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Bisaro F, Shuman HA, Feldman MF, Gebhardt MJ, Pukatzki S. Acinetobacter baumannii ATCC 17978 encodes a microcin system with antimicrobial properties for contact-independent competition. Microbiology (Reading) 2023; 169:001346. [PMID: 37289493 PMCID: PMC10333792 DOI: 10.1099/mic.0.001346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 05/25/2023] [Indexed: 06/09/2023]
Abstract
Acinetobacter baumannii is a multidrug-resistant opportunistic pathogen that persists in the hospital environment and causes various clinical infections, primarily affecting immunocompromised patients. A. baumannii has evolved a wide range of mechanisms to compete with neighbouring bacteria. One such competition strategy depends on small secreted peptides called microcins, which exert antimicrobial effects in a contact-independent manner. Here, we report that A. baumannii ATCC 17978 (AB17978) encodes the class II microcin 17 978 (Mcc17978) with antimicrobial activity against closely related Acinetobacter, and surprisingly, also Escherichia coli strains. We identified the genetic locus encoding the Mcc17978 system in AB17978. Using classical bacterial genetic approaches, we determined that the molecular receptor of Mcc17978 in E. coli is the iron-catecholate transporter Fiu, and in Acinetobacter is Fiu's homolog, PiuA. In bacteria, the Ferric uptake regulator (Fur) positively regulates siderophore systems and microcin systems under iron-deprived environments. We found that the Mcc17978 system is upregulated under low-iron conditions commonly found in the host environment and identified a putative Fur binding site upstream of the mcc17978 gene. When we tested the antimicrobial activity of Mcc17978 under different levels of iron availability, we observed that low iron levels not only triggered transcriptional induction of the microcin, but also led to enhanced microcin activity. Taken together, our findings suggest that A. baumannii may utilize microcins to compete with other microbes for resources during infection.
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Affiliation(s)
- Fabiana Bisaro
- Department of Biology, The City College, City University of New York, New York, NY 10031, USA
- Department of Molecular Microbiology, Washington University School of Medicine in St. Louis, St. Louis MO 63110, USA
| | - Howard A. Shuman
- Department of Microbiology, The University of Chicago, Chicago, IL 60637, USA
- Present address: P.O. Box 1088, Sheffield, MA 01257, USA
| | - Mario F. Feldman
- Department of Molecular Microbiology, Washington University School of Medicine in St. Louis, St. Louis MO 63110, USA
| | - Michael J. Gebhardt
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa 52242, USA
| | - Stefan Pukatzki
- Department of Biology, The City College, City University of New York, New York, NY 10031, USA
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2
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Zhou H, Gebhardt MJ, Czyz DM, Yao Y, Shuman HA. The gigA/gigB Genes Regulate the Growth, Stress Response, and Virulence of Acinetobacter baumannii ATCC 17978 Strain. Front Microbiol 2021; 12:723949. [PMID: 34421881 PMCID: PMC8371402 DOI: 10.3389/fmicb.2021.723949] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 07/16/2021] [Indexed: 12/03/2022] Open
Abstract
Acinetobacter baumannii is an important pathogen of nosocomial infection. Recently, a group of genes, named “gig” (for Growth in Galleria), have been identified in a contemporary multi-drug resistant clinical isolate of A. baumannii—strain AB5075. Among these so-called gig genes, gigA and gigB were found to promote antibiotic resistance, stress survival, and virulence of AB5075 by interacting with the nitrogen phosphotransferase system (PTSNtr). This study aimed to investigate the roles of gigA/gigB, which appear to comprise a stress-signaling pathway (encoding for an atypical two-component system response regulator and a predicted anti-anti-sigma factor, respectively), and the involvement of ptsP (encoding the Enzyme I component of the PTSNtr) in the growth, stress resistance, and virulence of the widely studied A. baumannii strain ATCC 17978. Genetic analyses of strains harboring mutations of gigA and gigB were performed to investigate the roles of these genes in bacterial growth, stress resistance, evading macrophage defense, and killing of Galleria mellonella larva. In contrast with findings from strain AB5075 where gigA and gigB contribute to aminoglycoside resistance, the data presented herein indicate that the loss of gigA/gigB does not impact antibiotic resistance of strain ATCC 17978. Interestingly, however, we found that deletion of gigA/gigB in the ATCC 17978 background imparts a general growth in laboratory medium and also conferred growth and replication defects within murine macrophages and an inability to kill G. mellonella larvae. Importantly, studies as well as the loss of ptsP restored the phenotypes of the gigA/gigB mutant to that of the wild-type. The data presented herein indicate that in A. baumannii ATCC 17978, the gigA/gigB genes play a key role in both growth and virulence traits, but are dispensable for other stress-resistance survival phenotypes, including aminoglycoside resistance. Our findings thus highlight several similarities and also important differences between the gigA/gigB stress-signaling pathway in two commonly studied isolates of this troublesome pathogen.
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Affiliation(s)
- Hua Zhou
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.,Department of Microbiology, University of Chicago, Chicago, IL, United States
| | - Michael J Gebhardt
- Department of Microbiology, University of Chicago, Chicago, IL, United States
| | - Daniel M Czyz
- Department of Microbiology, University of Chicago, Chicago, IL, United States.,Department of Microbiology and Cell Science, University of Florida, Gainesville, FL, United States
| | - Yake Yao
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Howard A Shuman
- Department of Microbiology, University of Chicago, Chicago, IL, United States
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3
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Zhang D, Tang Z, Huang H, Zhou G, Cui C, Weng Y, Liu W, Kim S, Lee S, Perez-Neut M, Ding J, Czyz D, Hu R, Ye Z, He M, Zheng YG, Shuman HA, Dai L, Ren B, Roeder RG, Becker L, Zhao Y. Metabolic regulation of gene expression by histone lactylation. Nature 2019; 574:575-580. [PMID: 31645732 PMCID: PMC6818755 DOI: 10.1038/s41586-019-1678-1] [Citation(s) in RCA: 1164] [Impact Index Per Article: 232.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 09/13/2019] [Indexed: 02/05/2023]
Abstract
The Warburg effect, originally describing augmented lactogenesis in cancer, is associated with diverse cellular processes such as angiogenesis, hypoxia, macrophage polarization, and T-cell activation. This phenomenon is intimately linked with multiple diseases including neoplasia, sepsis, and autoimmune diseases1,2. Lactate, a compound generated during Warburg effect, is widely known as an energy source and metabolic byproduct. However, its non-metabolic functions in physiology and disease remain unknown. Here we report lactate-derived histone lysine lactylation as a new epigenetic modification and demonstrate that histone lactylation directly stimulates gene transcription from chromatin. In total, we identify 28 lactylation sites on core histones in human and mouse cells. Hypoxia and bacterial challenges induce production of lactate through glycolysis that in turn serves as precursor for stimulating histone lactylation. Using bacterially exposed M1 macrophages as a model system, we demonstrate that histone lactylation has different temporal dynamics from acetylation. In the late phase of M1 macrophage polarization, elevated histone lactylation induces homeostatic genes involved in wound healing including arginase 1. Collectively, our results suggest the presence of an endogenous “lactate clock” in bacterially challenged M1 macrophages that turns on gene expression to promote homeostasis. Histone lactylation thus represents a new avenue for understanding the functions of lactate and its role in diverse pathophysiological conditions, including infection and cancer.
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Affiliation(s)
- Di Zhang
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, USA
| | - Zhanyun Tang
- Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY, USA
| | - He Huang
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, USA.,Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Guolin Zhou
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, USA
| | - Chang Cui
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, USA
| | - Yejing Weng
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, USA
| | - Wenchao Liu
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, USA
| | - Sunjoo Kim
- BK21 Plus KNU Multi-Omics based Creative Drug Research Team, College of Pharmacy, Research Institute of Pharmaceutical Sciences, Kyungpook National University, Daegu, South Korea
| | - Sangkyu Lee
- BK21 Plus KNU Multi-Omics based Creative Drug Research Team, College of Pharmacy, Research Institute of Pharmaceutical Sciences, Kyungpook National University, Daegu, South Korea
| | - Mathew Perez-Neut
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, USA
| | - Jun Ding
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, USA
| | - Daniel Czyz
- Department of Microbiology, The University of Chicago, Chicago, IL, USA
| | - Rong Hu
- Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, CA, USA.,Center for Epigenomics and Department of Cellular and Molecular Medicine, University of California, San Diego School of Medicine, La Jolla, CA, USA
| | - Zhen Ye
- Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, CA, USA.,Center for Epigenomics and Department of Cellular and Molecular Medicine, University of California, San Diego School of Medicine, La Jolla, CA, USA
| | - Maomao He
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA, USA
| | - Y George Zheng
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA, USA
| | - Howard A Shuman
- Department of Microbiology, The University of Chicago, Chicago, IL, USA
| | - Lunzhi Dai
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, USA.,Department of General Practice, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, and Collaborative Innovation Center of Biotherapy, Chengdu, China
| | - Bing Ren
- Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, CA, USA.,Center for Epigenomics and Department of Cellular and Molecular Medicine, University of California, San Diego School of Medicine, La Jolla, CA, USA
| | - Robert G Roeder
- Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY, USA
| | - Lev Becker
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, USA. .,University of Chicago Medicine Comprehensive Cancer Center, Chicago, IL, USA. .,Ludwig Center for Metastasis Research, The University of Chicago, Chicago, IL, USA.
| | - Yingming Zhao
- Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, USA. .,University of Chicago Medicine Comprehensive Cancer Center, Chicago, IL, USA.
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Goss CH, Kaneko Y, Khuu L, Anderson GD, Ravishankar S, Aitken ML, Lechtzin N, Zhou G, Czyz DM, McLean K, Olakanmi O, Shuman HA, Teresi M, Wilhelm E, Caldwell E, Salipante SJ, Hornick DB, Siehnel RJ, Becker L, Britigan BE, Singh PK. Gallium disrupts bacterial iron metabolism and has therapeutic effects in mice and humans with lung infections. Sci Transl Med 2018; 10:eaat7520. [PMID: 30257953 PMCID: PMC6637966 DOI: 10.1126/scitranslmed.aat7520] [Citation(s) in RCA: 164] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 09/06/2018] [Indexed: 12/12/2022]
Abstract
The lack of new antibiotics is among the most critical challenges facing medicine. The problem is particularly acute for Gram-negative bacteria. An unconventional antibiotic strategy is to target bacterial nutrition and metabolism. The metal gallium can disrupt bacterial iron metabolism because it substitutes for iron when taken up by bacteria. We investigated the antibiotic activity of gallium ex vivo, in a mouse model of airway infection, and in a phase 1 clinical trial in individuals with cystic fibrosis (CF) and chronic Pseudomonas aeruginosa airway infections. Our results show that micromolar concentrations of gallium inhibited P. aeruginosa growth in sputum samples from patients with CF. Ex vivo experiments indicated that gallium inhibited key iron-dependent bacterial enzymes and increased bacterial sensitivity to oxidants. Furthermore, gallium resistance developed slowly, its activity was synergistic with certain antibiotics, and gallium did not diminish the antibacterial activity of host macrophages. Systemic gallium treatment showed antibiotic activity in murine lung infections. In addition, systemic gallium treatment improved lung function in people with CF and chronic P. aeruginosa lung infection in a preliminary phase 1 clinical trial. These findings raise the possibility that human infections could be treated by targeting iron metabolism or other nutritional vulnerabilities of bacterial pathogens.
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Affiliation(s)
- Christopher H Goss
- Department of Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA
- Department of Pediatrics, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Yukihiro Kaneko
- Department of Bacteriology, Osaka City University School of Medicine, Osaka 545-0051, Japan
| | - Lisa Khuu
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Gail D Anderson
- Department of Pharmacy, University of Washington School of Pharmacy, Seattle, WA 98195, USA
| | - Sumedha Ravishankar
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Moira L Aitken
- Department of Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Noah Lechtzin
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Guolin Zhou
- Ben May Department for Cancer Research, University of Chicago, Chicago, IL 60637, USA
| | - Daniel M Czyz
- Department of Microbiology, The University of Chicago, Chicago, IL 60637, USA
| | - Kathryn McLean
- Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Oyebode Olakanmi
- University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
| | - Howard A Shuman
- Department of Microbiology, The University of Chicago, Chicago, IL 60637, USA
| | - Mary Teresi
- Department of Medicine, University of Nebraska School of Medicine, Omaha, NE 68105, USA
| | - Ellen Wilhelm
- Department of Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Ellen Caldwell
- Department of Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Stephen J Salipante
- Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Douglas B Hornick
- Department of Medicine, University of Nebraska School of Medicine, Omaha, NE 68105, USA
| | - Richard J Siehnel
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Lev Becker
- Ben May Department for Cancer Research, University of Chicago, Chicago, IL 60637, USA
| | - Bradley E Britigan
- Departments of Medicine and Pediatrics, University of Iowa, Iowa City, IA 52242, USA
| | - Pradeep K Singh
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA.
- Department of Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA
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5
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Gebhardt MJ, Jacobson RK, Shuman HA. Seeing red; the development of pON.mCherry, a broad-host range constitutive expression plasmid for Gram-negative bacteria. PLoS One 2017; 12:e0173116. [PMID: 28257493 PMCID: PMC5336243 DOI: 10.1371/journal.pone.0173116] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 02/15/2017] [Indexed: 01/16/2023] Open
Abstract
The development of plasmid-mediated gene expression control in bacteria revolutionized the field of bacteriology. Many of these expression control systems rely on the addition of small molecules, generally metabolites or non-metabolized analogs thereof, to the growth medium to induce expression of the genes of interest. The paradigmatic example of an expression control system is the lac system from Escherichia coli, which typically relies on the Ptac promoter and the Lac repressor, LacI. In many cases, however, constitutive gene expression is desired, and other experimental approaches require the coordinated control of multiple genes. While multiple systems have been developed for use in E. coli and its close relatives, the utility and/or functionality of these tools does not always translate to other species. For example, for the Gram-negative pathogen, Legionella pneumophila, a causative agent of Legionnaires' Disease, the aforementioned Ptac system represents the only well-established expression control system. In order to enhance the tools available to study bacterial gene expression in L. pneumophila, we developed a plasmid, pON.mCherry, which confers constitutive gene expression from a mutagenized LacI binding site. We demonstrate that pON.mCherry neither interferes with other plasmids harboring an intact LacI-Ptac expression system nor alters the growth of Legionella species during intracellular growth. Furthermore, the broad-host range plasmid backbone of pON.mCherry allows constitutive gene expression in a wide variety of Gram-negative bacterial species, making pON.mCherry a useful tool for the greater research community.
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Affiliation(s)
- Michael J. Gebhardt
- Department of Microbiology, University of Chicago, Chicago, Illinois, United States of America
| | - Rachael K. Jacobson
- Department of Microbiology, University of Chicago, Chicago, Illinois, United States of America
| | - Howard A. Shuman
- Department of Microbiology, University of Chicago, Chicago, Illinois, United States of America
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6
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Burstein D, Amaro F, Zusman T, Lifshitz Z, Cohen O, Gilbert JA, Pupko T, Shuman HA, Segal G. Genomic analysis of 38 Legionella species identifies large and diverse effector repertoires. Nat Genet 2016; 48:167-75. [PMID: 26752266 DOI: 10.1038/ng.3481] [Citation(s) in RCA: 180] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 12/08/2015] [Indexed: 11/09/2022]
Abstract
Infection by the human pathogen Legionella pneumophila relies on the translocation of ∼ 300 virulence proteins, termed effectors, which manipulate host cell processes. However, almost no information exists regarding effectors in other Legionella pathogens. Here we sequenced, assembled and characterized the genomes of 38 Legionella species and predicted their effector repertoires using a previously validated machine learning approach. This analysis identified 5,885 predicted effectors. The effector repertoires of different Legionella species were found to be largely non-overlapping, and only seven core effectors were shared by all species studied. Species-specific effectors had atypically low GC content, suggesting exogenous acquisition, possibly from the natural protozoan hosts of these species. Furthermore, we detected numerous new conserved effector domains and discovered new domain combinations, which allowed the inference of as yet undescribed effector functions. The effector collection and network of domain architectures described here can serve as a roadmap for future studies of effector function and evolution.
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Affiliation(s)
- David Burstein
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Francisco Amaro
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
| | - Tal Zusman
- Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ziv Lifshitz
- Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ofir Cohen
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Jack A Gilbert
- Biology Division, Argonne National Laboratory and Department of Ecology and Evolution, University of Chicago, Chicago, Illinois, USA
| | - Tal Pupko
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Howard A Shuman
- Department of Microbiology, University of Chicago, Chicago, Illinois, USA
| | - Gil Segal
- Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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7
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Abstract
Acinetobacter baumannii is a Gram-negative nosocomial pathogen of clinical importance. A lack of genetic tools has hindered the research of this organism in the past; however, recently, various methods have been designed, modified, and optimized to facilitate the genetic manipulation of A. baumannii. This unit describes some of the recent genetic advances and new recombinant tools developed for this pathogen, including standard transformation and conjugation techniques specifically developed for the bacteria. As the need to understand the basic biology of A. baumannii increases with the prospect of developing new therapeutics, the use of the basic genetic methods herein can provide the critical first step to identify genes required for infection.
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Affiliation(s)
- Anna C Jacobs
- Walter Reed Army Institute of Research, Department of Wound Infections, Silver Spring, Maryland
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8
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Abstract
Manipulation of the actin cytoskeleton is a commonly used process by which bacterial pathogens and viruses are able to neutralize host defense mechanisms and subvert them in order to replicate in a hostile environment. Diverse bacteria display a wide array of mechanisms of regulation of microfilaments to enter, move within or exit the host cell. A less studied subject is how pathogens may co-opt the actin cytoskeleton to disturb vesicle trafficking pathways, namely phagolysosomal fusion, and avoid degradation. In fact, although actin plays a role in endosomal trafficking and phagosome maturation, the knowledge on the exact mechanisms and additional players is still scarce. Recently, we found that the Legionella pneumophila virulence factor VipA is an actin nucleator, associates with actin filaments and early endosomes during infection, and interferes in yeast organelle trafficking pathways, suggesting it may be linking actin dynamics to endosome biogenesis. Further studies on this protein, together with work on other bacterial effectors, may help shed light in the role of actin in endosomal maturation.
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9
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Trigui H, Dudyk P, Sum J, Shuman HA, Faucher SP. Analysis of the transcriptome of Legionella pneumophila hfq mutant reveals a new mobile genetic element. Microbiology (Reading) 2013; 159:1649-1660. [PMID: 23728622 DOI: 10.1099/mic.0.067983-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Hfq is a small RNA-binding protein involved in the post-transcriptional regulation of gene expression by affecting the stability of the mRNA and by mediating efficient pairing between small regulatory RNAs and their target mRNAs. In Legionella pneumophila, the aetiological agent of Legionnaires' disease, mutation of hfq results in increased duration of the lag phase and reduced growth in low-iron medium. In an effort to uncover genes potentially regulated by Hfq, the transcriptome of an hfq mutant strain was compared to that of the wild-type. Unexpectedly, many genes located within a 100 kb genomic island, including a section of the previously identified efflux island, were overexpressed in the hfq mutant strain. Since this island contains a putative conjugative system and an integrase, it was postulated that it could be a new integrated mobile genetic element. PCR analysis revealed that this region exists both as an integrated and as an episomal form in the cell population and that it undergoes differential excision in the hfq mutant background, which was further confirmed by trans-complementation of the hfq mutation. This new plasmid-like element was named pLP100. Differential excision did not affect the copy number of pLP100 at the population level. This region contains a copper efflux pump encoded by copA, and increased resistance to copper was observed for the hfq mutant strain that was abrogated in the complemented strain. A strain carrying a mutation of hfq and a deletion of the right side recombination site, attR, showed that overexpression of pLP100 genes and increased copper resistance in the hfq mutant strain were dependent upon excision of pLP100.
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Affiliation(s)
- Hana Trigui
- Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada
| | - Paulina Dudyk
- Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada
| | - Janet Sum
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA
| | - Howard A Shuman
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA
| | - Sebastien P Faucher
- Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada
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10
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Yu KOA, Porcelli SA, Shuman HA. In vitro derivation of macrophage from guinea pig bone marrow with human M-CSF. J Immunol Methods 2013; 389:88-94. [PMID: 23333710 DOI: 10.1016/j.jim.2013.01.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 12/09/2012] [Accepted: 01/02/2013] [Indexed: 11/19/2022]
Abstract
The guinea pig has a storied history as a model in the study of infectious disease and immunology. Because of reproducibility of data and availability of various reagents, inbred mice have since supplanted the guinea pig as the animal model-of-choice in these fields. However, several clinically-significant microorganisms do not cause the same pathology in mice, or mice may not be susceptible to these infections. These demonstrate the utility of other animal models - either as the primary method to study a particular infection, or to confirm or refute findings in the mouse before translating basic science into clinical practice. The mononuclear phagocyte, or macrophage (Mφ), plays a key role in antigen presentation and the pathogenesis of intracellular bacteria, such as Mycobacterium tuberculosis and Legionella pneumophila. Because of variable yield and difficult extraction from tissue, the preferred method of producing Mφ for in vitro studies is to expand murine bone marrow (BM) precursors with mouse macrophage colony-stimulating factor (M-CSF). This has not been shown in the guinea pig. Here, we report the empiric observation that human M-CSF - but not mouse M-CSF, nor human granulocyte/macrophage colony-stimulating factor - can be used to induce BM precursor differentiation into bonafide Mφ. The differentiated cells appeared as enlarged adherent cells, capable of both pinocytosis and large particle phagocytosis. Furthermore, we showed that these guinea pig BM-derived Mφ, similar to human monocyte/Mφ lines but unlike most murine BM Mφ, support growth of wild type L. pneumophila. This method may prove useful for in vitro studies of Mφ in the guinea pig, as well as in the translation of results found using mouse BM-derived Mφ towards studies in human immunology and infectious disease.
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Affiliation(s)
- Karl O A Yu
- Section of Infectious Diseases, Department of Pediatrics, Comer Children's Hospital, University of Chicago Medical Center, Chicago, IL 60637, USA.
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11
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Abstract
The study of transcriptome responses can provide insight into the regulatory pathways and genetic factors that contribute to a specific phenotype. For bacterial pathogens, it can identify putative new virulence systems and shed light on the mechanisms underlying the regulation of virulence factors. Microarrays have been previously used to study gene regulation in Legionella pneumophila. In the past few years a sharp reduction of the costs associated with microarray experiments together with the availability of relatively inexpensive custom-designed commercial microarrays has made microarray technology an accessible tool for the majority of researchers. Here we describe the methodologies to conduct microarray experiments from in vitro and in vivo samples.
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Affiliation(s)
- Sebastien P Faucher
- Faculty of Agricultural and Environmental Sciences, Department of Natural Resource Sciences, McGill University, Quebec, Canada.
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12
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Franco IS, Shohdy N, Shuman HA. The Legionella pneumophila effector VipA is an actin nucleator that alters host cell organelle trafficking. PLoS Pathog 2012; 8:e1002546. [PMID: 22383880 PMCID: PMC3285593 DOI: 10.1371/journal.ppat.1002546] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 01/09/2012] [Indexed: 12/30/2022] Open
Abstract
Legionella pneumophila, the causative agent of Legionnaires' disease, invades and replicates within macrophages and protozoan cells inside a vacuole. The type IVB Icm/Dot secretion system is necessary for the translocation of effector proteins that modulate vesicle trafficking pathways in the host cell, thus avoiding phagosome-lysosome fusion. The Legionella VipA effector was previously identified by its ability to interfere with organelle trafficking in the Multivesicular Body (MVB) pathway when ectopically expressed in yeast. In this study, we show that VipA binds actin in vitro and directly polymerizes microfilaments without the requirement of additional proteins, displaying properties distinct from other bacterial actin nucleators. Microscopy studies revealed that fluorescently tagged VipA variants localize to puncta in eukaryotic cells. In yeast these puncta are associated with actin-rich regions and components of the Multivesicular Body pathway such as endosomes and the MVB-associated protein Bro1. During macrophage infection, native translocated VipA associated with actin patches and early endosomes. When ectopically expressed in mammalian cells, VipA-GFP displayed a similar distribution ruling out the requirement of additional effectors for binding to its eukaryotic targets. Interestingly, a mutant form of VipA, VipA-1, that does not interfere with organelle trafficking is also defective in actin binding as well as association with early endosomes and shows a homogeneous cytosolic localization. These results show that the ability of VipA to bind actin is related to its association with a specific subcellular location as well as its role in modulating organelle trafficking pathways. VipA constitutes a novel type of actin nucleator that may contribute to the intracellular lifestyle of Legionella by altering cytoskeleton dynamics to target host cell pathways.
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Affiliation(s)
- Irina Saraiva Franco
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, New York, USA.
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13
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Pronin SV, Martinez A, Kuznedelov K, Severinov K, Shuman HA, Kozmin SA. Chemical synthesis enables biochemical and antibacterial evaluation of streptolydigin antibiotics. J Am Chem Soc 2011; 133:12172-84. [PMID: 21714556 PMCID: PMC3174773 DOI: 10.1021/ja2041964] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Inhibition of bacterial transcription represents an effective and clinically validated anti-infective chemotherapeutic strategy. We describe the evolution of our approach to the streptolydigin class of antibiotics that target bacterial RNA polymerases (RNAPs). This effort resulted in the synthesis and biological evaluation of streptolydigin, streptolydiginone, streptolic acid, and a series of new streptolydigin-based agents. Subsequent biochemical evaluation of RNAP inhibition demonstrated that the presence of both streptolic acid and tetramic acid subunits was required for activity of this class of antibiotics. In addition, we identified 10,11-dihydrostreptolydigin as a new RNAP-targeting agent, which was assembled with high synthetic efficiency of 15 steps in the longest linear sequence. Dihydrostreptolydigin inhibited three representative bacterial RNAPs and displayed in vitro antibacterial activity against S. salivarius . The overall increase in synthetic efficiency combined with substantial antibacterial activity of this fully synthetic antibiotic demonstrates the power of organic synthesis in enabling design and comprehensive in vitro pharmacological evaluation of new chemical agents that target bacterial transcription.
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Affiliation(s)
- Sergey V. Pronin
- Department of Chemistry, University of Chicago, Chicago, Illinois 60607, United States
| | - Anthony Martinez
- Department of Chemistry, University of Chicago, Chicago, Illinois 60607, United States
| | - Konstantin Kuznedelov
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Konstantin Severinov
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, United States
- Institutes of Gene Biology and Molecualr Genetics, Russian Academy of Sciences, Moscow, Russia
| | - Howard A. Shuman
- Department of Microbiology, University of Chicago, Chicago, Illinois 60607, United States
| | - Sergey A. Kozmin
- Department of Chemistry, University of Chicago, Chicago, Illinois 60607, United States
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14
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Abstract
Legionella pneumophila is a gram-negative bacterial species that is ubiquitous in almost any aqueous environment. It is the agent of Legionnaires’ disease, an acute and often under-reported form of pneumonia. In mammals, L. pneumophila replicates inside macrophages within a modified vacuole. Many protein regulators have been identified that control virulence-related properties, including RpoS, LetA/LetS, and PmrA/PmrB. In the past few years, the importance of regulation of virulence factors by small regulatory RNA (sRNAs) has been increasingly appreciated. This is also the case in L. pneumophila where three sRNAs (RsmY, RsmZ, and 6S RNA) were recently shown to be important determinants of virulence regulation and 79 actively transcribed sRNAs were identified. In this review we describe current knowledge about sRNAs and their regulatory properties and how this relates to the known regulatory systems of L. pneumophila. We also provide a model for sRNA-mediated control of gene expression that serves as a framework for understanding the regulation of virulence-related properties of L. pneumophila.
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Affiliation(s)
- Sébastien P Faucher
- Complex Traits Group, Department of Microbiology, McGill University Montreal, QC, Canada
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15
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Anderson OR, Wang W, Faucher SP, Bi K, Shuman HA. A new heterolobosean amoeba Solumitrus palustris n. g., n. sp. isolated from freshwater marsh soil. J Eukaryot Microbiol 2011; 58:60-7. [PMID: 21182560 DOI: 10.1111/j.1550-7408.2010.00520.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
During the course of research on the bacterial feeding behavior and resistance of amoebae to virulent pathogens, we isolated a new strain of amoeba from organic rich soil at the margin of freshwater swamp in the northeastern United States. Light microscopic morphology is characteristically heterolobosean, resembling vahlkampfiids, including a broadened, limax shape, and eruptive locomotion, but occasionally becoming more contracted and less elongated with lateral or anterior bulges and somewhat branching sparse, uroidal filaments. Electron microscopic evidence, including mitochondria with flattened cristae surrounded by rough endoplasmic reticulum, further indicates a heterolobosean affinity. The solitary nucleus contains a centrally located nucleolus. Cysts are rounded with occasionally an eccentrically located nucleus. The cyst walls are relatively thin, becoming crenated, and loosely enclosing the cyst when mature. Molecular genetic evidence places this isolate among the Heterolobosea, branching most closely in a clade including Allovahlkampfia spelaea and previously isolated, un-named strains of soil amoebae. Based on differentiated features, including morphology of the uroid, cyst wall structure, and molecular genetic evidence that distinguish it from A. spelaea, a new genus and species, Solumitrus palustris, is proposed for this new heterolobosean.
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Affiliation(s)
- O Roger Anderson
- Division of Biology, Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA.
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16
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Faucher SP, Mueller CA, Shuman HA. Legionella Pneumophila Transcriptome during Intracellular Multiplication in Human Macrophages. Front Microbiol 2011; 2:60. [PMID: 21747786 PMCID: PMC3128937 DOI: 10.3389/fmicb.2011.00060] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Accepted: 03/18/2011] [Indexed: 01/08/2023] Open
Abstract
Legionella pneumophila is the causative agent of Legionnaires' disease, an acute pulmonary infection. L. pneumophila is able to infect and multiply in both phagocytic protozoa, such as Acanthamoeba castellanii, and mammalian professional phagocytes. The best-known L. pneumophila virulence determinant is the Icm/Dot type IVB secretion system, which is used to translocate more than 150 effector proteins into host cells. While the transcriptional response of Legionella to the intracellular environment of A. castellanii has been investigated, much less is known about the Legionella transcriptional response inside human macrophages. In this study, the transcriptome of L. pneumophila was monitored during exponential and post-exponential phase in rich AYE broth as well as during infection of human cultured macrophages. This was accomplished with microarrays and an RNA amplification procedure called selective capture of transcribed sequences to detect small amounts of mRNA from low numbers of intracellular bacteria. Among the genes induced intracellularly are those involved in amino acid biosynthetic pathways leading to l-arginine, l-histidine, and l-proline as well as many transport systems involved in amino acid and iron uptake. Genes involved in catabolism of glycerol are also induced during intracellular growth, suggesting that glycerol could be used as a carbon source. The genes encoding the Icm/Dot system are not differentially expressed inside cells compared to control bacteria grown in rich broth, but the genes encoding several translocated effectors are strongly induced. Moreover, we used the transcriptome data to predict previously unrecognized Icm/Dot effector genes based on their expression pattern and confirmed translocation for three candidates. This study provides a comprehensive view of how L. pneumophila responds to the human macrophage intracellular environment.
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Affiliation(s)
- Sébastien P Faucher
- Department of Microbiology and Immunology, Columbia University Medical Center New York, NY, USA
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17
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Paumet F, Wesolowski J, Garcia-Diaz A, Delevoye C, Aulner N, Shuman HA, Subtil A, Rothman JE. Intracellular bacteria encode inhibitory SNARE-like proteins. PLoS One 2009; 4:e7375. [PMID: 19823575 PMCID: PMC2756591 DOI: 10.1371/journal.pone.0007375] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Accepted: 09/15/2009] [Indexed: 11/24/2022] Open
Abstract
Pathogens use diverse molecular machines to penetrate host cells and manipulate intracellular vesicular trafficking. Viruses employ glycoproteins, functionally and structurally similar to the SNARE proteins, to induce eukaryotic membrane fusion. Intracellular pathogens, on the other hand, need to block fusion of their infectious phagosomes with various endocytic compartments to escape from the degradative pathway. The molecular details concerning the mechanisms underlying this process are lacking. Using both an in vitro liposome fusion assay and a cellular assay, we showed that SNARE-like bacterial proteins block membrane fusion in eukaryotic cells by directly inhibiting SNARE-mediated membrane fusion. More specifically, we showed that IncA and IcmG/DotF, two SNARE-like proteins respectively expressed by Chlamydia and Legionella, inhibit the endocytic SNARE machinery. Furthermore, we identified that the SNARE-like motif present in these bacterial proteins encodes the inhibitory function. This finding suggests that SNARE-like motifs are capable of specifically manipulating membrane fusion in a wide variety of biological environments. Ultimately, this motif may have been selected during evolution because it is an efficient structural motif for modifying eukaryotic membrane fusion and thus contribute to pathogen survival.
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Affiliation(s)
- Fabienne Paumet
- Thomas Jefferson University, Department of Microbiology and Immunology, Philadelphia, Pennsylvania, United States of America.
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18
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Plumlee CR, Lee C, Beg AA, Decker T, Shuman HA, Schindler C. Interferons direct an effective innate response to Legionella pneumophila infection. J Biol Chem 2009; 284:30058-66. [PMID: 19720834 DOI: 10.1074/jbc.m109.018283] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Legionella pneumophila remains an important opportunistic pathogen of human macrophages. Its more limited ability to replicate in murine macrophages has been attributed to redundant innate sensor systems that detect and effectively respond to this infection. The current studies evaluate the role of one of these innate response systems, the type I interferon (IFN-I) autocrine loop. The ability of L. pneumophila to induce IFN-I expression was found to be dependent on IRF-3, but not NF-kappaB. Secreted IFN-Is then in turn suppress the intracellular replication of L. pneumophila. Surprisingly, this suppression is mediated by a pathway that is independent of Stat1, Stat2, Stat3, but correlates with the polarization of macrophages toward the M1 or classically activated phenotype.
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Affiliation(s)
- Courtney R Plumlee
- Department of Biological Sciences, Columbia University, New York, New York 10032, USA
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19
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Reich-Slotky R, Kabbash CA, Della-Latta P, Blanchard JS, Feinmark SJ, Freeman S, Kaplan G, Shuman HA, Silverstein SC. Gemfibrozil inhibits Legionella pneumophila and Mycobacterium tuberculosis enoyl coenzyme A reductases and blocks intracellular growth of these bacteria in macrophages. J Bacteriol 2009; 191:5262-71. [PMID: 19429621 PMCID: PMC2725597 DOI: 10.1128/jb.00175-09] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Accepted: 04/30/2009] [Indexed: 11/20/2022] Open
Abstract
We report here that gemfibrozil (GFZ) inhibits axenic and intracellular growth of Legionella pneumophila and of 27 strains of wild-type and multidrug-resistant Mycobacterium tuberculosis in bacteriological medium and in human and mouse macrophages, respectively. At a concentration of 0.4 mM, GFZ completely inhibited L. pneumophila fatty acid synthesis, while at 0.12 mM it promoted cytoplasmic accumulation of polyhydroxybutyrate. To assess the mechanism(s) of these effects, we cloned an L. pneumophila FabI enoyl reductase homolog that complemented for growth an Escherichia coli strain carrying a temperature-sensitive enoyl reductase and rendered the complemented E. coli strain sensitive to GFZ at the nonpermissive temperature. GFZ noncompetitively inhibited this L. pneumophila FabI homolog, as well as M. tuberculosis InhA and E. coli FabI.
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Affiliation(s)
- Ronit Reich-Slotky
- Department of Physiology and Cellular Biophysics, Columbia University Medical Center, New York, NY 10032, USA
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20
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Charpentier X, Gabay JE, Reyes M, Zhu JW, Weiss A, Shuman HA. Chemical genetics reveals bacterial and host cell functions critical for type IV effector translocation by Legionella pneumophila. PLoS Pathog 2009; 5:e1000501. [PMID: 19578436 PMCID: PMC2698123 DOI: 10.1371/journal.ppat.1000501] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Accepted: 06/05/2009] [Indexed: 11/18/2022] Open
Abstract
Delivery of effector proteins is a process widely used by bacterial pathogens to subvert host cell functions and cause disease. Effector delivery is achieved by elaborate injection devices and can often be triggered by environmental stimuli. However, effector export by the L. pneumophila Icm/Dot Type IVB secretion system cannot be detected until the bacterium encounters a target host cell. We used chemical genetics, a perturbation strategy that utilizes small molecule inhibitors, to determine the mechanisms critical for L. pneumophila Icm/Dot activity. From a collection of more than 2,500 annotated molecules we identified specific inhibitors of effector translocation. We found that L. pneumophila effector translocation in macrophages requires host cell factors known to be involved in phagocytosis such as phosphoinositide 3-kinases, actin and tubulin. Moreover, we found that L. pneumophila phagocytosis and effector translocation also specifically require the receptor protein tyrosine phosphate phosphatases CD45 and CD148. We further show that phagocytosis is required to trigger effector delivery unless intimate contact between the bacteria and the host is artificially generated. In addition, real-time analysis of effector translocation suggests that effector export is rate-limited by phagocytosis. We propose a model in which L. pneumophila utilizes phagocytosis to initiate an intimate contact event required for the translocation of pre-synthesized effector molecules. We discuss the need for host cell participation in the initial step of the infection and its implications in the L. pneumophila lifestyle. Chemical genetic screening provides a novel approach to probe the host cell functions and factors involved in host-pathogen interactions.
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Affiliation(s)
- Xavier Charpentier
- Department of Microbiology, Columbia University Medical Center, New York, New York, United States of America
| | - Joëlle E. Gabay
- Department of Microbiology, Columbia University Medical Center, New York, New York, United States of America
| | - Moraima Reyes
- Department of Microbiology, Columbia University Medical Center, New York, New York, United States of America
| | - Jing W. Zhu
- Departments of Medicine and of Microbiology and Immunology, Howard Hughes Medical Institute, Rosalind Russell Medical Research Center for Arthritis, University of California, San Francisco, California, United States of America
| | - Arthur Weiss
- Departments of Medicine and of Microbiology and Immunology, Howard Hughes Medical Institute, Rosalind Russell Medical Research Center for Arthritis, University of California, San Francisco, California, United States of America
| | - Howard A. Shuman
- Department of Microbiology, Columbia University Medical Center, New York, New York, United States of America
- * E-mail:
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21
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Abstract
Only a limited number of bacterial pathogens evade destruction by phagocytic cells such as macrophages. Legionella pneumophila is a Gram-negative gamma-proteobacterial species that can infect and replicate in alveolar macrophages, causing Legionnaires' disease, a severe pneumonia. L. pneumophila uses a complex secretion system to inject host cells with effector proteins capable of disrupting or altering the host cell processes. The L. pneumophila effectors target multiple processes but are essentially aimed at modifying the properties of the L. pneumophila phagosome by altering vesicular trafficking, gradually creating a specialized vacuole in which the bacteria replicate robustly. In nature, L. pneumophila is thought to parasitize free-living protists, which may have selected for traits that promote virulence of L. pneumophila in humans. Indeed, many effector genes encode proteins with eukaryotic domains and are likely to be of protozoan origin. Sustained horizontal gene transfer events within the protozoan niche may have allowed L. pneumophila to become a professional parasite of phagocytes, simultaneously giving rise to its ability to infect macrophages, cells that constitute the first line of cellular defence against bacterial infections.
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Affiliation(s)
- Irina S Franco
- Department of Microbiology, Columbia University Medical Center, New York, NY 10032, USA
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22
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de Felipe KS, Glover RT, Charpentier X, Anderson OR, Reyes M, Pericone CD, Shuman HA. Legionella eukaryotic-like type IV substrates interfere with organelle trafficking. PLoS Pathog 2008; 4:e1000117. [PMID: 18670632 PMCID: PMC2475511 DOI: 10.1371/journal.ppat.1000117] [Citation(s) in RCA: 208] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Accepted: 07/07/2008] [Indexed: 11/18/2022] Open
Abstract
Legionella pneumophila, the causative agent of Legionnaires' disease, evades phago-lysosome fusion in mammalian and protozoan hosts to create a suitable niche for intracellular replication. To modulate vesicle trafficking pathways, L. pneumophila translocates effector proteins into eukaryotic cells through a Type IVB macro-molecular transport system called the Icm-Dot system. In this study, we employed a fluorescence-based translocation assay to show that 33 previously identified Legionella eukaryotic-like genes (leg) encode substrates of the Icm-Dot secretion system. To assess which of these proteins may contribute to the disruption of vesicle trafficking, we expressed each gene in yeast and looked for phenotypes related to vacuolar protein sorting. We found that LegC3-GFP and LegC7/YlfA-GFP caused the mis-secretion of CPY-Invertase, a fusion protein normally restricted to the yeast vacuole. We also found that LegC7/YlfA-GFP and its paralog LegC2/YlfB-GFP formed large structures around the yeast vacuole while LegC3-GFP localized to the plasma membrane and a fragmented vacuole. In mammalian cells, LegC2/YlfB-GFP and LegC7/YlfA-GFP were found within large structures that co-localized with anti-KDEL antibodies but excluded the lysosomal marker LAMP-1, similar to what is observed in Legionella-containing vacuoles. LegC3-GFP, in contrast, was observed as smaller structures which had no obvious co-localization with KDEL or LAMP-1. Finally, LegC3-GFP caused the accumulation of many endosome-like structures containing undigested material when expressed in the protozoan host Dictyostelium discoideum. Our results demonstrate that multiple Leg proteins are Icm/Dot-dependent substrates and that LegC3, LegC7/YlfA, and LegC2/YlfB may contribute to the intracellular trafficking of L. pneumophila by interfering with highly conserved pathways that modulate vesicle maturation.
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Affiliation(s)
- Karim Suwwan de Felipe
- Integrated Program in Cellular, Molecular, and Biophysical Studies, Columbia University Medical Center, New York, New York, United States of America
- Department of Microbiology, Columbia University Medical Center, New York, New York, United States of America
| | - Robert T. Glover
- Department of Microbiology, Columbia University Medical Center, New York, New York, United States of America
| | - Xavier Charpentier
- Department of Microbiology, Columbia University Medical Center, New York, New York, United States of America
| | - O. Roger Anderson
- Division of Biology and Paleo Environment, Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, United States of America
| | - Moraima Reyes
- Department of Microbiology, Columbia University Medical Center, New York, New York, United States of America
| | - Christopher D. Pericone
- Department of Microbiology, Columbia University Medical Center, New York, New York, United States of America
| | - Howard A. Shuman
- Integrated Program in Cellular, Molecular, and Biophysical Studies, Columbia University Medical Center, New York, New York, United States of America
- Department of Microbiology, Columbia University Medical Center, New York, New York, United States of America
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23
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Abstract
Legionella pneumophila is the Gram-negative bacterial agent of Legionnaires' disease, an acute, often fatal pneumonia. L. pneumophila infects alveolar macrophages, evading the antimicrobial defences of the phagocyte by preventing fusion of the phagosome with lysosomes and avoiding phagosome acidification. The bacteria then modulate the composition of the vacuole so that it takes on the characteristics of the endoplasmic reticulum. Similar events occur when the bacteria infect unicellular protozoa. It is thought that replication in fresh water protozoa provides an environmental reservoir for the organism. Several effector proteins are delivered to the host by the Icm/Dot type IV secretion system (TFSS). Some of these have been shown to participate in the trafficking of the Legionella phagosome. Here we describe the ability of the Icm/Dot TFSS to translocate two effectors, LepA and LepB, that play a role in the non-lytic release of Legionella from protozoa. We report that translocation of the Lep proteins is inhibited by agents that depolymerize actin filaments and that effectors may be secreted into the extracellular medium upon cell contact. Depletion of the Lep proteins by deletion of their genes results in increased ability to lyse red blood cells. In contrast, overexpression of Lep-containing hybrid proteins appears to specifically inhibit the activity of the Icm/Dot TFSS and may prevent the delivery of other effectors that are critical for intracellular multiplication.
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Affiliation(s)
- John Chen
- Department of Microbiology, Columbia University Medical Center, New York, NY 10032, USA
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24
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de Felipe KS, Pampou S, Jovanovic OS, Pericone CD, Ye SF, Kalachikov S, Shuman HA. Evidence for acquisition of Legionella type IV secretion substrates via interdomain horizontal gene transfer. J Bacteriol 2005; 187:7716-26. [PMID: 16267296 PMCID: PMC1280299 DOI: 10.1128/jb.187.22.7716-7726.2005] [Citation(s) in RCA: 223] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Intracellular pathogens exploit host cell functions to create a replication niche inside eukaryotic cells. The causative agent of Legionnaires' disease, the gamma-proteobacterium Legionella pneumophila, resides and replicates within a modified vacuole of protozoan and mammalian cells. L. pneumophila translocates effector proteins into host cells through the Icm-Dot complex, a specialized type IVB secretion system that is required for intracellular growth. To find out if some effector proteins may have been acquired through interdomain horizontal gene transfer (HGT), we performed a bioinformatic screen that searched for eukaryotic motifs in all open reading frames of the L. pneumophila Philadelphia-1 genome. We found 44 uncharacterized genes with many distinct eukaryotic motifs. Most of these genes contain G+C biases compared to other L. pneumophila genes, supporting the theory that they were acquired through HGT. Furthermore, we found that several of them are expressed and up-regulated in stationary phase in an RpoS-dependent manner. In addition, at least seven of these gene products are translocated into host cells via the Icm-Dot complex, confirming their role in the intracellular environment. Reminiscent of the case with most Icm-Dot substrates, most of the strains containing mutations in these genes grew comparably to the parent strain intracellularly. Our findings suggest that in L. pneumophila, interdomain HGT may have been a major mechanism for the acquisition of determinants of infection.
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Affiliation(s)
- Karim Suwwan de Felipe
- Integrated Program in Cellular, Molecular & Biophysical Studies, New York, New York 10032, USA
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25
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Albers U, Reus K, Shuman HA, Hilbi H. The amoebae plate test implicates a paralogue of lpxB in the interaction of Legionella pneumophila with Acanthamoeba castellanii. Microbiology (Reading) 2005; 151:167-182. [PMID: 15632436 DOI: 10.1099/mic.0.27563-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Legionella pneumophila is a bacterial parasite of freshwater amoebae which also grows in alveolar macrophages and thus causes the potentially fatal pneumonia Legionnaires' disease. Intracellular growth within amoebae and macrophages is mechanistically similar and requires the Icm/Dot type IV secretion system. This paper reports the development of an assay, the amoebae plate test (APT), to analyse growth of L. pneumophila wild-type and icm/dot mutant strains spotted on agar plates in the presence of Acanthamoeba castellanii. In the APT, wild-type L. pneumophila formed robust colonies even at high dilutions, icmT, -R, -P or dotB mutants failed to grow, and icmS or -G mutants were partially growth defective. The icmS or icmG mutant strains were used to screen an L. pneumophila chromosomal library for genes that suppress the growth defect in the presence of the amoebae. An icmS suppressor plasmid was isolated that harboured the icmS and flanking icm genes, indicating that this plasmid complements the intracellular growth defect of the mutant. In contrast, different icmG suppressor plasmids rendered the icmG mutant more cytotoxic for A. castellanii without enhancing intracellular multiplication in amoebae or RAW264.7 macrophages. Deletion of individual genes in the suppressor plasmids inserts identified lcs (Legionella cytotoxic suppressor) -A, -B, -C and -D as being required for enhanced cytotoxicity of an icmG mutant strain. The corresponding proteins show sequence similarity to hydrolases, NlpD-related metalloproteases, lipid A disaccharide synthases and ABC transporters, respectively. Overexpression of LcsC, a putative paralogue of the lipid A disaccharide synthase LpxB, increased cytotoxicity of an icmG mutant but not that of other icm/dot or rpoS mutant strains against A. castellanii. Based on sequence comparison and chromosomal location, lcsB and lcsC probably encode enzymes involved in cell wall maintenance and peptidoglycan metabolism. The APT established here may prove useful to identify other bacterial factors relevant for interactions with amoeba hosts.
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Affiliation(s)
- Urs Albers
- Institute of Microbiology, Swiss Federal Institute of Technology (ETH), Wolfgang-Pauli Str. 10, HCI G405, 8093 Zürich, Switzerland
| | - Katrin Reus
- Institute of Microbiology, Swiss Federal Institute of Technology (ETH), Wolfgang-Pauli Str. 10, HCI G405, 8093 Zürich, Switzerland
| | - Howard A Shuman
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, 701 West 168th Street, New York, NY 10032, USA
| | - Hubert Hilbi
- Institute of Microbiology, Swiss Federal Institute of Technology (ETH), Wolfgang-Pauli Str. 10, HCI G405, 8093 Zürich, Switzerland
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26
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Shohdy N, Efe JA, Emr SD, Shuman HA. Pathogen effector protein screening in yeast identifies Legionella factors that interfere with membrane trafficking. Proc Natl Acad Sci U S A 2005; 102:4866-71. [PMID: 15781869 PMCID: PMC555709 DOI: 10.1073/pnas.0501315102] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Legionella pneumophila invades and replicates intracellularly in human and protozoan hosts. The bacteria use the Icm/Dot type IVB secretion system to translocate effectors that inhibit phagosome maturation and modulate host vesicle trafficking pathways. To understand how L. pneumophila modulates organelle trafficking in host cells, we carried out pathogen effector protein screening in yeast, identifying L. pneumophila genes that produced membrane trafficking [vacuole protein sorting (VPS)] defects in yeast. We identified four L. pneumophila DNA fragments that perturb sorting of vacuolar proteins. Three encode ORFs of unknown function that are translocated via the Icm/Dot transporter from Legionella into macrophages. VPS inhibitor protein (Vip) A is a coiled-coil protein, VipD is a patatin domain-containing protein, and VipF contains an acetyltransferase domain. Processing studies in yeast indicate that VipA, VipD, and VipF inhibit lysosomal protein trafficking by different mechanisms; overexpressing VipA has an effect on carboxypeptidase Y trafficking, whereas VipD interferes with multivesicular body formation at the late endosome and endoplasmic reticulum-to-Golgi body transport. Such differences highlight the multiple strategies L. pneumophila effectors use to subvert host trafficking processes. Using yeast as an effector gene discovery tool allows for a powerful, genetic approach to both the identification of virulence factors and the study of their function.
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Affiliation(s)
- Nadim Shohdy
- Department of Microbiology, Columbia University Medical Center, 701 West 168th Street, New York, NY 10032, USA
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Chien M, Morozova I, Shi S, Sheng H, Chen J, Gomez SM, Asamani G, Hill K, Nuara J, Feder M, Rineer J, Greenberg JJ, Steshenko V, Park SH, Zhao B, Teplitskaya E, Edwards JR, Pampou S, Georghiou A, Chou IC, Iannuccilli W, Ulz ME, Kim DH, Geringer-Sameth A, Goldsberry C, Morozov P, Fischer SG, Segal G, Qu X, Rzhetsky A, Zhang P, Cayanis E, De Jong PJ, Ju J, Kalachikov S, Shuman HA, Russo JJ. The genomic sequence of the accidental pathogen Legionella pneumophila. Science 2004; 305:1966-8. [PMID: 15448271 DOI: 10.1126/science.1099776] [Citation(s) in RCA: 402] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We present the genomic sequence of Legionella pneumophila, the bacterial agent of Legionnaires' disease, a potentially fatal pneumonia acquired from aerosolized contaminated fresh water. The genome includes a 45-kilobase pair element that can exist in chromosomal and episomal forms, selective expansions of important gene families, genes for unexpected metabolic pathways, and previously unknown candidate virulence determinants. We highlight the genes that may account for Legionella's ability to survive in protozoa, mammalian macrophages, and inhospitable environmental niches and that may define new therapeutic targets.
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Affiliation(s)
- Minchen Chien
- Columbia Genome Center, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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28
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Abstract
Legionella pneumophila, the bacterial agent of legionnaires' disease, replicates intracellularly within a specialized vacuole of mammalian and protozoan host cells. Little is known about the specialized vacuole except that the Icm/Dot type IV secretion system is essential for its formation and maintenance. The Legionella genome database contains two open reading frames encoding polypeptides (LepA and LepB) with predicted coiled-coil regions and weak homology to SNAREs; these are delivered to host cells by an Icm/Dot-dependent mechanism. Analysis of mutant strains suggests that the Lep proteins may enable the Legionella to commandeer a protozoan exocytic pathway for dissemination of the pathogen.
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Affiliation(s)
- John Chen
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, 701 West 168th Street, New York, NY 10032, USA
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Morozova I, Qu X, Shi S, Asamani G, Greenberg JE, Shuman HA, Russo JJ. Comparative sequence analysis of the icm/dot genes in Legionella. Plasmid 2004; 51:127-47. [PMID: 15003709 DOI: 10.1016/j.plasmid.2003.12.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2003] [Revised: 11/21/2003] [Indexed: 11/19/2022]
Abstract
The icm/dot genes in Legionella pneumophila are essential for the ability of the bacteria to survive within macrophages in lung infections such as Legionnaires' disease, or amoebae in nature. The 22 genes of the complex, thought to encode a transport apparatus for transfer of effector molecules into the host cell cytoplasm, are located in two chromosomal loci. We demonstrate that these genes are present in all the L. pneumophila strains examined herein, but display a wide range of sequence variation among the different strains, none of which are clearly associated with virulence potential. The strains fall within seven phylogenetic groups, but discrepancies among the gene trees indicate a complicated evolutionary history for the icm/dot loci, with perhaps two independent gene acquisition events and subsequent genomic rearrangements. Significant findings include a probable t-SNARE domain in IcmG that may indicate a direct role for this putative inner membrane protein in altering the host's membrane fusion machinery, a potential functional domain in the central hydrophobic portion of IcmK that may allow it to participate in forming the pore of the secretion complex, and strict conservation of the amino acid physicochemical characteristics in the IcmP region corresponding to the trbA domain that could play a role in molecular transfer.
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Affiliation(s)
- Irina Morozova
- Columbia Genome Center, Columbia University College of Physicians and Surgeons, 1150 St. Nicholas Avenue, New York, NY 10032, USA
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Otto GP, Wu MY, Clarke M, Lu H, Anderson OR, Hilbi H, Shuman HA, Kessin RH. Macroautophagy is dispensable for intracellular replication of Legionella pneumophila in Dictyostelium discoideum. Mol Microbiol 2004; 51:63-72. [PMID: 14651611 DOI: 10.1046/j.1365-2958.2003.03826.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The Gram-negative bacterium Legionella pneumophila is a facultative intracellular pathogen of free-living amoebae and mammalian phagocytes. L. pneumophila is engulfed in phagosomes that initially avoid fusion with lysosomes. The phagosome associates with endoplasmic reticulum (ER) and mitochondria and eventually resembles ER. The morphological similarity of the replication vacuole to autophagosomes, and enhanced bacterial replication in response to macroautophagy-inducing starvation, led to the hypothesis that L. pneumophila infection requires macroautophagy. As L. pneumophila replicates in Dictyostelium discoideum, and macroautophagy genes have been identified and mutated in D. discoideum, we have taken a genetic and cell biological approach to evaluate the relationship between host macroautophagy and intracellular replication of L. pneumophila. Mutation of the apg1, apg5, apg6, apg7 and apg8 genes produced typical macroautophagy defects, including reduced bulk protein degradation and cell viability during starvation. We show that L. pneumophila replicates normally in D. discoideum macroautophagy mutants and produces replication vacuoles that are morphologically indistinguishable from those in wild-type D. discoideum. Furthermore, a green fluorescent protein (GFP)-tagged marker of autophagosomes, Apg8, does not systematically co-localize with DsRed-labelled L. pneumophila. We conclude that macroautophagy is dispensable for L. pneumophila intracellular replication in D. discoideum.
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Affiliation(s)
- Grant P Otto
- Department of Anatomy and Cell Biology, Columbia University, 630 West 168th St., New York, NY 10032, USA
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31
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Abstract
In this study, we examined whether virulence conversion occurs in Legionella pneumophila by conjugal transfer of chromosomal DNA. A virulent strain, K6, which has the genes for Kmr and LacZ+ transposed in the chromosome of strain Philadelphia-1, which belongs to serogroup 1, was used as one parent, and an avirulent strain, Chicago-2S, which is a spontaneous streptomycin-resistant derivative of strain Chicago-2 belonging to serogroup 6, was used as the other parent. Experiments in which K6 (approximately 2.6 x 10(9) CFU) and Chicago-2S (approximately 8.9 x 10(9) CFU) were mated typically yielded 10(3) Kmr Smr LacZ+ transconjugants. Thirty-two (about 2.8%) of 1,152 transconjugants belonging to serogroup 6 acquired the ability to grow intracellularly in Acanthamoeba castellanii and guinea pig macrophages. When guinea pigs were infected with sublethal doses of Legionella aerosols generated from one of these transconjugants (HM1011), they developed a severe pneumonia similar to that caused by donor strain K6. These results show that avirulent strain Chicago-2S changed into virulent strain HM1011 through conjugation with virulent strain K6. Furthermore, we showed that Legionella chromosomal virulence genes (icm-dot locus) were horizontally transferred by the conjugation system. The chromosomal conjugation system may play a role(s) in the evolution of L. pneumophila.
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Affiliation(s)
- Hiroshi Miyamoto
- Department of Microbiology, University of Occupational and Environmental Health, Yahatanishi-ku, Kitakyushu 807-8555, Japan.
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32
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Samanta S, Ayvaz T, Reyes M, Shuman HA, Chen J, Davidson AL. Disulfide cross-linking reveals a site of stable interaction between C-terminal regulatory domains of the two MalK subunits in the maltose transport complex. J Biol Chem 2003; 278:35265-71. [PMID: 12813052 DOI: 10.1074/jbc.m301171200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Understanding the structure and function of the ATP-binding cassette (ABC) transporters is very important because defects in ABC transporters lie at the root of several serious diseases including cystic fibrosis. MalK, the ATP-binding cassette of the maltose transporter of Escherichia coli, is distinct from most other ATP-binding cassettes in that it contains an additional C-terminal regulatory domain. The published structure of a MalK dimer is elongated with C-terminal domains at opposite poles (Diederichs, K., Diez, J., Greller, G., Muller, C., Breed, J., Schnell, C., Vonrhein, C., Boos, W., and Welte, W. (2000) EMBO J. 19, 5951-5961). Some uncertainty exists as to whether the orientation of MalK in the dimer structure is correct. Superpositioning of the N-terminal domains of MalK onto the ATP-binding domains of an alternate ABC dimer, in which ATP is bound along the dimer interface between Walker A and LSGGQ motifs, places both N- and C-terminal domains of MalK along the dimer interface. Consistent with this model, a cysteine substitution at position 313 in the C-terminal domain of an otherwise cysteine-free MalK triggered disulfide bond formation between two MalK subunits in an intact maltose transporter. Disulfide bond formation did not inhibit the function of the transporter, suggesting that the C-terminal domains of MalK remain in close proximity throughout the transport cycle. Enzyme IIAglc still inhibited the ATPase activity of the disulfide-linked transporter indicating that the mechanism of inducer exclusion was unaffected. These data support a model for ATP hydrolysis in which the C-terminal domains of MalK remain in contact whereas the N-terminal domains of MalK open and close to allow nucleotide binding and dissociation.
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Affiliation(s)
- Susmita Samanta
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030, USA
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33
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Popot JL, Berry EA, Charvolin D, Creuzenet C, Ebel C, Engelman DM, Flötenmeyer M, Giusti F, Gohon Y, Hong Q, Lakey JH, Leonard K, Shuman HA, Timmins P, Warschawski DE, Zito F, Zoonens M, Pucci B, Tribet C. Amphipols: polymeric surfactants for membrane biology research. Cell Mol Life Sci 2003; 60:1559-74. [PMID: 14513831 DOI: 10.1007/s00018-003-3169-6] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Membrane proteins classically are handled in aqueous solutions as complexes with detergents. The dissociating character of detergents, combined with the need to maintain an excess of them, frequently results in more or less rapid inactivation of the protein under study. Over the past few years, we have endeavored to develop a novel family of surfactants, dubbed amphipols (APs). APs are amphiphilic polymers that bind to the transmembrane surface of the protein in a noncovalent but, in the absence of a competing surfactant, quasi-irreversible manner. Membrane proteins complexed by APs are in their native state, stable, and they remain water-soluble in the absence of detergent or free APs. An update is presented of the current knowledge about these compounds and their demonstrated or putative uses in membrane biology.
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Affiliation(s)
- J-L Popot
- Laboratoire de Physico-Chimie Moléculaire des Membranes Biologiques and Université Paris-7, Paris, France.
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34
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Abstract
This article summarizes the general principles of selections and screens in Escherichia coli. The focus is on the lac operon, owing to its inherent simplicity and versatility. Examples of different strategies for mutagenesis and mutant discovery are described. In particular, the usefulness and effectiveness of simple colour-based screens are illustrated. The power of lac genetics can be applied to almost any bacterial system with gene fusions that hook any gene of interest to lacZ, which is the structural gene that encodes beta-galactosidase. The diversity of biological processes that can be studied with lac genetics is remarkable and includes DNA metabolism, gene regulation and signal transduction, protein localization and folding, and even electron transport.
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Affiliation(s)
- Howard A Shuman
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York 10032, USA
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35
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Affiliation(s)
- Howard A Shuman
- Department of Microbiology, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA.
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36
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Steenbergen JN, Shuman HA, Casadevall A. Cryptococcus neoformans interactions with amoebae suggest an explanation for its virulence and intracellular pathogenic strategy in macrophages. Proc Natl Acad Sci U S A 2001; 98:15245-50. [PMID: 11742090 PMCID: PMC65014 DOI: 10.1073/pnas.261418798] [Citation(s) in RCA: 348] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cryptococcus neoformans (Cn) is a soil fungus that causes life-threatening meningitis in immunocompromised patients and is a facultative intracellular pathogen capable of replication inside macrophages. The mechanism by which environmental fungi acquire and maintain virulence for mammalian hosts is unknown. We hypothesized that the survival strategies for Cn after ingestion by macrophages and amoebae were similar. Microscopy, fungal and amoebae killing assays, and phagocytosis assays revealed that Cn is phagocytosed by and replicates in Acanthamoeba castellanii, which leads to death of amoebae. An acapsular strain of Cn did not survive when incubated with amoebae, but melanization protected these cells against killing by amoebae. A phospholipase mutant had a decreased replication rate in amoebae compared with isogenic strains. These observations suggest that cryptococcal characteristics that contribute to mammalian virulence also promote fungal survival in amoebae. Intracellular replication was accompanied by the accumulation of polysaccharide containing vesicles similar to those described in Cn-infected macrophages. The results suggest that the virulence of Cn for mammalian cells is a consequence of adaptations that have evolved for protection against environmental predators such as amoebae and provide an explanation for the broad host range of this pathogenic fungus.
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Affiliation(s)
- J N Steenbergen
- Department of Microbiology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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37
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Abstract
Legionella pneumophila is the causative agent of Legionnaires' disease, a severe pneumonia. Dependent on the icm/dot loci, L. pneumophila survives and replicates in macrophages and amoebae within a specialized phagosome that does not fuse with lysosomes. Here, we report that phagocytosis of wild-type L. pneumophila is more efficient than uptake of icm/dot mutants. Compared with the wild-type strain JR32, about 10 times fewer icm/dot mutant bacteria were recovered from HL-60 macrophages in a gentamicin protection assay. The defect in phagocytosis of the mutants could be complemented by supplying the corresponding genes on a plasmid. Using fluorescence microscopy and green fluorescent protein (GFP)-expressing strains, 10-20 times fewer icm/dot mutant bacteria were found to be internalized by HL-60 cells and human monocyte-derived macrophages (HMMPhi). Compared with icm/dot mutants, wild-type L. pneumophila infected two to three times more macrophages and yielded a population of highly infected host cells (15-70 bacteria per macrophage) that was not observed with icm/dot mutant strains. Wild-type and icmT mutant bacteria were found to adhere similarly and compete for binding to HMMPhi. In addition, wild-type L. pneumophila was also phagocytosed more efficiently by Acanthamoeba castellanii, indicating that the process is independent of adherence receptor(s). Wild-type L. pneumophila enhanced phagocytosis of an icmT mutant strain in a synchronous co-infection, suggesting that increased phagocytosis results from (a) secreted effector(s) acting in trans.
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Affiliation(s)
- H Hilbi
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, 701 West 168th Street, New York, NY 10032, USA
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38
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Abstract
Wild-type Legionella pneumophila grows in human macrophages within a replicative phagosome, avoiding lysosomal fusion, while nonreplicative mutants are killed in lysosomes. Wortmannin, a phosphatidylinositol 3-kinase (PI3K) inhibitor, blocks phagocytosis of an avirulent mutant, but not of wild-type L. pneumophila, without affecting membrane ruffling and actin polymerization. These results show that wild-type and mutant Legionella strains use different entry pathways. They suggest that PI3Ks are involved in phagocytosis of an avirulent L. pneumophila mutant and regulate the ability of microorganisms to generate a replicative phagosome.
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Affiliation(s)
- N Khelef
- Department of Biochemistry, Weill Medical College of Cornell University, New York, New York 10021, USA.
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39
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Abstract
The maltose transporter FGK2 complex of Escherichia coli was purified with the aid of a glutathione S-transferase molecular tag. In contrast to the membrane-associated form of the complex, which requires liganded maltose binding protein (MBP) for ATPase activity, the purified detergent-soluble complex exhibited a very high level of ATPase activity. This uncoupled activity was not due to dissociation of the MalK ATPase subunit from the integral membrane protein MalF and MalG subunits. The detergent-soluble ATPase activity of the complex could be further stimulated by wild-type MBP but not by a signaling-defective mutant MBP. Wild-type MBP increased the V(max) of the ATPase 2.7-fold but had no effect on the K(m) of the enzyme for ATP. When the detergent-soluble complex was reconstituted in proteoliposomes, it returned to being dependent on MBP for activation of ATPase, consistent with the idea that the structural changes induced in the complex by detergent that result in activation of the ATPase are reversible. The uncoupled ATPase activity resembled the membrane-bound activity of the complex also with respect to sensitivity to NaN(3), as well as a mercurial, p-chloromercuribenzosulfonic acid. Verapamil, a compound that activates the ATPase activity of the multiple drug resistance P-glycoprotein, activated the maltose transporter ATPase as well. The activation of this bacterial transporter by verapamil suggests that a structural feature that is conserved among both eukaryotic and prokaryotic ATP binding cassette transporters is responsible for this activation.
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Affiliation(s)
- R Reich-Slotky
- Department of Microbiology, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA
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40
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Abstract
We describe here a Legionella pneumophila type IV secretion system that is distinct from the previously described icm/dot system. This type IV secretion system contains 11 genes (lvh ) homologous to genes of other type IV secretion systems, arranged in a similar manner. The lvh genes were found to be located on a DNA island with a GC content higher than the L. pneumophila chromosome. In contrast to the icm/dot system that was shown to be required for intracellular growth in HL-60-derived human macrophages and Acanthamoeba castellanii, the lvh system was found to be dispensable for intracellular growth in these two hosts. The lvh system was found to be partially required for RSF1010 conjugation, a process that was previously shown to be completely dependent on several icm/dot genes. However, results obtained from analysis of double mutants in the icm/dot genes and the lvh genes revealed that lvh genes can substitute for some components of the icm/dot system for RSF1010 conjugation, but not for intracellular growth. These results indicate that components of the icm/dot system and components of the lvh type IV secretion system are able to interact with one another.
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Affiliation(s)
- G Segal
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, 701 West 168th Street, New York, NY 10032, USA
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41
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Abstract
To investigate regulatory networks in Legionella pneumophila, the gene encoding the homolog of the Escherichia coli stress and stationary-phase sigma factor RpoS was identified by complementation of an E. coli rpoS mutation. An open reading frame that is approximately 60% identical to the E. coli rpoS gene was identified. Western blot analysis showed that the level of L. pneumophila RpoS increased in stationary phase. An insertion mutation was constructed in the rpoS gene on the chromosome of L. pneumophila, and the ability of this mutant strain to survive various stress conditions was assayed and compared with results for the wild-type strain. Both the mutant and wild-type strains were more resistant to stress when in stationary phase than when in the logarithmic phase of growth. This finding indicates that L. pneumophila RpoS is not required for a stationary-phase-dependent resistance to stress. Although the mutant strain was able to kill HL-60- and THP-1-derived macrophages, it could not replicate within a protozoan host, Acanthamoeba castellanii. These data suggest that L. pneumophila possesses a growth phase-dependent resistance to stress that is independent of RpoS control and that RpoS likely regulates genes that enable it to survive in the environment within protozoa. Our data indicate that the role of rpoS in L. pneumophila is very different from what has previously been reported for E. coli rpoS.
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Affiliation(s)
- L M Hales
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
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Hales LM, Shuman HA. Legionella pneumophila contains a type II general secretion pathway required for growth in amoebae as well as for secretion of the Msp protease. Infect Immun 1999; 67:3662-6. [PMID: 10377156 PMCID: PMC116561 DOI: 10.1128/iai.67.7.3662-3666.1999] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report the identification of a set of Legionella pneumophila genes that encode products with homology to proteins of the type II general secretion pathway of gram-negative bacteria. A strain containing a deletion-substitution mutation of two of these genes was unable to secrete the Msp protease. This strain was unable to multiply within the free-living amoeba Acanthamoeba castellanii yet was able to kill HL-60-derived macrophages. Because Msp is not required for growth in amoebae, other proteins which are important for growth in amoebae are likely secreted by this pathway.
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Affiliation(s)
- L M Hales
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
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44
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Abstract
In previous reports we described a 22-kb Legionella pneumophila chromosomal locus containing 18 genes. Thirteen of these genes (icmT, -R, -Q, -P, -O, -M, -L, -K, -E, -C, -D, -J, and -B) were found to be completely required for intracellular growth and killing of human macrophages. Three genes (icmS, -G, and -F) were found to be partially required, and two genes (lphA and tphA) were found to be dispensable for intracellular growth and killing of human macrophages. Here, we analyzed the requirement of these genes for intracellular growth in the protozoan host Acanthamoeba castellanii, a well-established important environmental host of L. pneumophila. We found that all the genes that are completely required for intracellular growth in human macrophages are also completely required for intracellular growth in A. castellanii. However, the genes that are partially required for intracellular growth in human macrophages are completely required for intracellular growth in A. castellanii. In addition, the lphA gene, which was shown to be dispensable for intracellular growth in human macrophages, is partially required for intracellular growth in A. castellanii. Our results indicate that L. pneumophila utilizes the same genes to grow intracellularly in both human macrophages and amoebae.
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Affiliation(s)
- G Segal
- Department of Microbiology, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA
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45
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Panagiotidis CH, Boos W, Shuman HA. The ATP-binding cassette subunit of the maltose transporter MalK antagonizes MalT, the activator of the Escherichia coli mal regulon. Mol Microbiol 1998; 30:535-46. [PMID: 9822819 DOI: 10.1046/j.1365-2958.1998.01084.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Transcription of the mal regulon of Escherichia coli K-12 is regulated by the positive activator, MalT. In the presence of ATP and maltotriose, MalT binds to decanucleotide MalT boxes that are found upstream of mal promoters and activates transcription at these sites. The earliest studies of the mal regulon, however, suggested a negative role for the MalK protein, the ATP-binding cassette subunit of the maltose transporter, in regulating mal gene expression. More recently, it was found that overexpression of the MalK protein resulted in very low levels of mal gene transcription. In this report we describe the use of tagged versions of MalT to provide evidence that it physically interacts with the MalK protein both in vitro and in vivo. In addition, we show that a novel malK mutation, malK941, results in an increased ability of MalK to down-modulate MalT activity in vivo. The fact that the MalK941 protein binds but does not hydrolyse ATP suggests that the MalK941 mutant protein mimics the inactive, ATP-bound form of the normal MalK protein. In contrast, cells with high levels of MalK ATPase show a reduced ability to down-modulate MalT and express several mal genes constitutively. These results are consistent with a model in which the inactive form of MalK down-modulates MalT and decreases transcription, whereas the active form of MalK does not. This model suggests that bacteria may be able to couple information about extracellular substrate availability to the transcriptional apparatus via the levels of ATP hydrolysis associated with transport.
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Affiliation(s)
- C H Panagiotidis
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, 701 West 168th Street, New York, NY 10032, USA
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46
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Segal G, Shuman HA. Intracellular multiplication and human macrophage killing by Legionella pneumophila are inhibited by conjugal components of IncQ plasmid RSF1010. Mol Microbiol 1998; 30:197-208. [PMID: 9786196 DOI: 10.1046/j.1365-2958.1998.01054.x] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Previously we have reported that Legionella pneumophila can mediate plasmid DNA transfer at a frequency of about 10(-3) transconjugants per donor and that this process is dependent on several icm genes. Here we characterize the icm-dependent conjugal ability of L. pneumophila and study its relationship to intracellular multiplication and host cell killing. We found that three icm genes and the RSF1010 mobA gene are completely required and that three icm genes and the RSF1010 mobC gene are partially required for conjugation. Conjugation occurred during lag phase and stopped when the cell number increased. Inhibition of transcription or translation in the donor had only a minor effect on conjugation frequency. These results suggest that stationary-phase bacteria contain a functional icm complex that can mediate conjugal DNA transfer and probably can initiate infection of human macrophages as well. We also found that a functional RSF1010 mobilization system inhibits intracellular multiplication and killing of human macrophages by L. pneumophila. The strongest inhibition was observed in icm insertion mutants complemented with wild-type icm genes on an RSF1010-derived plasmid. These results suggest that the conjugation substrate probably competes with the natural substrate of the L. pneumophila icm system for transfer outside the bacterial cell. We propose that the function of the L. pneumophila icm system is to transfer effector molecules to the host cell. These effector molecules may interact with components of the host cell that are involved in phagosome formation and fate.
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Affiliation(s)
- G Segal
- Department of Microbiology, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA
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Abstract
During infection, the Legionnaires' disease bacterium, Legionella pneumophila, survives and multiplies within a specialized phagosome that is near neutral pH and does not fuse with host lysosomes. In order to understand the molecular basis of this organism's ability to control its intracellular fate, we have isolated and characterized a group of transposon-generated mutants which were unable to kill macrophages and were subsequently found to be defective in intracellular multiplication. These mutations define a set of 20 genes (19 icm [for intracellular multiplication] genes and dotA [for defect in organelle trafficking]). In this report, we describe a quantitative assay for phagosome-lysosome fusion (PLF) and its use to measure the levels of PLF in cells that have been infected with either wild-type L. pneumophila or one of several mutants defective in different icm genes or dotA. By using quantitative confocal fluorescence microscopy, PLF could be scored on a per-bacterium basis by determining the extent to which fluorescein-labeled L. pneumophila colocalized with host lysosomes prelabeled with rhodamine-dextran. Remarkably, mutations in the six genes that were studied resulted in maximal levels of PLF as quickly as 30 min following infection. These results indicate that several, and possibly all, of the icm and dotA gene products act at an early step during phagosome establishment to determine whether L. pneumophila-containing phagosomes will fuse with lysosomes. Although not ruled out, subsequent activity of these gene products may not be necessary for successful intracellular replication.
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Affiliation(s)
- L A Wiater
- Departments of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
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Affiliation(s)
- C H Panagiotidis
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
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49
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Abstract
The following pair of articles, the first by Gil Segal and Howard Shuman, and the second by James Kirby and Ralph Isberg (Trends Microbiol. 6, 256-258), explore the genetics and function of the icm/dot genes of Legionella pneumophila. This gene family is implicated in several aspects of virulence and appears to constitute components of a conjugal transfer system that has been adopted to prevent phagosome-lysosome fusion in the host cell and to mediate host cytotoxicity by pore formation. Whether these functions are natural consequences or operate in parallel remains to be discovered.
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Affiliation(s)
- G Segal
- Dept of Microbiology, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA
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Purcell M, Shuman HA. The Legionella pneumophila icmGCDJBF genes are required for killing of human macrophages. Infect Immun 1998; 66:2245-55. [PMID: 9573114 PMCID: PMC108188 DOI: 10.1128/iai.66.5.2245-2255.1998] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/1997] [Accepted: 02/12/1998] [Indexed: 02/07/2023] Open
Abstract
Previously, a collection of mutants of Legionella pneumophila that had lost the ability to multiply within and kill human macrophages was generated by Tn903dIIlacZ transposon mutagenesis and classified into DNA hybridization groups. A subset of these mutants was complemented by a plasmid, pMW100, containing a 13.5-kb genomic DNA insert. This plasmid restored the ability to multiply within and produce cytopathic effects on human macrophages to members of DNA hybridization groups II, IV, VI, and XVII. A region of the genomic insert of pMW100 was sequenced, and eight potential genes were identified and named icmE, icmG, icmC, icmD, icmJ, icmB, icmF, and tphA. None of the genes encode potential protein products with significant homology to previously characterized proteins, except for tphA, whose product has significant homology to a family of metabolite/H+ symport proteins from gram-negative bacteria. The positions of the Tn903dIIlacZ insertions within the genes were determined by nucleotide sequencing. No Tn903dIIlacZ insertions mapped to icmG, icmJ, or tphA; therefore, these loci were mutated to test whether they were required for macrophage killing. Complementation analysis was used to evaluate the roles of the potential gene products and provide information on the organization of transcriptional units within the region. The results indicate that all identified open reading frames except tphA are required for killing of human macrophages.
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Affiliation(s)
- M Purcell
- Department of Microbiology, College of Physicians and Surgeons of Columbia University, New York, New York 10032, USA
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