scholarly journals Redox-Regulated Adaptation of Streptococcus oligofermentans to Hydrogen Peroxide Stress

mSystems ◽  
2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Huichun Tong ◽  
Yuzhu Dong ◽  
Xinhui Wang ◽  
Qingqing Hu ◽  
Fan Yang ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mass Spectrometry ◽  
Inductively Coupled Plasma ◽  
Molecular Mechanisms ◽  
Cysteine Oxidation ◽  
Mobility Shift ◽  
Adaptation Mechanism ◽  
Content Type ◽  
Oxidized Proteins ◽  
Thioredoxin System

ABSTRACT Preexposure to a low concentration of H2O2 significantly increases the survivability of catalase-negative streptococci in the presence of a higher concentration of H2O2. However, the mechanisms of this adaptation remain unknown. Here, using a redox proteomics assay, we identified 57 and 35 cysteine-oxidized proteins in Streptococcus oligofermentans bacteria that were anaerobically cultured and then pulsed with 40 μM H2O2 and that were statically grown in a 40-ml culture, respectively. The oxidized proteins included the peroxide-responsive repressor PerR, the manganese uptake repressor MntR, thioredoxin system proteins Trx and Tpx, and most glycolytic proteins. Cysteine oxidations of these proteins were verified through redox Western blotting, immunoprecipitation, and liquid chromatography-tandem mass spectrometry assays. In particular, Zn2+-coordinated Cys139 and Cys142 mutations eliminated the H2O2 oxidation of PerR, and inductively coupled plasma mass spectrometry detected significantly decreased amounts of Zn2+ in H2O2-treated PerR, demonstrating that cysteine oxidation results in Zn2+ loss. An electrophoretic mobility shift assay (EMSA) determined that the DNA binding of Mn2+-bound PerR protein (PerR:Zn,Mn) was abolished by H2O2 treatment but was restored by dithiothreitol reduction, verifying that H2O2 inactivates streptococcal PerR:Zn,Mn through cysteine oxidation, analogous to the findings for MntR. Quantitative PCR and EMSA demonstrated that tpx, mntA, mntR, and dpr belonged to the PerR regulons but that only dpr was directly regulated by PerR; mntA was also controlled by MntR. Deletion of mntR significantly reduced the low-H2O2-concentration-induced adaptation of S. oligofermentans to a higher H2O2 concentration, while the absence of PerR completely abolished the self-protection. Therefore, a low H2O2 concentration resulted in the cysteine-reversible oxidations of PerR and MntR to derepress their regulons, which function in cellular metal and redox homeostasis and which endow streptococci with the antioxidative capability. This work reveals a novel Cys redox-based H2O2 defense strategy employed by catalase-negative streptococci in Mn2+-rich cellular environments. IMPORTANCE The catalase-negative streptococci produce as well as tolerate high levels of H2O2. This work reports the molecular mechanisms of low-H2O2-concentration-induced adaptation to higher H2O2 stress in a Streptococcus species, in which the peroxide-responsive repressor PerR and its redox regulons play the major role. Distinct from the Bacillus subtilis PerR, which is inactivated by H2O2 through histidine oxidation by the Fe2+-triggered Fenton reaction, the streptococcal PerR is inactivated by H2O2 oxidation of the structural Zn2+ binding cysteine residues and thus derepresses the expression of genes defending against oxidative stress. The reversible cysteine oxidation could provide flexibility for PerR regulation in streptococci, and the mechanism might be widely used by lactic acid bacteria, including pathogenic streptococci, containing high levels of cellular manganese, in coping with oxidative stress. The adaptation mechanism could also be applied in oral hygiene by facilitating the fitness and adaptability of the oral commensal streptococci to suppress the pathogens.

scholarly journals The Helicobacter pylori CZB Cytoplasmic Chemoreceptor TlpD Forms an Autonomous Polar Chemotaxis Signaling Complex That Mediates a Tactic Response to Oxidative Stress

2016 ◽  
Vol 198 (11) ◽  
pp. 1563-1575 ◽  
Author(s):  
Kieran D. Collins ◽  
Tessa M. Andermann ◽  
Jenny Draper ◽  
Lisa Sanders ◽  
Susan M. Williams ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Helicobacter Pylori ◽  
Molecular Mechanisms ◽  
Reactive Oxygen ◽  
Host Cells ◽  
Oxygen Species ◽  
Content Type ◽  
Signaling Complex ◽  
H Pylori

ABSTRACTCytoplasmic chemoreceptors are widespread among prokaryotes but are far less understood than transmembrane chemoreceptors, despite being implicated in many processes. One such cytoplasmic chemoreceptor isHelicobacter pyloriTlpD, which is required for stomach colonization and drives a chemotaxis response to cellular energy levels. Neither the signals sensed by TlpD nor its molecular mechanisms of action are known. We report here that TlpD functions independently of the other chemoreceptors. When TlpD is the sole chemoreceptor, it is able to localize to the pole and recruits CheW, CheA, and at least two CheV proteins to this location. It loses the normal membrane association that appears to be driven by interactions with other chemoreceptors and with CheW, CheV1, and CheA. These results suggest that TlpD can form an autonomous signaling unit. We further determined that TlpD mediates a repellent chemotaxis response to conditions that promote oxidative stress, including being in the presence of iron, hydrogen peroxide, paraquat, and metronidazole. Last, we found that all testedH. pyloristrains express TlpD, whereas other chemoreceptors were present to various degrees. Our data suggest a model in which TlpD coordinates a signaling complex that responds to oxidative stress and may allowH. pylorito avoid areas of the stomach with high concentrations of reactive oxygen species.IMPORTANCEHelicobacter pylorisenses its environment with proteins called chemoreceptors. Chemoreceptors integrate this sensory information to affect flagellum-based motility in a process called chemotaxis. Chemotaxis is employed during infection and presumably aidsH. pyloriin encountering and colonizing preferred niches. A cytoplasmic chemoreceptor named TlpD is particularly important in this process, and we report here that this chemoreceptor is able to operate independently of other chemoreceptors to organize a chemotaxis signaling complex and mediate a repellent response to oxidative stress conditions.H. pyloriencounters and must cope with oxidative stress during infection due to oxygen and reactive oxygen species produced by host cells. TlpD's repellent response may allow the bacteria to escape niches experiencing inflammation and elevated reactive oxygen species (ROS) production.

scholarly journals Environmental effects on arsenosugars and arsenolipids in Ectocarpus (Phaeophyta)

2016 ◽  
Vol 13 (1) ◽  
pp. 21 ◽  
Author(s):  
Ásta H. Pétursdóttir ◽  
Kyle Fletcher ◽  
Helga Gunnlaugsdóttir ◽  
Eva Krupp ◽  
Frithjof C. Küpper ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mass Spectrometry ◽  
Inductively Coupled Plasma ◽  
High Performance ◽  
Natural Habitat ◽  
Significant Proportion ◽  
Stress Factors ◽  
Experimental Conditions ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry

Environmental context Arsenolipids, which are present in seaweed, can show high toxicity, emphasising the need for more information on these compounds. We investigated the effects of different stress factors on the arsenic compounds formed by cultures of brown algae, and compared the results with those from field-collected samples. We show that the arsenolipid and arsenosugar profiles differ depending on the experimental conditions, and that a deficiency in phosphate has a direct positive effect on the biosynthesis of arsenic-containing phospholipids. Abstract Seaweeds have recently been shown to contain a significant proportion of arsenic in the form of arsenolipids (AsLp). Three strains of the filamentous brown alga Ectocarpus species were grown in the laboratory with different simulations of environmental stress: control conditions (1/2 Provasoli-enriched seawater), low nitrate (30% of the amount of nitrates in the control), low phosphate (30% of the amount of phosphate in the control) and under oxidative stress levels (2mM H2O2). Generally, the major AsLp was an arsenic-containing hydrocarbon, AsHC360 (50–80%), but additionally, several arsenic-containing phospholipids (AsPL) were identified and quantified using high-performance liquid chromatography–inductively coupled plasma mass spectrometry and electrospray ionisation mass spectrometry (HPLC-ICP-MS/ESI-MS). The AsLps in cultures were compared with AsLps in Ectocarpus found in its natural habitat as well as with other brown filamentous algae. The AsLp and arsenosugar profiles differed depending on the experimental conditions. Under low phosphate conditions, a significant reduction of phosphorus-containing arsenosugars was noticed, and a significant increase of phosphate-containing AsLps was found when compared with the controls. Strains grown under oxidative stress showed a significant increase in AsLps as well as clear physiological changes.

scholarly journals Evidence that Oxidative Stress InducesspxA2Transcription in Bacillus anthracis Sterne through a Mechanism Requiring SpxA1 and Positive Autoregulation

2016 ◽  
Vol 198 (21) ◽  
pp. 2902-2913 ◽  
Author(s):  
Skye Barendt ◽  
Cierra Birch ◽  
Lea Mbengi ◽  
Peter Zuber
Keyword(s):  
Oxidative Stress ◽  
Bacillus Anthracis ◽  
Transcription Initiation ◽  
Bacterial Species ◽  
Negative Control ◽  
Mobility Shift ◽  
Content Type ◽  
Oxidative Protein Damage

ABSTRACTBacillus anthracispossesses two paralogs of the transcriptional regulator, Spx. SpxA1 and SpxA2 interact with RNA polymerase (RNAP) to activate the transcription of genes implicated in the prevention and alleviation of oxidative protein damage. ThespxA2gene is highly upregulated in infected macrophages, but how this is achieved is unknown. Previous studies have shown that thespxA2gene was under negative control by the Rrf2 family repressor protein, SaiR, whose activity is sensitive to oxidative stress. These studies also suggested thatspxA2was under positive autoregulation. In the present study, we show byin vivoandin vitroanalyses thatspxA2is under direct autoregulation but is also dependent on the SpxA1 paralogous protein. The deletion of eitherspxA1orspxA2reduced the diamide-inducible expression of anspxA2-lacZconstruct.In vitrotranscription reactions using purifiedB. anthracisRNAP showed that SpxA1 and SpxA2 protein stimulates transcription from a DNA fragment containing thespxA2promoter. Ectopically positionedspxA2-lacZfusion requires both SpxA1 and SpxA2 for expression, but the requirement for SpxA1 is partially overcome whensaiRis deleted. Electrophoretic mobility shift assays showed that SpxA1 and SpxA2 enhance the affinity of RNAP forspxA2promoter DNA and that this activity is sensitive to reductant. We hypothesize that the previously observed upregulation ofspxA2in the oxidative environment of the macrophage is at least partly due to SpxA1-mediated SaiR repressor inactivation and the positive autoregulation ofspxA2transcription.IMPORTANCERegulators of transcription initiation are known to govern the expression of genes required for virulence in pathogenic bacterial species. Members of the Spx family of transcription factors function in control of genes required for virulence and viability in low-GC Gram-positive bacteria. InBacillus anthracis, thespxA2gene is highly induced in infected macrophages, which suggests an important role in the control of virulence gene expression during the anthrax disease state. We provide evidence that elevated concentrations of oxidized, active SpxA2 result from an autoregulatory positive-feedback loop drivingspxA2transcription.

Aerosol extraction and direct laser ablation ICP-MS analysis of the fine and ultrafine fractions of regolith

2019 ◽  
Vol 20 (3) ◽  
pp. 280-298
Author(s):  
Paul A. Morris ◽  
Alex Christ ◽  
Edward J. Mikucki
Keyword(s):  
Mass Spectrometry ◽  
Laser Ablation ◽  
Inductively Coupled Plasma ◽  
Content Type ◽  
Inductively Coupled ◽  
Ms Analysis ◽  
Icp Ms ◽  
Direct Laser ◽  
Plasma Mass Spectrometry ◽  
Supplementary Material

The <10, <4, <2.5 and <1 µm fractions of eight regolith samples have been extracted as aerosols, then analysed for more than 60 elements by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Precision and accuracy rivals that of conventional digestion and ICP-MS analysis for most elements, but the aerosol extraction and ablation approach can be completed within 30 min, avoids compromising the sample by screening, column settling, fusion and/or digestion, and includes data for elements such as Br, Cl, I and Se that are conventionally analysed by individual procedures. Major element chemistry and scanning electron microscope (SEM) imagery show that the aerosol fractions of regolith are dominated by kaolinite, with quartz in aeolian regolith. The aerosol fractions of Si- and Ca-rich regolith have higher trace element concentrations than the coarser fraction (0.45–2 mm), but chalcophile elements are depleted in the aerosols of Fe-rich regolith relative to the coarser fraction. Improvements in in-field analytical technology coupled with aerosol extraction mean that fine and ultrafine fraction chemistry can be used to guide mineral exploration programmes in close to real time.Supplementary material: The results of the laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis of filter papers are available at https://doi.org/10.6084/m9.figshare.c.4562807

scholarly journals Regulation ofperRExpression by Iron and PerR in Campylobacter jejuni

2011 ◽  
Vol 193 (22) ◽  
pp. 6171-6178 ◽  
Author(s):  
Minkyeong Kim ◽  
Sunyoung Hwang ◽  
Sangryeol Ryu ◽  
Byeonghwa Jeon
Keyword(s):  
Oxidative Stress ◽  
Campylobacter Jejuni ◽  
Regulatory Region ◽  
Transcriptional Level ◽  
Mobility Shift ◽  
Content Type ◽  
Dnase I Footprinting ◽  
Transcriptional Changes ◽  
Electrophoretic Mobility Shift Assays ◽  
Binding Sequence

Campylobacter jejuniis a leading food-borne pathogen causing gastroenteritis in humans. Although OxyR is a widespread oxidative stress regulator in many Gram-negative bacteria,C. jejunilacks OxyR and instead possesses the metalloregulator PerR. Despite the important role played by PerR in oxidative stress defense, little is known about the factors influencingperRexpression inC. jejuni. In this study, aperRpromoter-lacZfusion assay demonstrated that iron significantly reduced the level ofperRtranscription, whereas other metal ions, such as copper, cobalt, manganese, and zinc, did not affectperRtranscription. Notably, aperRmutation substantially increased the level ofperRtranscription and intranscomplementation restored the transcriptional changes, suggestingperRis transcriptionally autoregulated inC. jejuni. In theperRmutant, iron did not repressperRtranscription, indicating the iron dependence ofperRexpression results fromperRautoregulation. Electrophoretic mobility shift assays showed that PerR binds to theperRpromoter, and DNase I footprinting assays identified a PerR binding site overlapping the −35 region of the twoperRpromoters, further supportingperRautoregulation at the transcriptional level. Alignment of the PerR binding sequence in theperRpromoter with the regulatory region of other PerR regulon genes ofC. jejunirevealed a 16-bp consensus PerR binding sequence, which shares high similarities to theBacillus subtilisPerR box. The results of this study demonstrated that PerR directly interacts with theperRpromoter and regulatesperRtranscription and thatperRautoregulation is responsible for the repression ofperRtranscription by iron inC. jejuni.

scholarly journals NanoTiO2 Sunscreen Does Not Prevent Systemic Oxidative Stress Caused by UV Radiation and a Minor Amount of NanoTiO2 is Absorbed in Humans

Nanomaterials ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 888 ◽  
Author(s):  
Daniela Pelclova ◽  
Tomas Navratil ◽  
Tereza Kacerova ◽  
Blanka Zamostna ◽  
Zdenka Fenclova ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mass Spectrometry ◽  
Uv Radiation ◽  
Inductively Coupled Plasma ◽  
Exhaled Breath Condensate ◽  
Prostaglandin F2α ◽  
Minor Amount ◽  
Exhaled Breath ◽  
Skin Absorption ◽  
Systemic Oxidative Stress

The present pilot study tested the efficiency of nanoTiO2 sunscreen to prevent the oxidative stress/inflammation caused by ultraviolet (UV) radiation using biomarkers in subjects’ blood, urine, and exhaled breath condensate (EBC). In addition, the skin absorption of nanoTiO2 was studied. Six identical subjects participated in three tests: (A) nanoTiO2 sunscreen, (B) UV radiation, and (C) sunscreen + UV. The first samples were collected before the test and the second after sunscreen application and/or UV exposure. On day 4, the third samples were collected, and the sunscreen was washed off, and the fourth samples were collected on day 11. The following biomarkers were measured: malondialdehyde, 4-hydroxy-trans-hexenal, 4-hydroxy-trans-nonenal, aldehydes C6-C12, 8-iso-Prostaglandin F2α, o-tyrosine, 3-chlorotyrosine, 3-nitrotyrosine, 8-hydroxy-2-deoxyguanosine, 8-hydroxyguanosine, 5-hydroxymethyl uracil, and leukotrienes, using liquid chromatography-electrospray ionisation-tandem mass spectrometry. Titania was measured using inductively coupled plasma mass spectrometry and TiO2 nanoparticles by transmission and scanning electron microscopy. Sunscreen alone did not elevate the markers, but UV increased the biomarkers in the plasma, urine, and EBC. The sunscreen prevented skin redness, however it did not inhibit the elevation of oxidative stress/inflammatory markers. Titania and nanoTiO2 particles were found in the plasma and urine (but not in the EBC) in all sunscreen users, suggesting their skin absorption.

scholarly journals Transcriptional Repressor PtvR Regulates Phenotypic Tolerance to Vancomycin in Streptococcus pneumoniae

2017 ◽  
Vol 199 (14) ◽  
Author(s):  
Xue Liu ◽  
Jing-Wen Li ◽  
Zhixing Feng ◽  
Youfu Luo ◽  
Jan-Willem Veening ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Treatment Failure ◽  
Molecular Mechanisms ◽  
Transcriptional Repressor ◽  
Drug Tolerance ◽  
Microbial Populations ◽  
Luciferase Reporter ◽  
Chronic Infections ◽  
Mobility Shift ◽  
Content Type

ABSTRACT Reversible or phenotypic tolerance to antibiotics within microbial populations has been implicated in treatment failure of chronic infections and development of persister cells. However, the molecular mechanisms regulating phenotypic drug tolerance are largely unknown. In this study, we identified a four-gene operon in Streptococcus pneumoniae that contributes to phenotypic tolerance to vancomycin (ptv). RNA sequencing, quantiative reverse transcriptase PCR, and transcriptional luciferase reporter experiments revealed that transcription of the ptv operon (consisting of ptvR, ptvA, ptvB, and ptvC) is induced by exposure to vancomycin. Further investigation showed that transcription of the ptv operon is repressed by PtvR, a PadR family repressor. Transcriptional induction of the ptv operon by vancomycin was achieved by transcriptional derepression of this locus, which was mediated by PtvR. Importantly, fully derepressing ptvABC by deleting ptvR or overexpressing the ptv operon with an exogenous promoter significantly enhanced vancomycin tolerance. Gene deletion analysis revealed that PtvA, PtvB, and PtvC are all required for the PtvR-regulated phenotypic tolerance to vancomycin. Finally, the results of an electrophoretic mobility shift assay with recombinant PtvR showed that PtvR represses the transcription of the ptv operon by binding to two palindromic sequences within the ptv promoter. Together, the ptv locus represents an inducible system in S. pneumoniae in response to stressful conditions, including those caused by antibiotics. IMPORTANCE Reversible or phenotypic tolerance to antibiotics within microbial populations is associated with treatment failure of bacterial diseases, but the underlying mechanisms regulating phenotypic drug tolerance remain obscure. This study reports our finding of a multigene locus that contributes to inducible tolerance to vancomycin in Streptococcus pneumoniae, an important opportunistic human pathogen. The vancomycin tolerance phenotype depends on the PtvR transcriptional repressor and three predicted membrane-associated proteins encoded by the ptv locus. This represents the first example of a gene locus in S. pneumoniae that is responsible for antibiotic tolerance and has important implications for further understanding bacterial responses and phenotypic tolerance to antibiotic treatment in this and other pathogens.

scholarly journals Diaphorina citri Nymphs Are Resistant to Morphological Changes Induced by “ Candidatus Liberibacter asiaticus” in Midgut Epithelial Cells

2018 ◽  
Vol 86 (4) ◽  
Author(s):  
Marina Mann ◽  
Somayeh Fattah-Hosseini ◽  
El-Desouky Ammar ◽  
Richard Stange ◽  
EricaRose Warrick ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Epithelial Cells ◽  
Molecular Mechanisms ◽  
Early Stage ◽  
Morphological Changes ◽  
Diaphorina Citri ◽  
Content Type ◽  
Citrus Greening Disease ◽  
Mitochondrial Superoxide ◽  
Liberibacter Asiaticus

ABSTRACT “ Candidatus Liberibacter asiaticus” is the causative bacterium associated with citrus greening disease. “ Ca . Liberibacter asiaticus” is transmitted by Diaphorina citri more efficiently when it is acquired by nymphs rather than adults. Why this occurs is not known. We compared midguts of D. citri insects reared on healthy or “ Ca . Liberibacter asiaticus”-infected citrus trees using quantitative PCR, confocal microscopy, and mitochondrial superoxide staining for evidence of oxidative stress. Consistent with its classification as propagative, “ Ca . Liberibacter asiaticus” titers were higher in adults than in nymphs. Our previous work showed that adult D. citri insects have basal levels of karyorrhexis (fragmentation of the nucleus) in midgut epithelial cells, which is increased in severity and frequency in response to “ Ca . Liberibacter asiaticus.” Here, we show that nymphs exhibit lower levels of early-stage karyorrhexis than adults and are refractory to the induction of advanced karyorrhexis by “ Ca . Liberibacter asiaticus” in the midgut epithelium. MitoSox Red staining showed that guts of infected adults, particularly males, experienced oxidative stress in response to “ Ca . Liberibacter asiaticus.” A positive correlation between the titers of “ Ca . Liberibacter asiaticus” and the Wolbachia endosymbiont was observed in adult and nymph midguts, suggesting an interplay between these bacteria during development. We hypothesize that the resistance of the nymph midgut to late-stage karyorrhexis through as yet unknown molecular mechanisms benefits “ Ca . Liberibacter asiaticus” for efficient invasion of midgut epithelial cells, which may be a factor explaining the developmental dependency of “ Ca . Liberibacter asiaticus” acquisition by the vector.

scholarly journals Inactivation of the Organic Hydroperoxide Stress Resistance Regulator OhrR Enhances Resistance to Oxidative Stress and Isoniazid in Mycobacterium smegmatis

2014 ◽  
Vol 197 (1) ◽  
pp. 51-62 ◽  
Author(s):  
Sankaralingam Saikolappan ◽  
Kishore Das ◽  
Subramanian Dhandayuthapani
Keyword(s):  
Oxidative Stress ◽  
Mutant Strain ◽  
Stress Resistance ◽  
Mycobacterium Smegmatis ◽  
Cumene Hydroperoxide ◽  
Wild Type ◽  
Mobility Shift ◽  
Organic Hydroperoxide ◽  
Content Type ◽  
Protein Levels

The organic hydroperoxide stress resistance regulator (OhrR) is a MarR type of transcriptional regulator that primarily regulates the expression of organic hydroperoxide reductase (Ohr) in bacteria. In mycobacteria, the genes encoding these proteins exist in only a few species, which include the fast-growing organismMycobacterium smegmatis. To delineate the roles of Ohr and OhrR in defense against oxidative stress inM. smegmatis, strains lacking the expression of these proteins were constructed by deleting theohrRandohrgenes, independently and together, through homologous recombination. The OhrR mutant strain (MSΔohrR) showed severalfold upregulation of Ohr expression, which could be observed at both the transcript and protein levels. Similar upregulation of Ohr expression was also noticed in anM. smegmatiswild-type strain (MSWt) induced with cumene hydroperoxide (CHP) andt-butyl hydroperoxide (t-BHP). The elevated Ohr expression in MSΔohrR correlated with heightened resistance to oxidative stress due to CHP andt-BHP and to inhibitory effects due to the antituberculosis drug isoniazid (INH). Further, this mutant strain exhibited significantly enhanced survival in the intracellular compartments of macrophages. In contrast, the strains lacking either Ohr alone (MSΔohr) or both Ohr and OhrR (MSΔohr-ohrR) displayed limited or no resistance to hydroperoxides and INH. Additionally, these strains showed no significant differences in intracellular survival from the wild type. Electrophoretic mobility shift assays (EMSAs) revealed that the overexpressed and purified OhrR interacts with theohr-ohrRintergenic region with a greater affinity and this interaction is contingent upon the redox state of the OhrR. These findings suggest that Ohr-OhrR is an important peroxide stress response system inM. smegmatis.

scholarly journals Gene bb0318 Is Critical for the Oxidative Stress Response and Infectivity of Borrelia burgdorferi

2016 ◽  
Vol 84 (11) ◽  
pp. 3141-3151 ◽  
Author(s):  
Adrienne C. Showman ◽  
George Aranjuez ◽  
Philip P. Adams ◽  
Mollie W. Jewett
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Borrelia Burgdorferi ◽  
Molecular Mechanisms ◽  
De Novo ◽  
Oxidative Stress Response ◽  
Growth Defect ◽  
Content Type

A greater understanding of the molecular mechanisms that Borrelia burgdorferi uses to survive during mammalian infection is critical for the development of novel diagnostic and therapeutic tools to improve the clinical management of Lyme disease. By use of an in vivo expression technology (IVET)-based approach to identify B. burgdorferi genes expressed in vivo , we discovered the bb0318 gene, which is thought to encode the ATPase component of a putative riboflavin ABC transport system. Riboflavin is a critical metabolite enabling all organisms to maintain redox homeostasis. B. burgdorferi appears to lack the metabolic capacity for de novo synthesis of riboflavin and so likely relies on scavenging riboflavin from the host environment. In this study, we sought to investigate the role of bb0318 in B. burgdorferi pathogenesis. No in vitro growth defect was observed for the Δ bb0318 clone. However, the mutant spirochetes displayed reduced levels of survival when exposed to exogenous hydrogen peroxide or murine macrophages. Spirochetes lacking bb0318 were found to have a 100-fold-higher 50% infectious dose than spirochetes containing bb0318 . In addition, at a high inoculum dose, bb0318 was found to be important for effective spirochete dissemination to deep tissues for as long as 3 weeks postinoculation and to be critical for B. burgdorferi infection of mouse hearts. Together, these data implicate bb0318 in the oxidative stress response of B. burgdorferi and indicate the contribution of bb0318 to B. burgdorferi mammalian infectivity.

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