Global Transcriptional Response to Organic Hydroperoxide and the Role of OhrR in the Control of Virulence Traits in Chromobacterium violaceum

ABSTRACT A major pathway for the detoxification of organic hydroperoxides, such as cumene hydroperoxide (CHP), involves the MarR family transcriptional regulator OhrR and the peroxidase OhrA. However, the effect of these peroxides on the global transcriptome and the contribution of the OhrA/OhrR system to bacterial virulence remain poorly explored. Here, we analyzed the transcriptome profiles of Chromobacterium violaceum exposed to CHP and after the deletion of ohrR, and we show that OhrR controls the virulence of this human opportunistic pathogen. DNA microarray and Northern blot analyses of CHP-treated cells revealed the upregulation of genes related to the detoxification of peroxides (antioxidant enzymes and thiol-reducing systems), the degradation of the aromatic moiety of CHP (oxygenases), and protection against other secondary stresses (DNA repair, heat shock, iron limitation, and nitrogen starvation responses). Furthermore, we identified two upregulated genes (ohrA and a putative diguanylate cyclase with a GGDEF domain for cyclic di-GMP [c-di-GMP] synthesis) and three downregulated genes (hemolysin, chitinase, and collagenase) in the ohrR mutant by transcriptome analysis. Importantly, we show that OhrR directly repressed the expression of the putative diguanylate cyclase. Using a mouse infection model, we demonstrate that the ohrR mutant was attenuated for virulence and showed a decreased bacterial burden in the liver. Moreover, an ohrR-diguanylate cyclase double mutant displayed the same virulence as the wild-type strain. In conclusion, we have defined the transcriptional response to CHP, identified potential virulence factors such as diguanylate cyclase as members of the OhrR regulon, and shown that C. violaceum uses the transcriptional regulator OhrR to modulate its virulence.

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Acinetobacter baumanniiOxyR Regulates the Transcriptional Response to Hydrogen Peroxide

Infection and Immunity ◽

10.1128/iai.00413-18 ◽

2018 ◽

Vol 87 (1) ◽

Cited By ~ 16

Author(s):

Lillian J. Juttukonda ◽

Erin R. Green ◽

Zachery R. Lonergan ◽

Marie C. Heffern ◽

Christopher J. Chang ◽

...

Keyword(s):

Hydrogen Peroxide ◽

Drug Targets ◽

Transcriptional Response ◽

Transcriptional Regulator ◽

Opportunistic Pathogen ◽

Multidrug Resistant ◽

Resistance Mechanisms ◽

World Health ◽

Content Type

ABSTRACTAcinetobacter baumanniiis a Gram-negative opportunistic pathogen that causes diverse infections, including pneumonia, bacteremia, and wound infections. Due to multiple intrinsic and acquired antimicrobial-resistance mechanisms,A. baumanniiisolates are commonly multidrug resistant, and infections are notoriously difficult to treat. The World Health Organization recently highlighted carbapenem-resistantA. baumanniias a “critical priority” for the development of new antimicrobials because of the risk to human health posed by this organism. Therefore, it is important to discover the mechanisms used byA. baumanniito survive stresses encountered during infection in order to identify new drug targets. In this study, by use ofin vivoimaging, we identified hydrogen peroxide (H2O2) as a stressor produced in the lung duringA. baumanniiinfection and defined OxyR as a transcriptional regulator of the H2O2stress response. Upon exposure to H2O2,A. baumanniidifferentially transcribes several hundred genes. However, the transcriptional upregulation of genes predicted to detoxify hydrogen peroxide is abolished in anA. baumanniistrain in which the transcriptional regulatoroxyRis genetically inactivated. Moreover, inactivation ofoxyRin both antimicrobial-susceptible and multidrug-resistantA. baumanniistrains impairs growth in the presence of H2O2. OxyR is a direct regulator ofkatEandahpF1, which encode the major H2O2-degrading enzymes inA. baumannii, as confirmed through measurement of promoter binding by recombinant OxyR in electromobility shift assays. Finally, anoxyRmutant is less fit than wild-typeA. baumanniiduring infection of the murine lung. This work reveals a mechanism used by this important human pathogen to survive H2O2stress encountered during infection.

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Arsenic Directly Binds to and Activates the Yeast AP-1-Like Transcription Factor Yap8

Molecular and Cellular Biology ◽

10.1128/mcb.00842-15 ◽

2015 ◽

Vol 36 (6) ◽

pp. 913-922 ◽

Cited By ~ 17

Author(s):

Nallani Vijay Kumar ◽

Jianbo Yang ◽

Jitesh K. Pillai ◽

Swati Rawat ◽

Carlos Solano ◽

...

Keyword(s):

Transcription Factor ◽

Transcriptional Activation ◽

Transcriptional Response ◽

Transcriptional Regulator ◽

Yeast Protein ◽

Content Type ◽

Arsenic Tolerance ◽

Arsenic Sensing

The AP-1-like transcription factor Yap8 is critical for arsenic tolerance in the yeastSaccharomyces cerevisiae. However, the mechanism by which Yap8 senses the presence of arsenic and activates transcription of detoxification genes is unknown. Here we demonstrate that Yap8 directly binds to trivalent arsenite [As(III)]in vitroandin vivoand that approximately one As(III) molecule is bound per molecule of Yap8. As(III) is coordinated by three sulfur atoms in purified Yap8, and our genetic and biochemical data identify the cysteine residues that form the binding site as Cys132, Cys137, and Cys274. As(III) binding by Yap8 does not require an additional yeast protein, and Yap8 is regulated neither at the level of localization nor at the level of DNA binding. Instead, our data are consistent with a model in which a DNA-bound form of Yap8 acts directly as an As(III) sensor. Binding of As(III) to Yap8 triggers a conformational change that in turn brings about a transcriptional response. Thus, As(III) binding to Yap8 acts as a molecular switch that converts inactive Yap8 into an active transcriptional regulator. This is the first report to demonstrate how a eukaryotic protein couples arsenic sensing to transcriptional activation.

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The zinc transporter ZnuABC is critical for the virulence of Chromobacterium violaceum and contributes to diverse zinc-dependent physiological processes

10.1101/2021.06.03.447022 ◽

2021 ◽

Author(s):

Renato E. R. S. Santos ◽

Waldir P. da Silva Júnior ◽

Simone A. Harrison ◽

Eric P Skaar ◽

Walter J. Chazin ◽

...

Keyword(s):

Mutant Strain ◽

Zinc Uptake ◽

Chromobacterium Violaceum ◽

Host Protein ◽

Infection Model ◽

Uptake System ◽

Environmental Bacterium ◽

Mouse Infection Model ◽

Synthetic Metal

Chromobacterium violaceum is a ubiquitous environmental bacterium that causes sporadic life-threatening infections in humans. How C. violaceum acquires zinc to colonize environmental and host niches is unknown. In this work, we demonstrated that C. violaceum employs the zinc uptake system ZnuABC to overcome zinc limitation in the host, ensuring the zinc supply for several physiological demands. Our data indicated that the C. violaceum ZnuABC transporter is encoded in a zur-CV_RS15045-CV_RS15040-znuCBA operon. This operon was repressed by the zinc uptake regulator Zur and derepressed in the presence of the host protein calprotectin (CP) and the synthetic metal chelator EDTA. A ΔznuCBA mutant strain showed impaired growth under these zinc-chelated conditions. Moreover, the deletion of znuCBA provoked a reduction in violacein production, swimming motility, biofilm formation, and bacterial competition. Remarkably, the ΔznuCBA mutant strain was highly attenuated for virulence in an in vivo mouse infection model and showed a low capacity to colonize the liver, grow in the presence of CP, and resist neutrophil killing. Overall, our findings demonstrate that ZnuABC is essential for C. violaceum virulence, contributing to subvert the zinc-based host nutritional immunity.

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Chemotherapy-Associated Changes of Histopathological Features of Mycobacterium ulcerans Lesions in a Buruli Ulcer Mouse Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.05543-11 ◽

2011 ◽

Vol 56 (2) ◽

pp. 687-696 ◽

Cited By ~ 18

Author(s):

Marie-Thérèse Ruf ◽

Daniela Schütte ◽

Aurélie Chauffour ◽

Vincent Jarlier ◽

Baohong Ji ◽

...

Keyword(s):

B Lymphocyte ◽

Buruli Ulcer ◽

Mycobacterium Ulcerans ◽

Infection Model ◽

Histopathological Study ◽

Content Type ◽

Histopathological Features ◽

Treatment Regimens ◽

Mouse Infection Model ◽

New Treatment

ABSTRACTCombination chemotherapy with rifampin and streptomycin (RIF-STR) for 8 weeks is currently recommended by the WHO as the first-line treatment forMycobacterium ulceransinfection (Buruli ulcer). To gain better insight into the mode of action of these antibiotics against establishedM. ulceransinfection foci and to characterize recovery of local immune responses during chemotherapy, we conducted a detailed histopathological study ofM. ulcerans-infected and RIF-STR-treated mice. Mice were inoculated withM. ulceransin the footpad and 11 weeks later treated with RIF-STR. Development of lesions during the first 11 weeks after infection and subsequent differences in disease progression between RIF-STR-treated and untreated mice were studied. Changes in histopathological features, footpad swelling, and number of CFU were analyzed. After inoculation withM. ulcerans, massive infiltrates dominated by polymorphonuclear leukocytes developed at the inoculation site but did not prevent bacterial multiplication. Huge clusters of extracellular bacteria located in large necrotic areas and surrounded by dead leukocytes developed in the untreated mice. Chemotherapy with RIF-STR led to a rapid drop in CFU associated with loss of solid Ziehl-Neelsen staining of acid-fast bacilli. Development of B-lymphocyte clusters and of macrophage accumulations surrounding the mycobacteria demonstrated the resolution of local immune suppression. Results demonstrate that the experimentalM. ulceransmouse infection model will be a valuable tool to investigate efficacy of new treatment regimens and of candidate vaccines.

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Nonribosomal Peptide Synthetase GenespesLandpes1Are Essential for Fumigaclavine C Production in Aspergillus fumigatus

Applied and Environmental Microbiology ◽

10.1128/aem.07249-11 ◽

2012 ◽

Vol 78 (9) ◽

pp. 3166-3176 ◽

Cited By ~ 33

Author(s):

Karen A. O'Hanlon ◽

Lorna Gallagher ◽

Markus Schrettl ◽

Christoph Jöchl ◽

Kevin Kavanagh ◽

...

Keyword(s):

Aspergillus Fumigatus ◽

Opportunistic Pathogen ◽

Mass Spectrometry Analysis ◽

Infection Model ◽

Nonribosomal Peptide ◽

Content Type ◽

Spectrometry Analysis ◽

Peptide Synthetases ◽

Increased Sensitivity

ABSTRACTThe identity of metabolites encoded by the majority of nonribosomal peptide synthetases in the opportunistic pathogen,Aspergillus fumigatus, remains outstanding. We found that the nonribosomal peptide (NRP) synthetases PesL and Pes1 were essential for fumigaclavine C biosynthesis, the end product of the complex ergot alkaloid (EA) pathway inA. fumigatus. Deletion of eitherpesL(ΔpesL) orpes1(Δpes1) resulted in complete loss of fumigaclavine C biosynthesis, relatively increased production of fumitremorgins such as TR-2, fumitremorgin C and verruculogen, increased sensitivity to H2O2, and increased sensitivity to the antifungals, voriconazole, and amphotericin B. Deletion ofpesLresulted in severely reduced virulence in an invertebrate infection model (P< 0.001). These findings indicate that NRP synthesis plays an essential role in mediating the final prenylation step of the EA pathway, despite the apparent absence of NRP synthetases in the proposed EA biosynthetic cluster forA. fumigatus. Liquid chromatography/diode array detection/mass spectrometry analysis also revealed the presence of fumiquinazolines A to F in bothA. fumigatuswild-type and ΔpesLstrains. This observation suggests that alternative NRP synthetases can also function in fumiquinazoline biosynthesis, since PesL has been shown to mediate fumiquinazoline biosynthesisin vitro. Furthermore, we provide here the first direct link between EA biosynthesis and virulence, in agreement with the observed toxicity associated with EA exposure. Finally, we demonstrate a possible cluster cross-talk phenomenon, a theme which is beginning to emerge in the literature.

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Simultaneous Administration of 2-Aminoethyl Diphenylborinate and Chloroquine Reverses Chloroquine Resistance in Malaria Parasites

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04805-14 ◽

2015 ◽

Vol 59 (5) ◽

pp. 2890-2892 ◽

Cited By ~ 1

Author(s):

Ehab Mossaad ◽

Wakako Furuyama ◽

Masahiro Enomoto ◽

Satoru Kawai ◽

Katsuhiko Mikoshiba ◽

...

Keyword(s):

Chloroquine Resistance ◽

Infection Model ◽

Simultaneous Administration ◽

Plasmodium Chabaudi ◽

Content Type ◽

Mouse Infection Model ◽

Complete Reversal ◽

The Mean

ABSTRACTA nearly complete reversal of chloroquine (CQ) resistance in the CQ-resistantPlasmodium falciparumK-1 strain, with a significant decrease in the mean ± standard deviation (SD) 50% inhibitory concentration (IC50) from 1,050 ± 95 nM to 14 ± 2 nM, was achievedin vitroby the simultaneous administration of 2-aminoethyl diphenylborinate (2-APB). The CQ resistance-reversing activity of 2-APB, which showed the same efficacy as verapamil, was also observed in anin vivomouse infection model with the CQ-resistantPlasmodium chabaudiAS(30CQ) strain.

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The Borrelia burgdorferi Glycosaminoglycan Binding Protein Bgp in the B31 Strain Is Not Essential for Infectivity despite Facilitating Adherence and Tissue Colonization

Infection and Immunity ◽

10.1128/iai.00667-17 ◽

2017 ◽

Vol 86 (2) ◽

Cited By ~ 5

Author(s):

Samantha Schlachter ◽

Janakiram Seshu ◽

Tao Lin ◽

Steven Norris ◽

Nikhat Parveen

Keyword(s):

Lyme Disease ◽

Borrelia Burgdorferi ◽

Binding Protein ◽

Mammalian Host ◽

Infection Model ◽

Binding Assays ◽

Content Type ◽

Mouse Infection Model ◽

Successful Infection

ABSTRACTThe Lyme disease-causing organismBorrelia burgdorferiis transmitted into the mammalian host by an infected-tick bite. Successful infection relies on the ability of this extracellular pathogen to persist and colonize different tissues.B. burgdorferiencodes a large number of adhesins that are able to interact with host ligands to facilitate adherence and tissue colonization. Multiple glycosaminoglycan binding proteins present inB. burgdorferioffer a degree of redundancy of function during infection, and this highlights the importance of glycosaminoglycans as host cell receptors for spirochete adherence. Of particular interest in this study isBorreliaglycosaminoglycan binding protein (Bgp), which binds to heparin-related glycosaminoglycans. The properties of abgptransposon mutant and atrans-complemented derivative were compared to those of the wild-typeB. burgdorferiin thein vitrobinding assays and in infection studies using a C3H/HeJ mouse infection model. We determined that the loss of Bgp impairs spirochete adherence, infectivity, and tissue colonization, resulting in a reduction of inflammatory manifestations of Lyme disease. Although Bgp is not essential for infectivity, it is an important virulence factor ofB. burgdorferithat allows adherence and tissue colonization and contributes to disease severity.

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Draft Genome Sequence of Chromobacterium violaceum RDN09, Isolated from a Patient with a Wound Infection in Bangladesh

Microbiology Resource Announcements ◽

10.1128/mra.00957-20 ◽

2020 ◽

Vol 9 (42) ◽

Author(s):

Razib Mazumder ◽

Ahmed Abdullah ◽

Arif Hussain ◽

Dilruba Ahmed ◽

Dinesh Mondal

Keyword(s):

Genome Sequence ◽

Genome Assembly ◽

Draft Genome ◽

Opportunistic Pathogen ◽

Chromobacterium Violaceum ◽

Draft Genome Sequence ◽

Infected Wound ◽

Content Type ◽

Life Threatening ◽

Adult Male Patient

ABSTRACT Chromobacterium violaceum is an emerging environmental opportunistic pathogen that causes life-threatening infections in humans. Here, we describe the draft genome sequence of Chromobacterium violaceum RDN09, isolated from the infected wound of an adult male patient in Bangladesh. The genome assembly consists of 4,736,739 bp spread across 84 contigs.

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Regulation of PACT-Mediated Protein Kinase Activation by the OV20.0 Protein of Orf Virus

Journal of Virology ◽

10.1128/jvi.01739-15 ◽

2015 ◽

Vol 89 (22) ◽

pp. 11619-11629 ◽

Cited By ~ 4

Author(s):

Yeu-Yang Tseng ◽

Guan-Ru Liao ◽

Ganes C. Sen ◽

Fong-Yuan Lin ◽

Wei-Li Hsu

Keyword(s):

Protein Kinase ◽

Rna Binding ◽

Small Ruminants ◽

Kinase Domain ◽

Orf Virus ◽

Infection Model ◽

Content Type ◽

Binding Domains ◽

Mouse Infection Model

ABSTRACTDouble-stranded RNA (dsRNA)-activated protein kinase (PKR), a major component of the cellular antiviral system, is activated by the binding of either dsRNA or the cellular PKR activator, the PACT protein. The suppression of PKR activation is one of the main strategies that viruses employ to circumvent interferon signaling. Orf virus (ORFV), a parapoxvirus from thePoxviridaefamily, causes contagious pustular dermatitis in small ruminants. Previous studies have demonstrated that various OV20.0 isoforms, encoded by the OV20.0L gene, are able to inhibit PKR activation both by sequestering dsRNA and by physically interacting with PKRin vitro. Thus, this gene acts as a virulence factor of ORFV when tested using a mouse infection model. In the present study, the regions within OV20.0 that interact with dsRNA and with PKR have been mapped. Furthermore, this study demonstrates for the first time that OV20.0 is also able to interact with the dsRNA binding domain of PACT and that the presence of dsRNA strengthened the interaction of these two molecules. The presence of OV20.0 diminishes PKR phosphorylation when this is stimulated by PACT. Nevertheless, the association of OV20.0 with PKR, rather than with PACT, was found to be essential for reducing PACT-mediated PKR phosphorylation. These observations elucidate a new strategy whereby innate immunity can be evaded by ORFV.IMPORTANCEOur previous study indicated that ORFV's two OV20.0 isoforms act as a PKR antagonist via sequestering the PKR activator, dsRNA, and by interacting with PKR, leading to an inhibition of PKR activation (Y. Y. Tseng, F. Y. Lin, S. F. Cheng, D. Tscharke, S. Chulakasian, C. C. Chou, Y. F. Liu, W. S. Chang, M. L. Wong, and W. L. Hsu, J Virol89:4966–4979, 2015, doi:10.1128/JVI.03714-14). In the current study, the possible mechanisms by which OV20.0 protein counteracts PKR activation were studied in depth. OV20.0 is able to bind PKR and its two activators, dsRNA and PACT. In addition, OV20.0 binds directly to the RNA binding domains (RBDs) of PKR, and this interaction does not require dsRNA. Moreover, OV20.0 interacts with or occupies the RBD2 and the kinase domain of PKR, which then prevents PACT binding to PKR. Finally, OV20.0 associates with PACT via the RBDs, which may reduce the ability of PACT to induce PKR activation. The findings in this study provide new concepts in relation to how ORFV modulates PKR activation.

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No Holes Barred: Invasion of the Intestinal Mucosa by Mycobacterium avium subsp. paratuberculosis

Infection and Immunity ◽

10.1128/iai.00575-13 ◽

2013 ◽

Vol 81 (11) ◽

pp. 3960-3965 ◽

Cited By ~ 19

Author(s):

John P. Bannantine ◽

Luiz E. Bermudez

Keyword(s):

Mycobacterium Avium ◽

Cell Communication ◽

Transcriptional Response ◽

Cell Types ◽

Effector Proteins ◽

Infection Model ◽

Content Type ◽

Expression Pathways ◽

Mycobacterium Avium Subsp Paratuberculosis ◽

Attachment Proteins

ABSTRACTThe infection biology ofMycobacterium aviumsubsp.paratuberculosishas recently crystallized, with added details surrounding intestinal invasion. The involvement of pathogen-derived effector proteins such as the major membrane protein, oxidoreductase, and fibronectin attachment proteins have been uncovered. Mutations constructed in this pathogen have also shed light on genes needed for invasion. The host cell types that are susceptible to invasion have been defined, along with their transcriptional response. Recent details have given a new appreciation for the dynamic interplay between the host and bacterium that occurs at the outset of infection. An initial look at the global expression pathways of the host has shown a circumvention of the cell communication pathway byM. aviumsubsp.paratuberculosis, which loosens the integrity of the tight junctions. We now know thatM. aviumsubsp.paratuberculosisactivates the epithelial layer and also actively recruits macrophages to the site of infection. These notable findings are summarized along with added mechanistic details of the early infection model. We conclude by proposing critical next steps to further elucidate the process ofM. aviumsubsp.paratuberculosisinvasion.

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