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di Leandro L, Colasante M, Pitari G, Ippoliti R. Hosts and Heterologous Expression Strategies of Recombinant Toxins for Therapeutic Purposes. Toxins (Basel) 2023; 15:699. [PMID: 38133203 PMCID: PMC10748335 DOI: 10.3390/toxins15120699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 12/05/2023] [Accepted: 12/07/2023] [Indexed: 12/23/2023] Open
Abstract
The production of therapeutic recombinant toxins requires careful host cell selection. Bacteria, yeast, and mammalian cells are common choices, but no universal solution exists. Achieving the delicate balance in toxin production is crucial due to potential self-intoxication. Recombinant toxins from various sources find applications in antimicrobials, biotechnology, cancer drugs, and vaccines. "Toxin-based therapy" targets diseased cells using three strategies. Targeted cancer therapy, like antibody-toxin conjugates, fusion toxins, or "suicide gene therapy", can selectively eliminate cancer cells, leaving healthy cells unharmed. Notable toxins from various biological sources may be used as full-length toxins, as plant (saporin) or animal (melittin) toxins, or as isolated domains that are typical of bacterial toxins, including Pseudomonas Exotoxin A (PE) and diphtheria toxin (DT). This paper outlines toxin expression methods and system advantages and disadvantages, emphasizing host cell selection's critical role.
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Affiliation(s)
| | | | | | - Rodolfo Ippoliti
- Department of Life, Health and Environmental Sciences, University of L’Aquila, 67100 L’Aquila, Italy; (L.d.L.); (M.C.); (G.P.)
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Analysis of the Manganese and MntR Regulon in Corynebacterium diphtheriae. J Bacteriol 2021; 203:e0027421. [PMID: 34370555 DOI: 10.1128/jb.00274-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Corynebacterium diphtheriae is the causative agent of a severe respiratory disease in humans. The bacterial systems required for infection are poorly understood, but the acquisition of metals such as manganese (Mn) is likely critical for host colonization. MntR is a Mn-dependent transcriptional regulator in C. diphtheriae that represses the expression of the mntABCD genes, which encode a putative ABC metal transporter. However, other targets of Mn and MntR regulation in C. diphtheriae have not been identified. In this study, we use comparisons between the gene expression profiles of wild-type C. diphtheriae strain 1737 grown without or with Mn supplementation and comparisons of gene expression between wild-type and an mntR deletion mutant to characterize the C. diphtheriae Mn and MntR regulon. MntR was observed to both repress and induce various target genes in a Mn-dependent manner. Genes induced by MntR include the Mn-superoxide dismutase, sodA, and the putative ABC transporter locus, iutABCD. DNA binding studies showed that MntR interacts with the promoter regions for several genes identified in the expression study, and a 17-bp consensus MntR DNA binding site was identified. We found that an mntR mutant displayed increased sensitivity to Mn and cadmium that could be alleviated by the additional deletion of the mntABCD transport locus, providing evidence that the MntABCD transporter functions as a Mn uptake system in C. diphtheriae. The findings in this study further our understanding of metal uptake systems and global metal regulatory networks in this important human pathogen. Importance Mechanisms for metal scavenging are critical to the survival and success of bacterial pathogens, including Corynebacterium diphtheriae. Metal import systems in pathogenic bacteria have been studied as possible vaccine components due to high conservation, critical functionality, and surface localization. In this study, we expand our understanding of the genes controlled by the global manganese regulator, MntR. We determined a role for the MntABCD transporter in manganese import using evidence from manganese and cadmium toxicity assays. Understanding the nutritional requirements of C. diphtheriae and the tools used to acquire essential metals will aid in the development of future vaccines.
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Peng ED, Schmitt MP. Identification of zinc and Zur-regulated genes in Corynebacterium diphtheriae. PLoS One 2019; 14:e0221711. [PMID: 31454392 PMCID: PMC6711530 DOI: 10.1371/journal.pone.0221711] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 08/13/2019] [Indexed: 11/18/2022] Open
Abstract
Corynebacterium diphtheriae is a Gram-positive bacterial pathogen and the causative agent of diphtheria, a severe disease of the upper respiratory tract of humans. Factors required for C. diphtheriae to survive in the human host are not well defined, but likely include the acquisition of essential metals such as zinc. In C. diphtheriae, zinc-responsive global gene regulation is controlled by the Zinc Uptake Regulator (Zur), a member of the Fur-family of transcriptional regulators. In this study, we use transcriptomics to identify zinc-regulated genes in C. diphtheriae by comparing gene expression of a wild-type strain grown without and with zinc supplementation. Zur-regulated genes were identified by comparing wild-type gene expression with that of an isogenic zur mutant. We observed zinc repression of several putative surface proteins, the heme efflux system hrtBA, various ABC transporters, and the non-ribosomal peptide synthetase/polyketide synthase cluster sidAB. Furthermore, increased gene expression in response to zinc was observed for the alcohol dehydrogenase, adhA. Zinc and Zur regulation were confirmed for several genes by complementing the zur deletion and subsequent RT-qPCR analysis. We used MEME to predict Zur binding sites within the promoter regions of zinc- and Zur-regulated genes, and verified Zur binding by electrophoretic mobility shift assays. Additionally, we characterized cztA (dip1101), which encodes a putative cobalt/zinc/cadmium efflux family protein. Deletion of cztA results in increased sensitivity to zinc, but not to cobalt or cadmium. This study advances our knowledge of changes to Zur-dependent global gene expression in response to zinc in C. diphtheriae. The identification of zinc-regulated ABC transporters herein will facilitate future studies to characterize zinc transport in C. diphtheriae.
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Affiliation(s)
- Eric D. Peng
- Laboratory of Respiratory and Special Pathogens, Division of Bacterial, Parasitic, and Allergenic Products, Center for Biologics Evaluation and Research, Food and Drug Administration,Silver Spring, MD, United States of America
- * E-mail: (MS); (EP)
| | - Michael P. Schmitt
- Laboratory of Respiratory and Special Pathogens, Division of Bacterial, Parasitic, and Allergenic Products, Center for Biologics Evaluation and Research, Food and Drug Administration,Silver Spring, MD, United States of America
- * E-mail: (MS); (EP)
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Iron and Zinc Regulate Expression of a Putative ABC Metal Transporter in Corynebacterium diphtheriae. J Bacteriol 2018; 200:JB.00051-18. [PMID: 29507090 DOI: 10.1128/jb.00051-18] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 02/28/2018] [Indexed: 11/20/2022] Open
Abstract
Corynebacterium diphtheriae, a Gram-positive, aerobic bacterium, is the causative agent of diphtheria and cutaneous infections. While mechanisms required for heme iron acquisition are well known in C. diphtheriae, systems involved in the acquisition of other metals such as zinc and manganese remain poorly characterized. In this study, we identified a genetic region that encodes an ABC-type transporter (iutBCD) and that is flanked by two genes (iutA and iutE) encoding putative substrate binding proteins of the cluster 9 family, a related group of transporters associated primarily with the import of Mn and Zn. We showed that IutA and IutE are both membrane proteins with comparable Mn and Zn binding abilities. We demonstrated that the iutABCD genes are cotranscribed and repressed in response to iron by the iron-responsive repressor DtxR. Transcription of iutE was positively regulated in response to iron availability in a DtxR-dependent manner and was repressed in response to Zn by the Zn-dependent repressor Zur. Electrophoretic mobility shift assays showed that DtxR does not bind to the iutE upstream region, which indicates that DtxR regulation of iutE is indirect and that other regulatory factors controlled by DtxR are likely responsible for the iron-responsive regulation. Analysis of the iutE promoter region identified a 50-bp sequence at the 3' end of the iutD gene that is required for the DtxR-dependent and iron-responsive activation of the iutE gene. These findings indicate that transcription of iutE is controlled by a complex mechanism that involves multiple regulatory factors whose activity is impacted by both Zn and Fe.IMPORTANCE Vaccination against diphtheria prevents toxin-related symptoms but does not inhibit bacterial colonization of the human host by the bacterium. Thus, Corynebacterium diphtheriae remains an important human pathogen that poses a significant health risk to unvaccinated individuals. The ability to acquire iron, zinc, and manganese is critical to the pathogenesis of many disease-causing organisms. Here, we describe a gene cluster in C. diphtheriae that encodes a metal importer that is homologous to broadly distributed metal transport systems, some with important roles in virulence in other bacterial pathogens. Two metal binding components of the gene cluster encode surface exposed proteins, and studies of such proteins may guide the development of second-generation vaccines for C. diphtheriae.
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Corynebacterium diphtheriae Iron-Regulated Surface Protein HbpA Is Involved in the Utilization of the Hemoglobin-Haptoglobin Complex as an Iron Source. J Bacteriol 2018; 200:JB.00676-17. [PMID: 29311283 DOI: 10.1128/jb.00676-17] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 12/28/2017] [Indexed: 11/20/2022] Open
Abstract
Corynebacterium diphtheriae utilizes various heme-containing proteins, including hemoglobin (Hb) and the hemoglobin-haptoglobin complex (Hb-Hp), as iron sources during growth in iron-depleted environments. The ability to utilize Hb-Hp as an iron source requires the surface-anchored proteins HtaA and either ChtA or ChtC. The ability to bind hemin, Hb, and Hb-Hp by each of these C. diphtheriae proteins requires the previously characterized conserved region (CR) domain. In this study, we identified an Hb-Hp binding protein, HbpA (38.5 kDa), which is involved in the acquisition of hemin iron from Hb-Hp. HbpA was initially identified from total cell lysates as an iron-regulated protein that binds to both Hb and Hb-Hp in situ HbpA does not contain a CR domain and has sequence similarity only to homologous proteins present in a limited number of C. diphtheriae strains. Transcription of hbpA is regulated in an iron-dependent manner that is mediated by DtxR, a global iron-dependent regulator. Deletion of hbpA from C. diphtheriae results in a reduced ability to utilize Hb-Hp as an iron source but has little or no effect on the ability to use Hb or hemin as an iron source. Cell fractionation studies showed that HbpA is both secreted into the culture supernatant and associated with the membrane, where its exposure on the bacterial surface allows HbpA to bind Hb and Hb-Hp. The identification and analysis of HbpA enhance our understanding of iron uptake in C. diphtheriae and indicate that the acquisition of hemin iron from Hb-Hp may involve a complex mechanism that requires multiple surface proteins.IMPORTANCE The ability to utilize host iron sources, such as heme and heme-containing proteins, is essential for many bacterial pathogens to cause disease. In this study, we have identified a novel factor (HbpA) that is crucial for the use of hemin iron from the hemoglobin-haptoglobin complex (Hb-Hp). Hb-Hp is considered one of the primary sources of iron for certain bacterial pathogens. HbpA has no similarity to the previously identified Hb-Hp binding proteins, HtaA and ChtA/C, and is found only in a limited group of C. diphtheriae strains. Understanding the function of HbpA may significantly increase our knowledge of how this important human pathogen can acquire host iron that allows it to survive and cause disease in the human respiratory tract.
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Little AS, Okkotsu Y, Reinhart AA, Damron FH, Barbier M, Barrett B, Oglesby-Sherrouse AG, Goldberg JB, Cody WL, Schurr MJ, Vasil ML, Schurr MJ. Pseudomonas aeruginosa AlgR Phosphorylation Status Differentially Regulates Pyocyanin and Pyoverdine Production. mBio 2018; 9:e02318-17. [PMID: 29382736 PMCID: PMC5790918 DOI: 10.1128/mbio.02318-17] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 12/18/2017] [Indexed: 12/31/2022] Open
Abstract
Pseudomonas aeruginosa employs numerous, complex regulatory elements to control expression of its many virulence systems. The P. aeruginosa AlgZR two-component regulatory system controls the expression of several crucial virulence phenotypes. We recently determined, through transcriptomic profiling of a PAO1 ΔalgR mutant strain compared to wild-type PAO1, that algZR and hemCD are cotranscribed and show differential iron-dependent gene expression. Previous expression profiling was performed in strains without algR and revealed that AlgR acts as either an activator or repressor, depending on the gene. Thus, examination of P. aeruginosa gene expression from cells locked into different AlgR phosphorylation states reveals greater physiological relevance. Therefore, gene expression from strains carrying algR alleles encoding a phosphomimetic (AlgR D54E) or a phosphoablative (AlgR D54N) form were compared by microarray to PAO1. Transcriptome analyses of these strains revealed 25 differentially expressed genes associated with iron siderophore biosynthesis or heme acquisition or production. The PAO1 algR D54N mutant produced lower levels of pyoverdine but increased expression of the small RNAs prrf1 and prrf2 compared to PAO1. In contrast, the algR D54N mutant produced more pyocyanin than wild-type PAO1. On the other hand, the PAO1 algR D54E mutant produced higher levels of pyoverdine, likely due to increased expression of an iron-regulated gene encoding the sigma factor pvdS, but it had decreased pyocyanin production. AlgR specifically bound to the prrf2 and pvdS promoters in vitro AlgR-dependent pyoverdine production was additionally influenced by carbon source rather than the extracellular iron concentration per se AlgR phosphorylation effects were also examined in a Drosophila melanogaster feeding, murine acute pneumonia, and punch wound infection models. Abrogation of AlgR phosphorylation attenuated P. aeruginosa virulence in these infection models. These results show that the AlgR phosphorylation state can directly, as well as indirectly, modulate the expression of iron acquisition genes that may ultimately impact the ability of P. aeruginosa to establish and maintain an infection.IMPORTANCE Pyoverdine and pyocyanin production are well-known P. aeruginosa virulence factors that obtain extracellular iron from the environment and from host proteins in different manners. Here, we show that the AlgR phosphorylation state inversely controls pyoverdine and pyocyanin production and that this control is carbon source dependent. P. aeruginosa expressing AlgR D54N, mimicking the constitutively unphosphorylated state, produced more pyocyanin than cells expressing wild-type AlgR. In contrast, a strain expressing an AlgR phosphomimetic (AlgR D54E) produced higher levels of pyoverdine. Pyoverdine production was directly controlled through the prrf2 small regulatory RNA and the pyoverdine sigma factor, PvdS. Abrogating pyoverdine or pyocyanin gene expression has been shown to attenuate virulence in a variety of models. Moreover, the inability to phosphorylate AlgR attenuates virulence in three different models, a Drosophila melanogaster feeding model, a murine acute pneumonia model, and a wound infection model. Interestingly, AlgR-dependent pyoverdine production was responsive to carbon source, indicating that this regulation has additional complexities that merit further study.
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Affiliation(s)
- Alexander S. Little
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Yuta Okkotsu
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Alexandria A. Reinhart
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - F. Heath Damron
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Mariette Barbier
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Brandon Barrett
- Department of Biology, University of Dallas, Irving, Texas, USA
| | - Amanda G. Oglesby-Sherrouse
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, USA
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Joanna B. Goldberg
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA
- Center for Cystic Fibrosis and Airways Disease Research, Children’s Healthcare of Atlanta, Atlanta, Georgia, USA
| | - William L. Cody
- Department of Biology, University of Dallas, Irving, Texas, USA
| | - Michael J. Schurr
- Department of Surgery, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Michael L. Vasil
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Michael J. Schurr
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
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Wittchen M, Busche T, Gaspar AH, Lee JH, Ton-That H, Kalinowski J, Tauch A. Transcriptome sequencing of the human pathogen Corynebacterium diphtheriae NCTC 13129 provides detailed insights into its transcriptional landscape and into DtxR-mediated transcriptional regulation. BMC Genomics 2018; 19:82. [PMID: 29370758 PMCID: PMC5784534 DOI: 10.1186/s12864-018-4481-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 01/16/2018] [Indexed: 12/27/2022] Open
Abstract
Background The human pathogen Corynebacterium diphtheriae is the causative agent of diphtheria. In the 1990s a large diphtheria outbreak in Eastern Europe was caused by the strain C. diphtheriae NCTC 13129. Although the genome was sequenced more than a decade ago, not much is known about its transcriptome. Our aim was to use transcriptome sequencing (RNA-Seq) to close this knowledge gap and gain insights into the transcriptional landscape of a C. diphtheriae tox+ strain. Results We applied two different RNA-Seq techniques, one to retrieve 5′-ends of primary transcripts and the other to characterize the whole transcriptional landscape in order to gain insights into various features of the C. diphtheriae NCTC 13129 transcriptome. By examining the data we identified 1656 transcription start sites (TSS), of which 1202 were assigned to genes and 454 to putative novel transcripts. By using the TSS data promoter regions recognized by the housekeeping sigma factor σA and its motifs were analyzed in detail, revealing a well conserved −10 but an only weakly conserved −35 motif, respectively. Furthermore, with the TSS data 5’-UTR lengths were explored. The observed 5’-UTRs range from zero length (leaderless transcripts), which make up 20% of all genes, up to over 450 nt long leaders, which may harbor regulatory functions. The C. diphtheriae transcriptome consists of 471 operons which are further divided into 167 sub-operon structures. In a differential expression analysis approach, we discovered that genetic disruption of the iron-sensing transcription regulator DtxR, which controls expression of diphtheria toxin (DT), causes a strong influence on general gene expression. Nearly 15% of the genome is differentially transcribed, indicating that DtxR might have other regulatory functions in addition to regulation of iron metabolism and DT. Furthermore, our findings shed light on the transcriptional landscape of the DT encoding gene tox and present evidence for two tox antisense RNAs, which point to a new way of transcriptional regulation of toxin production. Conclusions This study presents extensive insights into the transcriptome of C. diphtheriae and provides a basis for future studies regarding gene characterization, transcriptional regulatory networks, and regulation of the tox gene in particular. Electronic supplementary material The online version of this article (10.1186/s12864-018-4481-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Manuel Wittchen
- Center for Biotechnology (CeBiTec), Bielefeld University, Bielefeld, Germany
| | - Tobias Busche
- Center for Biotechnology (CeBiTec), Bielefeld University, Bielefeld, Germany.,Institute for Biology-Microbiology, Freie Universität Berlin, D-14195, Berlin, Germany
| | - Andrew H Gaspar
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA
| | - Ju Huck Lee
- Department of Microbiology & Molecular Genetics, University of Texas McGovern Medical School at Houston, Houston, USA.,Present address: Biological Resource Center, Korea Research Institute of Bioscience and Biotechnology, 181 Ipsin-gil, Jeollabuk-do, 56212, Republic of Korea
| | - Hung Ton-That
- Department of Microbiology & Molecular Genetics, University of Texas McGovern Medical School at Houston, Houston, USA
| | - Jörn Kalinowski
- Center for Biotechnology (CeBiTec), Bielefeld University, Bielefeld, Germany.
| | - Andreas Tauch
- Center for Biotechnology (CeBiTec), Bielefeld University, Bielefeld, Germany
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Goffin P, Dewerchin M, De Rop P, Blais N, Dehottay P. High-yield production of recombinant CRM197, a non-toxic mutant of diphtheria toxin, in the periplasm ofEscherichia coli. Biotechnol J 2017; 12. [DOI: 10.1002/biot.201700168] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/05/2017] [Accepted: 04/10/2017] [Indexed: 02/06/2023]
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The ChrSA and HrrSA Two-Component Systems Are Required for Transcriptional Regulation of the hemA Promoter in Corynebacterium diphtheriae. J Bacteriol 2016; 198:2419-30. [PMID: 27381918 DOI: 10.1128/jb.00339-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 06/20/2016] [Indexed: 01/11/2023] Open
Abstract
UNLABELLED Corynebacterium diphtheriae utilizes heme and hemoglobin (Hb) as iron sources for growth in low-iron environments. In C. diphtheriae, the two-component signal transduction systems (TCSs) ChrSA and HrrSA are responsive to Hb levels and regulate the transcription of promoters for hmuO, hrtAB, and hemA ChrSA and HrrSA activate transcription at the hmuO promoter and repress transcription at hemA in an Hb-dependent manner. In this study, we show that HrrSA is the predominant repressor at hemA and that its activity results in transcriptional repression in the presence and absence of Hb, whereas repression of hemA by ChrSA is primarily responsive to Hb. DNA binding studies showed that both ChrA and HrrA bind to the hemA promoter region at virtually identical sequences. ChrA binding was enhanced by phosphorylation, while binding to DNA by HrrA was independent of its phosphorylation state. ChrA and HrrA are phosphorylated in vitro by the sensor kinase ChrS, whereas no kinase activity was observed with HrrS in vitro Phosphorylated ChrA was not observed in vivo, even in the presence of Hb, which is likely due to the instability of the phosphate moiety on ChrA. However, phosphorylation of HrrA was observed in vivo regardless of the presence of the Hb inducer, and genetic analysis indicates that ChrS is responsible for most of the phosphorylation of HrrA in vivo Phosphorylation studies strongly suggest that HrrS functions primarily as a phosphatase and has only minimal kinase activity. These findings collectively show a complex mechanism of regulation at the hemA promoter, where both two-component systems act in concert to optimize expression of heme biosynthetic enzymes. IMPORTANCE Understanding the mechanism by which two-component signal transduction systems function to respond to environmental stimuli is critical to the study of bacterial pathogenesis. The current study expands on the previous analyses of the ChrSA and HrrSA TCSs in the human pathogen C. diphtheriae The findings here underscore the complex interactions between the ChrSA and HrrSA systems in the regulation of the hemA promoter and demonstrate how the two systems complement one another to refine and control transcription in the presence and absence of Hb.
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Souza BM, Castro TLDP, Carvalho RDDO, Seyffert N, Silva A, Miyoshi A, Azevedo V. σ(ECF) factors of gram-positive bacteria: a focus on Bacillus subtilis and the CMNR group. Virulence 2014; 5:587-600. [PMID: 24921931 PMCID: PMC4105308 DOI: 10.4161/viru.29514] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The survival of bacteria to different environmental conditions depends on the activation of adaptive mechanisms, which are intricately driven through gene regulation. Because transcriptional initiation is considered to be the major step in the control of bacterial genes, we discuss the characteristics and roles of the sigma factors, addressing (1) their structural, functional and phylogenetic classification; (2) how their activity is regulated; and (3) the promoters recognized by these factors. Finally, we focus on a specific group of alternative sigma factors, the so-called σ(ECF) factors, in Bacillus subtilis and some of the main species that comprise the CMNR group, providing information on the roles they play in the microorganisms' physiology and indicating some of the genes whose transcription they regulate.
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Affiliation(s)
- Bianca Mendes Souza
- Laboratório de Genética Celular e Molecular; Instituto de Ciências Biológicas; Departamento de Biologia Geral; Universidade Federal de Minas Gerais; Belo Horizonte, MG Brazil
| | - Thiago Luiz de Paula Castro
- Laboratório de Genética Celular e Molecular; Instituto de Ciências Biológicas; Departamento de Biologia Geral; Universidade Federal de Minas Gerais; Belo Horizonte, MG Brazil
| | - Rodrigo Dias de Oliveira Carvalho
- Laboratório de Genética Celular e Molecular; Instituto de Ciências Biológicas; Departamento de Biologia Geral; Universidade Federal de Minas Gerais; Belo Horizonte, MG Brazil
| | - Nubia Seyffert
- Laboratório de Genética Celular e Molecular; Instituto de Ciências Biológicas; Departamento de Biologia Geral; Universidade Federal de Minas Gerais; Belo Horizonte, MG Brazil
| | - Artur Silva
- Laboratório de Polimorfismo de DNA; Instituto de Ciências Biológicas; Departamento de Genética; Universidade Federal do Pará; Belém, PA Brazil
| | - Anderson Miyoshi
- Laboratório de Genética Celular e Molecular; Instituto de Ciências Biológicas; Departamento de Biologia Geral; Universidade Federal de Minas Gerais; Belo Horizonte, MG Brazil
| | - Vasco Azevedo
- Laboratório de Genética Celular e Molecular; Instituto de Ciências Biológicas; Departamento de Biologia Geral; Universidade Federal de Minas Gerais; Belo Horizonte, MG Brazil
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Analysis of novel iron-regulated, surface-anchored hemin-binding proteins in Corynebacterium diphtheriae. J Bacteriol 2013; 195:2852-63. [PMID: 23585541 DOI: 10.1128/jb.00244-13] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Corynebacterium diphtheriae utilizes hemin and hemoglobin (Hb) as iron sources during growth in iron-depleted environments, and recent studies have shown that the surface-exposed HtaA protein binds both hemin and Hb and also contributes to the utilization of hemin iron. Conserved (CR) domains within HtaA and in the associated hemin-binding protein, HtaB, are required for the ability to bind hemin and Hb. In this study, we identified and characterized two novel genetic loci in C. diphtheriae that encode factors that bind hemin and Hb. Both genetic systems contain two-gene operons that are transcriptionally regulated by DtxR and iron. The gene products of these operons are ChtA-ChtB and ChtC-CirA (previously DIP0522-DIP0523). The chtA and chtB genes are carried on a putative composite transposon associated with C. diphtheriae isolates that dominated the diphtheria outbreak in the former Soviet Union in the 1990s. ChtA and ChtC each contain a single N-terminal CR domain and exhibit significant sequence similarity to each other but only limited similarity with HtaA. The chtB and htaB gene products exhibited a high level of sequence similarity throughout their sequences, and both proteins contain a single CR domain. Whole-cell binding studies as well as protease analysis indicated that all four of the proteins encoded by these two operons are surface exposed, which is consistent with the presence of a transmembrane segment in their C-terminal regions. ChtA, ChtB, and ChtC are able to bind hemin and Hb, with ChtA showing the highest affinity. Site-directed mutagenesis showed that specific tyrosine residues within the ChtA CR domain were critical for hemin and Hb binding. Hemin iron utilization assays using various C. diphtheriae mutants indicate that deletion of the chtA-chtB region and the chtC gene has no affect on the ability of C. diphtheriae to use hemin or Hb as iron sources; however, a chtB htaB double mutant exhibits a significant decrease in hemin iron use, indicating a role in hemin transport for HtaB and ChtB.
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12
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Purification and structural characterization of siderophore (corynebactin) from Corynebacterium diphtheriae. PLoS One 2012; 7:e34591. [PMID: 22514641 PMCID: PMC3326035 DOI: 10.1371/journal.pone.0034591] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 03/02/2012] [Indexed: 12/31/2022] Open
Abstract
During infection, Corynebacterium diphtheriae must compete with host iron-sequestering mechanisms for iron. C. diphtheriae can acquire iron by a siderophore-dependent iron-uptake pathway, by uptake and degradation of heme, or both. Previous studies showed that production of siderophore (corynebactin) by C. diphtheriae is repressed under high-iron growth conditions by the iron-activated diphtheria toxin repressor (DtxR) and that partially purified corynebactin fails to react in chemical assays for catecholate or hydroxamate compounds. In this study, we purified corynebactin from supernatants of low-iron cultures of the siderophore-overproducing, DtxR-negative mutant strain C. diphtheriae C7(β) ΔdtxR by sequential anion-exchange chromatography on AG1-X2 and Source 15Q resins, followed by reverse-phase high-performance liquid chromatography (RP-HPLC) on Zorbax C8 resin. The Chrome Azurol S (CAS) chemical assay for siderophores was used to detect and measure corynebactin during purification, and the biological activity of purified corynebactin was shown by its ability to promote growth and iron uptake in siderophore-deficient mutant strains of C. diphtheriae under iron-limiting conditions. Mass spectrometry and NMR analysis demonstrated that corynebactin has a novel structure, consisting of a central lysine residue linked through its α- and ε- amino groups by amide bonds to the terminal carboxyl groups of two different citrate residues. Corynebactin from C. diphtheriae is structurally related to staphyloferrin A from Staphylococcus aureus and rhizoferrin from Rhizopus microsporus in which d-ornithine or 1,4-diaminobutane, respectively, replaces the central lysine residue that is present in corynebactin.
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Kim JS, Holmes RK. Characterization of OxyR as a negative transcriptional regulator that represses catalase production in Corynebacterium diphtheriae. PLoS One 2012; 7:e31709. [PMID: 22438866 PMCID: PMC3306370 DOI: 10.1371/journal.pone.0031709] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 01/11/2012] [Indexed: 11/19/2022] Open
Abstract
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 H(2)O(2). 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 H(2)O(2). In contrast, exposure of C. diphtheriae C7(β) to H(2)O(2) 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 H(2)O(2) 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 H(2)O(2). 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 H(2)O(2) 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 H(2)O(2).
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Affiliation(s)
| | - Randall K. Holmes
- Dept of Microbiology, University of Colorado School of Medicine, Aurora, Colorado, United States of America
- * E-mail:
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The ChrA response regulator in Corynebacterium diphtheriae controls hemin-regulated gene expression through binding to the hmuO and hrtAB promoter regions. J Bacteriol 2012; 194:1717-29. [PMID: 22287525 DOI: 10.1128/jb.06801-11] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Corynebacterium diphtheriae, the etiologic agent of diphtheria, utilizes heme and hemoglobin (Hb) as iron sources for growth. Heme-iron utilization involves HmuO, a heme oxygenase that degrades cytosolic heme, resulting in the release of heme-associated iron. Expression of the hmuO promoter is under dual regulation, in which transcription is repressed by DtxR and iron and activated by a heme source, such as hemin or Hb. Hemin-dependent activation is mediated primarily by the ChrAS two-component system, in which ChrS is a putative heme-responsive sensor kinase while ChrA is proposed to serve as a response regulator that activates transcription. It was recently shown that the ChrAS system similarly regulates the hrtAB genes, which encode an ABC transporter involved in the protection of C. diphtheriae from hemin toxicity. In this study, we characterized the phosphorelay mechanism in the ChrAS system and provide evidence for the direct regulation of the hmuO and hrtAB promoters by ChrA. A fluorescence staining method was used to show that ChrS undergoes autophosphorylation and that the phosphate moiety is subsequently transferred to ChrA. Promoter fusion studies identified regions upstream of the hmuO and hrtAB promoters that are critical for the heme-dependent regulation by ChrA. Electrophoretic mobility shift assays revealed that ChrA specifically binds at the hmuO and hrtAB promoter regions and that binding is phosphorylation dependent. A phosphorylation-defective mutant of ChrA [ChrA(D50A)] exhibited significantly diminished binding to the hmuO promoter region relative to that of wild-type ChrA. DNase I footprint analysis further defined the sequences in the hmuO and hrtAB promoters that are involved in ChrA binding, and this analysis revealed that the DtxR binding site at the hmuO promoter partially overlaps the binding site for ChrA. DNase I protection studies as well as promoter fusion analysis suggest that ChrA and DtxR compete for binding at the hmuO promoter. Collectively, these data demonstrate that the ChrA response regulator directly controls the expression of hmuO and the hrtAB genes and the binding activity of ChrA is dependent on phosphorylation by its cognate sensor kinase ChrS.
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15
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Schröder J, Tauch A. Transcriptional regulation of gene expression inCorynebacterium glutamicum: the role of global, master and local regulators in the modular and hierarchical gene regulatory network. FEMS Microbiol Rev 2010; 34:685-737. [DOI: 10.1111/j.1574-6976.2010.00228.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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16
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Iwaki M, Komiya T, Yamamoto A, Ishiwa A, Nagata N, Arakawa Y, Takahashi M. Genome organization and pathogenicity of Corynebacterium diphtheriae C7(-) and PW8 strains. Infect Immun 2010; 78:3791-800. [PMID: 20547743 PMCID: PMC2937438 DOI: 10.1128/iai.00049-10] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Revised: 05/19/2010] [Accepted: 06/06/2010] [Indexed: 11/20/2022] Open
Abstract
Corynebacterium diphtheriae is the causative agent of diphtheria. In 2003, the complete genomic nucleotide sequence of an isolate (NCTC13129) from a large outbreak in the former Soviet Union was published, in which the presence of 13 putative pathogenicity islands (PAIs) was demonstrated. In contrast, earlier work on diphtheria mainly employed the C7(-) strain for genetic analysis; therefore, current knowledge of the molecular genetics of the bacterium is limited to that strain. However, genomic information on the NCTC13129 strain has scarcely been compared to strain C7(-). Another important C. diphtheriae strain is Park-Williams no. 8 (PW8), which has been the only major strain used in toxoid vaccine production and for which genomic information also is not available. Here, we show by comparative genomic hybridization that at least 37 regions from the reference genome, including 11 of the 13 PAIs, are considered to be absent in the C7(-) genome. Despite this, the C7(-) strain still retained signs of pathogenicity, showing a degree of adhesion to Detroit 562 cells, as well as the formation of and persistence in abscesses in animal skin comparable to that of the NCTC13129 strain. In contrast, the PW8 strain, suggested to lack 14 genomic regions, including 3 PAIs, exhibited more reduced signs of pathogenicity. These results, together with great diversity in the presence of the 37 genomic regions among various C. diphtheriae strains shown by PCR analyses, suggest great heterogeneity of this pathogen, not only in genome organization, but also in pathogenicity.
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Affiliation(s)
- Masaaki Iwaki
- Department of Bacteriology II, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashimurayama-shi, Tokyo 208-0011, Japan.
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17
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The ABC transporter HrtAB confers resistance to hemin toxicity and is regulated in a hemin-dependent manner by the ChrAS two-component system in Corynebacterium diphtheriae. J Bacteriol 2010; 192:4606-17. [PMID: 20639324 DOI: 10.1128/jb.00525-10] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Corynebacterium diphtheriae, the causative agent of the severe respiratory disease diphtheria, utilizes hemin and hemoglobin as iron sources for growth in iron-depleted environments. Because of the toxicity of high levels of hemin and iron, these compounds are often tightly regulated in bacterial systems. In this report, we identify and characterize the C. diphtheriae hrtAB genes, which encode a putative ABC type transporter involved in conferring resistance to the toxic effects of hemin. Deletion of the hrtAB genes in C. diphtheriae produced increased sensitivity to hemin, which was complemented by a plasmid harboring the cloned hrtAB locus. The HrtAB system was not involved in the uptake and use of hemin as an iron source. The hrtAB genes are located on the C. diphtheriae genome upstream from the chrSA operon, which encodes a previously characterized two-component signal transduction system that regulates gene expression in a heme-dependent manner. The hrtB promoter is activated by the ChrAS system in the presence of hemin or hemoglobin, and mutations in the chrSA genes abolish heme-activated expression from the hrtB promoter. It was also observed that transcription from the hrtB promoter is reduced in a dtxR deletion mutant, suggesting that DtxR is required for optimal expression of hrtAB. Previous studies proposed that the ChrS sensor kinase may be responsive to an environmental signal, such as hemin. We show that specific point mutations in the ChrS N-terminal transmembrane domain result in a reduced ability to activate the hrtB promoter in the presence of a heme source, suggesting that this putative sensor region is essential for the detection of a signal produced in response to hemin exposure. This study shows that the HrtAB system is required for protection from hemin toxicity and that expression of the hrtAB genes is regulated by the ChrAS two-component system. This study demonstrates a direct correlation between the detection of heme or a heme-associated signal by the N-terminal sensor domain of ChrS and the transcriptional activation of the hrtAB genes.
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Spinler JK, Zajdowicz SLW, Haller JC, Oram DM, Gill RE, Holmes RK. Development and use of a selectable, broad-host-range reporter transposon for identifying environmentally regulated promoters in bacteria. FEMS Microbiol Lett 2009; 291:143-50. [PMID: 19146571 DOI: 10.1111/j.1574-6968.2008.01430.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
This report describes the development and use of TnKnXSp, a selectable broad-host-range reporter transposon with a promoterless aphA gene. Insertion of TnKnXSp into the chromosome of a kanamycin-susceptible bacterium confers resistance to kanamycin only if aphA is transcribed from an active promoter adjacent to the insertion site. We designed TnKnXSp as a tool for identifying environmentally regulated promoters in bacteria and developed general methods for initial characterization of any TnKnXSp integrant. To identify putative iron-regulated promoters in Corynebacterium diphtheriae, we constructed TnKnXSp integrants and identified a subgroup that expressed kanamycin resistance under low-iron, but not high-iron, conditions. We characterized representative integrants with this phenotype, located the TnKnXSp insertion in each, and demonstrated that transcription of aphA was repressed under high-iron vs. low-iron growth conditions. We also demonstrated that TnKnXSp can be used in bacteria other than C. diphtheriae, including Escherichia coli and Bacillus subtilis. Our findings validate TnKnXSp as a useful tool for identifying environmentally regulated promoters in bacteria.
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Affiliation(s)
- Jennifer K Spinler
- Department of Microbiology, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA
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Regulation and activity of a zinc uptake regulator, Zur, in Corynebacterium diphtheriae. J Bacteriol 2008; 191:1595-603. [PMID: 19074382 DOI: 10.1128/jb.01392-08] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Regulation of metal ion homeostasis is essential to bacterial cell survival, and in most species it is controlled by metal-dependent transcriptional regulators. In this study, we describe a Corynebacterium diphtheriae ferric uptake regulator-family protein, Zur, that controls expression of genes involved in zinc uptake. By measuring promoter activities and mRNA levels, we demonstrate that Zur represses transcription of three genes (zrg, cmrA, and troA) in zinc-replete conditions. All three of these genes have similarity to genes involved in zinc uptake. Transcription of zrg and cmrA was also shown to be regulated in response to iron and manganese, respectively, by mechanisms that are independent of Zur. We demonstrate that the activity of the zur promoter is slightly decreased under low zinc conditions in a process that is dependent on Zur itself. This regulation of zur transcription is distinctive and has not yet been described for any other zur. An adjacent gene, predicted to encode a metal-dependent transcriptional regulator in the ArsR/SmtB family, is transcribed from a separate promoter whose activity is unaffected by Zur. A C. diphtheriae zur mutant was more sensitive to peroxide stress, which suggests that zur has a role in protecting the bacterium from oxidative damage. Our studies provide the first evidence of a zinc specific transcriptional regulator in C. diphtheriae and give new insights into the intricate regulatory network responsible for regulating metal ion concentrations in this toxigenic human pathogen.
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Oram M, Woolston JE, Jacobson AD, Holmes RK, Oram DM. Bacteriophage-based vectors for site-specific insertion of DNA in the chromosome of Corynebacteria. Gene 2006; 391:53-62. [PMID: 17275217 PMCID: PMC1913493 DOI: 10.1016/j.gene.2006.12.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Revised: 12/01/2006] [Accepted: 12/04/2006] [Indexed: 11/18/2022]
Abstract
In Corynebacterium diphtheriae, diphtheria toxin is encoded by the tox gene of some temperate corynephages such as beta. beta-like corynephages are capable of inserting into the C. diphtheriae chromosome at two specific sites, attB1 and attB2. Transcription of the phage-encoded tox gene, and many chromosomally encoded genes, is regulated by the DtxR protein in response to Fe(2+) levels. Characterizing DtxR-dependent gene regulation is pivotal in understanding diphtheria pathogenesis and mechanisms of iron-dependent gene expression; although this has been hampered by a lack of molecular genetic tools in C. diphtheriae and related Coryneform species. To expand the systems for genetic manipulation of C. diphtheriae, we constructed plasmid vectors capable of integrating into the chromosome. These plasmids contain the beta-encoded attP site and the DIP0182 integrase gene of C. diphtheriae NCTC13129. When these vectors were delivered to the cytoplasm of non-lysogenic C. diphtheriae, they integrated into either the attB1 or attB2 sites with comparable frequency. Lysogens were also transformed with these vectors, by virtue of the second attB site. An integrated vector carrying an intact dtxR gene complemented the mutant phenotypes of a C. diphtheriae DeltadtxR strain. Additionally, strains of beta-susceptible C. ulcerans, and C. glutamicum, a species non-permissive for beta, were each transformed with these vectors. This work significantly extends the tools available for targeted transformation of both pathogenic and non-pathogenic Corynebacterium species.
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Affiliation(s)
- Mark Oram
- Department of Biomedical Sciences, University of Maryland Baltimore Baltimore MD 21201, USA
| | - Joelle E. Woolston
- Department of Biomedical Sciences, University of Maryland Baltimore Baltimore MD 21201, USA
| | - Andrew D. Jacobson
- University of Colorado School of Medicine, Department of Microbiology, Aurora, CO 80045, USA
| | - Randall K. Holmes
- University of Colorado School of Medicine, Department of Microbiology, Aurora, CO 80045, USA
| | - Diana M. Oram
- Department of Biomedical Sciences, University of Maryland Baltimore Baltimore MD 21201, USA
- *Corresponding author: Department of Biomedical Sciences. Rm 4E-04, University of Maryland Dental School, 666 W. Baltimore St., Baltimore, MD 21201, Phone: 00 1 410 706 8705, Fax: 00 1 410 706 0865,
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