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Lopez AE, Grigoryeva LS, Barajas A, Cianciotto NP. Legionella pneumophila Rhizoferrin Promotes Bacterial Biofilm Formation and Growth within Amoebae and Macrophages. Infect Immun 2023; 91:e0007223. [PMID: 37428036 PMCID: PMC10429650 DOI: 10.1128/iai.00072-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 06/20/2023] [Indexed: 07/11/2023] Open
Abstract
Previously, we showed that Legionella pneumophila secretes rhizoferrin, a polycarboxylate siderophore that promotes bacterial growth in iron-deplete media and the murine lung. Yet, past studies failed to identify a role for the rhizoferrin biosynthetic gene (lbtA) in L. pneumophila infection of host cells, suggesting the siderophore's importance was solely linked to extracellular survival. To test the possibility that rhizoferrin's relevance to intracellular infection was missed due to functional redundancy with the ferrous iron transport (FeoB) pathway, we characterized a new mutant lacking both lbtA and feoB. This mutant was highly impaired for growth on bacteriological media that were only modestly depleted of iron, confirming that rhizoferrin-mediated ferric iron uptake and FeoB-mediated ferrous iron uptake are critical for iron acquisition. The lbtA feoB mutant, but not its lbtA-containing complement, was also highly defective for biofilm formation on plastic surfaces, demonstrating a new role for the L. pneumophila siderophore in extracellular survival. Finally, the lbtA feoB mutant, but not its complement containing lbtA, proved to be greatly impaired for growth in Acanthamoeba castellanii, Vermamoeba vermiformis, and human U937 cell macrophages, revealing that rhizoferrin does promote intracellular infection by L. pneumophila. Moreover, the application of purified rhizoferrin triggered cytokine production from the U937 cells. Rhizoferrin-associated genes were fully conserved across the many sequenced strains of L. pneumophila examined but were variably present among strains from the other species of Legionella. Outside of Legionella, the closest match to the L. pneumophila rhizoferrin genes was in Aquicella siphonis, another facultative intracellular parasite of amoebae.
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Affiliation(s)
- Alberto E. Lopez
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois, USA
| | - Lubov S. Grigoryeva
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois, USA
| | - Armando Barajas
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois, USA
| | - Nicholas P. Cianciotto
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois, USA
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2
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Shames SR. Eat or Be Eaten: Strategies Used by Legionella to Acquire Host-Derived Nutrients and Evade Lysosomal Degradation. Infect Immun 2023; 91:e0044122. [PMID: 36912646 PMCID: PMC10112212 DOI: 10.1128/iai.00441-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2023] Open
Abstract
To replicate within host cells, bacterial pathogens must acquire host-derived nutrients while avoiding degradative antimicrobial pathways. Fundamental insights into bacterial pathogenicity have been revealed by bacteria of the genus Legionella, which naturally parasitize free-living protozoa by establishing a membrane-bound replicative niche termed the Legionella-containing vacuole (LCV). Biogenesis of the LCV and intracellular replication rely on rapid evasion of the endocytic pathway and acquisition of host-derived nutrients, much of which is mediated by bacterial effector proteins translocated into host cells by a Dot/Icm type IV secretion system. Billions of years of co-evolution with eukaryotic hosts and broad host tropism have resulted in expansion of the Legionella genome to accommodate a massive repertoire of effector proteins that promote LCV biogenesis, safeguard the LCV from endolysosomal maturation, and mediate the acquisition of host nutrients. This minireview is focused on the mechanisms by which an ancient intracellular pathogen leverages effector proteins and hijacks host cell biology to obtain essential host-derived nutrients and prevent lysosomal degradation.
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Affiliation(s)
- Stephanie R. Shames
- Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
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3
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Cavallaro A, Rhoads WJ, Huwiler SG, Stachler E, Hammes F. Potential probiotic approaches to control Legionella in engineered aquatic ecosystems. FEMS Microbiol Ecol 2022; 98:6604835. [PMID: 35679082 PMCID: PMC9333994 DOI: 10.1093/femsec/fiac071] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 05/20/2022] [Accepted: 06/07/2022] [Indexed: 11/25/2022] Open
Abstract
Opportunistic pathogens belonging to the genus Legionella are among the most reported waterborne-associated pathogens in industrialized countries. Legionella colonize a variety of engineered aquatic ecosystems and persist in biofilms where they interact with a multitude of other resident microorganisms. In this review, we assess how some of these interactions could be used to develop a biological-driven “probiotic” control approach against Legionella. We focus on: (i) mechanisms limiting the ability of Legionella to establish and replicate within some of their natural protozoan hosts; (ii) exploitative and interference competitive interactions between Legionella and other microorganisms; and (iii) the potential of predatory bacteria and phages against Legionella. This field is still emergent, and we therefore specifically highlight research for future investigations, and propose perspectives on the feasibility and public acceptance of a potential probiotic approach.
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Affiliation(s)
- Alessio Cavallaro
- Department of Environmental Microbiology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland.,Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zurich, Switzerland
| | - William J Rhoads
- Department of Environmental Microbiology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Simona G Huwiler
- Department of Plant and Microbial Biology, University of Zurich, 8008 Zurich, Switzerland
| | - Elyse Stachler
- Department of Environmental Microbiology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Frederik Hammes
- Department of Environmental Microbiology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
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4
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Mraz AL, Weir MH. Knowledge to Predict Pathogens: Legionella pneumophila Lifecycle Systematic Review Part II Growth within and Egress from a Host Cell. Microorganisms 2022; 10:141. [PMID: 35056590 PMCID: PMC8780890 DOI: 10.3390/microorganisms10010141] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 12/30/2021] [Accepted: 01/04/2022] [Indexed: 11/17/2022] Open
Abstract
Legionella pneumophila (L. pneumophila) is a pathogenic bacterium of increasing concern, due to its ability to cause a severe pneumonia, Legionnaires' Disease (LD), and the challenges in controlling the bacteria within premise plumbing systems. L. pneumophila can thrive within the biofilm of premise plumbing systems, utilizing protozoan hosts for protection from environmental stressors and to increase its growth rate, which increases the bacteria's infectivity to human host cells. Typical disinfectant techniques have proven to be inadequate in controlling L. pneumophila in the premise plumbing system, exposing users to LD risks. As the bacteria have limited infectivity to human macrophages without replicating within a host protozoan cell, the replication within, and egress from, a protozoan host cell is an integral part of the bacteria's lifecycle. While there is a great deal of information regarding how L. pneumophila interacts with protozoa, the ability to use this data in a model to attempt to predict a concentration of L. pneumophila in a water system is not known. This systematic review summarizes the information in the literature regarding L. pneumophila's growth within and egress from the host cell, summarizes the genes which affect these processes, and calculates how oxidative stress can downregulate those genes.
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Affiliation(s)
- Alexis L. Mraz
- School of Nursing, Health, Exercise Science, The College of New Jersey, P.O. Box 7718, 2000 Pennington Rd., Ewing, NJ 08628, USA
| | - Mark H. Weir
- Division of Environmental Health Sciences, College of Public Health, The Ohio State University, Columbus, OH 43210, USA;
- Sustainability Institute, The Ohio State University, Columbus, OH 43210, USA
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5
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Christenson ET, Isaac DT, Yoshida K, Lipo E, Kim JS, Ghirlando R, Isberg RR, Banerjee A. The iron-regulated vacuolar Legionella pneumophila MavN protein is a transition-metal transporter. Proc Natl Acad Sci U S A 2019; 116:17775-17785. [PMID: 31431530 PMCID: PMC6731752 DOI: 10.1073/pnas.1902806116] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Legionella pneumophila causes a potentially fatal form of pneumonia by replicating within macrophages in the Legionella-containing vacuole (LCV). Bacterial survival and proliferation within the LCV rely on hundreds of secreted effector proteins comprising high functional redundancy. The vacuolar membrane-localized MavN, hypothesized to support iron transport, is unique among effectors because loss-of-function mutations result in severe intracellular growth defects. We show here an iron starvation response by L. pneumophila after infection of macrophages that was prematurely induced in the absence of MavN, consistent with MavN granting access to limiting cellular iron stores. MavN cysteine accessibilities to a membrane-impermeant label were determined during macrophage infections, revealing a topological pattern supporting multipass membrane transporter models. Mutations to several highly conserved residues that can take part in metal recognition and transport resulted in defective intracellular growth. Purified MavN and mutant derivatives were directly tested for transporter activity after heterologous purification and liposome reconstitution. Proteoliposomes harboring MavN exhibited robust transport of Fe2+, with the severity of defect of most mutants closely mimicking the magnitude of defects during intracellular growth. Surprisingly, MavN was equivalently proficient at transporting Fe2+, Mn2+, Co2+, or Zn2+ Consequently, flooding infected cells with either Mn2+ or Zn2+ allowed collaboration with iron to enhance intracellular growth of L. pneumophila ΔmavN strains, indicating a clear role for MavN in transporting each of these ions. These findings reveal that MavN is a transition-metal-ion transporter that plays a critical role in response to iron limitation during Legionella infection.
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Affiliation(s)
- Eric T Christenson
- Unit on Structural and Chemical Biology of Membrane Proteins, Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
| | - Dervla T Isaac
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111
| | - Karin Yoshida
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111
| | - Erion Lipo
- Program in Genetics, Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111
| | - Jin-Sik Kim
- Unit on Structural and Chemical Biology of Membrane Proteins, Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
| | - Rodolfo Ghirlando
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Ralph R Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111;
| | - Anirban Banerjee
- Unit on Structural and Chemical Biology of Membrane Proteins, Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892;
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6
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Analysis of Iron Requirements and Siderophore Production. Methods Mol Biol 2019. [PMID: 30694482 DOI: 10.1007/978-1-4939-9048-1_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
This chapter describes the methods for inducing, detecting, and purifying the Legionella pneumophila siderophore. The first protocol details the methods by which L. pneumophila is cultured to facilitate production of the siderophore, rhizoferrin. This chapter then describes how to purify siderophore from culture supernatants through sequential reversed-phase/weak-anion exchange chromatography and high-performance liquid chromatography. The next section describes assays which allow the detection of the iron-binding capability and the biological activity of the purified siderophore. Lastly, this chapter describes the growth of L. pneumophila in chemically defined liquid medium (CDM) containing various iron sources as a method to assess the iron requirements of L. pneumophila.
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7
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Knowledge to Predict Pathogens: Legionella pneumophila Lifecycle Critical Review Part I Uptake into Host Cells. WATER 2018. [DOI: 10.3390/w10020132] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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8
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Machuca A, Martinez V. Transcriptome Analysis of the Intracellular Facultative Pathogen Piscirickettsia salmonis: Expression of Putative Groups of Genes Associated with Virulence and Iron Metabolism. PLoS One 2016; 11:e0168855. [PMID: 28033422 PMCID: PMC5199080 DOI: 10.1371/journal.pone.0168855] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 12/07/2016] [Indexed: 01/01/2023] Open
Abstract
The intracellular facultative bacteria Piscirickettsia salmonis is one of the most important pathogens of the Chilean aquaculture. However, there is a lack of information regarding the whole genomic transcriptional response according to different extracellular environments. We used next generation sequencing (NGS) of RNA (RNA-seq) to study the whole transcriptome of an isolate of P. salmonis (FAVET-INBIOGEN) using a cell line culture and a modified cell-free liquid medium, with or without iron supplementation. This was done in order to obtain information about the factors there are involved in virulence and iron acquisition. First, the isolate was grown in the Sf21 cell line; then, the bacteria were cultured into a cell-free liquid medium supplemented or not with iron. We identified in the transcriptome, genes associated with type IV secretion systems, genes related to flagellar structure assembly, several proteases and sigma factors, and genes related to the development of drug resistance. Additionally, we identified for the first time several iron-metabolism associated genes including at least two iron uptake pathways (ferrous iron and ferric iron uptake) that are actually expressed in the different conditions analyzed. We further describe putative genes that are related with the use and storage of iron in the bacteria, which have not been previously described. Several sets of genes related to virulence were expressed in both the cell line and cell-free culture media (for example those related to flagellar structure; such as basal body, MS-ring, C-ring, proximal and distal rod, and filament), which may play roles in other basic processes rather than been restricted to virulence.
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Affiliation(s)
- Alvaro Machuca
- FAVET-INBIOGEN, Faculty of Veterinary Sciences, University of Chile, Santiago, Chile
| | - Victor Martinez
- FAVET-INBIOGEN, Faculty of Veterinary Sciences, University of Chile, Santiago, Chile
- * E-mail:
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9
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Tobias NJ, Ahrendt T, Schell U, Miltenberger M, Hilbi H, Bode HB. Legionella shows a diverse secondary metabolism dependent on a broad spectrum Sfp-type phosphopantetheinyl transferase. PeerJ 2016; 4:e2720. [PMID: 27904811 PMCID: PMC5126622 DOI: 10.7717/peerj.2720] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 10/25/2016] [Indexed: 01/01/2023] Open
Abstract
Several members of the genus Legionella cause Legionnaires' disease, a potentially debilitating form of pneumonia. Studies frequently focus on the abundant number of virulence factors present in this genus. However, what is often overlooked is the role of secondary metabolites from Legionella. Following whole genome sequencing, we assembled and annotated the Legionella parisiensis DSM 19216 genome. Together with 14 other members of the Legionella, we performed comparative genomics and analysed the secondary metabolite potential of each strain. We found that Legionella contains a huge variety of biosynthetic gene clusters (BGCs) that are potentially making a significant number of novel natural products with undefined function. Surprisingly, only a single Sfp-like phosphopantetheinyl transferase is found in all Legionella strains analyzed that might be responsible for the activation of all carrier proteins in primary (fatty acid biosynthesis) and secondary metabolism (polyketide and non-ribosomal peptide synthesis). Using conserved active site motifs, we predict some novel compounds that are probably involved in cell-cell communication, differing to known communication systems. We identify several gene clusters, which may represent novel signaling mechanisms and demonstrate the natural product potential of Legionella.
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Affiliation(s)
- Nicholas J. Tobias
- Fachbereich Biowissenschaften, Merck Stiftungsprofessur für Molekulare Biotechnologie, Goethe Universität, Frankfurt am Main, Germany
| | - Tilman Ahrendt
- Fachbereich Biowissenschaften, Merck Stiftungsprofessur für Molekulare Biotechnologie, Goethe Universität, Frankfurt am Main, Germany
| | - Ursula Schell
- Max von Pettenkofer Institute, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Melissa Miltenberger
- Fachbereich Biowissenschaften, Merck Stiftungsprofessur für Molekulare Biotechnologie, Goethe Universität, Frankfurt am Main, Germany
| | - Hubert Hilbi
- Max von Pettenkofer Institute, Ludwig-Maximilians-Universität München, Munich, Germany
- Institute of Medical Microbiology, University of Zürich, Zürich, Switzerland
| | - Helge B. Bode
- Fachbereich Biowissenschaften, Merck Stiftungsprofessur für Molekulare Biotechnologie, Goethe Universität, Frankfurt am Main, Germany
- Buchmann Institute for Molecular Life Sciences, Goethe Universität, Frankfurt am Main, Germany
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10
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Portier E, Bertaux J, Labanowski J, Hechard Y. Iron Availability Modulates the Persistence of Legionella pneumophila in Complex Biofilms. Microbes Environ 2016; 31:387-394. [PMID: 27629106 PMCID: PMC5158110 DOI: 10.1264/jsme2.me16010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Legionella pneumophila is a pathogenic bacteria found in biofilms in freshwater. Iron is an essential nutrient for L. pneumophila growth. In this study, complex biofilms were developed using river water spiked with L. pneumophila, and the persistence of L. pneumophila in these complex biofilms was evaluated. In order to study the role of iron in the persistence of L. pneumophila, river water was supplied with either iron pyrophosphate or iron chelators (deferoxamine mesylate, DFX for ferric iron and dipyridyl, DIP for ferrous iron) to modulate iron availability. The addition of iron pyrophosphate and DFX did not markedly affect the persistence of L. pneumophila in the biofilms, whereas that of DIP had a beneficial effect. Since DIP specifically chelates ferrous iron, we hypothesized that DIP may protect L. pneumophila from the deleterious effects of ferrous iron. In conclusion, ferrous iron appears to be important for the persistence of L. pneumophila in complex biofilms. However, further studies are needed in order to obtain a better understanding of the role of ferrous iron in the behavior of this bacterium in the environment.
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Affiliation(s)
- Emilie Portier
- University of Poitiers, Laboratory of Ecology and Biology of Interactions, UMR CNRS 7267, Team of Microbiology of Water
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11
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Caicedo C, Beutel S, Scheper T, Rosenwinkel KH, Nogueira R. Occurrence of Legionella in wastewater treatment plants linked to wastewater characteristics. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:16873-16881. [PMID: 27376367 DOI: 10.1007/s11356-016-7090-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 06/13/2016] [Indexed: 06/06/2023]
Abstract
In recent years, the occurrence of Legionella in wastewater treatment plants (WWTP) has often been reported. However, until now there is limited knowledge about the factors that promote Legionella's growth in such systems. The aim of this study was to investigate the chemical wastewater parameters that might be correlated to the concentration of Legionella spp. in WWTP receiving industrial effluents. For this purpose, samples were collected at different processes in three WWTP. In 100 % of the samples taken from the activated sludge tanks Legionella spp. were detected at varying concentrations (4.8 to 5.6 log GU/mL) by the quantitative real-time polymerase chain reaction method, but not by the culture method. Statistical analysis with various parameters yielded positive correlations of Legionella spp. concentration with particulate chemical oxygen demand, Kjeldahl nitrogen and protein concentration. Amino acids were quantified in wastewater and activated sludge samples at concentrations that may not support the growth of Legionella, suggesting that in activated sludge tanks this bacterium multiplied in protozoan hosts.
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Affiliation(s)
- C Caicedo
- Institute for Sanitary Engineering and Waste Management, Leibniz University Hannover, Welfengarten 1, Hannover, 30167, Germany
| | - S Beutel
- Institute of Technical Chemistry, Leibniz University Hannover, Hannover, 30167, Germany
| | - T Scheper
- Institute of Technical Chemistry, Leibniz University Hannover, Hannover, 30167, Germany
| | - K H Rosenwinkel
- Institute for Sanitary Engineering and Waste Management, Leibniz University Hannover, Welfengarten 1, Hannover, 30167, Germany
| | - R Nogueira
- Institute for Sanitary Engineering and Waste Management, Leibniz University Hannover, Welfengarten 1, Hannover, 30167, Germany.
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12
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Cianciotto NP. An update on iron acquisition by Legionella pneumophila: new pathways for siderophore uptake and ferric iron reduction. Future Microbiol 2016; 10:841-51. [PMID: 26000653 DOI: 10.2217/fmb.15.21] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Iron acquisition is critical for the growth and pathogenesis of Legionella pneumophila, the causative agent of Legionnaires' disease. L. pneumophila utilizes two main modes of iron assimilation, namely ferrous iron uptake via the FeoB system and ferric iron acquisition through the action of the siderophore legiobactin. This review highlights recent studies concerning the mechanism of legiobactin assimilation, the impact of c-type cytochromes on siderophore production, the importance of legiobactin in lung infection and a newfound role for a bacterial pyomelanin in iron acquisition. These data demonstrate that key aspects of L. pneumophila iron acquisition are significantly distinct from those of long-studied, 'model' organisms. Indeed, L. pneumophila may represent a new paradigm for a variety of other intracellular parasites, pathogens and under-studied bacteria.
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13
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Rakić A, Štambuk-Giljanović N. Physical and chemical parameter correlations with technical and technological characteristics of heating systems and the presence of Legionella spp. in the hot water supply. ENVIRONMENTAL MONITORING AND ASSESSMENT 2016; 188:73. [PMID: 26733467 DOI: 10.1007/s10661-015-5047-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 12/10/2015] [Indexed: 06/05/2023]
Abstract
The purpose of this study was to evaluate the prevalence of Legionella spp. and compare the quality of hot water between four facilities for accommodation located in Southern Croatia (the Split-Dalmatian County). The research included data collection on the technical and technological characteristics in the period from 2009 to 2012. The survey included a type of construction material for the distribution and internal networks, heating system water heater type, and water consumption. Changes in water quality were monitored by determination of the physical and chemical parameters (temperature, pH, free chlorine residual concentrations, iron, zinc, copper and manganese) in the samples, as well as the presence and concentration of bacteria Legionella spp. The temperature is an important factor for the development of biofilms, and it is in negative correlation with the appearance of Legionella spp. Positive correlations between the Fe and Zn concentrations and Legionella spp. were established, while the inhibitory effect of a higher Cu concentration on the Legionella spp. concentration was proven. Legionella spp. were identified in 38/126 (30.2%) of the water samples from the heating system with zinc-coated pipes, as well as in 78/299 (26.1%) of the samples from systems with plastic pipes. A similar number of Legionella spp. positive samples were established regardless of the type of the water heating system (central or independent). The study confirms the necessity of regular microbial contamination monitoring of the drinking water distribution systems (DWDSs).
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Affiliation(s)
- Anita Rakić
- Public Health Institute of Split-Dalmatian County, Vukovarska 46, 21000, Split, Croatia.
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14
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Vibrio cholerae FeoA, FeoB, and FeoC Interact To Form a Complex. J Bacteriol 2016; 198:1160-70. [PMID: 26833408 DOI: 10.1128/jb.00930-15] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 01/24/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Feo is the major ferrous iron transport system in prokaryotes. Despite having been discovered over 25 years ago and found to be widely distributed among bacteria, Feo is poorly understood, as its structure and mechanism of iron transport have not been determined. The feo operon in Vibrio cholerae is made up of three genes, encoding the FeoA, FeoB, and FeoC proteins, which are all required for Feo system function. FeoA and FeoC are both small cytoplasmic proteins, and their function remains unclear. FeoB, which is thought to function as a ferrous iron permease, is a large integral membrane protein made up of an N-terminal GTPase domain and a C-terminal membrane-spanning region. To date, structural studies of FeoB have been carried out using a truncated form of the protein encompassing only the N-terminal GTPase region. In this report, we show that full-length FeoB forms higher-order complexes when cross-linked in vivo in V. cholerae. Our analysis of these complexes revealed that FeoB can simultaneously associate with both FeoA and FeoC to form a large complex, an observation that has not been reported previously. We demonstrate that interactions between FeoB and FeoA, but not between FeoB and FeoC, are required for complex formation. Additionally, we identify amino acid residues in the GTPase region of FeoB that are required for function of the Feo system and for complex formation. These observations suggest that this large Feo complex may be the active form of Feo that is used for ferrous iron transport. IMPORTANCE The Feo system is the major route for ferrous iron transport in bacteria. In this work, the Vibrio cholerae Feo proteins, FeoA, FeoB, and FeoC, are shown to interact to form a large inner membrane complex in vivo. This is the first report showing an interaction among all three Feo proteins. It is also determined that FeoA, but not FeoC, is required for Feo complex assembly.
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15
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Helfrich EJN, Piel J. Biosynthesis of polyketides by trans-AT polyketide synthases. Nat Prod Rep 2016; 33:231-316. [DOI: 10.1039/c5np00125k] [Citation(s) in RCA: 230] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
This review discusses the biosynthesis of natural products that are generated bytrans-AT polyketide synthases, a family of catalytically versatile enzymes that represents one of the major group of proteins involved in the production of bioactive polyketides.
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Affiliation(s)
- Eric J. N. Helfrich
- Institute of Microbiology
- Eidgenössische Technische Hochschule (ETH) Zurich
- 8093 Zurich
- Switzerland
| | - Jörn Piel
- Institute of Microbiology
- Eidgenössische Technische Hochschule (ETH) Zurich
- 8093 Zurich
- Switzerland
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16
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Lau CKY, Krewulak KD, Vogel HJ. Bacterial ferrous iron transport: the Feo system. FEMS Microbiol Rev 2015; 40:273-98. [PMID: 26684538 DOI: 10.1093/femsre/fuv049] [Citation(s) in RCA: 212] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2015] [Indexed: 01/24/2023] Open
Abstract
To maintain iron homeostasis within the cell, bacteria have evolved various types of iron acquisition systems. Ferric iron (Fe(3+)) is the dominant species in an oxygenated environment, while ferrous iron (Fe(2+)) is more abundant under anaerobic conditions or at low pH. For organisms that must combat oxygen limitation for their everyday survival, pathways for the uptake of ferrous iron are essential. Several bacterial ferrous iron transport systems have been described; however, only the Feo system appears to be widely distributed and is exclusively dedicated to the transport of iron. In recent years, many studies have explored the role of the FeoB and FeoA proteins in ferrous iron transport and their contribution toward bacterial virulence. The three-dimensional structures for the Feo proteins have recently been determined and provide insight into the molecular details of the transport system. A highly select group of bacteria also express the FeoC protein from the same operon. This review will provide a comprehensive look at the structural and functional aspects of the Feo system. In addition, bioinformatics analyses of the feo operon and the Feo proteins have been performed to complement our understanding of this ubiquitous bacterial uptake system, providing a new outlook for future studies.
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Affiliation(s)
- Cheryl K Y Lau
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada
| | - Karla D Krewulak
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada
| | - Hans J Vogel
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada
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Aubi O, Flydal MI, Zheng H, Skjærven L, Rekand I, Leiros HKS, Haug BE, Cianciotto NP, Martinez A, Underhaug J. Discovery of a Specific Inhibitor of Pyomelanin Synthesis in Legionella pneumophila. J Med Chem 2015; 58:8402-12. [DOI: 10.1021/acs.jmedchem.5b01589] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Oscar Aubi
- Department
of Biomedicine, University of Bergen, Bergen, Norway
| | - Marte I. Flydal
- Department
of Biomedicine, University of Bergen, Bergen, Norway
| | - Huaixin Zheng
- Department
of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois 60611, United States
| | - Lars Skjærven
- Department
of Biomedicine, University of Bergen, Bergen, Norway
| | - Illimar Rekand
- Department
of Chemistry and Centre for Pharmacy, University of Bergen, Bergen, Norway
| | - Hanna-Kirsti S. Leiros
- The
Norwegian Structural Biology Centre (NorStruct), Department of Chemistry, UiT The Arctic University of Norway, Tromsø, Norway
| | - Bengt Erik Haug
- Department
of Chemistry and Centre for Pharmacy, University of Bergen, Bergen, Norway
| | - Nicholas P. Cianciotto
- Department
of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois 60611, United States
| | - Aurora Martinez
- Department
of Biomedicine, University of Bergen, Bergen, Norway
| | - Jarl Underhaug
- Department
of Biomedicine, University of Bergen, Bergen, Norway
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18
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Mendis N, McBride P, Faucher SP. Short-Term and Long-Term Survival and Virulence of Legionella pneumophila in the Defined Freshwater Medium Fraquil. PLoS One 2015; 10:e0139277. [PMID: 26406895 PMCID: PMC4583229 DOI: 10.1371/journal.pone.0139277] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 09/09/2015] [Indexed: 12/03/2022] Open
Abstract
Legionella pneumophila (Lp) is the etiological agent responsible for Legionnaires’ disease, a potentially fatal pulmonary infection. Lp lives and multiplies inside protozoa in a variety of natural and man-made water systems prior to human infection. Fraquil, a defined freshwater medium, was used as a highly reproducible medium to study the behaviour of Lp in water. Adopting a reductionist approach, Fraquil was used to study the impact of temperature, pH and trace metal levels on the survival and subsequent intracellular multiplication of Lp in Acanthamoeba castellanii, a freshwater protozoan and a natural host of Legionella. We show that temperature has a significant impact on the short- and long-term survival of Lp, but that the bacterium retains intracellular multiplication potential for over six months in Fraquil. Moreover, incubation in Fraquil at pH 4.0 resulted in a rapid decline in colony forming units, but was not detrimental to intracellular multiplication. In contrast, variations in trace metal concentrations had no impact on either survival or intracellular multiplication in amoeba. Our data show that Lp is a resilient bacterium in the water environment, remaining infectious to host cells after six months under the nutrient-deprived conditions of Fraquil.
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Affiliation(s)
- Nilmini Mendis
- Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University, Sainte-Anne-de-Bellevue, QC, Canada
| | - Peter McBride
- Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University, Sainte-Anne-de-Bellevue, QC, Canada
| | - Sébastien P. Faucher
- Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University, Sainte-Anne-de-Bellevue, QC, Canada
- * E-mail:
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The Legionella pneumophila Siderophore Legiobactin Is a Polycarboxylate That Is Identical in Structure to Rhizoferrin. Infect Immun 2015. [PMID: 26195554 DOI: 10.1128/iai.00808-15] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Legionella pneumophila, the agent of Legionnaires' disease, secretes a siderophore (legiobactin) that promotes bacterial infection of the lung. In past work, we determined that cytoplasmic LbtA (from Legiobactin gene A) promotes synthesis of legiobactin, inner membrane LbtB aids in export of the siderophore, and outer membrane LbtU and inner membrane LbtC help mediate ferrilegiobactin uptake and assimilation. However, the past studies examined legiobactin contained within bacterial culture supernatants. By utilizing high-pressure liquid chromatography that incorporates hydrophilic interaction-based chemistry, we have now purified legiobactin from supernatants of virulent strain 130b that is suitable for detailed chemical analysis. High-resolution mass spectrometry (MS) revealed that the molecular mass of (protonated) legiobactin is 437.140 Da. On the basis of the results obtained from both MS analysis and various forms of nuclear magnetic resonance, we found that legiobactin is composed of two citric acid residues linked by a putrescine bridge and thus is identical in structure to rhizoferrin, a polycarboxylate-type siderophore made by many fungi and several unrelated bacteria. Both purified legiobactin and rhizoferrin obtained from the fungus Cunninghamella elegans were able to promote Fe(3+) uptake by wild-type L. pneumophila as well as enhance growth of iron-starved bacteria. These results did not occur with 130b mutants lacking lbtU or lbtC, indicating that both endogenously made legiobactin and exogenously derived rhizoferrin are assimilated by L. pneumophila in an LbtU- and LbtC-dependent manner.
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Robertson P, Abdelhady H, Garduño RA. The many forms of a pleomorphic bacterial pathogen-the developmental network of Legionella pneumophila. Front Microbiol 2014; 5:670. [PMID: 25566200 PMCID: PMC4273665 DOI: 10.3389/fmicb.2014.00670] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 11/18/2014] [Indexed: 01/18/2023] Open
Abstract
Legionella pneumophila is a natural intracellular bacterial parasite of free-living freshwater protozoa and an accidental human pathogen that causes Legionnaires' disease. L. pneumophila differentiates, and does it in style. Recent experimental data on L. pneumophila's differentiation point at the existence of a complex network that involves many developmental forms. We intend readers to: (i) understand the biological relevance of L. pneumophila's forms found in freshwater and their potential to transmit Legionnaires' disease, and (ii) learn that the common depiction of L. pneumophila's differentiation as a biphasic developmental cycle that alternates between a replicative and a transmissive form is but an oversimplification of the actual process. Our specific objectives are to provide updates on the molecular factors that regulate L. pneumophila's differentiation (Section The Differentiation Process and Its Regulation), and describe the developmental network of L. pneumophila (Section Dissecting Lp's Developmental Network), which for clarity's sake we have dissected into five separate developmental cycles. Finally, since each developmental form seems to contribute differently to the human pathogenic process and the transmission of Legionnaires' disease, readers are presented with a challenge to develop novel methods to detect the various L. pneumophila forms present in water (Section Practical Implications), as a means to improve our assessment of risk and more effectively prevent legionellosis outbreaks.
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Affiliation(s)
- Peter Robertson
- Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada
| | - Hany Abdelhady
- Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada
| | - Rafael A Garduño
- Department of Microbiology and Immunology, Dalhousie University Halifax, NS, Canada ; Division of Infectious Diseases, Department of Medicine, Dalhousie University Halifax, NS, Canada
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21
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Weber S, Stirnimann CU, Wieser M, Frey D, Meier R, Engelhardt S, Li X, Capitani G, Kammerer RA, Hilbi H. A type IV translocated Legionella cysteine phytase counteracts intracellular growth restriction by phytate. J Biol Chem 2014; 289:34175-88. [PMID: 25339170 DOI: 10.1074/jbc.m114.592568] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The causative agent of Legionnaires' pneumonia, Legionella pneumophila, colonizes diverse environmental niches, including biofilms, plant material, and protozoa. In these habitats, myo-inositol hexakisphosphate (phytate) is prevalent and used as a phosphate storage compound or as a siderophore. L. pneumophila replicates in protozoa and mammalian phagocytes within a unique "Legionella-containing vacuole." The bacteria govern host cell interactions through the Icm/Dot type IV secretion system (T4SS) and ∼300 different "effector" proteins. Here we characterize a hitherto unrecognized Icm/Dot substrate, LppA, as a phytate phosphatase (phytase). Phytase activity of recombinant LppA required catalytically essential cysteine (Cys(231)) and arginine (Arg(237)) residues. The structure of LppA at 1.4 Å resolution revealed a mainly α-helical globular protein stabilized by four antiparallel β-sheets that binds two phosphate moieties. The phosphates localize to a P-loop active site characteristic of dual specificity phosphatases or to a non-catalytic site, respectively. Phytate reversibly abolished growth of L. pneumophila in broth, and growth inhibition was relieved by overproduction of LppA or by metal ion titration. L. pneumophila lacking lppA replicated less efficiently in phytate-loaded Acanthamoeba castellanii or Dictyostelium discoideum, and the intracellular growth defect was complemented by the phytase gene. These findings identify the chelator phytate as an intracellular bacteriostatic component of cell-autonomous host immunity and reveal a T4SS-translocated L. pneumophila phytase that counteracts intracellular bacterial growth restriction by phytate. Thus, bacterial phytases might represent therapeutic targets to combat intracellular pathogens.
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Affiliation(s)
- Stephen Weber
- From the Max von Pettenkofer Institute, Department of Medicine, Ludwig-Maximilians University Munich, 80336 Munich, Germany
| | - Christian U Stirnimann
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Mara Wieser
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Daniel Frey
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Roger Meier
- the Scientific Center for Optical and Electron Microscopy, ETH Zurich, 8093 Zurich, Switzerland
| | - Sabrina Engelhardt
- the Institute of Veterinary Physiology and Zurich Center for Integrative Human Physiology (ZIHP), Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland, and
| | - Xiaodan Li
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Guido Capitani
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Richard A Kammerer
- the Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Hubert Hilbi
- From the Max von Pettenkofer Institute, Department of Medicine, Ludwig-Maximilians University Munich, 80336 Munich, Germany, the Institute of Medical Microbiology, Department of Medicine, University of Zurich, 8006 Zurich, Switzerland
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22
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Factors influencing persistence of Legionella pneumophila serogroup 1 in laboratory cocultures. BMC Microbiol 2014; 14:249. [PMID: 25277877 PMCID: PMC4195868 DOI: 10.1186/s12866-014-0249-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 09/17/2014] [Indexed: 12/03/2022] Open
Abstract
Background Risk for infections from Legionella pneumophila for immunocompromised individuals increases greatly when this species is present within the biofilm of the water distribution systems of hospitals or other health facilities. Multiplication and persistence of Legionella may dependent also upon planktonic growth in alternative to sessile growth. Here we compared the persistence of L. pneumophila serogroup 1 in experimental planktonic co-cultures subsided with iron, Pseudomonas aeruginosa and other non Legionella bacteria (quantified as Heterotrophic Plate Count, HPC at 37°C), isolated from drinking water sources of a large hospital. Results Concentrations of L. pneumophila showed a decreasing pattern with incubation time in all co-cultures, the degree of reduction depending on the experimental treatment. In co-cultures with added P. aeruginosa, no L. pneumophila was detectable already after 4 days of incubation. In contrast in co-cultures without P. aeruginosa, HPC but not iron were significant factors in explaining the pattern of L. pneumophila, although the HPC effect was different according to the incubation time (HPC x time interaction, p < 0.01). Conclusions Our results highlight the need of controlling for both HPC and metal constituents of the water systems of buildings used by individuals at particular risk to the effects of Legionella exposure.
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23
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Portier E, Zheng H, Sahr T, Burnside DM, Mallama C, Buchrieser C, Cianciotto NP, Héchard Y. IroT/mavN, a new iron-regulated gene involved in Legionella pneumophila virulence against amoebae and macrophages. Environ Microbiol 2014; 17:1338-50. [PMID: 25141909 DOI: 10.1111/1462-2920.12604] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 08/14/2014] [Indexed: 10/24/2022]
Abstract
Legionella pneumophila is a pathogenic bacterium commonly found in water. Eventually, it could be transmitted to humans via inhalation of contaminated aerosols. Iron is known as a key requirement for the growth of L. pneumophila in the environment and within its hosts. Many studies were performed to understand iron utilization by L. pneumophila but no global approaches were conducted. In this study, transcriptomic analyses were performed, comparing gene expression in L. pneumophila in standard versus iron restricted conditions. Among the regulated genes, a newly described one, lpp_2867, was highly induced in iron-restricted conditions. Mutants lacking this gene in L. pneumophila were not affected in siderophore synthesis or utilization. On the contrary, they were defective for growth on iron-depleted solid media and for ferrous iron uptake. A sequence analysis predicts that Lpp_2867 is a membrane protein, suggesting that it is involved in ferrous iron transport. We thus named it IroT, for iron transporter. Infection assays showed that the mutants are highly impaired in intracellular growth within their environmental host Acanthamoeba castellanii and human macrophages. Taken together, our results show that IroT is involved, directly or indirectly, in ferrous iron transport and is a key virulence factor for L. pneumophila.
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Affiliation(s)
- Emilie Portier
- Laboratoire Ecologie et Biologie des Interactions, UMR CNRS 7267, Equipe Microbiologie de l'Eau, Université de Poitiers, Poitiers, France
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24
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Fonseca MV, Swanson MS. Nutrient salvaging and metabolism by the intracellular pathogen Legionella pneumophila. Front Cell Infect Microbiol 2014; 4:12. [PMID: 24575391 PMCID: PMC3920079 DOI: 10.3389/fcimb.2014.00012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Accepted: 01/23/2014] [Indexed: 11/13/2022] Open
Abstract
The Gram-negative bacterium Legionella pneumophila is ubiquitous in freshwater environments as a free-swimming organism, resident of biofilms, or parasite of protozoa. If the bacterium is aerosolized and inhaled by a susceptible human host, it can infect alveolar macrophages and cause a severe pneumonia known as Legionnaires' disease. A sophisticated cell differentiation program equips L. pneumophila to persist in both extracellular and intracellular niches. During its life cycle, L. pneumophila alternates between at least two distinct forms: a transmissive form equipped to infect host cells and evade lysosomal degradation, and a replicative form that multiplies within a phagosomal compartment that it has retooled to its advantage. The efficient changeover between transmissive and replicative states is fundamental to L. pneumophila's fitness as an intracellular pathogen. The transmission and replication programs of L. pneumophila are governed by a number of metabolic cues that signal whether conditions are favorable for replication or instead trigger escape from a spent host. Several lines of experimental evidence gathered over the past decade establish strong links between metabolism, cellular differentiation, and virulence of L. pneumophila. Herein, we focus on current knowledge of the metabolic components employed by intracellular L. pneumophila for cell differentiation, nutrient salvaging and utilization of host factors. Specifically, we highlight the metabolic cues that are coupled to bacterial differentiation, nutrient acquisition systems, and the strategies utilized by L. pneumophila to exploit host metabolites for intracellular replication.
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Affiliation(s)
- Maris V Fonseca
- Science and Mathematics Division, Monroe County Community College Monroe, MI, USA
| | - Michele S Swanson
- Department of Microbiology and Immunology, University of Michigan Medical School Ann Arbor, MI, USA
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25
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Abdel-Nour M, Duncan C, Low DE, Guyard C. Biofilms: the stronghold of Legionella pneumophila. Int J Mol Sci 2013; 14:21660-75. [PMID: 24185913 PMCID: PMC3856027 DOI: 10.3390/ijms141121660] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 09/07/2013] [Accepted: 10/14/2013] [Indexed: 11/28/2022] Open
Abstract
Legionellosis is mostly caused by Legionella pneumophila and is defined as a severe respiratory illness with a case fatality rate ranging from 5% to 80%. L. pneumophila is ubiquitous in natural and anthropogenic water systems. L. pneumophila is transmitted by inhalation of contaminated aerosols produced by a variety of devices. While L. pneumophila replicates within environmental protozoa, colonization and persistence in its natural environment are also mediated by biofilm formation and colonization within multispecies microbial communities. There is now evidence that some legionellosis outbreaks are correlated with the presence of biofilms. Thus, preventing biofilm formation appears as one of the strategies to reduce water system contamination. However, we lack information about the chemical and biophysical conditions, as well as the molecular mechanisms that allow the production of biofilms by L. pneumophila. Here, we discuss the molecular basis of biofilm formation by L. pneumophila and the roles of other microbial species in L. pneumophila biofilm colonization. In addition, we discuss the protective roles of biofilms against current L. pneumophila sanitation strategies along with the initial data available on the regulation of L. pneumophila biofilm formation.
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Affiliation(s)
- Mena Abdel-Nour
- Ontario Agency for Health Protection and Promotion (OAHPP), Toronto, ON M9P 3T1, Canada; E-Mails: (M.A.-N.); (C.D.)
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada
- Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada
| | - Carla Duncan
- Ontario Agency for Health Protection and Promotion (OAHPP), Toronto, ON M9P 3T1, Canada; E-Mails: (M.A.-N.); (C.D.)
| | - Donald E. Low
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada
- Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada
| | - Cyril Guyard
- Ontario Agency for Health Protection and Promotion (OAHPP), Toronto, ON M9P 3T1, Canada; E-Mails: (M.A.-N.); (C.D.)
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada
- Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-416-880-1339; Fax: +1-416-235-6281
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26
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Loza-Correa M, Sahr T, Rolando M, Daniels C, Petit P, Skarina T, Gomez Valero L, Dervins-Ravault D, Honoré N, Savchenko A, Buchrieser C. The Legionella pneumophila kai operon is implicated in stress response and confers fitness in competitive environments. Environ Microbiol 2013; 16:359-81. [PMID: 23957615 DOI: 10.1111/1462-2920.12223] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 07/16/2013] [Accepted: 07/19/2013] [Indexed: 01/22/2023]
Abstract
Legionella pneumophila uses aquatic protozoa as replication niche and protection from harsh environments. Although L. pneumophila is not known to have a circadian clock, it encodes homologues of the KaiBC proteins of Cyanobacteria that regulate circadian gene expression. We show that L. pneumophila kaiB, kaiC and the downstream gene lpp1114, are transcribed as a unit under the control of the stress sigma factor RpoS. KaiC and KaiB of L. pneumophila do not interact as evidenced by yeast and bacterial two-hybrid analyses. Fusion of the C-terminal residues of cyanobacterial KaiB to Legionella KaiB restores their interaction. In contrast, KaiC of L. pneumophila conserved autophosphorylation activity, but KaiB does not trigger the dephosphorylation of KaiC like in Cyanobacteria. The crystal structure of L. pneumophila KaiB suggests that it is an oxidoreductase-like protein with a typical thioredoxin fold. Indeed, mutant analyses revealed that the kai operon-encoded proteins increase fitness of L. pneumophila in competitive environments, and confer higher resistance to oxidative and sodium stress. The phylogenetic analysis indicates that L. pneumophila KaiBC resemble Synechosystis KaiC2B2 and not circadian KaiB1C1. Thus, the L. pneumophila Kai proteins do not encode a circadian clock, but enhance stress resistance and adaption to changes in the environments.
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Affiliation(s)
- Maria Loza-Correa
- Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France; CNRS UMR 3525, Paris, France
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27
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Taylor M, Ross K, Bentham R. Spatial arrangement of legionella colonies in intact biofilms from a model cooling water system. Microbiol Insights 2013; 6:49-57. [PMID: 24826074 PMCID: PMC3987755 DOI: 10.4137/mbi.s12196] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
There is disagreement among microbiologists about whether Legionella requires a protozoan host in order to replicate. This research sought to determine where in biofilm Legionellae are found and whether all biofilm associated Legionella would be located within protozoan hosts. While it is accepted that Legionella colonizes biofilm, its life cycle and nutritional fastidiousness suggest that Legionella employs multiple survival strategies to persist within microbial systems. Fluorescent in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM) demonstrated an undulating biofilm surface architecture and a roughly homogenous distribution of heterotrophic bacteria with clusters of protozoa. Legionella displayed 3 distinct spatial arrangements either contained within or directly associated with protozoa, or dispersed in loosely associated clusters or in tightly packed aggregations of cells forming dense colonial clusters. The formation of discreet clusters of tightly packed Legionella suggests that colony formation is influenced by specific environmental conditions allowing for limited extracellular replication. This work represents the first time that an environmentally representative, multispecies biofilm containing Legionella has been fluorescently tagged and Legionella colony morphology noted within a complex microbial system.
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Affiliation(s)
- Michael Taylor
- School of the Environment, Flinders University of South Australia, Adelaide, Australia
| | - Kirstin Ross
- School of the Environment, Flinders University of South Australia, Adelaide, Australia
| | - Richard Bentham
- School of the Environment, Flinders University of South Australia, Adelaide, Australia
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28
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Ahrendt T, Miltenberger M, Haneburger I, Kirchner F, Kronenwerth M, Brachmann AO, Hilbi H, Bode HB. Biosynthesis of the natural fluorophore legioliulin from legionella. Chembiochem 2013; 14:1415-8. [PMID: 23821465 DOI: 10.1002/cbic.201300373] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Indexed: 11/07/2022]
Abstract
Let it shine: The biosynthesis of the UV fluorophore legioliulin (1) from Legionella spp. was elucidated and the phenylalanine ammonium lyase LglD responsible for the formation of the starter unit cinnamic acid was biochemically characterized. Additionally, two novel derivatives differing in the starter unit have been identified by mutasynthesis experiments.
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Affiliation(s)
- Tilman Ahrendt
- Merck Stiftungsprofessur für Molekulare Biotechnologie, Fachbereich Biowissenschaften, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
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29
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Escoll P, Rolando M, Gomez-Valero L, Buchrieser C. From amoeba to macrophages: exploring the molecular mechanisms of Legionella pneumophila infection in both hosts. Curr Top Microbiol Immunol 2013; 376:1-34. [PMID: 23949285 DOI: 10.1007/82_2013_351] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Legionella pneumophila is a Gram-negative bacterium and the causative agent of Legionnaires' disease. It replicates within amoeba and infects accidentally human macrophages. Several similarities are seen in the L. pneumophila-infection cycle in both hosts, suggesting that the tools necessary for macrophage infection may have evolved during co-evolution of L. pneumophila and amoeba. The establishment of the Legionella-containing vacuole (LCV) within the host cytoplasm requires the remodeling of the LCV surface and the hijacking of vesicles and organelles. Then L. pneumophila replicates in a safe intracellular niche in amoeba and macrophages. In this review we will summarize the existing knowledge of the L. pneumophila infection cycle in both hosts at the molecular level and compare the factors involved within amoeba and macrophages. This knowledge will be discussed in the light of recent findings from the Acanthamoeba castellanii genome analyses suggesting the existence of a primitive immune-like system in amoeba.
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Affiliation(s)
- Pedro Escoll
- Institut Pasteur, Biologie des Bactéries Intracellulaires and CNRS UMR, 3525, Paris, France
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30
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Beeckman DS, De Puysseleyr L, De Puysseleyr K, Vanrompay D. Chlamydial biology and its associated virulence blockers. Crit Rev Microbiol 2012; 40:313-28. [PMID: 23134414 DOI: 10.3109/1040841x.2012.726210] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Chlamydiales are obligate intracellular parasites of eukaryotic cells. They can be distinguished from other Gram-negative bacteria through their characteristic developmental cycle, in addition to special biochemical and physical adaptations to subvert the eukaryotic host cell. The host spectrum includes humans and other mammals, fish, birds, reptiles, insects and even amoeba, causing a plethora of diseases. The first part of this review focuses on the specific chlamydial infection biology and metabolism. As resistance to classical antibiotics is emerging among Chlamydiae as well, the second part elaborates on specific compounds and tools to block chlamydial virulence traits, such as adhesion and internalization, Type III secretion and modulation of gene expression.
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Affiliation(s)
- Delphine S Beeckman
- Department of Molecular Biotechnology, Faculty of Bioscience Engineering, Ghent University , Coupure Links 653, B-9000 Ghent , Belgium
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Flydal MI, Chatfield CH, Zheng H, Gunderson FF, Aubi O, Cianciotto NP, Martinez A. Phenylalanine hydroxylase from Legionella pneumophila is a thermostable enzyme with a major functional role in pyomelanin synthesis. PLoS One 2012; 7:e46209. [PMID: 23049981 PMCID: PMC3458870 DOI: 10.1371/journal.pone.0046209] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 08/29/2012] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Legionella pneumophila is a pathogenic bacterium that can cause Legionnaires' disease and other non-pneumonic infections in humans. This bacterium produces a pyomelanin pigment, a potential virulence factor with ferric reductase activity. In this work, we have investigated the role of phenylalanine hydroxylase from L. pneumophila (lpPAH), the product of the phhA gene, in the synthesis of the pyomelanin pigment and the growth of the bacterium in defined compositions. METHODOLOGY/PRINCIPAL FINDINGS Comparative studies of wild-type and phhA mutant corroborate that lpPAH provides the excess tyrosine for pigment synthesis. phhA and letA (gacA) appear transcriptionally linked when bacteria were grown in buffered yeast extract medium at 37°C. phhA is expressed in L. pneumophila growing in macrophages. We also cloned and characterized lpPAH, which showed many characteristics of other PAHs studied so far, including Fe(II) requirement for activity. However, it also showed many particular properties such as dimerization, a high conformational thermal stability, with a midpoint denaturation temperature (T(m)) = 79 ± 0.5°C, a high specific activity at 37°C (10.2 ± 0.3 µmol L-Tyr/mg/min) and low affinity for the substrate (K(m) (L-Phe) = 735 ± 50 µM. CONCLUSIONS/SIGNIFICANCE lpPAH has a major functional role in the synthesis of pyomelanin and promotes growth in low-tyrosine media. The high thermal stability of lpPAH might reflect the adaptation of the enzyme to withstand relatively high survival temperatures.
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Affiliation(s)
- Marte I. Flydal
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Christa H. Chatfield
- Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois, United States of America
| | - Huaixin Zheng
- Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois, United States of America
| | - Felizza F. Gunderson
- Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois, United States of America
| | - Oscar Aubi
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Nicholas P. Cianciotto
- Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois, United States of America
| | - Aurora Martinez
- Department of Biomedicine, University of Bergen, Bergen, Norway
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The Yfe and Feo transporters are involved in microaerobic growth and virulence of Yersinia pestis in bubonic plague. Infect Immun 2012; 80:3880-91. [PMID: 22927049 DOI: 10.1128/iai.00086-12] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The Yfe/Sit and Feo transport systems are important for the growth of a variety of bacteria. In Yersinia pestis, single mutations in either yfe or feo result in reduced growth under static (limited aeration), iron-chelated conditions, while a yfe feo double mutant has a more severe growth defect. These growth defects were not observed when bacteria were grown under aerobic conditions or in strains capable of producing the siderophore yersiniabactin (Ybt) and the putative ferrous transporter FetMP. Both fetP and a downstream locus (flp for fet linked phenotype) were required for growth of a yfe feo ybt mutant under static, iron-limiting conditions. An feoB mutation alone had no effect on the virulence of Y. pestis in either bubonic or pneumonic plague models. An feo yfe double mutant was still fully virulent in a pneumonic plague model but had an ∼90-fold increase in the 50% lethal dose (LD(50)) relative to the Yfe(+) Feo(+) parent strain in a bubonic plague model. Thus, Yfe and Feo, in addition to Ybt, play an important role in the progression of bubonic plague. Finally, we examined the factors affecting the expression of the feo operon in Y. pestis. Under static growth conditions, the Y. pestis feo::lacZ fusion was repressed by iron in a Fur-dependent manner but not in cells grown aerobically. Mutations in feoC, fnr, arcA, oxyR, or rstAB had no significant effect on transcription of the Y. pestis feo promoter. Thus, the factor(s) that prevents repression by Fur under aerobic growth conditions remains to be identified.
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Chatfield CH, Mulhern BJ, Viswanathan VK, Cianciotto NP. The major facilitator superfamily-type protein LbtC promotes the utilization of the legiobactin siderophore by Legionella pneumophila. MICROBIOLOGY-SGM 2011; 158:721-735. [PMID: 22160401 DOI: 10.1099/mic.0.055533-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The Gram-negative bacterium Legionella pneumophila elaborates the siderophore legiobactin. We previously showed that cytoplasmic LbtA helps mediate legiobactin synthesis, inner-membrane LbtB promotes export of legiobactin, and outer-membrane LbtU acts as the ferrisiderophore receptor. RT-PCR analyses now identified lbtC as an iron-repressed gene that is the final gene in an operon containing lbtA and lbtB. In silico analysis predicted that LbtC is an inner-membrane protein that belongs to the major facilitator superfamily (MFS). Although capable of normal growth in standard media, lbtC mutants were defective for growth on iron-depleted agar media. While producing normal levels of legiobactin, lbtC mutants were unable to utilize supplied legiobactin to stimulate growth on iron-depleted media and displayed an impaired ability to take up radiolabelled iron. All lbtC mutant phenotypes were complemented by reintroduction of an intact copy of lbtC. When a cloned copy of both lbtC and lbtU was introduced into a heterologous bacterium (Legionella longbeachae), the organism acquired the ability to utilize legiobactin to grow better on low-iron media. Together, these data indicate that LbtC is involved in the uptake of legiobactin, and based upon its predicted location is most likely the mediator of ferrilegiobactin transport across the inner membrane. The data are also a unique documentation of how an MFS protein can promote bacterial iron-siderophore import, standing in contrast to the vast majority of studies which have defined ABC-type permeases as the mediators of siderophore import across the Gram-negative inner membrane or the Gram-positive cytoplasmic membrane.
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Affiliation(s)
- Christa H Chatfield
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, IL 60611, USA
| | - Brendan J Mulhern
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, IL 60611, USA
| | - V K Viswanathan
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, IL 60611, USA
| | - Nicholas P Cianciotto
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, IL 60611, USA
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Shevchuk O, Jäger J, Steinert M. Virulence properties of the legionella pneumophila cell envelope. Front Microbiol 2011; 2:74. [PMID: 21747794 PMCID: PMC3129009 DOI: 10.3389/fmicb.2011.00074] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Accepted: 03/30/2011] [Indexed: 01/15/2023] Open
Abstract
The bacterial envelope plays a crucial role in the pathogenesis of infectious diseases. In this review, we summarize the current knowledge of the structure and molecular composition of the Legionella pneumophila cell envelope. We describe lipopolysaccharides biosynthesis and the biological activities of membrane and periplasmic proteins and discuss their decisive functions during the pathogen–host interaction. In addition to adherence, invasion, and intracellular survival of L. pneumophila, special emphasis is laid on iron acquisition, detoxification, key elicitors of the immune response and the diverse functions of outer membrane vesicles. The critical analysis of the literature reveals that the dynamics and phenotypic plasticity of the Legionella cell surface during the different metabolic stages require more attention in the future.
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Affiliation(s)
- Olga Shevchuk
- Institut für Mikrobiologie, Technische Universität Braunschweig Braunschweig, Germany
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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] [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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Legionella pneumophila LbtU acts as a novel, TonB-independent receptor for the legiobactin siderophore. J Bacteriol 2011; 193:1563-75. [PMID: 21278293 DOI: 10.1128/jb.01111-10] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gram-negative Legionella pneumophila produces a siderophore (legiobactin) that promotes lung infection. We previously determined that lbtA and lbtB are required for the synthesis and secretion of legiobactin. DNA sequence and reverse transcription-PCR (RT-PCR) analyses now reveal the presence of an iron-repressed gene (lbtU) directly upstream of the lbtAB-containing operon. In silico analysis predicted that LbtU is an outer membrane protein consisting of a 16-stranded transmembrane β-barrel, multiple extracellular domains, and short periplasmic tails. Immunoblot analysis of cell fractions confirmed an outer membrane location for LbtU. Although replicating normally in standard media, lbtU mutants, like lbtA mutants, were impaired for growth on iron-depleted agar media. While producing typical levels of legiobactin, lbtU mutants were unable to use supplied legiobactin to stimulate growth on iron-depleted media and displayed an inability to take up iron. Complemented lbtU mutants behaved as the wild type did. The lbtU mutants were also impaired for infection in a legiobactin-dependent manner. Together, these data indicate that LbtU is involved in the uptake of legiobactin and, based upon its location, is most likely the Legionella siderophore receptor. The sequence and predicted two-dimensional (2D) and 3D structures of LbtU were distinct from those of all known siderophore receptors, which generally contain a 22-stranded β-barrel and an extended N terminus that binds TonB in order to transduce energy from the inner membrane. This observation coupled with the fact that L. pneumophila does not encode TonB suggests that LbtU is a new type of receptor that participates in a form of iron uptake that is mechanistically distinct from the existing paradigm.
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Khweek AA, Amer A. Replication of Legionella Pneumophila in Human Cells: Why are We Susceptible? Front Microbiol 2010; 1:133. [PMID: 21687775 PMCID: PMC3109522 DOI: 10.3389/fmicb.2010.00133] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Accepted: 11/16/2010] [Indexed: 11/13/2022] Open
Abstract
Legionella pneumophila is the causative agent of Legionnaires’ disease, a serious and often fatal form of pneumonia. The susceptibility to L. pneumophila arises from the ability of this intracellular pathogen to multiply in human alveolar macrophages and monocytes. L. pneumophila also replicates in several professional and non-professional phagocytic human-derived cell lines. With the exception of the A/J mouse strain, most mice strains are restrictive, thus they do not support L. pneumophila replication. Mice lacking the NOD-like receptor Nlrc4 or caspase-1 are also susceptible to L. pneumophila. On the other hand, in the susceptible human hosts, L. pneumophila utilizes several strategies to ensure intracellular replication and protect itself against the host immune system. Most of these strategies converge to prevent the fusion of the L. pneumophila phagosome with the lysosome, inhibiting host cell apoptosis, activating survival pathways, and sequestering essential nutrients for replication and pathogenesis. In this review, we summarize survival mechanisms employed by L. pneumophila to maintain its replication in human cells. In addition, we highlight different human-derived cell lines that support the multiplication of this intracellular bacterium. Therefore, these in vitro models can be applicable and are reproducible when investigating L. pneumophila/phagocyte interactions at the molecular and cellular levels in the human host.
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Affiliation(s)
- Arwa Abu Khweek
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Center for Microbial Interface Biology and the Department of Internal Medicine, Ohio State University Columbus, OH, USA
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Yip ES, Burnside DM, Cianciotto NP. Cytochrome c4 is required for siderophore expression by Legionella pneumophila, whereas cytochromes c1 and c5 promote intracellular infection. MICROBIOLOGY-SGM 2010; 157:868-878. [PMID: 21178169 PMCID: PMC3081086 DOI: 10.1099/mic.0.046490-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A panel of cytochrome c maturation (ccm) mutants of Legionella pneumophila displayed a loss of siderophore (legiobactin) expression, as measured by both the chrome azurol S assay and a Legionella-specific bioassay. These data, coupled with the finding that ccm transcripts are expressed by wild-type bacteria grown in deferrated medium, indicate that the Ccm system promotes siderophore expression by L. pneumophila. To determine the basis of this newfound role for Ccm, we constructed and tested a set of mutants specifically lacking individual c-type cytochromes. Whereas ubiquinol-cytochrome c reductase (petC) mutants specifically lacking cytochrome c1 and cycB mutants lacking cytochrome c5 had normal siderophore expression, cyc4 mutants defective for cytochrome c4 completely lacked legiobactin. These data, along with the expression pattern of cyc4 mRNA, indicate that cytochrome c4 in particular promotes siderophore expression. In intracellular infection assays, petC mutants and cycB mutants, but not cyc4 mutants, had a reduced ability to infect both amoebae and macrophage hosts. Like ccm mutants, the cycB mutants were completely unable to grow in amoebae, highlighting a major role for cytochrome c5 in intracellular infection. To our knowledge, these data represent both the first direct documentation of the importance of a c-type cytochrome in expression of a biologically active siderophore and the first insight into the relative importance of c-type cytochromes in intracellular infection events.
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Affiliation(s)
- Emily S Yip
- Department of Microbiology and Immunology, Northwestern University Medical School, 320 East Superior St, Chicago, IL 60611, USA
| | - Denise M Burnside
- Department of Microbiology and Immunology, Northwestern University Medical School, 320 East Superior St, Chicago, IL 60611, USA
| | - Nicholas P Cianciotto
- Department of Microbiology and Immunology, Northwestern University Medical School, 320 East Superior St, Chicago, IL 60611, USA
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Abstract
The genus Legionella contains more than 50 species, of which at least 24 have been associated with human infection. The best-characterized member of the genus, Legionella pneumophila, is the major causative agent of Legionnaires' disease, a severe form of acute pneumonia. L. pneumophila is an intracellular pathogen, and as part of its pathogenesis, the bacteria avoid phagolysosome fusion and replicate within alveolar macrophages and epithelial cells in a vacuole that exhibits many characteristics of the endoplasmic reticulum (ER). The formation of the unusual L. pneumophila vacuole is a feature of its interaction with the host, yet the mechanisms by which the bacteria avoid classical endosome fusion and recruit markers of the ER are incompletely understood. Here we review the factors that contribute to the ability of L. pneumophila to infect and replicate in human cells and amoebae with an emphasis on proteins that are secreted by the bacteria into the Legionella vacuole and/or the host cell. Many of these factors undermine eukaryotic trafficking and signaling pathways by acting as functional and, in some cases, structural mimics of eukaryotic proteins. We discuss the consequences of this mimicry for the biology of the infected cell and also for immune responses to L. pneumophila infection.
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40
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Clinical potential of C-reactive protein and procalcitonin serum concentrations to guide differential diagnosis and clinical management of pneumococcal and Legionella pneumonia. J Clin Microbiol 2010; 48:1915-7. [PMID: 20220163 DOI: 10.1128/jcm.01348-09] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We retrospectively analyzed the records of 61 hospitalized patients with community-acquired pneumonia (CAP) caused by Streptococcus pneumoniae or Legionella pneumophila. We found that serum procalcitonin and sodium concentrations were significantly lower, and ferritin levels were significantly higher, in patients infected with L. pneumophila than in those infected with S. pneumoniae. The ratio of C-reactive protein to procalcitonin significantly distinguished between the groups. High procalcitonin levels were associated with an adverse clinical course.
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42
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Structure of the GTPase and GDI domains of FeoB, the ferrous iron transporter of Legionella pneumophila. FEBS Lett 2009; 584:733-8. [DOI: 10.1016/j.febslet.2009.12.045] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 12/21/2009] [Indexed: 01/04/2023]
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Yu MJ, Ren J, Zeng YL, Zhou SN, Lu YJ. The Legionella pneumophila Dps homolog is regulated by iron and involved in multiple stress tolerance. J Basic Microbiol 2009; 49 Suppl 1:S79-86. [PMID: 19455515 DOI: 10.1002/jobm.200800357] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Iron homeostasis is essential to almost all organisms. In this study, we identified the putative homolog of the iron-storage protein-encoding gene, dpsL, in the intracellular pathogen Legionella pneumophila and demonstrated its expression under iron-limited conditions and its responses to multiple stresses. Quantitative real-time PCR analysis indicated that the expression of dpsL was enhanced under iron limitation regardless of the growth phase. Compared with the wild-type cells, the cells devoid of dpsL were heat and H(2)O(2)-sensitive. In contrast to the dps mutants of other bacteria, the growth of the dpsL mutant in an iron-deprived medium was delayed but finally reached the same cell density as wild-type cells during the stationary phase of growth. The finding that the dpsL mutant is salt resistant suggested the involvement of DpsL in virulence.
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Affiliation(s)
- Ming-Jia Yu
- Department of Biochemistry, Sun Yat-sen University Guangzhou, China
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44
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Palusińska-Szysz M, Cendrowska-Pinkosz M. Pathogenicity of the family Legionellaceae. Arch Immunol Ther Exp (Warsz) 2009; 57:279-90. [DOI: 10.1007/s00005-009-0035-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 01/30/2009] [Indexed: 10/20/2022]
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45
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Purification of Legiobactin and importance of this siderophore in lung infection by Legionella pneumophila. Infect Immun 2009; 77:2887-95. [PMID: 19398549 DOI: 10.1128/iai.00087-09] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
When cultured in a low-iron medium, Legionella pneumophila secretes a siderophore (legiobactin) that is both reactive in the chrome azurol S (CAS) assay and capable of stimulating the growth of iron-starved legionellae. Using anion-exchange high-pressure liquid chromatography (HPLC), we purified legiobactin from culture supernatants of a virulent strain of L. pneumophila. In the process, we detected the ferrated form of legiobactin as well as other CAS-reactive substances. Purified legiobactin had a yellow-gold color and absorbed primarily from 220 nm and below. In accordance, nuclear magnetic resonance spectroscopy revealed that legiobactin lacks aromatic carbons, and among the 13 aliphatics present, there were 3 carbonyls. When examined by HPLC, supernatants from L. pneumophila mutants inactivated for lbtA and lbtB completely lacked legiobactin, indicating that the LbtA and LbtB proteins are absolutely required for siderophore activity. Independently derived lbtA mutants, but not a complemented derivative, displayed a reduced ability to infect the lungs of A/J mice after intratracheal inoculation, indicating that legiobactin is required for optimal intrapulmonary survival by L. pneumophila. This defect, however, was not evident when the lbtA mutant and its parental strain were coinoculated into the lung, indicating that legiobactin secreted by the wild type can promote growth of the mutant in trans. Legiobactin mutants grew normally in murine lung macrophages and alveolar epithelial cells, suggesting that legiobactin promotes something other than intracellular infection of resident lung cells. Overall, these data represent the first documentation of a role for siderophore expression in the virulence of L. pneumophila.
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De Buck E, Lammertyn E, Anné J. The importance of the twin-arginine translocation pathway for bacterial virulence. Trends Microbiol 2008; 16:442-53. [PMID: 18715784 DOI: 10.1016/j.tim.2008.06.004] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 05/23/2008] [Accepted: 06/19/2008] [Indexed: 10/21/2022]
Abstract
The twin-arginine translocation (Tat) pathway is a prokaryotic transport system that enables the transport of folded proteins across the cytoplasmic membrane. The Tat pathway was originally thought to transport only proteins that bind cofactors in the cytoplasm and, thus, fold before transport, like many proteins related to energy metabolism. However, in recent years it has become clear that the Tat pathway has a broader role and is also an important virulence factor in different bacterial pathogens. Because the Tat pathway is well conserved among important bacterial pathogens and absent from mammalian cells, it could be a target for novel antimicrobial compounds. In this review, we highlight the importance of the Tat system for virulence in several human and plant pathogens.
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Affiliation(s)
- Emmy De Buck
- Laboratory of Bacteriology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium
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Abstract
Many intracellular pathogens infect macrophages and these pathogens require iron for growth. Here we demonstrate in vitro that the intracellular growth of Chlamydia psittaci, trachomatis, and Legionella pneumophila is regulated by the levels of intracellular iron. Macrophages that express cell surface ferroportin, the only known cellular iron exporter, limit the intracellular growth of these bacteria. Hepcidin is an antimicrobial peptide secreted by the liver in response to inflammation. Hepcidin binds to ferroportin mediating its internalization and degradation. Addition of hepcidin to infected macrophages enhanced the intracellular growth of these pathogens. Macrophages from flatiron mice, a strain heterozygous for a loss-of-function ferroportin mutation, showed enhanced intracellular bacterial growth independent of the presence of exogenous hepcidin. Macrophages, from wild-type or flatiron mice, incubated with the oral iron chelator deferriprone or desferasirox showed reduced intracellular bacterial growth suggesting that these chelators might be therapeutic in chronic intracellular bacterial infections.
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48
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Huston WM, Naylor J, Cianciotto NP, Jennings MP, McEwan AG. Functional analysis of the multi-copper oxidase from Legionella pneumophila. Microbes Infect 2008; 10:497-503. [PMID: 18403241 DOI: 10.1016/j.micinf.2008.01.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 12/20/2007] [Accepted: 01/16/2008] [Indexed: 11/30/2022]
Abstract
Multicopper oxidases have been described to have functions in copper tolerance, manganese oxidation, and iron oxidation in a range of bacteria. The putative cytoplasmic membrane multicopper oxidase from Legionella pneumophila was investigated. The mcoL gene was found to be critical for aerobic extracellular growth under either iron-limiting conditions or in the presence of ferrous Fe(II) iron, as a sole source of this essential metal. The mcoL mutants showed minor growth defects when grown in the presence of Fe(III) as the iron source. In contrast, intracellular growth and survival was not affected by the absence of the mcoL gene regardless of available iron concentration. The evidence presented here could indicate a possible role for mcoL in prevention of the toxic effects of ferrous iron during aerobic conditions. However, a function in high-affinity acquisition of iron could also be possible given the inability of the McoL mutants to grow aerobically under iron-limiting conditions.
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Affiliation(s)
- Wilhelmina M Huston
- Centre for Metals in Biology and School of Molecular and Microbial Sciences, University of Queensland, St Lucia, QLD 4072, Australia
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Hindré T, Brüggemann H, Buchrieser C, Héchard Y. Transcriptional profiling of Legionella pneumophila biofilm cells and the influence of iron on biofilm formation. Microbiology (Reading) 2008; 154:30-41. [DOI: 10.1099/mic.0.2007/008698-0] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Affiliation(s)
- Thomas Hindré
- Laboratoire de Chimie de l'Eau et de l'Environnement, UMR 6008, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers Cedex, France
| | - Holger Brüggemann
- Unité de Génomique des Microorganismes Pathogènes and CNRS URA 2171, Institut Pasteur, 28 Rue du Dr Roux, 75724 Paris, France
| | - Carmen Buchrieser
- Unité de Génomique des Microorganismes Pathogènes and CNRS URA 2171, Institut Pasteur, 28 Rue du Dr Roux, 75724 Paris, France
| | - Yann Héchard
- Laboratoire de Chimie de l'Eau et de l'Environnement, UMR 6008, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers Cedex, France
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Boulette ML, Payne SM. Anaerobic regulation of Shigella flexneri virulence: ArcA regulates Fur and iron acquisition genes. J Bacteriol 2007; 189:6957-67. [PMID: 17660284 PMCID: PMC2045222 DOI: 10.1128/jb.00621-07] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Invasion and plaque formation in epithelial monolayers are routinely used to assess the virulence of Shigella flexneri, a causative agent of dysentery. A modified plaque assay was developed to identify factors contributing to the virulence of S. flexneri under the anaerobic conditions present in the colon. This assay demonstrated the importance of the ferrous iron transport system Feo, as well as the global transcription factors Fur, ArcA, and Fnr, for Shigella plaque formation in anoxic environments. Transcriptional analyses of S. flexneri iron transport genes indicated that anaerobic conditions activated feoABC while repressing genes encoding two other iron transport systems, the ABC transporter Sit and the Iuc/Iut aerobactin siderophore synthesis and transport system. The anaerobic transcription factors ArcA and Fnr activated expression of feoABC, while ArcA repressed iucABCD iutA. Transcription of fur, encoding the iron-responsive transcriptional repressor of bacterial iron acquisition, was also repressed anaerobically in an ArcA-dependent manner.
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