Phage viruses shape the evolution and virulence of their bacterial hosts. The genome encodes several stress-inducible prophages. The Gifsy-1 prophage terminase protein, whose canonical function is to process phage DNA for packaging in the virus head, unexpectedly acts as a transfer ribonuclease (tRNase) under oxidative stress, cleaving the anticodon loop of tRNA.
View Article and Find Full Text PDFIntracellular Salmonella experiencing oxidative stress downregulates aerobic respiration. To maintain cellular energetics during periods of oxidative stress, intracellular Salmonella must utilize terminal electron acceptors of lower energetic value than molecular oxygen. We show here that intracellular Salmonella undergoes anaerobic respiration during adaptation to the respiratory burst of the phagocyte NADPH oxidase in macrophages and in mice.
View Article and Find Full Text PDFDetoxification, scavenging, and repair systems embody the archetypical antioxidant defenses of prokaryotic and eukaryotic cells. Metabolic rewiring also aids with the adaptation of bacteria to oxidative stress. Evolutionarily diverse bacteria combat the toxicity of reactive oxygen species (ROS) by actively engaging the stringent response, a stress program that controls many metabolic pathways at the level of transcription initiation via guanosine tetraphosphate and the α-helical DksA protein.
View Article and Find Full Text PDFThe exquisite specificity between a sensor kinase and its cognate response regulator ensures faithful partner selectivity within two-component pairs concurrently firing in a single bacterium, minimizing crosstalk with other members of this conserved family of paralogous proteins. We show that conserved hydrophobic and charged residues on the surface of thioredoxin serve as a docking station for structurally diverse response regulators. Using the OmpR protein, we identify residues in the flexible linker and the C-terminal β-hairpin that enable associations of this archetypical response regulator with thioredoxin, but are dispensable for interactions of this transcription factor to its cognate sensor kinase EnvZ, DNA or RNA polymerase.
View Article and Find Full Text PDFThe type III secretion system encoded in the Salmonella pathogenicity island-2 (SPI-2) gene cluster facilitates intracellular growth of nontyphoidal Salmonella by interfering with the maturation of Salmonella-containing vacuoles along the degradative pathway. SPI-2 gene products also protect Salmonella against the antimicrobial activity of reactive oxygen species (ROS) synthesized by the phagocyte NADPH oxidase 2 (NOX2). However, a potential relationship between inflammatory ROS and the activation of transcription of SPI-2 genes by intracellular Salmonella is unclear.
View Article and Find Full Text PDFMetabolic and growth arrest are primary drivers of antibiotic tolerance and persistence in clinically diverse bacterial pathogens. We recently showed that adenosine (ADO) suppresses bacterial growth under nutrient-limiting conditions. In the current study, we show that despite the growth-suppressive effect of ADO, extracellular ADO enhances antibiotic killing in both Gram-negative and Gram-positive bacteria by up to 5 orders of magnitude.
View Article and Find Full Text PDFJ Korean Med Sci
December 2021
Our previous biochemical approaches showed that the oxidoreductase activity of the DnaJ protein facilitates the interaction of oxidized DksA with RNA polymerase. Investigations herein demonstrate that under biologically relevant conditions the DnaJ- and DksA-codependent activation of the stringent response in undergoing oxidative stress involves the DnaK chaperone. Oxidation of DksA cysteine residues stimulates redox-based and holdase interactions with zinc-binding and C-terminal domains of DnaJ.
View Article and Find Full Text PDFThe 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.
View Article and Find Full Text PDFIn response to nutrient depletion, the RelA and SpoT proteins generate the signaling molecule (p)ppGpp, which then controls a number of downstream effectors to modulate cell physiology. In strain AB5075, a ortholog () was identified by a transposon insertion that conferred an unusual colony phenotype. An in-frame deletion in (Δ) failed to produce detectable levels of ppGpp when amino acid starvation was induced with serine hydroxamate.
View Article and Find Full Text PDFCytostasis is the most salient manifestation of the potent antimicrobial activity of nitric oxide (NO), yet the mechanism by which NO disrupts bacterial cell division is unknown. Here, we show that in respiring , and , NO arrests the first step in division, namely, the GTP-dependent assembly of the bacterial tubulin homolog FtsZ into a cytokinetic ring. FtsZ assembly fails in respiring cells because NO inactivates inosine 5'-monophosphate dehydrogenase in de novo purine nucleotide biosynthesis and quinol oxidases in the electron transport chain, leading to drastic depletion of nucleoside triphosphates, including the GTP needed for the polymerization of FtsZ.
View Article and Find Full Text PDFGuanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), together named (p)ppGpp, regulate diverse aspects of pathogenesis, including synthesis of nutrients, resistance to inflammatory mediators, and expression of secretion systems. In , 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.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
December 2018
RNA polymerase is the only known protein partner of the transcriptional regulator DksA. Herein, we demonstrate that the chaperone DnaJ establishes direct, redox-based interactions with oxidized DksA. Cysteine residues in the zinc finger of DksA become oxidized in exposed to low concentrations of hydrogen peroxide (HO).
View Article and Find Full Text PDFThe repressive activity of ancestral histone-like proteins helps integrate transcription of foreign genes with discrepant AT content into existing regulatory networks. Our investigations indicate that the AT-rich discriminator region located between the -10 promoter element and the transcription start site of the regulatory gene ssrA plays a distinct role in the balanced expression of the Salmonella pathogenicity island-2 (SPI2) type III secretion system. The RNA polymerase-binding protein DksA activates the ssrAB regulon post-transcriptionally, whereas the alarmone guanosine tetraphosphate (ppGpp) relieves the negative regulation imposed by the AT-rich ssrA discriminator region.
View Article and Find Full Text PDFThe adaptations that protect pathogenic microorganisms against the cytotoxicity of nitric oxide (NO) engendered in the immune response are incompletely understood. We show here that salmonellae experiencing nitrosative stress suffer dramatic losses of the nucleoside triphosphates ATP, GTP, CTP, and UTP while simultaneously generating a massive burst of the alarmone nucleotide guanosine tetraphosphate. RelA proteins associated with ribosomes overwhelmingly synthesize guanosine tetraphosphate in response to NO as a feedback mechanism to transient branched-chain amino acid auxotrophies.
View Article and Find Full Text PDFThe thiol-disulfide oxidoreductase CXXC catalytic domain of thioredoxin contributes to antioxidant defense in phylogenetically diverse organisms. We find that although the oxidoreductase activity of thioredoxin-1 protects Salmonella enterica serovar Typhimurium from hydrogen peroxide in vitro, it does not appear to contribute to Salmonella's antioxidant defenses in vivo. Nonetheless, thioredoxin-1 defends Salmonella from oxidative stress resulting from NADPH phagocyte oxidase macrophage expression during the innate immune response in mice.
View Article and Find Full Text PDFCorynebacterium diphtheriae and Corynebacterium glutamicum each have one gene (cat) encoding catalase. In-frame Δcat mutants of C. diphtheriae and C.
View Article and Find Full Text PDFObjectives: This study presents the information system for Pusan National University Hospital (PNUH), evaluates its performance qualitatively, and conducts economic analysis.
Methods: Information system for PNUH was designed by component-based development and developed by internet technologies. Order Communication System, Electronic Medical Record, and Clinical Decision Support System were newly developed.
The photosynthetic growth of Synechocystis sp. PCC6803 ceased upon expression of Rhodobacter sphaeroides chlorophyllide a reductase (COR). However, an increase in cytosolic superoxide dismutase level in the recombinant Synechocystis sp.
View Article and Find Full Text PDFChlorophyllide a reductase of Rhodobacter sphaeroides, which were reconstituted with the purified subunits of BchX, BchY, and BchZ, reduced ring B of chlorophyllide a using NADH under anaerobic conditions. Interestingly, suppressor mutations rescuing the inability of R. sphaeroides Fe-SOD mutant to grow in succinate-based minimal medium were predominantly mapped to BchZ subunit of chlorophyllide a reductase.
View Article and Find Full Text PDFJ Microbiol Biotechnol
August 2007
The virulence of superoxide dismutase (SOD) mutants of Vibrio vulnificus, as tested by intraperitoneal injection into mice, decreases in the order of sodC mutant, sodA mutant, and sodB mutant lacking CuZnSOD, MnSOD, and FeSOD, respectively. The survival of SOD mutants under superoxide stress also decreases in the same order. The virulence of soxR mutant, which is unable to induce MnSOD in response to superoxide, is similar to that of the sodA mutant, as the survival of the soxR mutant under superoxide stress is similar to that of the sodA mutant.
View Article and Find Full Text PDFAn electron paramagnetic resonance (EPR) signal characteristic of the 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO)-OH spin adduct, which is formed from the reaction of DMPO with superoxide radicals generated by xanthine oxidase-mediated reaction, was significantly reduced by the cadaverine or Escherichia coli Mn-containing superoxide dismutase (MnSOD). Likewise, cytochrome c reduction by superoxide was inhibited by cadaverine, and the inhibition level increased in proportion to the level of cadaverine. The cadA mutant of Vibrio vulnificus, which does not produce cadaverine because of the lack of lysine decarboxylase, exhibits less tolerance to superoxide stress in comparison with wild type.
View Article and Find Full Text PDFLysine decarboxylase expression by Vibrio vulnificus, which is up-regulated by CadC in response to acid stress, is also induced by SoxR in response to superoxide stress. SoxR binds to the promoter region of the cadBA operon, coding for a lysine-cadaverine antiporter (CadB) and a lysine decarboxylase (CadA). The induction of cadBA transcription by SoxR is independent of CadC.
View Article and Find Full Text PDFThe manganese-containing superoxide dismutase (MnSOD) of Vibrio vulnificus, normally detected after the onset of the stationary phase, is expressed during the lag that immediately follows the transfer of cells grown exponentially to a fresh medium acidified to pH 5.0, whereas Fe-containing SOD is constitutively expressed. The signal triggering the growth lag and MnSOD induction therein is not low pH but intracellular superoxide accumulated under these conditions, since addition of a superoxide scavenger not only shortened the lag but also abrogated the MnSOD induction.
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