochondrial function and cellular redox balance. This would allow reducing the susceptibility of risk groups and the cascade of events after SARS-CoV-2 infection, responsible for the clinical picture, triggered by the imbalance towards oxidation, inflammation, and cytokine storm. Possible strategies to follow through the use of substances of food origin would include: a) the promotion of mitophagy to remove dysfunctional mitochondria originating from free radicals, proton imbalance and virus evasion of the immune system; b) the administration of transition metals whose redox activity would lead to their own oxidation and the consequent generation of a reduced environment, which would normalize the oxidative state and the intracellular pH; c) the administration of molecules with demonstrated antioxidant capacity; d) the administration of compounds with anti-inflammatory and vasodilatory activity; e) the administration of immunomodulatory compounds.

Influence of lipid composition on the ability of liposome loaded voacamine to improve the reversion of doxorubicin resistant osteosarcoma cells.

The plant alkaloid voacamine (VOA) displays many interesting pharmacological activities thus, considering its scarce solubility in water, its encapsulation into liposome formulations for its delivery is an important goal. Different cationic liposome formulations containing a phospholipid, cholesterol and one of two diasteromeric cationic surfactants resulted able to maintain a stable transmembrane difference in ammonium sulfate concentration and/or pH gradient and to accumulate VOA in their internal aqueous bulk. The fluidity of the lipid bilayer affects both the ability to maintain a stable imbalance of protons and/or ammonium ions across the membrane and the entrapment efficiency. It was shown that VOA loaded into liposomes is more efficient than the free alkaloid to revert resistance of osteosarcoma cells resistant to doxorubicin to an extent depending on their composition.

Proton-Neutron Equilibration Takes Just 0.3 Zeptoseconds

The equilibration of nuclei containing a large imbalance of protons and neutrons can occur in 3×10−22 seconds, according to experiments—important information for models of element-creation in supernovae.

A preliminary implementation of metabolic-based pH control to reduce CO2 usage in outdoor flat-panel photobioreactor cultivation of Nannochloropsis oceanica microalgae

A crucial challenge associated with high-density, commercial-scale, outdoor microalgal cultivation is maintaining pH stability without excessive use of CO2 buffering. This includes a media-dependent, intracellular metabolic proton imbalance leading to the alkalization or acidification of growth media that results when algae consume, respectively, nitrate or ammonium ions. Feeding these two nitrogen sources can theoretically achieve balanced proton metabolism as well as pH control that is economically more favorable as compared to CO2 buffering or acid/base addition. To accomplish this, a fed-batch nutrient feeding strategy must be adopted as a component of a model-based pH control system, particularly in the case of ammonium preference. This work represents a preliminary study of the challenges of implementing a nitrogen metabolism based open-loop pH control strategy in the challenging environment of an outdoor photobioreactor at the DOE-ATP3 testbed facility in Mesa, Arizona during the high solar insolation period of summer 2015. The approach was limited to twice daily fed-batch addition while accounting for ammonium-N preference in a background of nitrate-based algae growth media. Despite these limitations, growth achieved for a photobioreactor operated based on predicted metabolic nitrogen demand (PND) was comparable to ‘CO2-on-demand’ (CoD) for pH control. PND reduced CO2 usage to <10% of CoD control, where the reduced buffering resulted in much greater pH fluctuations due to daily variations in light availability, and a much lower and more consistent media alkalinity (5.73–5.79mEq/L) as compared to the CoD control (6.51–8.49mEq/L). While this effort illustrates the utility of feed-forward model-based control, it further illustrates the need for far more sophisticated ‘real time’ monitoring and modeling to accommodate the dynamic outdoor conditions. A need for improved analytics for accurate closure of nitrogen mass balance is also indicated.

Proton stoichiometric imbalance during algae photosynthetic growth on various nitrogen sources: toward metabolic pH control

The use of algae as a potential platform for fuels or biochemical production requires process design and control that can be implemented at agronomic scales. Toward achieving pH control in large unmixed systems, we present a rigorous set of direct measurements of non-buffered proton uptake and efflux during growth on ammonium and nitrate, observing nearly unit molar proton imbalance H+/OH− respectively for these nitrogen sources. This proton imbalance can be shown to be consistent with the initial assimilation steps of nitrogen from glutamate to peptide bonds which indicates that the remainder of metabolism is largely net proton balanced. These results are refined by demonstrating pH balance for growth with incrementally fed nitric acid and ammonium hydroxide. In contrast to the typical assumption of simple charge balance, each displays a slight proton uptake (around 10 % excess) that is considerably lower than urea, which displayed a molar H+ uptake per N assimilated of up to 33 %. This work illustrates details of proton imbalance that have been largely obscured in laboratory work due to use of elevated CO2 and its associated carbonate equilibrium. Combined with the recent demonstration of preferential, mutually exclusive assimilation of ammonium over nitrate in Chlorella and Chlamydomonas, these results provide the stoichiometry and dynamics of photosynthetic algae growth needed to implement large-scale pH control in the absence of buffering.

Evidence for a new nuclear ‘magic number’ from the level structure of 54Ca

Atomic nuclei are finite quantum systems composed of two distinct types of fermion--protons and neutrons. In a manner similar to that of electrons orbiting in an atom, protons and neutrons in a nucleus form shell structures. In the case of stable, naturally occurring nuclei, large energy gaps exist between shells that fill completely when the proton or neutron number is equal to 2, 8, 20, 28, 50, 82 or 126 (ref. 1). Away from stability, however, these so-called 'magic numbers' are known to evolve in systems with a large imbalance of protons and neutrons. Although some of the standard shell closures can disappear, new ones are known to appear. Studies aiming to identify and understand such behaviour are of major importance in the field of experimental and theoretical nuclear physics. Here we report a spectroscopic study of the neutron-rich nucleus (54)Ca (a bound system composed of 20 protons and 34 neutrons) using proton knockout reactions involving fast radioactive projectiles. The results highlight the doubly magic nature of (54)Ca and provide direct experimental evidence for the onset of a sizable subshell closure at neutron number 34 in isotopes far from stability.

Achieving pH control in microalgal cultures through fed-batch addition of stoichiometrically-balanced growth media

BackgroundLack of accounting for proton uptake and secretion has confounded interpretation of the stoichiometry of photosynthetic growth of algae. This is also problematic for achieving growth of microalgae to high cell concentrations which is necessary to improve productivity and the economic feasibility of commercial-scale chemical production systems. Since microalgae are capable of consuming both nitrate and ammonium, this represents an opportunity to balance culture pH based on a nitrogen feeding strategy that does not utilize gas-phase CO2 buffering. Stoichiometry suggests that approximately 36 weight%N-NH4+ (balance nitrogen as NO3-) would minimize the proton imbalance and permit high-density photoautotrophic growth as it does in higher plant tissue culture. However, algal media almost exclusively utilize nitrate, and ammonium is often viewed as ‘toxic’ to algae.ResultsThe microalgae Chlorella vulgaris and Chlamydomonas reinhardtii exclusively utilize ammonium when both ammonium and nitrate are provided during growth on excess CO2. The resulting proton imbalance from preferential ammonium utilization causes the pH to drop too low to sustain further growth when ammonium was only 9% of the total nitrogen (0.027 gN-NH4+/L). However, providing smaller amounts of ammonium sequentially in the presence of nitrate maintained the pH of a Chlorella vulgaris culture for improved growth on 0.3 gN/L to 5 gDW/L under 5% CO2 gas-phase supplementation. Bioreactor pH dynamics are shown to be predictable based on simple nitrogen assimilation as long as there is sufficient CO2 availability.ConclusionsThis work provides both a media formulation and a feeding strategy with a focus on nitrogen metabolism and regulation to support high-density algal culture without buffering. The instability in culture pH that is observed in microalgal cultures in the absence of buffers can be overcome through alternating utilization of ammonium and nitrate. Despite the highly regulated array of nitrogen transporters, providing a nitrogen source with a balanced degree of reduction minimizes pH fluctuations. Understanding and accommodating the behavior of nitrogen utilization in microalgae is key to avoiding ‘culture crash’ and reliance on gas phase CO2 buffering, which becomes both ineffective and cost-prohibitive for commercial-scale algal culture.

The straight line hypothesis elaborated: Case reference obesity, an argument for acidosis, oxidative stress, and disease conglomeration?

Studies report on the association between obesity and oxidative stress, with and without additional diseases. Macrophages in adipocytes, and hypoxia in adipose tissue have been suggested to explain how obesity can relate to oxidative stress. The straight line hypothesis using the lactic acid trap construct has been put forward to explain how proton imbalance can relate to obesity. Proton imbalance has been also reported to associate with the production of reactive oxygen species by inhibition of mitochondrial energy production. This review brings together existing literature and concepts to explain how obesity can relate to oxidative stress via protons, uniquely for itself or, as often observed, in conglomeration of additional diseases.