Characterization of OxyR as a Negative Transcriptional Regulator That Represses Catalase Production in Corynebacterium diphtheriae

Corynebacterium diphtheriae and Corynebacterium glutamicum each have one gene (cat) encoding catalase. In-frame Δcat mutants of C. diphtheriae and C. glutamicum were hyper-sensitive to growth inhibition and killing by H2O2. In C. diphtheriae C7(β), both catalase activity and cat transcription decreased ∼2-fold during transition from exponential growth to early stationary phase. Prototypic OxyR in Escherichia coli senses oxidative stress and it activates katG transcription and catalase production in response to H2O2. In contrast, exposure of C. diphtheriae C7(β) to H2O2 did not stimulate transcription of cat. OxyR from C. diphtheriae and C. glutamicum have 52% similarity with E. coli OxyR and contain homologs of the two cysteine residues involved in H2O2 sensing by E. coli OxyR. In-frame ΔoxyR deletion mutants of C. diphtheriae C7(β), C. diphtheriae NCTC13129, and C. glutamicum were much more resistant than their parental wild type strains to growth inhibition by H2O2. In the C. diphtheriae C7(β) ΔoxyR mutant, cat transcripts were about 8-fold more abundant and catalase activity was about 20-fold greater than in the C7(β) wild type strain. The oxyR gene from C. diphtheriae or C. glutamicum, but not from E. coli, complemented the defect in ΔoxyR mutants of C. diphtheriae and C. glutamicum and decreased their H2O2 resistance to the level of their parental strains. Gel-mobility shift, DNaseI footprint, and primer extension assays showed that purified OxyR from C. diphtheriae C7(β) bound, in the presence or absence of DTT, to a sequence in the cat promoter region that extends from nucleotide position −55 to −10 with respect to the +1 nucleotide in the cat ORF. These results demonstrate that OxyR from C. diphtheriae or C. glutamicum functions as a transcriptional repressor of the cat gene by a mechanism that is independent of oxidative stress induced by H2O2

Glycolytic reprograming in Salmonella counters NOX2-mediated dissipation of ΔpH.

The microbial adaptations to the respiratory burst remain poorly understood, and establishing how the NADPH oxidase (NOX2) kills microbes has proven elusive. Here we demonstrate that NOX2 collapses the ΔpH of intracellular Salmonella Typhimurium. The depolarization experienced by Salmonella undergoing oxidative stress impairs folding of periplasmic proteins. Depolarization in respiring Salmonella mediates intense bactericidal activity of reactive oxygen species (ROS). Salmonella adapts to the challenges oxidative stress imposes on membrane bioenergetics by shifting redox balance to glycolysis and fermentation, thereby diminishing electron flow through the membrane, meeting energetic requirements and anaplerotically generating tricarboxylic acid intermediates. By diverting electrons away from the respiratory chain, glycolysis also enables thiol/disulfide exchange-mediated folding of bacterial cell envelope proteins during periods of oxidative stress. Thus, primordial metabolic pathways, already present in bacteria before aerobic respiration evolved, offer a solution to the stress ROS exert on molecular targets at the bacterial cell envelope

The incidence and clinical characteristics of myocarditis and pericarditis following mRNA-based COVID-19 vaccination in Republic of Korea adolescents from July 2021 to September 2022

Objectives Age-specific information regarding myocarditis/pericarditis in adolescents following mRNA-based coronavirus disease 2019 (COVID-19) vaccination in Asia remains insufficient. This study investigated the incidence and clinical characteristics of myocarditis/pericarditis in Republic of Korea adolescents after mRNA-based COVID-19 vaccination. Methods This retrospective descriptive study utilized patient data from the Korea Immunization Management System. Incidence rates were calculated according to age and sex. Clinical characteristics (symptoms/signs, laboratory values, and imaging results) were compared between mild and severe cases. Results Between July 19, 2021 and September 30, 2022, 3,728,224 individuals aged 12 to 19 years received 6,484,165 mRNA-based COVID-19 vaccines, and 173 cases met the case definition for myocarditis/pericarditis: 151 mild (87.3%) and 22 severe (12.7%). The incidence was 3.8-fold higher in males than in females. Troponin I/troponin T was elevated in 96% of myocarditis cases, demonstrating higher sensitivity than creatine kinase-myocardial band (67.6%) or C-reactive protein (75.2%). ST-segment or Twave on electrography abnormalities were found in 60.3% (85/141). Paroxysmal/sustained atrial/ventricular arrhythmias were more common in severe than in mild cases (45.5% vs. 16.8%, p=0.008). Edema on T2-weighted magnetic imaging occurred in 21.6% (8/37) and 62.5% (5/8) of mild and severe cases, respectively (p=0.03). Abnormal pericardial fluid collection or pericardial inflammation was found in 75.4% of pericarditis cases (49/65). Conclusion Myocarditis/pericarditis occurred in rare cases following mRNA-based COVID-19 vaccination. Most cases were mild, but the incidence was higher in adolescent males and after the second dose. As bivalent severe acute respiratory syndrome coronavirus 2 mRNA vaccination started in South Korea in October 2022, the post-vaccination incidence of myocarditis/pericarditis should be closely monitored, considering clinical characteristics

SpoT Induces Intracellular Salmonella Virulence Programs in the Phagosome.

Guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), together named (p)ppGpp, regulate diverse aspects of Salmonella pathogenesis, including synthesis of nutrients, resistance to inflammatory mediators, and expression of secretion systems. In Salmonella, these nucleotide alarmones are generated by the synthetase activities of RelA and SpoT proteins. In addition, the (p)ppGpp hydrolase activity of the bifunctional SpoT protein is essential to preserve cell viability. The contribution of SpoT to physiology and pathogenesis has proven elusive in organisms such as Salmonella, because the hydrolytic activity of this RelA and SpoT homologue (RSH) is vital to prevent inhibitory effects of (p)ppGpp produced by a functional RelA. Here, we describe the biochemical and functional characterization of a spoT-Δctd mutant Salmonella strain encoding a SpoT protein that lacks the C-terminal regulatory elements collectively referred to as "ctd." Salmonella expressing the spoT-Δctd variant hydrolyzes (p)ppGpp with similar kinetics to those of wild-type bacteria, but it is defective at synthesizing (p)ppGpp in response to acidic pH. Salmonella spoT-Δctd mutants have virtually normal adaptations to nutritional, nitrosative, and oxidative stresses, but poorly induce metal cation uptake systems and Salmonella pathogenicity island 2 (SPI-2) genes in response to the acidic pH of the phagosome. Importantly, spoT-Δctd mutant Salmonella replicates poorly intracellularly and is attenuated in a murine model of acute salmonellosis. Collectively, these investigations indicate that (p)ppGpp synthesized by SpoT serves a unique function in the adaptation of Salmonella to the intracellular environment of host phagocytes that cannot be compensated by the presence of a functional RelA.IMPORTANCE Pathogenic bacteria experience nutritional challenges during colonization and infection of mammalian hosts. Binding of the alarmone nucleotide guanosine tetraphosphate (ppGpp) to RNA polymerase coordinates metabolic adaptations and virulence gene transcription, increasing the fitness of diverse Gram-positive and Gram-negative bacteria as well as that of actinomycetes. Gammaproteobacteria such as Salmonella synthesize ppGpp by the combined activities of the closely related RelA and SpoT synthetases. Due to its profound inhibitory effects on growth, ppGpp must be removed; in Salmonella, this process is catalyzed by the vital hydrolytic activity of the bifunctional SpoT protein. Because SpoT hydrolase activity is essential in cells expressing a functional RelA, we have a very limited understanding of unique roles these two synthetases may assume during interactions of bacterial pathogens with their hosts. We describe here a SpoT truncation mutant that lacks ppGpp synthetase activity and all C-terminal regulatory domains but retains excellent hydrolase activity. Our studies of this mutant reveal that SpoT uniquely senses the acidification of phagosomes, inducing virulence programs that increase Salmonella fitness in an acute model of infection. Our investigations indicate that the coexistence of RelA/SpoT homologues in a bacterial cell is driven by the need to mount a stringent response to a myriad of physiological and host-specific signatures

Gender differences in the distal radial artery diameter for the snuffbox approach

Background: Recently, interventional cardiologists have been increasingly interested in snuffbox approach for coronary angiography (CAG) and percutaneous coronary intervention (PCI). However, there is lack of data regarding distal radial artery (RA) diameter according to gender. Therefore, the aim herein was to investigate gender differences in the diameter of distal RA diameter. Methods: Left snuffbox approach was done in 117 patients who had planned CAG or PCI for suspected myocardial ischemia between 1 December 2017 and 28 February 2018 at the Chonnam National University Hospital, Gwangju, Korea. Left RA angiography was achieved from 101 patients. Among 101 individuals, 69 (68.3%) men and 32 (31.7%) women were enrolled. There was no significant difference in systolic and diastolic blood pressure, body mass index, left ventricular systolic function, or patients with acute coronary syndrome in either group. Results: The average diameter of distal RA was 2.57 mm in all patients. Women had a significantly smaller diameter of distal RA than men (2.40 mm vs. 2.65 mm, p = 0.016). Nevertheless, CAG via snuffbox approach by 6 Fr sheath was successfully performed in all 117 patients. Regarding success rate of the distal RA approach, women had a lower success rate (32/38) compared with men (72/79), but not significantly (84.2% vs. 91.1%, p = 0.264). Conclusions: Females has a significantly smaller distal RA diameter compared to males. Moreover, the success rate of the distal RA approach tends to be higher in men than in women