scholarly journals Organic Peroxide-Sensing Repressor OhrR Regulates Organic Hydroperoxide Stress Resistance and Avermectin Production in Streptomyces avermitilis

2018 ◽  
Vol 9 ◽  
Author(s):  
Meng Sun ◽  
Mengya Lyu ◽  
Ying Wen ◽  
Yuan Song ◽  
Jilun Li ◽  
...  
Keyword(s):  
Stress Resistance ◽  
Organic Peroxide ◽  
Streptomyces Avermitilis ◽  
Organic Hydroperoxide

scholarly journals Ohr and OhrR Are Critical for Organic Peroxide Resistance and Symbiosis in Azorhizobium caulinodans ORS571

Genes ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 335
Author(s):  
Yang Si ◽  
Dongsen Guo ◽  
Shuoxue Deng ◽  
Xiuming Lu ◽  
Juanjuan Zhu ◽  
...  
Keyword(s):  
Nitrogenase Activity ◽  
Organic Peroxide ◽  
Nodule Formation ◽  
Azorhizobium Caulinodans ◽  
Reporter System ◽  
Mobility Shift ◽  
Organic Hydroperoxide ◽  
Direct Binding ◽  
Plant Assays ◽  
Electrophoretic Mobility Shift Assays

Azorhizobium caulinodans is a symbiotic nitrogen-fixing bacterium that forms both root and stem nodules on Sesbania rostrata. During nodule formation, bacteria have to withstand organic peroxides that are produced by plant. Previous studies have elaborated on resistance to these oxygen radicals in several bacteria; however, to the best of our knowledge, none have investigated this process in A. caulinodans. In this study, we identified and characterised the organic hydroperoxide resistance gene ohr (AZC_2977) and its regulator ohrR (AZC_3555) in A. caulinodans ORS571. Hypersensitivity to organic hydroperoxide was observed in an ohr mutant. While using a lacZ-based reporter system, we revealed that OhrR repressed the expression of ohr. Moreover, electrophoretic mobility shift assays demonstrated that OhrR regulated ohr by direct binding to its promoter region. We showed that this binding was prevented by OhrR oxidation under aerobic conditions, which promoted OhrR dimerization and the activation of ohr. Furthermore, we showed that one of the two conserved cysteine residues in OhrR, Cys11, was critical for the sensitivity to organic hydroperoxides. Plant assays revealed that the inactivation of Ohr decreased the number of stem nodules and nitrogenase activity. Our data demonstrated that Ohr and OhrR are required for protecting A. caulinodans from organic hydroperoxide stress and play an important role in the interaction of the bacterium with plants. The results that were obtained in our study suggested that a thiol-based switch in A. caulinodans might sense host organic peroxide signals and enhance symbiosis.

Characterization of Organic Hydroperoxide Resistance Gene VPA1681 against Organic Peroxides in the Presence of Alkylhydroperoxide Reductase Genes in Vibrio parahaemolyticus

2021 ◽  
Author(s):  
Ning-Xin Chen ◽  
Ying-Jr Chu ◽  
Bin Ni ◽  
Paula Hsu ◽  
Hin-chung Wong
Keyword(s):  
Resistance Gene ◽  
Mutant Strain ◽  
Vibrio Parahaemolyticus ◽  
Reductase Activity ◽  
Cumene Hydroperoxide ◽  
Organic Peroxide ◽  
Reduced Form ◽  
Organic Peroxides ◽  
Organic Hydroperoxide ◽  
Mutant Strains

The marine foodborne enteropathogen Vibrio parahaemolyticus contains the chief organic peroxide reductases AphC1-AhpC2 and a putative organic hydroperoxide resistance enzyme (Ohr, VPA1681) against different peroxides. This study investigated the function of the Ohr under the presence of AhpC1-AhpC2 in this pathogen by gene mutation. Experimental results demonstrated that the ohr gene product was a weak scavenger of H 2 O 2 only in the mutant strains that lacked the peroxide sensor/regulator oxyR and ahpC1 - ahpC2 genes. The Ohr of V. parahaemolyticus was highly effective in scavenging organic peroxide, as demonstrated by assaying the defective changes in the △ ohr mutant strain and determining the detoxifying activity of the purified recombinant V. parahaemolyticus Ohr vp protein in the reduced form. The Ohr and AhpC1-AhpC2 exhibited similar functions against organic peroxides; however, only the △ ahpC1△ahpC2 mutant strain showed a significant increase in susceptibility to several disinfectants, organic acids, and antibiotics compared to the wild-type strain. The transcription of the ohr gene depended on exogenous cumene hydroperoxide (cumene) stress and was markedly enhanced in the △ ohrR (VPA1682) mutant strains. This study revealed the organic hydroperoxide reductase activity of the Ohr in V. parahaemolyticus , and its role probably depends on the sophisticated regulation by OhrR. IMPORTANCE Vibrio parahaemolyticus is the most prevalent foodborne pathogen in Taiwan and some other coastal Asian countries, and its antioxidative activity contributes to the tolerance of this bacterium to different environmental stresses. This study reports on the function of the organic hydroperoxide resistance gene ( ohr , VPA1681) and its gene regulator ohrR (VPA1682) in this pathogen. The strain with ohr gene was effective in protection against organic peroxide, and the recombinant Ohr vp was active in its reduced form. The function of Ohr was significant mostly in strains in which the function o f AhpC1-AhpC2 was limited. The ohrR repressor of the ohr gene was effective at low concentrations of organic peroxide. Other common Vibrio species contain homologous ohr , ohrR , ahpC1, and ahpC2 genes, which are phylogenetically close to those of V. parahaemolyticus may probably share similar functions to those revealed in this study.

scholarly journals Role of a Bacterial Organic Hydroperoxide Detoxification System in Preventing Catalase Inactivation

2004 ◽  
Vol 279 (50) ◽  
pp. 51908-51914 ◽  
Author(s):  
Ge Wang ◽  
Richard C. Conover ◽  
Stephane Benoit ◽  
Adriana A. Olczak ◽  
Jonathan W. Olson ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Stress Resistance ◽  
Molar Ratio ◽  
Wild Type ◽  
Organic Hydroperoxide ◽  
Organic Hydroperoxides ◽  
Detoxification System ◽  
H Pylori ◽  
Mutant Cells

In the gastric pathogenHelicobacter pylori, catalase (KatA) and alkyl hydroperoxide reductase (AhpC) are two highly abundant enzymes that are crucial for oxidative stress resistance and survival of the bacterium in the host. Here we report a connection unidentified previously between the two stress resistance enzymes. We observed that the catalase inahpCmutant cells in comparison with the parent strain is inactivated partially (approximately 50%). The decrease of catalase activity is well correlated with the perturbation of the heme environment in catalase, as detected by electron paramagnetic resonance spectroscopy. To understand the reason for this catalase inactivation, we examined the inhibitory effects of hydroperoxides onH. pyloricatalase (either present in cell extracts or added to the purified enzyme) by monitoring the enzyme activity and the EPR signal of catalase.H. pyloricatalase is highly resistant to its own substrate, without the loss of enzyme activity by treatment with a molar ratio of 1:3000 H2O2. However, it inactivated is by lower concentrations of organic hydroperoxides (the substrate of AhpC). Treatment with a molar ratio of 1:400t-butyl hydroperoxide resulted in an inactivation of catalase by approximately 50%. UV-visible absorption spectra indicated that the catalase inactivation by organic hydroperoxides is caused by the formation of a catalytically incompetent compound II species. To further support the idea that organic hydroperoxides, which accumulate in theahpCmutant cells, are responsible for the inactivation of catalase, we compared the level of lipid peroxidation found inahpCmutant cells with that found in wild type cells. The results showed that the total amount of extractable lipid hydroperoxides in theahpCmutant cells is approximately three times that in the wild type cells. Our findings reveal a novel role of the organic hydroperoxide detoxification system in preventing catalase inactivation.

scholarly journals OhrR Is a Repressor of ohrA, a Key Organic Hydroperoxide Resistance Determinant in Bacillus subtilis

2001 ◽  
Vol 183 (14) ◽  
pp. 4134-4141 ◽  
Author(s):  
Mayuree Fuangthong ◽  
Sopapan Atichartpongkul ◽  
Skorn Mongkolsuk ◽  
John D. Helmann
Keyword(s):  
Reactive Oxygen Species ◽  
Bacillus Subtilis ◽  
Stress Responses ◽  
Xanthomonas Campestris ◽  
Reactive Oxygen ◽  
Organic Peroxide ◽  
Repeat Sequence ◽  
Oxygen Species ◽  
Organic Hydroperoxide ◽  
Complex Adaptive

ABSTRACT Bacillus subtilis displays a complex adaptive response to the presence of reactive oxygen species. To date, most proteins that protect against reactive oxygen species are members of the peroxide-inducible PerR and ςB regulons. We investigated the function of two B. subtilis homologs of theXanthomonas campestris organic hydroperoxide resistance (ohr) gene. Mutational analyses indicate that bothohrA and ohrB contribute to organic peroxide resistance in B. subtilis, with the OhrA protein playing the more important role in growing cells. Expression ofohrA, but not ohrB, is strongly and specifically induced by organic peroxides. Regulation ofohrA requires the convergently transcribed gene,ohrR, which encodes a member of the MarR family of transcriptional repressors. In an ohrR mutant,ohrA expression is constitutive, whereas expression of the neighboring ohrB gene is unaffected. Selection for mutant strains that are derepressed for ohrA transcription identifies a perfect inverted repeat sequence that is required for OhrR-mediated regulation and likely defines an OhrR binding site. Thus,B. subtilis contains at least three regulons (ςB, PerR, and OhrR) that contribute to peroxide stress responses.

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 Dual Role of OhrR as a Repressor and an Activator in Response to Organic Hydroperoxides in Streptomyces coelicolor

2007 ◽  
Vol 189 (17) ◽  
pp. 6284-6292 ◽  
Author(s):  
So-Young Oh ◽  
Jung-Ho Shin ◽  
Jung-Hye Roe
Keyword(s):  
Binding Affinity ◽  
Intergenic Region ◽  
Membrane Lipids ◽  
Streptomyces Coelicolor ◽  
Organic Peroxide ◽  
Cooperative Binding ◽  
Aerobic Bacterium ◽  
Organic Hydroperoxide ◽  
Organic Hydroperoxides ◽  
Dual Action

ABSTRACT Organic hydroperoxide resistance in bacteria is achieved primarily through reducing oxidized membrane lipids. The soil-inhabiting aerobic bacterium Streptomyces coelicolor contains three paralogous genes for organic hydroperoxide resistance: ohrA, ohrB, and ohrC. The ohrA gene is transcribed divergently from ohrR, which encodes a putative regulator of MarR family. Both the ohrA and ohrR genes were induced highly by various organic hydroperoxides. The ohrA gene was induced through removal of repression by OhrR, whereas the ohrR gene was induced through activation by OhrR. Reduced OhrR bound to the ohrA-ohrR intergenic region, which contains a central (primary) and two adjacent (secondary) inverted-repeat motifs that overlap with promoter elements. Organic peroxide decreased the binding affinity of OhrR for the primary site, with a concomitant decrease in cooperative binding to the adjacent secondary sites. The single cysteine C28 in OhrR was involved in sensing oxidants, as determined by substitution mutagenesis. The C28S mutant of OhrR bound to the intergenic region without any change in binding affinity in response to organic peroxides. These results lead us to propose a model for the dual action of OhrR as a repressor and an activator in S. coelicolor. Under reduced conditions, OhrR binds cooperatively to the intergenic region, repressing transcription from both genes. Upon oxidation, the binding affinity of OhrR decreases, with a concomitant loss of cooperative binding, which allows RNA polymerase to bind to both the ohrA and ohrR promoters. The loosely bound oxidized OhrR can further activate transcription from the ohrR promoter.

Efficiency of β-glucan utilisation in fish culture

2019 ◽  
Vol 19 (4A) ◽  
pp. 167-174
Author(s):  
Do Huu Hoang
Keyword(s):  
Human Health ◽  
Stress Resistance ◽  
Antibiotic Use ◽  
Fish Culture ◽  
Growth Promoter ◽  
Sustainable Aquaculture ◽  
Major Benefit

In the last three decades aquaculture is a rapidly developing sector worldwide and antibiotics are used popularly as growth promoter. Antibiotic use was banned because research proved that antibiotic has caused many effects on environment and human health. Therefore, finding antibiotic alternatives is the first priority. The most prospect products today are probiotic and prebiotic. β-glucan is one of the immunostimulants which showed a variety of benefits to the health of many aquaculture species. In this paper only the results of β-glucan, a kind of prebiotic supplied in aquaculture, were summarized. The major benefit of β-glucan are to boost growth, to reduce mortality, to enhance tolerance or stress resistance to environmental or pathogen challenges. Although the applications of β-glucan are popular worldwide, its use in aquaculture in Vietnam is still limited. This paper provides an important reference for β-glucan utilisation which may help to develop a sustainable aquaculture in Vietnam.

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