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MBio Apr 2022The bacterial response to antibiotics eliciting resistance is one of the key challenges in global health. Despite many attempts to understand intrinsic antibiotic...
The bacterial response to antibiotics eliciting resistance is one of the key challenges in global health. Despite many attempts to understand intrinsic antibiotic resistance, many of the underlying mechanisms still remain elusive. In this study, we found that iron supplementation promoted antibiotic resistance in Streptomyces coelicolor. Iron-promoted resistance occurred specifically against bactericidal antibiotics, irrespective of the primary target of antibiotics. Transcriptome profiling revealed that some genes in the central metabolism and respiration were upregulated under iron-replete conditions. Iron supported the growth of S. coelicolor even under anaerobic conditions. In the presence of potassium cyanide, which reduces aerobic respiration of cells, iron still promoted respiration and antibiotic resistance. This suggests the involvement of a KCN-insensitive type of respiration in the iron effect. This phenomenon was also observed in another actinobacterium, Mycobacterium smegmatis. Taken together, these findings provide insight into a bacterial resistance strategy that mitigates the activity of bactericidal antibiotics whose efficacy accompanies oxidative damage by switching the respiration mode. A widely investigated mode of antibiotic resistance occurs via mutations and/or by horizontal acquisition of resistance genes. In addition to this acquired resistance, most bacteria exhibit intrinsic resistance as an inducible and adaptive response to different classes of antibiotics. Increasing attention has been paid recently to intrinsic resistance mechanisms because this may provide novel therapeutic targets that help rejuvenate the efficacy of the current antibiotic regimen. In this study, we demonstrate that iron promotes the intrinsic resistance of aerobic actinomycetes Streptomyces coelicolor and Mycobacterium smegmatis against bactericidal antibiotics. A surprising role of iron to increase respiration, especially in a mode of using less oxygen, appears a fitting strategy to cope with bactericidal antibiotics known to kill bacteria through oxidative damage. This provides new insights into developing antimicrobial treatments based on the availability of iron and oxygen.
Topics: Actinobacteria; Anti-Bacterial Agents; Bacteria; Drug Resistance, Microbial; Iron; Oxygen; Respiration; Streptomyces coelicolor
PubMed: 35357210
DOI: 10.1128/mbio.00425-22 -
Journal of Occupational and... Mar 2022Following the introduction of lead-free frangible ammunition in United States Air Force small arms firing ranges, Combat Arms instructors have routinely reported...
Following the introduction of lead-free frangible ammunition in United States Air Force small arms firing ranges, Combat Arms instructors have routinely reported experiencing adverse health symptoms during live fire training exercises, including sore throat, cough, and headache. Previous studies have found that these symptoms occur despite occupational exposure limits not being exceeded. To better characterize the potential source and mechanisms for health symptoms, a comprehensive characterization of the physicochemical properties of gases and aerosols emitted during the firing of the M9 pistol and M4 rifle using lead-free frangible ammunition was completed. Weapons were fired within a sealed chamber using a remote firing mechanism. A suite of direct-reading instruments and collection-based analytical methods were used to determine the composition of the emissions. Emissions were dominated by carbon monoxide and ultrafine particles. Other prevalent gases included carbon dioxide, ammonia, formaldehyde, hydrogen cyanide, and nitric oxide when measured using Fourier-transform infrared spectroscopy. An electrical, low-pressure impactor showed that, on average, the count median diameter immediately after firing was 36 ± 4 nm (n = 10 rounds) and 32 ± 3 nm (n = 14 rounds) for the M9 pistol and M4 rifle, respectively. Analytical methods were used to determine that emitted particles were primarily composed of soot, copper, and potassium, with trace amounts of calcium, silicon, sodium, sulfur, and zinc. Results from this research confirm prior work and expand upon the characterization of emissions generated from firing lead-free frangible ammunition. By employing multiple methods to measure and analyze data we were able to quantify both total and respirable particle fractions and determine particle morphology and composition. Characterization of the emissions provides insight into potential exposure risks that may lead to the development of adverse health symptoms allowing for the development of strategies for risk mitigation.
Topics: Carbon Monoxide; Firearms; Gases; Occupational Exposure; Particulate Matter
PubMed: 35285785
DOI: 10.1080/15459624.2021.2023162 -
Drug Metabolism and Disposition: the... May 2022We recently established the mechanism-based inactivation (MBI) of cytochrome P450 3A (CYP3A) by the fibroblast growth factor receptor (FGFR) inhibitors erdafitinib and...
We recently established the mechanism-based inactivation (MBI) of cytochrome P450 3A (CYP3A) by the fibroblast growth factor receptor (FGFR) inhibitors erdafitinib and infigratinib. Serendipitously, our preliminary data have also revealed that pemigatinib (PEM), another clinically approved FGFR1-3 inhibitor, similarly elicited time-dependent inhibition of CYP3A. This was rather unexpected, as it was previously purported that PEM did not pose any metabolism-dependent liabilities due to the absence of glutathione-related conjugates in metabolic profiling experiments conducted in human liver microsomes. Here, we confirmed that PEM inhibited both CYP3A isoforms in a time-, concentration-, and cofactor-dependent manner consistent with MBI, with inactivator concentration at half-maximum rate constant, maximum inactivation rate constant, and partition ratio of 8.69 and 11.95 M, 0.108 and 0.042 min, and approximately 44 and approximately 47 for CYP3A4 and CYP3A5, respectively. Although the rate of inactivation was diminished by coincubation with an alternative substrate or direct inhibitor of CYP3A, the inclusion of nucleophilic trapping agents afforded no such protection. Furthermore, the lack of catalytic activity recovery following dialysis and oxidation with potassium ferricyanide coupled with the absence of a spectrally resolvable peak in the Soret region collectively implied that the underlying mechanism of inactivation was not elicited via the formation of pseudo-irreversible metabolite-intermediate complexes. Finally, utilizing cyanide trapping and high-resolution mass spectrometry, we illuminated the direct and sequential oxidative bioactivation of PEM and its major -desmethylated metabolite at its distal morpholine moiety to reactive iminium ion hard electrophilic species that could covalently inactivate CYP3A via MBI. SIGNIFICANCE STATEMENT: This study reports for the first time the covalent MBI of CYP3A by PEM and deciphered its bioactivation pathway involving the metabolic activation of PEM and its major -desmethylated metabolite to reactive iminium ion intermediates. Following which, a unique covalent docking methodology was harnessed to unravel the structural and molecular determinants underpinning its inactivation. Findings from this study lay the foundation for future investigation of clinically relevant drug-drug interactions between PEM and concomitant substrates of CYP3A.
Topics: Cytochrome P-450 CYP3A; Cytochrome P-450 CYP3A Inhibitors; Humans; Microsomes, Liver; Morpholines; Pyrimidines; Pyrroles; Renal Dialysis
PubMed: 35153194
DOI: 10.1124/dmd.121.000804 -
Chemosphere May 2022In spite of available information demonstrating the assimilation of cyanide (CN) by β-cyanoalanine synthase (β-CAS) in plants, involvement of sulfurtransferase (ST) in...
In spite of available information demonstrating the assimilation of cyanide (CN) by β-cyanoalanine synthase (β-CAS) in plants, involvement of sulfurtransferase (ST) in CN assimilation in rice plants is still undefined. In this study, a microcosmic hydroponic system was used to investigate the involvement of β-cyanoalanine synthase (β-CAS) and sulfurtransferase (ST) in the CN assimilation in rice seedlings under the exposure of potassium cyanide (KCN) in presence or absence of 1-amino-cyclopropane-1-carboxylic acid (ACC). Our results indicated that the measurable thiocyanate (SCN) was detected in both rice roots and shoots under KCN exposure, and the abundances of ST-related transcripts were up-regulated significantly (p < 0.05), suggesting that the ST pathway is involved in CN assimilation in the rice plants. The application of exogenous ACC significantly (p < 0.05) decreased the accumulation of CN and SCN in rice tissues after KCN exposures, and also up-regulated the expression of β-CAS and ST genes and their enzymatic activities, suggesting a positive interaction between aminocyclopropane-1-carboxylate oxidase (ACO), β-CAS and ST in rice plants during the CN assimilation. This is the first attempt to experimentally clarify the involvement of ST in CN assimilation in rice seedlings.
Topics: Cyanides; Lyases; Oryza; Seedlings; Sulfurtransferases
PubMed: 35101430
DOI: 10.1016/j.chemosphere.2022.133789 -
Current Research in Microbial Sciences 2022Modern intensive agricultural practices face numerous challenges that pose major threats to global food security. In order to address the nutritional requirements of the... (Review)
Review
Modern intensive agricultural practices face numerous challenges that pose major threats to global food security. In order to address the nutritional requirements of the ever-increasing world population, chemical fertilizers and pesticides are applied on large scale to increase crop production. However, the injudicious use of agrochemicals has resulted in environmental pollution leading to public health hazards. Moreover, agriculture soils are continuously losing their quality and physical properties as well as their chemical (imbalance of nutrients) and biological health. Plant-associated microbes with their plant growth- promoting traits have enormous potential to solve these challenges and play a crucial role in enhancing plant biomass and crop yield. The beneficial mechanisms of plant growth improvement include enhanced nutrient availability, phytohormone modulation, biocontrol of phytopathogens and amelioration of biotic and abiotic stresses. Solid-based or liquid bioinoculant formulation comprises inoculum preparation, addition of cell protectants such as glycerol, lactose, starch, a good carrier material, proper packaging and best delivery methods. Recent developments of formulation include entrapment/microencapsulation, nano-immobilization of microbial bioinoculants and biofilm-based biofertilizers. This review critically examines the current state-of-art on use of microbial strains as biofertilizers and the important roles performed by these beneficial microbes in maintaining soil fertility and enhancing crop productivity.
PubMed: 35024641
DOI: 10.1016/j.crmicr.2021.100094 -
Chemical Communications (Cambridge,... Jan 2022We report two methods that use either NMR spectroscopy or direct magnetic susceptibility measurements for (strictly ) determination of the state of charge of redox flow...
We report two methods that use either NMR spectroscopy or direct magnetic susceptibility measurements for (strictly ) determination of the state of charge of redox flow batteries. These methods are demonstrated on the inorganic, redox-active potassium ferro/ferri cyanide catholyte cycled against 2,6-dihydroxyanthraquinone as the anolyte in a full cell, and should be applicable to a wide range of redox couples, provided that the magnetization of the electrolyte solution depends on its oxidation state.
PubMed: 34986212
DOI: 10.1039/d1cc01895g -
Parasitology International Apr 2022Acanthamoeba castellanii (A. castellanii) is an important opportunistic parasite. Induction of oxidative stress by the host immune system is one of the most important...
Acanthamoeba castellanii (A. castellanii) is an important opportunistic parasite. Induction of oxidative stress by the host immune system is one of the most important defense strategies against parasites. Hence, parasites partly deal with oxidative stress by different mechanisms. Identifying resistance mechanisms of A. castellanii parasites against oxidative stress is important to achieve a new therapeutic approach. Thus, this study aimed to understand the resistance mechanisms of A. castellanii, against oxidative stress. Trophozoites of A. castellanii were treated with different concentrations of HO. The half maximal inhibitory concentration (IC) of HO was determined using the MTT assay. The induction of oxidative stress was confirmed by flow cytometer. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) were determined. The gene expression levels of CAT and SOD were measured by qRT-PCR. Furthermore, 3-amino-1:2:4-triazole (3-AT) and potassium cyanide (KCN) were used as specific inhibitors of CAT and SOD, respectively. Cell cycle assay and the apoptosis were evaluated by flow cytometer. The activities of SOD, CAT, GR, and GPx, showed an increase in oxidative stress. The cell cycle analysis revealed that most of the cellular population was in G0 and G1 phases. The apoptosis increased in oxidative stress conditions. Moreover, the apoptosis significantly increased after the specific inhibition of CAT and SOD under oxidative stress. The gene expression levels of CAT and SOD significantly increased under oxidative stress. A. castellanii can resist the host immune system through various mechanisms, including evoking its antioxidant enzymes. Therefore, by reducing or inhibiting the activity of the parasite's antioxidant enzymes such as SOD and CAT, it is possible to cope with A. castellanii.
Topics: Acanthamoeba castellanii; Animals; Antioxidants; Apoptosis; Catalase; Cell Cycle; Gene Expression Regulation, Enzymologic; Genotype; Glutathione Peroxidase; Glutathione Reductase; Hydrogen Peroxide; Inhibitory Concentration 50; Oxidative Stress; Superoxide Dismutase
PubMed: 34929407
DOI: 10.1016/j.parint.2021.102523 -
Nuclear Medicine and Biology 2021Hydrogen cyanide (HCN) is a versatile synthon for generating carbon‑carbon and carbon-heteroatom bonds. Unlike other one-carbon synthons (i.e., CO, CO), HCN can... (Review)
Review
Hydrogen cyanide (HCN) is a versatile synthon for generating carbon‑carbon and carbon-heteroatom bonds. Unlike other one-carbon synthons (i.e., CO, CO), HCN can function as a nucleophile (as in potassium cyanide, KCN) and an electrophile (as in cyanogen bromide, (CN)Br). The incorporation of the CN motif into organic molecules generates nitriles, hydantoins and (thio)cyanates, which can be converted to carboxylic acids, aldehydes, amides and amines. Such versatile chemistry is particularly attractive in PET radiochemistry where diverse bioactive small molecules incorporating carbon-11 in different positions need to be produced. The first examples of making [C]HCN for radiolabeling date back to the 1960s. During the ensuing decades, [C]cyanide labeling was popular for producing biologically important molecules including C-labeled α-amino acids, sugars and neurotransmitters. [C]cyanation is now reemerging in many PET centers due to its versatility for making novel tracers. Here, we summarize the chemistry of [C]HCN, review the methods to make [C]HCN past and present, describe methods for labeling different types of molecules with [C]HCN, and provide an overview of the reactions available to convert nitriles into other functional groups. Finally, we discuss some of the challenges and opportunities in [C]HCN labeling such as developing more robust methods to produce [C]HCN and developing rapid and selective methods to convert nitriles into other functional groups in complex molecules.
Topics: Positron-Emission Tomography
PubMed: 34624831
DOI: 10.1016/j.nucmedbio.2021.09.002 -
Chemistry, An Asian Journal Nov 2021Nitrogen transfer from cyanide anion to an aldehyde is emerging as a promising method for the synthesis of aromatic nitriles. However, this method still suffers from a...
Nitrogen transfer from cyanide anion to an aldehyde is emerging as a promising method for the synthesis of aromatic nitriles. However, this method still suffers from a disadvantage that a use of stoichiometric Cu(II) or Cu(I) salts is required to enable the reaction. As we report herein, we overcame this drawback and developed a catalytic method for nitrogen transfer from cyanide anion to an alcohol via the complete cleavage of the C≡N triple bond using phen/Cu O as the catalyst. The present condition allowed a series of benzyl alcohols to be smoothly converted into aromatic nitriles in moderate to high yields. In addition, the present method could be extended to the conversion of cinnamic alcohol to 3-phenylacrylonitrile.
PubMed: 34523819
DOI: 10.1002/asia.202100776 -
Enzyme and Microbial Technology Oct 2021Aromatic nitriles are important structural motifs that frequently existed in pharmaceutical drugs. Due to the convenient synthesis of aldoximes from aldehydes, the...
Aromatic nitriles are important structural motifs that frequently existed in pharmaceutical drugs. Due to the convenient synthesis of aldoximes from aldehydes, the dehydration of aldoximes to corresponding nitriles by aldoxime dehydratases (Oxds) is considered as a safe and robust enzymatic production route. Although the Oxd genes are widely distributed in microbial kingdom, so far less than ten Oxds were expressed and further characterized. In this study, we found 26 predicted putative Oxd genes from the GenBank database using a genome mining strategy. The Oxd gene from Pseudomonas putida F1 was cloned and functionally expressed in Escherichia coli BL21 (DE3). The amino acid sequence of OxdF1 shows high identities of 33∼85 % to other characterized Oxds, and contained a ferrous heme as the catalytic site. The optimum reaction pH and temperature of recombinant OxdF1 were 7.0 and 35 °C, respectively. OxdF1 was stable in pH 7.0 potassium phosphate buffer at 30 °C, and its half-life was approximately 3.8 h. OxdF1 can efficiently dehydrate aromatic and heterocyclic aldoximes to nitriles, such as 2-bromobenzaldoxime, 2-chloro-6-fluorobenzaldoxime, thiophene-2-carboxaldoxime, and pyridine-3-aldoxime. Therefore, the recombinant OxdF1 shows a potential application in the cyanide-free synthesis of aromatic nitriles.
Topics: Heme; Hydro-Lyases; Nitriles; Oximes; Pseudomonas putida
PubMed: 34489036
DOI: 10.1016/j.enzmictec.2021.109883