scholarly journals Role of Mn2+and Compatible Solutes in the Radiation Resistance of Thermophilic Bacteria and Archaea

Archaea ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Kimberly M. Webb ◽  
Jocelyne DiRuggiero
Keyword(s):  
Radiation Resistance ◽  
Thermophilic Bacteria ◽  
Inositol Phosphate ◽  
Compatible Solutes ◽  
Halobacterium Salinarum ◽  
Hyperthermophilic Archaea ◽  
Resistant Bacteria ◽  
Ros Scavenging

Radiation-resistant bacteria have garnered a great deal of attention from scientists seeking to expose the mechanisms underlying their incredible survival abilities. Recent analyses showed that the resistance to ionizing radiation (IR) in the archaeonHalobacterium salinarumis dependent upon Mn-antioxidant complexes responsible for the scavenging of reactive oxygen species (ROS) generated by radiation. Here we examined the role of the compatible solutes trehalose, mannosylglycerate, anddi-myo-inositolphosphate in the radiation resistance of aerobic and anaerobic thermophiles. We found that the IR resistance of the thermophilic bacteriaRubrobacter xylanophilusandRubrobacter radiotoleranswas highly correlated to the accumulation of high intracellular concentration of trehalose in association with Mn, supporting the model of Mn2+-dependent ROS scavenging in the aerobes. In contrast, the hyperthermophilic archaeaThermococcus gammatoleransandPyrococcus furiosusdid not contain significant amounts of intracellular Mn, and we found no significant antioxidant activity from mannosylglycerate and di-myo-inositol phosphatein vitro. We therefore propose that the low levels of IR-generated ROS under anaerobic conditions combined with highly constitutively expressed detoxification systems in these anaerobes are key to their radiation resistance and circumvent the need for the accumulation of Mn-antioxidant complexes in the cell.

scholarly journals Ferroptosis-Inhibitory Difference between Chebulagic Acid and Chebulinic Acid Indicates Beneficial Role of HHDP

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4300
Author(s):  
Lin Yang ◽  
Yangping Liu ◽  
Wenhui Zhang ◽  
Yujie Hua ◽  
Ban Chen ◽  
...  
Keyword(s):  
Iron Chelation ◽  
Chair Conformation ◽  
Boat Conformation ◽  
Ros Scavenging ◽  
Hydrolyzable Tannins ◽  
Cell Death Pathway ◽  
Chebulagic Acid ◽  
Recycling Pathway

The search for a safe and effective inhibitor of ferroptosis, a recently described cell death pathway, has attracted increasing interest from scientists. Two hydrolyzable tannins, chebulagic acid and chebulinic acid, were selected for the study. Their optimized conformations were calculated using computational chemistry at the B3LYP-D3(BJ)/6-31G and B3LYP-D3(BJ)/6-311 + G(d,p) levels. The results suggested that (1) chebulagic acid presented a chair conformation, while chebulinic acid presented a skew-boat conformation; (2) the formation of chebulagic acid requires 762.1729 kcal/mol more molecular energy than chebulinic acid; and (3) the 3,6-HHDP (hexahydroxydiphenoyl) moiety was shown to be in an (R)- absolute stereoconfiguration. Subsequently, the ferroptosis inhibition of both tannins was determined using a erastin-treated bone marrow-derived mesenchymal stem cells (bmMSCs) model and compared to that of ferrostatin-1 (Fer-1). The relative inhibitory levels decreased in the following order: Fer-1 > chebulagic acid > chebulinic acid, as also revealed by the in vitro antioxidant assays. The UHPLC–ESI-Q-TOF-MS analysis suggested that, when treated with 16-(2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy free radicals, Fer-1 generated dimeric products, whereas the two acids did not. In conclusion, two hydrolyzable tannins, chebulagic acid and chebulinic acid, can act as natural ferroptosis inhibitors. Their ferroptosis inhibition is mediated by regular antioxidant pathways (ROS scavenging and iron chelation), rather than the redox-based catalytic recycling pathway exhibited by Fer-1. Through antioxidant pathways, the HHDP moiety in chebulagic acid enables ferroptosis-inhibitory action of hydrolyzable tannins.

scholarly journals Edwardsiella piscicida YefM-YoeB: A Type II Toxin-Antitoxin System That Is Related to Antibiotic Resistance, Biofilm Formation, Serum Survival, and Host Infection

2021 ◽  
Vol 12 ◽  
Author(s):  
Dongmei Ma ◽  
Hanjie Gu ◽  
Yanjie Shi ◽  
Huiqin Huang ◽  
Dongmei Sun ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Pathogenic Bacteria ◽  
Wild Strain ◽  
Host Cells ◽  
Resistant Bacteria ◽  
Serum Resistance ◽  
Type Ii ◽  
Edwardsiella Piscicida

The emergence of drug resistant bacteria is a tricky and confronted problem in modern medicine, and one of important reasons is the widespread of toxin-antitoxin (TA) systems in pathogenic bacteria. Edwardsiella piscicida (also known as E. tarda) is the leading pathogen threatening worldwide fresh and seawater aquaculture industries and has been considered as a model organism for studying intracellular and systemic infections. However, the role of type II TA systems are completely unknown in aquatic pathogenic bacteria. In this study, we identified and characterized a type II TA system, YefM-YoeB, of E. piscicida, where YefM is the antitoxin and YoeB is the toxin. yefM and yoeB are co-expressed in a bicistronic operon. When expressed in E. coli, YoeB cause bacterial growth arrest, which was restored by the addition of YefM. To investigate the biological role of the TA system, two markerless yoeB and yefM-yoeB in-frame mutant strains, TX01ΔyoeB and TX01ΔyefM-yoeB, were constructed, respectively. Compared to the wild strain TX01, TX01ΔyefM-yoeB exhibited markedly reduced resistance against oxidative stress and antibiotic, and markedly reduced ability to form persistent bacteria. The deletion of yefM-yoeB enhanced the bacterial ability of high temperature tolerance, biofilm formation, and host serum resistance, which is the first study about the relationship between type II TA system and serum resistance. In vitro infection experiment showed that the inactivation of yefM-yoeB greatly enhanced bacterial capability of adhesion in host cells. Consistently, in vivo experiment suggested that the yefM-yoeB mutation had an obvious positive effect on bacteria dissemination of fish tissues and general virulence. Introduction of a trans-expressed yefM-yoeB restored the virulence of TX01ΔyefM-yoeB. These findings suggest that YefM-YoeB is involved in responding adverse circumstance and pathogenicity of E. piscicida. In addition, we found that YefM-YoeB negatively autoregulated the expression of yefM-yoeB and YefM could directly bind with own promoter. This study provides first insights into the biological activity of type II TA system YefM-YoeB in aquatic pathogenic bacteria and contributes to understand the pathogenesis of E. piscicida.

scholarly journals Gating by ionic strength and safety check by cyclic-di-AMP in the ABC transporter OpuA

2020 ◽  
Vol 6 (47) ◽  
pp. eabd7697 ◽  
Author(s):  
Hendrik R. Sikkema ◽  
Marco van den Noort ◽  
Jan Rheinberger ◽  
Marijn de Boer ◽  
Sabrina T. Krepel ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Molecular Level ◽  
Compatible Solutes ◽  
Second Messenger ◽  
In Vitro Activity ◽  
Cellular Processes ◽  
Cryo Electron Microscopy ◽  
Micro Organisms

(Micro)organisms are exposed to fluctuating environmental conditions, and adaptation to stress is essential for survival. Increased osmolality (hypertonicity) causes outflow of water and loss of turgor and is dangerous if the cell is not capable of rapidly restoring its volume. The osmoregulatory adenosine triphosphate–binding cassette transporter OpuA restores the cell volume by accumulating large amounts of compatible solute. OpuA is gated by ionic strength and inhibited by the second messenger cyclic-di-AMP, a molecule recently shown to affect many cellular processes. Despite the master regulatory role of cyclic-di-AMP, structural and functional insights into how the second messenger regulates (transport) proteins on the molecular level are lacking. Here, we present high-resolution cryo–electron microscopy structures of OpuA and in vitro activity assays that show how the osmoregulator OpuA is activated by high ionic strength and how cyclic-di-AMP acts as a backstop to prevent unbridled uptake of compatible solutes.

scholarly journals In Vitro Responses of Alfalfa Root (Medicago Sativa L.) to Salt stress and Melatonin

2021 ◽  
Author(s):  
Shabnam Jalili ◽  
Ali Akbar Ehsanpour
Keyword(s):  
Principal Component Analysis ◽  
Salt Stress ◽  
Medicago Sativa ◽  
Compatible Solutes ◽  
Principal Component ◽  
Component Analysis ◽  
Soluble Carbohydrate ◽  
Indol Acetic Acid

Abstract Alfalfa (Medicago sativa L.) is the most cultivated forage legume. The growth and development of alfalfa roots are limited by salt stress. Growth regulator is an essential role of melatonin in plants, especially in root involved in stress tolerance. In this study, alfalfa roots under in vitro salt stress (150 and 200 mM NaCl) were pretreated with different concentrations of melatonin (0.1, 10 and 15 μM). principal component analysis to find out the best targets for melatonin and salinity. Exogenous utilization of melatonin in alfalfa roots significantly elevated the compatible solutes particularly glycin betaein (GB), soluble carbohydrate and K+ content. Principal component analysis revealed that, Indol acetic acid (IAA) content, GB, flavonoids, carbohydrate and Na+ were the best melatonin targets. Furthermore, salinity affected ROS, H2O2, O2-, malondialdehyde (MDA), phenylalanine ammonia-lyase (PAL), K+/Na+ ratio and tyrosine ammonia-lyase (TAL) enzymes were augmented, and electrolyte leakage, Na+ accumulation decreased in the saline medium.

Evaluation of the role of enzymatic and nonenzymatic antioxidant systems in the radiation resistance of Deinococcus

2010 ◽  
Vol 56 (3) ◽  
pp. 195-201 ◽  
Author(s):  
Ravindranath Shashidhar ◽  
Sanjukta A. Kumar ◽  
Hari S. Misra ◽  
Jayant R. Bandekar
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Peroxide ◽  
Stress Resistance ◽  
Radiation Resistance ◽  
Resistant Bacteria ◽  
Antioxidant Systems ◽  
Defense Systems ◽  
Antioxidant Metabolites ◽  
Radiation Resistant

Antioxidant enzymes and antioxidant metabolites appear to have different roles in the oxidative stress resistance responses of radiation-resistant bacteria belonging to the Deinococcus – Thermus group. Twelve distinct strains belonging to 7 Deinococcus species were characterized for their responses to hydrogen peroxide, ciprofloxacin, and ionizing radiation. The levels of catalase and peroxidase activities in these strains showed a positive correlation with resistance to hydrogen peroxide and ciprofloxacin. However, the levels of these enzymes and carotenoids did not appear to contribute significantly to radiation resistance. Our findings support the idea that enzymatic defense systems are not sufficient to account for the extreme radiation resistance of Deinococcus species. Consistent with previously published reports, the Deinococcus strains had high intracellular manganese/iron ratios. No significant correlation was found between intracellular manganese/iron ratios and radiation resistance within different Deinococcus species, suggesting that other components are involved in conferring radiation resistance.

scholarly journals The Role of IgG Subclass in Antibody-Mediated Protection against Carbapenem-Resistant Klebsiella pneumoniae

2020 ◽  
Author(s):  
Michael P. Motley ◽  
Elizabet Diago-Navarro ◽  
Kasturi Banerjee ◽  
Sean Inzerillo ◽  
Bettina C. Fries
Keyword(s):  
Monoclonal Antibodies ◽  
Klebsiella Pneumoniae ◽  
Resistant Bacteria ◽  
Infection Model ◽  
Lethal Challenge ◽  
Carbapenem Resistant ◽  
Neutropenic Patients ◽  
Antibody Subclass

ABSTRACTMonoclonal antibodies (Abs) have the potential to assist in the battle against multidrug-resistant bacteria such as Carbapenem-Resistant Klebsiella pneumoniae (CR-Kp). However, the characteristics by which these Abs function, such as the role of antibody subclass, must be determined before such modalities can be carried from the bench to the bedside. We performed a subclass switch on anti-capsular monoclonal murine IgG3 (mIgG3) hybridomas and identified and purified a murine IgG1 (mIgG1) hybridoma line through sib selection. We then compared the ability of the mIgG1 and mIgG3 antibodies to control CR-Kp ST258 infection both in vitro and in vivo. We found by ELISA and flow cytometry that mIgG3 has superior binding to CR-Kp CPS and superior agglutinating ability compared to mIgG1. The mIgG3 also predictably had better complement-mediated serum bactericidal activity than the mIgG1 and also promoted neutrophil-mediated killing at concentrations lower than the mIgG1. In contrast, the mIgG1 had marginally better activity in improving macrophage-mediated phagocytosis. Comparing their activities in a pulmonary infection model with wild type as well as neutropenic mice, both antibodies reduced organ burden in a non-lethal challenge, regardless of neutrophil status, with mIgG1 having the highest overall burden reduction in both scenarios. However, at a lethal inoculum, both antibodies showed reduced efficacy in neutropenic mice, with mIgG3 retaining the most activity. These findings suggest the viability of monoclonal Ab adjunctive therapy in neutropenic patients that cannot mount their own immune response, while also providing some insight into the relative contributions of immune mediators in CR-Kp protection.ImportanceCarbapenem-resistant Klebsiella pneumoniae is an urgent public health threat that causes life-threatening infections in immunocompromised hosts. Its resistance to nearly all antibiotics necessitates novel strategies to treat it, including the use of monoclonal antibodies. Monoclonal antibodies are emerging as important adjuncts to traditional pharmaceuticals, and studying how they protect against specific bacteria such as Klebsiella pneumoniae is crucial to their development as effective therapies. Antibody subclass is often overlooked but is a major factor in how an antibody interacts with other mediators of immunity. This paper is the first to examine how the subclass of anti-capsular monoclonal antibodies can affect efficacy against CR-Kp. Additionally, this work sheds light on the viability of monoclonal antibody therapy in neutropenic patients, who are most vulnerable to CR-Kp infection.

The role of silicon in forages: A quantitative X-Ray study

1987 ◽  
Vol 45 ◽  
pp. 416-417
Author(s):  
Janet H. Woodward ◽  
D. E. Akin
Keyword(s):  
Sodium Acetate ◽  
Dry Matter ◽  
Acetate Buffer ◽  
Plant Tissues ◽  
Sodium Acetate Buffer ◽  
X Ray ◽  
Dry Matter Digestibility ◽  
Percent Composition

Silicon (Si) is distributed throughout plant tissues, but its role in forages has not been clarified. Although Si has been suggested as an antiquality factor which limits the digestibility of structural carbohydrates, other research indicates that its presence in plants does not affect digestibility. We employed x-ray microanalysis to evaluate Si as an antiquality factor at specific sites of two cultivars of bermuda grass (Cynodon dactvlon (L.) Pers.). “Coastal” and “Tifton-78” were chosen for this study because previous work in our lab has shown that, although these two grasses are similar ultrastructurally, they differ in in vitro dry matter digestibility and in percent composition of Si.Two millimeter leaf sections of Tifton-7 8 (Tift-7 8) and Coastal (CBG) were incubated for 72 hr in 2.5% (w/v) cellulase in 0.05 M sodium acetate buffer, pH 5.0. For controls, sections were incubated in the sodium acetate buffer or were not treated.

An integrated screening method for evaluating the pulmonary toxicity of inhaled particulates: Role of microscopic techniques in assessing pulmonary macrophage clearance functions

1990 ◽  
Vol 48 (3) ◽  
pp. 826-827
Author(s):  
David B. Warheit ◽  
Lena Achinko ◽  
Mark A. Hartsky
Keyword(s):  
Bronchoalveolar Lavage ◽  
Pulmonary Toxicity ◽  
Screening Method ◽  
Pulmonary Response ◽  
Inhaled Particles ◽  
Cytochemical Analysis ◽  
Pulmonary Macrophages ◽  
Integrated Screening

There is a great need for the development of a rapid and reliable bioassay to evaluate the pulmonary toxicity of inhaled particles. A number of methods have been proposed, including lung clearance studies, bronchoalveolar lavage analysis, and in vitro cytotoxicity tests. These methods are often limited in scope inasmuch as they measure only one dimension of the pulmonary response to inhaled, instilled or incubated dusts. Accordingly, a comprehensive approach to lung toxicity studies has been developed.To validate the method, rats were exposed for 6 hours or 3 days to various concentrations of either aerosolized alpha quartz silica (Si) or carbonyl iron (CI) particles. Cells and fluids from groups of sham and dust-exposed animals were recovered by bronchoalveolar lavage (BAL). Alkaline phosphatase, LDH and protein values were measured in BAL fluids at several time points postexposure. Cells were counted and evaluated for viability, as well as differential and cytochemical analysis. In addition, pulmonary macrophages (PM) were cultured and studied for morphology, chemotaxis, and phagocytosis by scanning electron microscopy.

The Role of Polyphenols in the Modulation of Plasma Non-Enzymatic Antioxidant Capacity (NEAC)

2012 ◽  
Vol 82 (3) ◽  
pp. 228-232 ◽  
Author(s):  
Mauro Serafini ◽  
Giuseppa Morabito
Keyword(s):  
Antioxidant Capacity ◽  
Dietary Intervention ◽  
Ex Vivo ◽  
The Body ◽  
Dietary Polyphenols ◽  
Enzymatic Antioxidant ◽  
Endogenous Antioxidant

Dietary polyphenols have been shown to scavenge free radicals, modulating cellular redox transcription factors in different in vitro and ex vivo models. Dietary intervention studies have shown that consumption of plant foods modulates plasma Non-Enzymatic Antioxidant Capacity (NEAC), a biomarker of the endogenous antioxidant network, in human subjects. However, the identification of the molecules responsible for this effect are yet to be obtained and evidences of an antioxidant in vivo action of polyphenols are conflicting. There is a clear discrepancy between polyphenols (PP) concentration in body fluids and the extent of increase of plasma NEAC. The low degree of absorption and the extensive metabolism of PP within the body have raised questions about their contribution to the endogenous antioxidant network. This work will discuss the role of polyphenols from galenic preparation, food extracts, and selected dietary sources as modulators of plasma NEAC in humans.

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