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Haemophilus ducreyi Infection Induces Oxidative Stress, Central Metabolic Changes, and a Mixed Pro- and Anti-inflammatory Environment in the Human Host. mBio 2022; 13:e0312522. [PMID: 36453940 PMCID: PMC9765465 DOI: 10.1128/mbio.03125-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Few studies have investigated host-bacterial interactions at sites of infection in humans using transcriptomics and metabolomics. Haemophilus ducreyi causes cutaneous ulcers in children and the genital ulcer disease chancroid in adults. We developed a human challenge model in which healthy adult volunteers are infected with H. ducreyi on the upper arm until they develop pustules. Here, we characterized host-pathogen interactions in pustules using transcriptomics and metabolomics and examined interactions between the host transcriptome and metabolome using integrated omics. In a previous pilot study, we determined the human and H. ducreyi transcriptomes and the metabolome of pustule and wounded sites of 4 volunteers (B. Griesenauer, T. M. Tran, K. R. Fortney, D. M. Janowicz, et al., mBio 10:e01193-19, 2019, https://doi.org/10.1128/mBio.01193-19). While we could form provisional transcriptional networks between the host and H. ducreyi, the study was underpowered to integrate the metabolome with the host transcriptome. To better define and integrate the transcriptomes and metabolome, we used samples from both the pilot study (n = 4) and new volunteers (n = 8) to identify 5,495 human differentially expressed genes (DEGs), 123 H. ducreyi DEGs, 205 differentially abundant positive ions, and 198 differentially abundant negative ions. We identified 42 positively correlated and 29 negatively correlated human-H. ducreyi transcriptome clusters. In addition, we defined human transcriptome-metabolome networks consisting of 9 total clusters, which highlighted changes in fatty acid metabolism and mitigation of oxidative damage. Taken together, the data suggest a mixed pro- and anti-inflammatory environment and rewired central metabolism in the host that provides a hostile, nutrient-limited environment for H. ducreyi. IMPORTANCE Interactions between the host and bacteria at sites of infection in humans are poorly understood. We inoculated human volunteers on the upper arm with the skin pathogen H. ducreyi or a buffer control and biopsied the resulting infected and sham-inoculated sites. We performed dual transcriptome sequencing (RNA-seq) and metabolic analysis on the biopsy samples. Network analyses between the host and bacterial transcriptomes and the host transcriptome-metabolome network were used to identify molecules that may be important for the virulence of H. ducreyi in the human host. Our results suggest that the pustule is highly oxidative, contains both pro- and anti-inflammatory components, and causes metabolic shifts in the host, to which H. ducreyi adapts to survive. To our knowledge, this is the first study to integrate transcriptomic and metabolomic responses to a single bacterial pathogen in the human host.
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Brothwell JA, Griesenauer B, Chen L, Spinola SM. Interactions of the Skin Pathogen Haemophilus ducreyi With the Human Host. Front Immunol 2021; 11:615402. [PMID: 33613541 PMCID: PMC7886810 DOI: 10.3389/fimmu.2020.615402] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 12/21/2020] [Indexed: 12/29/2022] Open
Abstract
The obligate human pathogen Haemophilus ducreyi causes both cutaneous ulcers in children and sexually transmitted genital ulcers (chancroid) in adults. Pathogenesis is dependent on avoiding phagocytosis and exploiting the suppurative granuloma-like niche, which contains a myriad of innate immune cells and memory T cells. Despite this immune infiltrate, long-lived immune protection does not develop against repeated H. ducreyi infections—even with the same strain. Most of what we know about infectious skin diseases comes from naturally occurring infections and/or animal models; however, for H. ducreyi, this information comes from an experimental model of infection in human volunteers that was developed nearly three decades ago. The model mirrors the progression of natural disease and serves as a valuable tool to determine the composition of the immune cell infiltrate early in disease and to identify host and bacterial factors that are required for the establishment of infection and disease progression. Most recently, holistic investigation of the experimentally infected skin microenvironment using multiple “omics” techniques has revealed that non-canonical bacterial virulence factors, such as genes involved in central metabolism, may be relevant to disease progression. Thus, the immune system not only defends the host against H. ducreyi, but also dictates the nutrient availability for the invading bacteria, which must adapt their gene expression to exploit the inflammatory metabolic niche. These findings have broadened our view of the host-pathogen interaction network from considering only classical, effector-based virulence paradigms to include adaptations to the metabolic environment. How both host and bacterial factors interact to determine infection outcome is a current focus in the field. Here, we review what we have learned from experimental H. ducreyi infection about host-pathogen interactions, make comparisons to what is known for other skin pathogens, and discuss how novel technologies will deepen our understanding of this infection.
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Affiliation(s)
- Julie A Brothwell
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Brad Griesenauer
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Li Chen
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Stanley M Spinola
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, United States.,Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, United States.,Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN, United States
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Determination of an Interaction Network between an Extracellular Bacterial Pathogen and the Human Host. mBio 2019; 10:mBio.01193-19. [PMID: 31213562 PMCID: PMC6581864 DOI: 10.1128/mbio.01193-19] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Dual RNA sequencing (RNA-seq) offers the promise of determining an interactome at a transcriptional level between a bacterium and the host but has yet to be done on any bacterial infection in human tissue. We performed dual RNA-seq and metabolomics analyses on wounded and infected sites following experimental infection of the arm with H. ducreyi. Our results suggest that H. ducreyi survives in an abscess by utilizing l-ascorbate as an alternative carbon source, possibly taking advantage of host ascorbic acid recycling, and that H. ducreyi also adapts by upregulating genes involved in anaerobic metabolism and inorganic ion and nutrient transport. To our knowledge, this is the first description of an interaction network between a bacterium and the human host at a site of infection. A major gap in understanding infectious diseases is the lack of information about molecular interaction networks between pathogens and the human host. Haemophilus ducreyi causes the genital ulcer disease chancroid in adults and is a leading cause of cutaneous ulcers in children in the tropics. We developed a model in which human volunteers are infected on the upper arm with H. ducreyi until they develop pustules. To define the H. ducreyi and human interactome, we determined bacterial and host transcriptomic and host metabolomic changes in pustules. We found that in vivoH. ducreyi transcripts were distinct from those in the inocula, as were host transcripts in pustule and wounded control sites. Many of the upregulated H. ducreyi genes were found to be involved in ascorbic acid and anaerobic metabolism and inorganic ion/nutrient transport. The top 20 significantly expressed human pathways showed that all were involved in immune responses. We generated a bipartite network for interactions between host and bacterial gene transcription; multiple positively correlated networks contained H. ducreyi genes involved in anaerobic metabolism and host genes involved with the immune response. Metabolomic studies showed that pustule and wounded samples had different metabolite compositions; the top ion pathway involved ascorbate and aldarate metabolism, which correlated with the H. ducreyi transcriptional response and upregulation of host genes involved in ascorbic acid recycling. These data show that an interactome exists between H. ducreyi and the human host and suggest that H. ducreyi exploits the metabolic niche created by the host immune response.
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Marks M, Fookes M, Wagner J, Ghinai R, Sokana O, Sarkodie YA, Solomon AW, Mabey DC, Thomson NR. Direct Whole-Genome Sequencing of Cutaneous Strains of Haemophilus ducreyi. Emerg Infect Dis 2018; 24:786-789. [PMID: 29553314 PMCID: PMC5875288 DOI: 10.3201/eid2404.171726] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Haemophilus ducreyi, which causes chancroid, has emerged as a cause of pediatric skin disease. Isolation of H. ducreyi in low-income settings is challenging, limiting phylogenetic investigation. Next-generation sequencing demonstrates that cutaneous strains arise from class I and II H. ducreyi clades and that class II may represent a distinct subspecies.
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Affiliation(s)
| | | | - Josef Wagner
- London School of Hygiene & Tropical Medicine, London, UK (M. Marks, R. Ghinai, A.W. Solomon, D.C.W. Mabey, N.R. Thomson)
- Hospital for Tropical Diseases, London (M. Marks, A.W. Solomon, D.C.W. Mabey)
- Wellcome Trust Sanger Centre, Cambridge, UK (M. Fookes, J. Wagner, N.R. Thomson)
- Solomon Islands Ministry of Health and Medical Services, Honiara, Solomon Islands (O. Sokana)
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana (Y.-A. Sarkodie)
| | - Rosanna Ghinai
- London School of Hygiene & Tropical Medicine, London, UK (M. Marks, R. Ghinai, A.W. Solomon, D.C.W. Mabey, N.R. Thomson)
- Hospital for Tropical Diseases, London (M. Marks, A.W. Solomon, D.C.W. Mabey)
- Wellcome Trust Sanger Centre, Cambridge, UK (M. Fookes, J. Wagner, N.R. Thomson)
- Solomon Islands Ministry of Health and Medical Services, Honiara, Solomon Islands (O. Sokana)
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana (Y.-A. Sarkodie)
| | - Oliver Sokana
- London School of Hygiene & Tropical Medicine, London, UK (M. Marks, R. Ghinai, A.W. Solomon, D.C.W. Mabey, N.R. Thomson)
- Hospital for Tropical Diseases, London (M. Marks, A.W. Solomon, D.C.W. Mabey)
- Wellcome Trust Sanger Centre, Cambridge, UK (M. Fookes, J. Wagner, N.R. Thomson)
- Solomon Islands Ministry of Health and Medical Services, Honiara, Solomon Islands (O. Sokana)
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana (Y.-A. Sarkodie)
| | - Yaw-Adu Sarkodie
- London School of Hygiene & Tropical Medicine, London, UK (M. Marks, R. Ghinai, A.W. Solomon, D.C.W. Mabey, N.R. Thomson)
- Hospital for Tropical Diseases, London (M. Marks, A.W. Solomon, D.C.W. Mabey)
- Wellcome Trust Sanger Centre, Cambridge, UK (M. Fookes, J. Wagner, N.R. Thomson)
- Solomon Islands Ministry of Health and Medical Services, Honiara, Solomon Islands (O. Sokana)
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana (Y.-A. Sarkodie)
| | - Anthony W. Solomon
- London School of Hygiene & Tropical Medicine, London, UK (M. Marks, R. Ghinai, A.W. Solomon, D.C.W. Mabey, N.R. Thomson)
- Hospital for Tropical Diseases, London (M. Marks, A.W. Solomon, D.C.W. Mabey)
- Wellcome Trust Sanger Centre, Cambridge, UK (M. Fookes, J. Wagner, N.R. Thomson)
- Solomon Islands Ministry of Health and Medical Services, Honiara, Solomon Islands (O. Sokana)
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana (Y.-A. Sarkodie)
| | - David C.W. Mabey
- London School of Hygiene & Tropical Medicine, London, UK (M. Marks, R. Ghinai, A.W. Solomon, D.C.W. Mabey, N.R. Thomson)
- Hospital for Tropical Diseases, London (M. Marks, A.W. Solomon, D.C.W. Mabey)
- Wellcome Trust Sanger Centre, Cambridge, UK (M. Fookes, J. Wagner, N.R. Thomson)
- Solomon Islands Ministry of Health and Medical Services, Honiara, Solomon Islands (O. Sokana)
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana (Y.-A. Sarkodie)
| | - Nicholas R. Thomson
- London School of Hygiene & Tropical Medicine, London, UK (M. Marks, R. Ghinai, A.W. Solomon, D.C.W. Mabey, N.R. Thomson)
- Hospital for Tropical Diseases, London (M. Marks, A.W. Solomon, D.C.W. Mabey)
- Wellcome Trust Sanger Centre, Cambridge, UK (M. Fookes, J. Wagner, N.R. Thomson)
- Solomon Islands Ministry of Health and Medical Services, Honiara, Solomon Islands (O. Sokana)
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana (Y.-A. Sarkodie)
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Oliveira T, Costa I, Marinho V, Carvalho V, Uchôa K, Ayres C, Teixeira S, Vasconcelos DFP. Human foreskin fibroblasts: from waste bag to important biomedical applications. JOURNAL OF CLINICAL UROLOGY 2018. [DOI: 10.1177/2051415818761526] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Circumcision is one of the most performed surgical procedures worldwide, and it is estimated that one in three men worldwide is circumcised, which makes the preputial skin removed after surgery an abundant material for possible applications. In particular, it is possible efficiently to isolate the cells of the foreskin, with fibroblasts being the most abundant cells of the dermis and the most used in biomedical research. This work aimed to review the knowledge and obtain a broad view of the main applications of human foreskin fibroblast cell culture. A literature search was conducted, including clinical trials, preclinical basic research studies, reviews and experimental studies. Several medical and laboratory applications of human foreskin fibroblast cell culture have been described, especially when it comes to the use of human foreskin fibroblasts as feeder cells for the cultivation of human embryonic stem cells, in addition to co-culture with other cell types. The culture of foreskin fibroblasts has also been used to: obtain induced pluripotent stem cells; the diagnosis of Clostridium difficile; to test the toxicity and effect of substances on normal cells, especially the toxicity of possible antineoplastic drugs; in viral culture, mainly of the human cytomegalovirus, study of the pathogenesis of other microorganisms; varied studies of cellular physiology and cellular interactions. Fibroblasts are important for cell models for varied application cultures, demonstrating how the preputial material can be reused, making possible new applications. Level of evidence: Not applicable for this multicentre audit.
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Affiliation(s)
- Thomaz Oliveira
- Genetics and Molecular Biology Laboratory, Federal University of Piauí (UFPI), Brazil
- Brain Mapping and Plasticity Laboratory, Federal University of Piauí (UFPI), Brazil
- Biomedical Sciences, Federal University of Piauí (UFPI), Brazil
| | - Ilana Costa
- Biomedical Sciences, Federal University of Piauí (UFPI), Brazil
| | - Victor Marinho
- Genetics and Molecular Biology Laboratory, Federal University of Piauí (UFPI), Brazil
- Brain Mapping and Plasticity Laboratory, Federal University of Piauí (UFPI), Brazil
- Biomedical Sciences, Federal University of Piauí (UFPI), Brazil
| | - Valécia Carvalho
- Brain Mapping and Plasticity Laboratory, Federal University of Piauí (UFPI), Brazil
- Biomedical Sciences, Federal University of Piauí (UFPI), Brazil
| | - Karla Uchôa
- Genetics and Molecular Biology Laboratory, Federal University of Piauí (UFPI), Brazil
- Biomedical Sciences, Federal University of Piauí (UFPI), Brazil
| | - Carla Ayres
- Brain Mapping and Plasticity Laboratory, Federal University of Piauí (UFPI), Brazil
| | - Silmar Teixeira
- Brain Mapping and Plasticity Laboratory, Federal University of Piauí (UFPI), Brazil
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Identification and Characterization of Differentially-Regulated Type IVb Pilin Genes Necessary for Predation in Obligate Bacterial Predators. Sci Rep 2017; 7:1013. [PMID: 28432347 PMCID: PMC5430801 DOI: 10.1038/s41598-017-00951-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 03/17/2017] [Indexed: 11/08/2022] Open
Abstract
Bdellovibrio bacteriovorus is an obligate predator of bacteria that grows and divides within the periplasm of its prey. Functions involved in the early steps of predation have been identified and characterized, but mediators of prey invasion are still poorly detailed. By combining omics data available for Bdellovibrio and like organisms (BALO’s), we identified 43 genes expressed in B. bacteriovorus during the early interaction with prey. These included genes in a tight adherence (TAD) operon encoding for two type IVb fimbriae-like pilin proteins (flp1 and flp2), and their processing and export machinery. Two additional flp genes (flp3 and flp4) were computationally identified at other locations along the chromosome, defining the largest and most diverse type IVb complement known in bacteria to date. Only flp1, flp2 and flp4 were expressed; their respective gene knock-outs resulted in a complete loss of the predatory ability without losing the ability to adhere to prey cells. Additionally, we further demonstrate differential regulation of the flp genes as the TAD operon of BALOs with different predatory strategies is controlled by a flagellar sigma factor FliA, while flp4 is not. Finally, we show that FliA, a known flagellar transcriptional regulator in other bacteria, is an essential Bdellovibrio gene.
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Haemophilus ducreyi Seeks Alternative Carbon Sources and Adapts to Nutrient Stress and Anaerobiosis during Experimental Infection of Human Volunteers. Infect Immun 2016; 84:1514-1525. [PMID: 26930707 DOI: 10.1128/iai.00048-16] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 02/25/2016] [Indexed: 12/14/2022] Open
Abstract
Haemophilus ducreyi causes the sexually transmitted disease chancroid in adults and cutaneous ulcers in children. In humans, H. ducreyi resides in an abscess and must adapt to a variety of stresses. Previous studies (D. Gangaiah, M. Labandeira-Rey, X. Zhang, K. R. Fortney, S. Ellinger, B. Zwickl, B. Baker, Y. Liu, D. M. Janowicz, B. P. Katz, C. A. Brautigam, R. S. MunsonJr, E. J. Hansen, and S. M. Spinola, mBio 5:e01081-13, 2014, http://dx.doi.org/10.1128/mBio.01081-13) suggested that H. ducreyi encounters growth conditions in human lesions resembling those found in stationary phase. However, how H. ducreyi transcriptionally responds to stress during human infection is unknown. Here, we determined the H. ducreyi transcriptome in biopsy specimens of human lesions and compared it to the transcriptomes of bacteria grown to mid-log, transition, and stationary phases. Multidimensional scaling showed that the in vivo transcriptome is distinct from those of in vitro growth. Compared to the inoculum (mid-log-phase bacteria), H. ducreyi harvested from pustules differentially expressed ∼93 genes, of which 62 were upregulated. The upregulated genes encode homologs of proteins involved in nutrient transport, alternative carbon pathways (l-ascorbate utilization and metabolism), growth arrest response, heat shock response, DNA recombination, and anaerobiosis. H. ducreyi upregulated few genes (hgbA, flp-tad, and lspB-lspA2) encoding virulence determinants required for human infection. Most genes regulated by CpxRA, RpoE, Hfq, (p)ppGpp, and DksA, which control the expression of virulence determinants and adaptation to a variety of stresses, were not differentially expressed in vivo, suggesting that these systems are cycling on and off during infection. Taken together, these data suggest that the in vivo transcriptome is distinct from those of in vitro growth and that adaptation to nutrient stress and anaerobiosis is crucial for H. ducreyi survival in humans.
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DksA and (p)ppGpp have unique and overlapping contributions to Haemophilus ducreyi pathogenesis in humans. Infect Immun 2015; 83:3281-92. [PMID: 26056381 DOI: 10.1128/iai.00692-15] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 05/29/2015] [Indexed: 01/10/2023] Open
Abstract
The (p)ppGpp-mediated stringent response is important for bacterial survival in nutrient limiting conditions. For maximal effect, (p)ppGpp interacts with the cofactor DksA, which stabilizes (p)ppGpp's interaction with RNA polymerase. We previously demonstrated that (p)ppGpp was required for the virulence of Haemophilus ducreyi in humans. Here, we constructed an H. ducreyi dksA mutant and showed it was also partially attenuated for pustule formation in human volunteers. To understand the roles of (p)ppGpp and DksA in gene regulation in H. ducreyi, we defined genes potentially altered by (p)ppGpp and DksA deficiency using transcriptome sequencing (RNA-seq). In bacteria collected at stationary phase, lack of (p)ppGpp and DksA altered expression of 28% and 17% of H. ducreyi open reading frames, respectively, including genes involved in transcription, translation, and metabolism. There was significant overlap in genes differentially expressed in the (p)ppGpp mutant relative to the dksA mutant. Loss of (p)ppGpp or DksA resulted in the dysregulation of several known virulence determinants. Deletion of dksA downregulated lspB and rendered the organism less resistant to phagocytosis and increased its sensitivity to oxidative stress. Both mutants had reduced ability to attach to human foreskin fibroblasts; the defect correlated with reduced expression of the Flp adhesin proteins in the (p)ppGpp mutant but not in the dksA mutant, suggesting that DksA regulates the expression of an unknown cofactor(s) required for Flp-mediated adherence. We conclude that both (p)ppGpp and DksA serve as major regulators of H. ducreyi gene expression in stationary phase and have both overlapping and unique contributions to pathogenesis.
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Abstract
To adapt to stresses encountered in stationary phase, Gram-negative bacteria utilize the alternative sigma factor RpoS. However, some species lack RpoS; thus, it is unclear how stationary-phase adaptation is regulated in these organisms. Here we defined the growth-phase-dependent transcriptomes of Haemophilus ducreyi, which lacks an RpoS homolog. Compared to mid-log-phase organisms, cells harvested from the stationary phase upregulated genes encoding several virulence determinants and a homolog of hfq. Insertional inactivation of hfq altered the expression of ~16% of the H. ducreyi genes. Importantly, there were a significant overlap and an inverse correlation in the transcript levels of genes differentially expressed in the hfq inactivation mutant relative to its parent and the genes differentially expressed in stationary phase relative to mid-log phase in the parent. Inactivation of hfq downregulated genes in the flp-tad and lspB-lspA2 operons, which encode several virulence determinants. To comply with FDA guidelines for human inoculation experiments, an unmarked hfq deletion mutant was constructed and was fully attenuated for virulence in humans. Inactivation or deletion of hfq downregulated Flp1 and impaired the ability of H. ducreyi to form microcolonies, downregulated DsrA and rendered H. ducreyi serum susceptible, and downregulated LspB and LspA2, which allow H. ducreyi to resist phagocytosis. We propose that, in the absence of an RpoS homolog, Hfq serves as a major contributor of H. ducreyi stationary-phase and virulence gene regulation. The contribution of Hfq to stationary-phase gene regulation may have broad implications for other organisms that lack an RpoS homolog. Pathogenic bacteria encounter a wide range of stresses in their hosts, including nutrient limitation; the ability to sense and respond to such stresses is crucial for bacterial pathogens to successfully establish an infection. Gram-negative bacteria frequently utilize the alternative sigma factor RpoS to adapt to stresses and stationary phase. However, homologs of RpoS are absent in some bacterial pathogens, including Haemophilus ducreyi, which causes chancroid and facilitates the acquisition and transmission of HIV-1. Here, we provide evidence that, in the absence of an RpoS homolog, Hfq serves as a major contributor of stationary-phase gene regulation and that Hfq is required for H. ducreyi to infect humans. To our knowledge, this is the first study describing Hfq as a major contributor of stationary-phase gene regulation in bacteria and the requirement of Hfq for the virulence of a bacterial pathogen in humans.
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The Haemophilus ducreyi Fis protein is involved in controlling expression of the lspB-lspA2 operon and other virulence factors. Infect Immun 2013; 81:4160-70. [PMID: 23980107 DOI: 10.1128/iai.00714-13] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Expression of the lspB-lspA2 operon encoding a virulence-related two-partner secretion system in Haemophilus ducreyi 35000HP is directly regulated by the CpxRA regulatory system (M. Labandeira-Rey, J. R. Mock, and E. J. Hansen, Infect. Immun. 77:3402-3411, 2009). In the present study, we show that this secretion system is also regulated by the small nucleoid-associated protein Fis. Inactivation of the H. ducreyi fis gene resulted in a reduction in expression of both the H. ducreyi LspB and LspA2 proteins. DNA microarray experiments showed that a H. ducreyi fis deletion mutant exhibited altered expression levels of genes encoding other important H. ducreyi virulence factors, including DsrA and Flp1, suggesting a possible global role for Fis in the control of virulence in this obligate human pathogen. While the H. ducreyi Fis protein has a high degree of sequence and structural similarity to the Fis proteins of other bacteria, its temporal pattern of expression was very different from that of enterobacterial Fis proteins. The use of a lacZ-based transcriptional reporter provided evidence which indicated that the H. ducreyi Fis homolog is a positive regulator of gyrB, a gene that is negatively regulated by Fis in enteric bacteria. Taken together, the Fis protein expression data and the observed regulatory effects of Fis in H. ducreyi suggest that this small DNA binding protein has a regulatory role in H. ducreyi which may differ in substantial ways from that of other Fis proteins.
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Activation of CpxRA in Haemophilus ducreyi primarily inhibits the expression of its targets, including major virulence determinants. J Bacteriol 2013; 195:3486-502. [PMID: 23729647 DOI: 10.1128/jb.00372-13] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Haemophilus ducreyi causes chancroid, a genital ulcer disease that facilitates the transmission of human immunodeficiency virus type 1. In humans, H. ducreyi is surrounded by phagocytes and must adapt to a hostile environment to survive. To sense and respond to environmental cues, bacteria frequently use two-component signal transduction (2CST) systems. The only obvious 2CST system in H. ducreyi is CpxRA; CpxR is a response regulator, and CpxA is a sensor kinase. Previous studies by Hansen and coworkers showed that CpxR directly represses the expression of dsrA, the lspB-lspA2 operon, and the flp operon, which are required for virulence in humans. They further showed that CpxA functions predominantly as a phosphatase in vitro to maintain the expression of virulence determinants. Since a cpxA mutant is avirulent while a cpxR mutant is fully virulent in humans, CpxA also likely functions predominantly as a phosphatase in vivo. To better understand the role of H. ducreyi CpxRA in controlling virulence determinants, here we defined genes potentially regulated by CpxRA by using RNA-Seq. Activation of CpxR by deletion of cpxA repressed nearly 70% of its targets, including seven established virulence determinants. Inactivation of CpxR by deletion of cpxR differentially regulated few genes and increased the expression of one virulence determinant. We identified a CpxR binding motif that was enriched in downregulated but not upregulated targets. These data reinforce the hypothesis that CpxA phosphatase activity plays a critical role in controlling H. ducreyi virulence in vivo. Characterization of the downregulated genes may offer new insights into pathogenesis.
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Carbon storage regulator A contributes to the virulence of Haemophilus ducreyi in humans by multiple mechanisms. Infect Immun 2012; 81:608-17. [PMID: 23230298 DOI: 10.1128/iai.01239-12] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The carbon storage regulator A (CsrA) controls a wide variety of bacterial processes, including metabolism, adherence, stress responses, and virulence. Haemophilus ducreyi, the causative agent of chancroid, harbors a homolog of csrA. Here, we generated an unmarked, in-frame deletion mutant of csrA to assess its contribution to H. ducreyi pathogenesis. In human inoculation experiments, the csrA mutant was partially attenuated for pustule formation compared to its parent. Deletion of csrA resulted in decreased adherence of H. ducreyi to human foreskin fibroblasts (HFF); Flp1 and Flp2, the determinants of H. ducreyi adherence to HFF cells, were downregulated in the csrA mutant. Compared to its parent, the csrA mutant had a significantly reduced ability to tolerate oxidative stress and heat shock. The enhanced sensitivity of the mutant to oxidative stress was more pronounced in bacteria grown to stationary phase compared to that in bacteria grown to mid-log phase. The csrA mutant also had a significant survival defect within human macrophages when the bacteria were grown to stationary phase but not to mid-log phase. Complementation in trans partially or fully restored the mutant phenotypes. These data suggest that CsrA contributes to virulence by multiple mechanisms and that these contributions may be more profound in bacterial cell populations that are not rapidly dividing in the human host.
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Roux N, Spagnolo J, de Bentzmann S. Neglected but amazingly diverse type IVb pili. Res Microbiol 2012; 163:659-73. [PMID: 23103334 DOI: 10.1016/j.resmic.2012.10.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 10/19/2012] [Indexed: 01/12/2023]
Abstract
This review provides an overview of current knowledge concerning type IVb pili in Gram-negative bacteria. The number of these pili identified is steadily increasing with genome sequencing and mining studies, but studies of these pili are somewhat uneven, because their expression is tightly regulated and the signals or regulators controlling expression need to be identified. However, as illustrated here, they have a number of interesting functional, assembly-related and regulatory features.
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Affiliation(s)
- Nicolas Roux
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS UMR7255 - Aix Marseille University, Institut de Microbiologie de la Méditerranée, 31 Chemin Joseph Aiguier, 13402, cédex 20, Marseille, France
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Seventeen Sxy-dependent cyclic AMP receptor protein site-regulated genes are needed for natural transformation in Haemophilus influenzae. J Bacteriol 2012; 194:5245-54. [PMID: 22821979 DOI: 10.1128/jb.00671-12] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Natural competence is the ability of bacteria to actively take up extracellular DNA. This DNA can recombine with the host chromosome, transforming the host cell and altering its genotype. In Haemophilus influenzae, natural competence is induced by energy starvation and the depletion of nucleotide pools. This induces a 26-gene competence regulon (Sxy-dependent cyclic AMP receptor protein [CRP-S] regulon) whose expression is controlled by two regulators, CRP and Sxy. The role of most of the CRP-S genes in DNA uptake and transformation is not known. We have therefore created in-frame deletions of each CRP-S gene and studied their competence phenotypes. All but one gene (ssb) could be deleted. Although none of the remaining CRP-S genes were required for growth in rich medium or survival under starvation conditions, DNA uptake and transformation were abolished or reduced in most of the mutants. Seventeen genes were absolutely required for transformation, with 14 of these genes being specifically required for the assembly and function of the type IV pilus DNA uptake machinery. Only five genes were dispensable for both competence and transformation. This is the first competence regulon for which all genes have been mutationally characterized.
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Sialylation of lipooligosaccharides is dispensable for the virulence of Haemophilus ducreyi in humans. Infect Immun 2011; 80:679-87. [PMID: 22144477 DOI: 10.1128/iai.05826-11] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Sialylated glycoconjugates on the surfaces of mammalian cells play important roles in intercellular communication and self-recognition. The sialic acid preferentially expressed in human tissues is N-acetylneuraminic acid (Neu5Ac). In a process called molecular mimicry, many bacterial pathogens decorate their cell surface glycolipids with Neu5Ac. Incorporation of Neu5Ac into bacterial glycolipids promotes bacterial interactions with host cell receptors called Siglecs. These interactions affect bacterial adherence, resistance to serum killing and phagocytosis, and innate immune responses. Haemophilus ducreyi, the etiologic agent of chancroid, expresses lipooligosaccharides (LOS) that are highly sialylated. However, an H. ducreyi sialyltransferase (lst) mutant, whose LOS contain reduced levels of Neu5Ac, is fully virulent in human volunteers. Recently, a second sialyltransferase gene (Hd0053) was discovered in H. ducreyi, raising the possibility that Hd0053 compensated for the loss of lst during human infection. CMP-Neu5Ac is the obligate nucleotide sugar donor for all bacterial sialyltransferases; LOS derived from an H. ducreyi CMP-Neu5Ac synthetase (neuA) mutant has no detectable Neu5Ac. Here, we compared an H. ducreyi neuA mutant to its wild-type parent in several models of pathogenesis. In human inoculation experiments, the neuA mutant formed papules and pustules at rates that were no different than those of its parent. When grown in media with and without Neu5Ac supplementation, the neuA mutant and its parent had similar phenotypes in bactericidal, macrophage uptake, and dendritic cell activation assays. Although we cannot preclude a contribution of LOS sialylation to ulcerative disease, these data strongly suggest that sialylation of LOS is dispensable for H. ducreyi pathogenesis in humans.
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