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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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Legionella pneumophila PPIase Mip Interacts with the Bacterial Proteins SspB, Lpc2061, and FlaA and Promotes Flagellation. Infect Immun 2022; 90:e0027622. [PMID: 36314784 PMCID: PMC9670971 DOI: 10.1128/iai.00276-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The peptidyl-prolyl-
cis/trans
-isomerase (PPIase) macrophage infectivity potentiator (Mip) contributes to the pathogenicity and fitness of
L. pneumophila
, the causative agent of Legionnaires’ disease. Here, we identified the stringent starvation protein SspB, hypothetical protein Lpc2061, and flagellin FlaA as bacterial interaction partners of Mip.
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3
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Campbell JA, Cianciotto NP. Legionella pneumophila Cas2 Promotes the Expression of Small Heat Shock Protein C2 That Is Required for Thermal Tolerance and Optimal Intracellular Infection. Infect Immun 2022; 90:e0036922. [PMID: 36073935 PMCID: PMC9584283 DOI: 10.1128/iai.00369-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 08/24/2022] [Indexed: 11/20/2022] Open
Abstract
Previously, we demonstrated that Cas2 encoded within the CRISPR-Cas locus of Legionella pneumophila strain 130b promotes the ability of the Legionella pathogen to infect amoebal hosts. Given that L. pneumophila Cas2 has RNase activity, we posited that the cytoplasmic protein is regulating the expression of another Legionella gene(s) that fosters intracellular infection. Proteomics revealed 10 proteins at diminished levels in the cas2 mutant, and reverse transcription-quantitative (qRT-PCR) confirmed the reduced expression of a gene encoding putative small heat shock protein C2 (HspC2), among several others. As predicted, the gene was expressed more highly at 37°C to 50°C than that at 30°C, and an hspC2 mutant, but not its complemented derivative, displayed ~100-fold reduced CFU following heat shock at 55°C. Compatible with the effect of Cas2 on hspC2 expression, strains lacking Cas2 also had impaired thermal tolerance. The hspC2 mutant, like the cas2 mutant before it, was greatly impaired for infection of Acanthamoeba castellanii, a frequent host for legionellae in waters. HspC2 and Cas2 were not required for entry into these host cells but promoted the replicative phase of intracellular infection. Finally, the hspC2 mutant exhibited an additional defect during the infection of macrophages, which are the primary host for legionellae during lung infection. In summary, hspC2 is upregulated by the presence of Cas2, and HspC2 uniquely promotes both L. pneumophila extracellular survival at high temperatures and infection of amoebal and human host cells. To our knowledge, these findings also represent the first genetic proof linking Cas2 to thermotolerance, expanding the repertoire of noncanonical functions associated with CRISPR-Cas proteins.
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Affiliation(s)
- Jackson A. Campbell
- 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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Human macrophages utilize a wide range of pathogen recognition receptors to recognize Legionella pneumophila, including Toll-Like Receptor 4 engaging Legionella lipopolysaccharide and the Toll-like Receptor 3 nucleic-acid sensor. PLoS Pathog 2021; 17:e1009781. [PMID: 34280250 PMCID: PMC8321404 DOI: 10.1371/journal.ppat.1009781] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 07/29/2021] [Accepted: 07/03/2021] [Indexed: 12/15/2022] Open
Abstract
Cytokines made by macrophages play a critical role in determining the course of Legionella pneumophila infection. Prior murine-based modeling indicated that this cytokine response is initiated upon recognition of L. pneumophila by a subset of Toll-like receptors, namely TLR2, TLR5, and TLR9. Through the use of shRNA/siRNA knockdowns and subsequently CRISPR/Cas9 knockouts (KO), we determined that TRIF, an adaptor downstream of endosomal TLR3 and TLR4, is required for full cytokine secretion by human primary and cell-line macrophages. By characterizing a further set of TLR KO's in human U937 cells, we discerned that, contrary to the viewpoint garnered from murine-based studies, TLR3 and TLR4 (along with TLR2 and TLR5) are in fact vital to the macrophage response in the early stages of L. pneumophila infection. This conclusion was bolstered by showing that i) chemical inhibitors of TLR3 and TLR4 dampen the cytokine output of primary human macrophages and ii) transfection of TLR3 and TLR4 into HEK cells conferred an ability to sense L. pneumophila. TLR3- and TLR4-dependent cytokines promoted migration of human HL-60 neutrophils across an epithelial layer, pointing to the biological importance for the newfound signaling pathway. The response of U937 cells to L. pneumophila LPS was dependent upon TLR4, a further contradiction to murine-based studies, which had concluded that TLR2 is the receptor for Legionella LPS. Given the role of TLR3 in sensing nucleic acid (i.e., dsRNA), we utilized newly-made KO U937 cells to document that DNA-sensing by cGAS-STING and DNA-PK are also needed for the response of human macrophages to L. pneumophila. Given the lack of attention given them in the bacterial field, C-type lectin receptors were similarly examined; but, they were not required. Overall, this study arguably represents the most extensive, single-characterization of Legionella-recognition receptors within human macrophages.
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Hasni I, Jarry A, Quelard B, Carlino A, Eberst JB, Abbe O, Demanèche S. Intracellular Behaviour of Three Legionella pneumophila Strains within Three Amoeba Strains, Including Willaertia magna C2c Maky. Pathogens 2020; 9:pathogens9020105. [PMID: 32041369 PMCID: PMC7168187 DOI: 10.3390/pathogens9020105] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 02/04/2020] [Accepted: 02/05/2020] [Indexed: 12/12/2022] Open
Abstract
Legionella pneumophila is a facultative intracellular pathogen found in aquatic environments as planktonic cells within biofilms and as intracellular parasites of free-living amoebae such as Acanthamoeba castellanii. This pathogen bypasses the elimination mechanism to replicate within amoebae; however, not all amoeba species support the growth of L. pneumophila. Willaertia magna C2c Maky, a non-pathogenic amoeba, was previously demonstrated to possess the ability to eliminate the L. pneumophila strain Paris. Here, we study the intracellular behaviour of three L. pneumophila strains (Paris, Philadelphia, and Lens) within W. magna C2c Maky and compare this strain to A. castellanii and W. magna Z503, which are used as controls. We observe the intracellular growth of strain Lens within W. magna Z503 and A. castellanii at 22 °C and 37 °C. Strain Paris grows within A. castellanii at any temperature, while it only grows at 22 °C within W. magna Z503. Strain Philadelphia proliferates only within A. castellanii at 37 °C. Within W. magna C2c Maky, none of the three legionella strains exhibit intracellular growth. Additionally, the ability of W. magna C2c Maky to decrease the number of internalized L. pneumophila is confirmed. These results support the idea that W. magna C2c Maky possesses unique behaviour in regard to L. pneumophila strains.
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Affiliation(s)
- Issam Hasni
- Microbes, Evolution, Phylogeny and Infection Department, Institut de Recherche pour le Développement IRD 198, Institut Hospitalo-Universitaire (IHU), Aix-Marseille Université, 13007 Marseille, France;
- R&D Department, Amoéba, 38 Avenue des Frères Montgolfier, 69680 Chassieu, France; (A.J.); (B.Q.); (A.C.); (J.-B.E.); (O.A.)
| | - Antoine Jarry
- R&D Department, Amoéba, 38 Avenue des Frères Montgolfier, 69680 Chassieu, France; (A.J.); (B.Q.); (A.C.); (J.-B.E.); (O.A.)
| | - Benjamin Quelard
- R&D Department, Amoéba, 38 Avenue des Frères Montgolfier, 69680 Chassieu, France; (A.J.); (B.Q.); (A.C.); (J.-B.E.); (O.A.)
| | - Antoine Carlino
- R&D Department, Amoéba, 38 Avenue des Frères Montgolfier, 69680 Chassieu, France; (A.J.); (B.Q.); (A.C.); (J.-B.E.); (O.A.)
| | - Jean-Baptiste Eberst
- R&D Department, Amoéba, 38 Avenue des Frères Montgolfier, 69680 Chassieu, France; (A.J.); (B.Q.); (A.C.); (J.-B.E.); (O.A.)
| | - Olivier Abbe
- R&D Department, Amoéba, 38 Avenue des Frères Montgolfier, 69680 Chassieu, France; (A.J.); (B.Q.); (A.C.); (J.-B.E.); (O.A.)
| | - Sandrine Demanèche
- R&D Department, Amoéba, 38 Avenue des Frères Montgolfier, 69680 Chassieu, France; (A.J.); (B.Q.); (A.C.); (J.-B.E.); (O.A.)
- Correspondence:
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Hasni I, Chelkha N, Baptiste E, Mameri MR, Lachuer J, Plasson F, Colson P, La Scola B. Investigation of potential pathogenicity of Willaertia magna by investigating the transfer of bacteria pathogenicity genes into its genome. Sci Rep 2019; 9:18318. [PMID: 31797948 PMCID: PMC6892926 DOI: 10.1038/s41598-019-54580-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 11/10/2019] [Indexed: 12/14/2022] Open
Abstract
Willaertia magna c2c maky is a thermophilic amoeba closely related to the genus Naegleria. This free-living amoeba has the ability to eliminate Legionella pneumophila, which is an amoeba-resisting bacterium living in an aquatic environment. To prevent the proliferation of L. pneumophila in cooling towers, the use of W. magna as natural biocide has been proposed. To provide a better understanding of the W. magna genome, whole-genome sequencing was performed through the study of virulence factors and lateral gene transfers. This amoeba harbors a genome of 36.5 megabases with 18,519 predicted genes. BLASTp analyses reported protein homology between 136 W. magna sequences and amoeba-resistant microorganisms. Horizontal gene transfers were observed based on the basis of the phylogenetic reconstruction hypothesis. We detected 15 homologs of N. fowleri genes related to virulence, although these latter were also found in the genome of N. gruberi, which is a non-pathogenic amoeba. Furthermore, the cytotoxicity test performed on human cells supports the hypothesis that the strain c2c maky is a non-pathogenic amoeba. This work explores the genomic repertory for the first draft genome of genus Willaertia and provides genomic data for further comparative studies on virulence of related pathogenic amoeba, N. fowleri.
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Affiliation(s)
- Issam Hasni
- Aix-Marseille Université UM63, Institut de Recherche pour le Développement IRD 198, Assistance Publique - Hôpitaux de Marseille (AP-HM), Microbes, Evolution, Phylogeny and Infection (MEΦI), Institut Hospitalo-Universitaire (IHU) - Méditerranée Infection, Marseille, France.,Amoéba, Chassieu, France
| | - Nisrine Chelkha
- Aix-Marseille Université UM63, Institut de Recherche pour le Développement IRD 198, Assistance Publique - Hôpitaux de Marseille (AP-HM), Microbes, Evolution, Phylogeny and Infection (MEΦI), Institut Hospitalo-Universitaire (IHU) - Méditerranée Infection, Marseille, France
| | - Emeline Baptiste
- Aix-Marseille Université UM63, Institut de Recherche pour le Développement IRD 198, Assistance Publique - Hôpitaux de Marseille (AP-HM), Microbes, Evolution, Phylogeny and Infection (MEΦI), Institut Hospitalo-Universitaire (IHU) - Méditerranée Infection, Marseille, France
| | | | - Joel Lachuer
- ProfileXpert/Viroscan3D, UCBL UMS 3453 CNRS - US7 INSERM, Lyon, France.,Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Lyon, France.,Université de Lyon, Lyon, France
| | | | - Philippe Colson
- Aix-Marseille Université UM63, Institut de Recherche pour le Développement IRD 198, Assistance Publique - Hôpitaux de Marseille (AP-HM), Microbes, Evolution, Phylogeny and Infection (MEΦI), Institut Hospitalo-Universitaire (IHU) - Méditerranée Infection, Marseille, France
| | - Bernard La Scola
- Aix-Marseille Université UM63, Institut de Recherche pour le Développement IRD 198, Assistance Publique - Hôpitaux de Marseille (AP-HM), Microbes, Evolution, Phylogeny and Infection (MEΦI), Institut Hospitalo-Universitaire (IHU) - Méditerranée Infection, Marseille, France.
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7
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Tsao HF, Scheikl U, Herbold C, Indra A, Walochnik J, Horn M. The cooling tower water microbiota: Seasonal dynamics and co-occurrence of bacterial and protist phylotypes. WATER RESEARCH 2019; 159:464-479. [PMID: 31128471 PMCID: PMC6554697 DOI: 10.1016/j.watres.2019.04.028] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 04/04/2019] [Accepted: 04/13/2019] [Indexed: 05/30/2023]
Abstract
Cooling towers for heating, ventilation and air conditioning are ubiquitous in the built environment. Often located on rooftops, their semi-open water basins provide a suitable environment for microbial growth. They are recognized as a potential source of bacterial pathogens and have been associated with disease outbreaks such as Legionnaires' disease. While measures to minimize public health risks are in place, the general microbial and protist community structure and dynamics in these systems remain largely elusive. In this study, we analysed the microbiome of the bulk water from the basins of three cooling towers by 16S and 18S rRNA gene amplicon sequencing over the course of one year. Bacterial diversity in all three towers was broadly comparable to other freshwater systems, yet less diverse than natural environments; the most abundant taxa are also frequently found in freshwater or drinking water. While each cooling tower had a pronounced site-specific microbial community, taxa shared among all locations mainly included groups generally associated with biofilm formation. We also detected several groups related to known opportunistic pathogens, such as Legionella, Mycobacterium, and Pseudomonas species, albeit at generally low abundance. Although cooling towers represent a rather stable environment, microbial community composition was highly dynamic and subject to seasonal change. Protists are important members of the cooling tower water microbiome and known reservoirs for bacterial pathogens. Co-occurrence analysis of bacteria and protist taxa successfully captured known interactions between amoeba-associated bacteria and their hosts, and predicted a large number of additional relationships involving ciliates and other protists. Together, this study provides an unbiased and comprehensive overview of microbial diversity of cooling tower water basins, establishing a framework for investigating and assessing public health risks associated with these man-made freshwater environments.
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Affiliation(s)
- Han-Fei Tsao
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Ute Scheikl
- Institute of Specific Prophylaxis and Tropical Medicine, Medical University of Vienna, Vienna, Austria
| | - Craig Herbold
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Alexander Indra
- Department of Mycobacteriology and Clinical Molecular Biology, AGES, Vienna, Austria
| | - Julia Walochnik
- Institute of Specific Prophylaxis and Tropical Medicine, Medical University of Vienna, Vienna, Austria
| | - Matthias Horn
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria.
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Unsal T, Cansever N, Ilhan-Sungur E. Impact of biofilm in the maturation process on the corrosion behavior of galvanized steel: long-term evaluation by EIS. World J Microbiol Biotechnol 2019; 35:22. [PMID: 30656423 DOI: 10.1007/s11274-019-2592-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 01/10/2019] [Indexed: 01/06/2023]
Abstract
In this study, the effect of biofilm in the maturation process on the corrosion behavior of galvanized steel was investigated in a model of a recirculating water system over 6 months. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods were used to determine the corrosion behavior of galvanized steel. The biofilm and corrosion products on the galvanized steel surfaces were investigated by using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). EIS results showed that the structure of the biofilm changed during the maturation process over time and the altering structure of the biofilm affects the corrosion behavior of galvanized steel. Also, EIS analyses validated that the biofilm has a dynamic and complex structure. The data obtained from SEM and macroscopic images indicated that EIS is an effective method for monitoring the biofilm-development process.
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Affiliation(s)
- Tuba Unsal
- Faculty of Science, Department of Biology, Istanbul University, Vezneciler, 34134, Istanbul, Turkey.
| | - Nurhan Cansever
- Faculty of Chemistry-Metallurgy, Metallurgical and Materials Engineering Department, Yildiz Technical University, Esenler, 34210, Istanbul, Turkey
| | - Esra Ilhan-Sungur
- Faculty of Science, Department of Biology, Istanbul University, Vezneciler, 34134, Istanbul, Turkey
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9
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Miller HC, Morgan MJ, Walsh T, Wylie JT, Kaksonen AH, Puzon GJ. Preferential feeding in Naegleria fowleri; intracellular bacteria isolated from amoebae in operational drinking water distribution systems. WATER RESEARCH 2018; 141:126-134. [PMID: 29783165 DOI: 10.1016/j.watres.2018.05.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 05/04/2018] [Accepted: 05/04/2018] [Indexed: 06/08/2023]
Abstract
The amoeba Naegleria fowleri is the causative agent of the highly fatal disease, primary amoebic meningoencephalitis, and estimated to cause 16 deaths per year in the United States alone. Colonisation of drinking water distribution systems (DWDSs) by the N. fowleri is a significant public health issue. Understanding the factors which enable this pathogen to colonise and thrive in DWDSs is critical for proper management. The microbial ecology within DWDSs may influence the ability of N. fowleri to colonise DWDSs by facilitating the availability of an appropriate food source. Using biofilm samples obtained from operational DWDSs, 16S rRNA amplicon metabarcoding was combined with genus-specific PCR and Sanger sequencing of intracellular associated bacteria from isolated amoeba and their parental biofilms to identify Meiothermus chliarophilus as a potential food source for N. fowleri. Meiothermus was confirmed as a food source for N. fowleri following successful serial culturing of axenic N. fowleri with M. chliarophilus or M. ruber as the sole food source. The ability to identify environmental and ecological conditions favourable to N. fowleri colonisation, including the detection of appropriate food sources such as Meiothermus, could provide water utilities with a predictive tool for managing N. fowleri colonisation within the DWDS.
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Affiliation(s)
- Haylea C Miller
- CSIRO Land and Water, Private Bag No.5, Wembley, Western Australia 6913, Australia; School of Biomedical Sciences, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
| | - Matthew J Morgan
- CSIRO Land and Water, Black Mountain Laboratories, P.O. Box 1700, Canberra, ACT, 2601, Australia
| | - Tom Walsh
- CSIRO Land and Water, Black Mountain Laboratories, P.O. Box 1700, Canberra, ACT, 2601, Australia
| | - Jason T Wylie
- CSIRO Land and Water, Private Bag No.5, Wembley, Western Australia 6913, Australia
| | - Anna H Kaksonen
- CSIRO Land and Water, Private Bag No.5, Wembley, Western Australia 6913, Australia; School of Biomedical Sciences, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
| | - Geoffrey J Puzon
- CSIRO Land and Water, Private Bag No.5, Wembley, Western Australia 6913, Australia.
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Gomaa F, Gersh M, Cavanaugh CM. Diverse Legionella-Like Bacteria Associated with Testate Amoebae of the Genus Arcella (Arcellinida: Amoebozoa). J Eukaryot Microbiol 2018; 65:661-668. [PMID: 29443446 DOI: 10.1111/jeu.12511] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 01/03/2018] [Accepted: 02/03/2018] [Indexed: 12/11/2022]
Abstract
Diverse species of Legionella and Legionella-like amoebal pathogens (LLAPs) have been identified as intracellular bacteria in many amoeboid protists. There are, however, other amoeboid groups such as testate amoeba for which we know little about their potential to host such bacteria. In this study, we assessed the occurrence and diversity of Legionella spp. in cultures and environmental isolates of freshwater arcellinid testate amoebae species, Arcella hemispherica, Arcella intermedia, and Arcella vulgaris, via 16S rRNA gene sequence analyses and fluorescent in situ hybridization (FISH). Analysis of the 16S rRNA gene sequences indicated that A. hemispherica, A. intermedia, and A. vulgaris host Legionella-like bacteria with 94-98% identity to other Legionella spp. based on NCBI BLAST search. Phylogenetic analysis placed Legionella-like Arcella-associated bacteria (LLAB) in three different clusters within a tree containing all other members of Legionella and LLAPs. The intracellular localization of the Legionella within Arcella hosts was confirmed using FISH with a Legionella-specific probe. This study demonstrates that the host range of Legionella and Legionella-like bacteria in the Amoebozoa extends beyond members of "naked" amoebae species, with members of the testate amoebae potentially serving an ecological role in the dispersal, protection, and replication of Legionella spp. in natural environments.
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Affiliation(s)
- Fatma Gomaa
- Department of Organismic and Evolutionary Biology, Biological Laboratory, Harvard University, Cambridge, Massachusetts, 02138, USA
| | - Maxim Gersh
- Department of Organismic and Evolutionary Biology, Biological Laboratory, Harvard University, Cambridge, Massachusetts, 02138, USA
| | - Colleen M Cavanaugh
- Department of Organismic and Evolutionary Biology, Biological Laboratory, Harvard University, Cambridge, Massachusetts, 02138, USA
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11
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Llewellyn AC, Lucas CE, Roberts SE, Brown EW, Nayak BS, Raphael BH, Winchell JM. Distribution of Legionella and bacterial community composition among regionally diverse US cooling towers. PLoS One 2017; 12:e0189937. [PMID: 29261791 PMCID: PMC5738086 DOI: 10.1371/journal.pone.0189937] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 12/05/2017] [Indexed: 11/19/2022] Open
Abstract
Cooling towers (CTs) are a leading source of outbreaks of Legionnaires' disease (LD), a severe form of pneumonia caused by inhalation of aerosols containing Legionella bacteria. Accordingly, proper maintenance of CTs is vital for the prevention of LD. The aim of this study was to determine the distribution of Legionella in a subset of regionally diverse US CTs and characterize the associated microbial communities. Between July and September of 2016, we obtained aliquots from water samples collected for routine Legionella testing from 196 CTs located in eight of the nine continental US climate regions. After screening for Legionella by PCR, positive samples were cultured and the resulting Legionella isolates were further characterized. Overall, 84% (164) were PCR-positive, including samples from every region studied. Of the PCR-positive samples, Legionella spp were isolated from 47% (78), L. pneumophila was isolated from 32% (53), and L. pneumophila serogroup 1 (Lp1) was isolated from 24% (40). Overall, 144 unique Legionella isolates were identified; 53% (76) of these were Legionella pneumophila. Of the 76 L. pneumophila isolates, 51% (39) were Lp1. Legionella were isolated from CTs in seven of the eight US regions examined. 16S rRNA amplicon sequencing was used to compare the bacterial communities of CT waters with and without detectable Legionella as well as the microbiomes of waters from different climate regions. Interestingly, the microbial communities were homogenous across climate regions. When a subset of seven CTs sampled in April and July were compared, there was no association with changes in corresponding CT microbiomes over time in the samples that became culture-positive for Legionella. Legionella species and Lp1 were detected frequently among the samples examined in this first large-scale study of Legionella in US CTs. Our findings highlight that, under the right conditions, there is the potential for CT-related LD outbreaks to occur throughout the US.
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Affiliation(s)
- Anna C. Llewellyn
- Laboratory Leadership Service, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
- Pneumonia Response and Surveillance Laboratory, Respiratory Disease Branch, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Claressa E. Lucas
- Pneumonia Response and Surveillance Laboratory, Respiratory Disease Branch, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Sarah E. Roberts
- Pneumonia Response and Surveillance Laboratory, Respiratory Disease Branch, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Ellen W. Brown
- Pneumonia Response and Surveillance Laboratory, Respiratory Disease Branch, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Bina S. Nayak
- Water Quality Division, Pinellas County Utilities, Largo, FL, United States of America
| | - Brian H. Raphael
- Pneumonia Response and Surveillance Laboratory, Respiratory Disease Branch, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Jonas M. Winchell
- Pneumonia Response and Surveillance Laboratory, Respiratory Disease Branch, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
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Iervolino M, Mancini B, Cristino S. Industrial Cooling Tower Disinfection Treatment to Prevent Legionella spp. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2017; 14:E1125. [PMID: 28954435 PMCID: PMC5664626 DOI: 10.3390/ijerph14101125] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 09/19/2017] [Accepted: 09/22/2017] [Indexed: 01/22/2023]
Abstract
The contamination of industrial cooling towers has been identified as one cause of legionellosis, but the real risk has been underestimated. Two different disinfection treatments were tested on Legionella colonization in an industrial Cooling Tower System (CTS). Environmental monitoring of Legionella, P. aeruginosa, and a heterotrophic plate count (HPC) at 36 °C was performed from June to October 2016. The disinfection procedures adopted were based on hydrogen peroxide (H₂O₂) and silver salts (Ag⁺), in addition to an anti-algal treatment, then using hyperclorination as a shock, and then continuous treatment by sodium hypochlorite (NaClO). L. pneumophila serogroup 8 was found at a concentration of 5.06 Log cfu/L after the CTS filling; a shock treatment performed by H₂O₂/Ag⁺ produced a rapid increase in contamination up to 6.14 Log cfu/L. The CTS activity was stopped and two subsequent shock treatments were performed using NaClO, followed by continuous hyperclorination. These procedures showed a significant decrease (p < 0.05) in Legionella concentration (1.77 Log cfu/L). The same trend was observed for P. aeruginosa (0.55 Log cfu/100 mL) and HPC (1.95 Log cfu/mL) at 36 °C. Environmental monitoring and the adoption of maintenance procedures, including anti-scale treatment, and physical, chemical, and microbiological control, ensure the good performance of a CTS, reducing the Legionella risk for public health.
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Affiliation(s)
- Matteo Iervolino
- Department of Biological, Geological and Environmental Sciences, BiGeA, University of Bologna, via San Giacomo 12, 40126 Bologna, Italy.
| | - Benedetta Mancini
- Department of Biological, Geological and Environmental Sciences, BiGeA, University of Bologna, via San Giacomo 12, 40126 Bologna, Italy.
| | - Sandra Cristino
- Department of Biological, Geological and Environmental Sciences, BiGeA, University of Bologna, via San Giacomo 12, 40126 Bologna, Italy.
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Occurrence of Infected Free-Living Amoebae in Cooling Towers of Southern Brazil. Curr Microbiol 2017; 74:1461-1468. [PMID: 28840339 DOI: 10.1007/s00284-017-1341-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 08/17/2017] [Indexed: 12/25/2022]
Abstract
This study determined the occurrence of potentially pathogenic free-living amoebae (FLA) and bacteria associated with amoebae in air-conditioning cooling towers in southern Brazil. Water samples were collected from 36 cooling systems from air-conditioning in the state of Rio Grande do Sul, Brazil. The organisms were identified using polymerase chain reaction (PCR) and sequencing automated. The results showed that these aquatic environments, with variable temperature, are potential "hot spots" for emerging human pathogens like free-living amoebae and bacteria associated. In total, 92% of the cooling-tower samples analyzed were positive for FLA, and Acanthamoeba was the dominant genus by culture and PCR. Amoebal isolates revealed intracellular bacteria in 39.3% of them and all were confirmed as members of the genus Pseudomonas. The results obtained show the important role of cooling towers as a source of amoebae-associated pathogens.
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White RC, Cianciotto NP. Type II Secretion Is Necessary for Optimal Association of the Legionella-Containing Vacuole with Macrophage Rab1B but Enhances Intracellular Replication Mainly by Rab1B-Independent Mechanisms. Infect Immun 2016; 84:3313-3327. [PMID: 27600508 PMCID: PMC5116710 DOI: 10.1128/iai.00750-16] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 08/31/2016] [Indexed: 12/12/2022] Open
Abstract
Previously, we documented that type II secretion (T2S) promotes intracellular infection of macrophages by Legionella pneumophila In the present study, we identified infection events that are modulated by T2S by comparing the behaviors of wild-type and T2S mutant bacteria in murine bone marrow-derived macrophages and human U937 cells. Although the two strains behaved similarly for entry into the host cells and evasion of lysosomal fusion, the mutant was impaired in the ability to initiate replication between 4 and 8 h postentry and to grow to large numbers in the Legionella-containing vacuole (LCV), as evident at 12 h. At 4 h postinoculation, mutant LCVs had a significantly reduced association with Rab1B, a host GTPase that facilitates the tethering of endoplasmic reticulum (ER)-derived vesicles to LCVs. The mutant did not lose expression or translocation of six type IV secretion effectors (e.g., SidM) that are well known for mediating Rab1B association with the LCV, indicating that T2S promotes the interaction between the LCV and Rab1B via a novel mechanism. Interestingly, the mutant's growth defect was exacerbated in macrophages that had been depleted of Rab1B by short hairpin RNA (shRNA) treatment, indicating that T2S also potentiates events beyond Rab1B association. In support of this, a sidM lspF double mutant had an intracellular growth defect that was more dramatic than that of the lspF mutant (and a sidM mutant) and showed a growth difference of as much as a 400-fold compared to the wild type. Together, these data reveal a new role for T2S in intracellular infection that involves both Rab1B-dependent and Rab1B-independent processes.
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Affiliation(s)
- Richard C White
- 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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Scheikl U, Tsao HF, Horn M, Indra A, Walochnik J. Free-living amoebae and their associated bacteria in Austrian cooling towers: a 1-year routine screening. Parasitol Res 2016; 115:3365-74. [PMID: 27177720 PMCID: PMC4980419 DOI: 10.1007/s00436-016-5097-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 04/27/2016] [Indexed: 12/15/2022]
Abstract
Free-living amoebae (FLA) are widely spread in the environment and known to cause rare but often serious infections. Besides this, FLA may serve as vehicles for bacterial pathogens. In particular, Legionella pneumophila is known to replicate within FLA thereby also gaining enhanced infectivity. Cooling towers have been the source of outbreaks of Legionnaires' disease in the past and are thus usually screened for legionellae on a routine basis, not considering, however, FLA and their vehicle function. The aim of this study was to incorporate a screening system for host amoebae into a Legionella routine screening. A new real-time PCR-based screening system for various groups of FLA was established. Three cooling towers were screened every 2 weeks over the period of 1 year for FLA and Legionella spp., by culture and molecular methods in parallel. Altogether, 83.3 % of the cooling tower samples were positive for FLA, Acanthamoeba being the dominating genus. Interestingly, 69.7 % of the cooling tower samples were not suitable for the standard Legionella screening due to their high organic burden. In the remaining samples, positivity for Legionella spp. was 25 % by culture, but overall positivity was 50 % by molecular methods. Several amoebal isolates revealed intracellular bacteria.
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Affiliation(s)
- Ute Scheikl
- Institute of Specific Prophylaxis and Tropical Medicine, Medical University of Vienna, Vienna, Austria
| | - Han-Fei Tsao
- Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, University of Vienna, Vienna, Austria
| | - Matthias Horn
- Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, University of Vienna, Vienna, Austria
| | - Alexander Indra
- Department of Mycobacteriology and Clinical Molecular Biology, AGES, Vienna, Austria
| | - Julia Walochnik
- Institute of Specific Prophylaxis and Tropical Medicine, Medical University of Vienna, Vienna, Austria.
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16
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Pécastaings S, Allombert J, Lajoie B, Doublet P, Roques C, Vianney A. New insights into Legionella pneumophila biofilm regulation by c-di-GMP signaling. BIOFOULING 2016; 32:935-948. [PMID: 27494738 DOI: 10.1080/08927014.2016.1212988] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Accepted: 07/07/2016] [Indexed: 06/06/2023]
Abstract
The waterborne pathogen Legionella pneumophila grows as a biofilm, freely or inside amoebae. Cyclic-di-GMP (c-di-GMP), a bacterial second messenger frequently implicated in biofilm formation, is synthesized and degraded by diguanylate cyclases (DGCs) and phosphodiesterases (PDEs), respectively. To characterize the c-di-GMP-metabolizing enzymes involved in L. pneumophila biofilm regulation, the consequences on biofilm formation and the c-di-GMP concentration of each corresponding gene inactivation were assessed in the Lens strain. The results showed that one DGC and two PDEs enhance different aspects of biofilm formation, while two proteins with dual activity (DGC/PDE) inhibit biofilm growth. Surprisingly, only two mutants exhibited a change in global c-di-GMP concentration. This study highlights that specific c-di-GMP pathways control L. pneumophila biofilm formation, most likely via temporary and/or local modulation of c-di-GMP concentration. Furthermore, Lpl1054 DGC is required to enable the formation a dense biofilm in response to nitric oxide, a signal for biofilm dispersion in many other species.
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Affiliation(s)
- Sophie Pécastaings
- a Laboratoire de Génie chimique UMR 5503 , UPS, Université de Toulouse , Toulouse , France
| | - Julie Allombert
- b CIRI, International Center for Infectiology Research , Legionella Pathogenesis Group, Université de Lyon , Lyon , France
- c Inserm , Lyon , France
- d Ecole Normale Supérieure de Lyon , Lyon , France
- e Université Lyon 1, CIRI, International Center for Infectiology Research , Lyon , France
- f CNRS , Lyon , France
| | - Barbora Lajoie
- a Laboratoire de Génie chimique UMR 5503 , UPS, Université de Toulouse , Toulouse , France
| | - Patricia Doublet
- b CIRI, International Center for Infectiology Research , Legionella Pathogenesis Group, Université de Lyon , Lyon , France
- c Inserm , Lyon , France
- d Ecole Normale Supérieure de Lyon , Lyon , France
- e Université Lyon 1, CIRI, International Center for Infectiology Research , Lyon , France
- f CNRS , Lyon , France
| | - Christine Roques
- a Laboratoire de Génie chimique UMR 5503 , UPS, Université de Toulouse , Toulouse , France
| | - Anne Vianney
- b CIRI, International Center for Infectiology Research , Legionella Pathogenesis Group, Université de Lyon , Lyon , France
- c Inserm , Lyon , France
- d Ecole Normale Supérieure de Lyon , Lyon , France
- e Université Lyon 1, CIRI, International Center for Infectiology Research , Lyon , France
- f CNRS , Lyon , France
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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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18
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Paquet VE, Charette SJ. Amoeba-resisting bacteria found in multilamellar bodies secreted by Dictyostelium discoideum: social amoebae can also package bacteria. FEMS Microbiol Ecol 2016; 92:fiw025. [PMID: 26862140 DOI: 10.1093/femsec/fiw025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/02/2016] [Indexed: 11/14/2022] Open
Abstract
Many bacteria can resist phagocytic digestion by various protozoa. Some of these bacteria (all human pathogens) are known to be packaged in multilamellar bodies produced in the phagocytic pathway of the protozoa and that are secreted into the extracellular milieu. Packaged bacteria are protected from harsh conditions, and the packaging process is suspected to promote bacterial persistence in the environment. To date, only a limited number of protozoa, belonging to free-living amoebae and ciliates, have been shown to perform bacteria packaging. It is still unknown if social amoebae can do bacteria packaging. The link between the capacity of 136 bacterial isolates to resist the grazing of the social amoeba Dictyostelium discoideum and to be packaged by this amoeba was investigated in the present study. The 45 bacterial isolates displaying a resisting phenotype were tested for their capacity to be packaged. A total of seven isolates from Cupriavidus, Micrococcus, Microbacterium and Rathayibacter genera seemed to be packaged and secreted by D. discoideum based on immunofluorescence results. Electron microscopy confirmed that the Cupriavidus and Rathayibacter isolates were formally packaged. These results show that social amoebae can package some bacteria from the environment revealing a new aspect of microbial ecology.
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Affiliation(s)
- Valérie E Paquet
- Institut de Biologie Intégrative et des Systèmes, Pavillon Charles-Eugène-Marchand, Université Laval, Quebec City, QC, G1V 0A6, Canada Centre de recherche de l'Institut universitaire de cardiologie et de pneumologie de Québec, Hôpital Laval, Quebec City, QC, G1V 4G5, Canada
| | - Steve J Charette
- Institut de Biologie Intégrative et des Systèmes, Pavillon Charles-Eugène-Marchand, Université Laval, Quebec City, QC, G1V 0A6, Canada Centre de recherche de l'Institut universitaire de cardiologie et de pneumologie de Québec, Hôpital Laval, Quebec City, QC, G1V 4G5, Canada Département de biochimie, de microbiologie et de bio-informatique, Faculté des sciences et de génie, Université Laval, Quebec City, QC, G1V 0A6, Canada
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19
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Main photoautotrophic components of biofilms in natural draft cooling towers. Folia Microbiol (Praha) 2015; 61:255-60. [PMID: 26508444 DOI: 10.1007/s12223-015-0429-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 10/15/2015] [Indexed: 10/22/2022]
Abstract
While photoautotrophic organisms are an important component of biofilms that live in certain regions of natural draft cooling towers, little is known about these communities. We therefore examined 18 towers at nine sites to identify the general patterns of community assembly in three distinct tower parts, and we examined how community structures differ depending on geography. We also compared the newly acquired data with previously published data. The bottom sections of draft cooling towers are mainly settled by large filamentous algae, primarily Cladophora glomerata. The central portions of towers host a small amount of planktic algae biomass originating in the cooling water. The upper fourths of towers are colonized by biofilms primarily dominated by cyanobacteria, e.g., members of the genera Gloeocapsa and Scytonema. A total of 41 taxa of phototrophic microorganisms were identified. Species composition of the upper fourth of all towers was significantly affected by cardinal position. There was different species composition at positions facing north compared to positions facing south. West- and east-facing positions were transitory and highly similar to each other in terms of species composition. Biofilms contribute to the degradation of paint coatings inside towers.
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20
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Nuclease activity of Legionella pneumophila Cas2 promotes intracellular infection of amoebal host cells. Infect Immun 2014; 83:1008-18. [PMID: 25547789 DOI: 10.1128/iai.03102-14] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Legionella pneumophila, the primary agent of Legionnaires' disease, flourishes in both natural and man-made environments by growing in a wide variety of aquatic amoebae. Recently, we determined that the Cas2 protein of L. pneumophila promotes intracellular infection of Acanthamoeba castellanii and Hartmannella vermiformis, the two amoebae most commonly linked to cases of disease. The Cas2 family of proteins is best known for its role in the bacterial and archeal clustered regularly interspaced short palindromic repeat (CRISPR)-CRISPR-associated protein (Cas) system that constitutes a form of adaptive immunity against phage and plasmid. However, the infection event mediated by L. pneumophila Cas2 appeared to be distinct from this function, because cas2 mutants exhibited infectivity defects in the absence of added phage or plasmid and since mutants lacking the CRISPR array or any one of the other cas genes were not impaired in infection ability. We now report that the Cas2 protein of L. pneumophila has both RNase and DNase activities, with the RNase activity being more pronounced. By characterizing a catalytically deficient version of Cas2, we determined that nuclease activity is critical for promoting infection of amoebae. Also, introduction of Cas2, but not its catalytic mutant form, into a strain of L. pneumophila that naturally lacks a CRISPR-Cas locus caused that strain to be 40- to 80-fold more infective for amoebae, unequivocally demonstrating that Cas2 facilitates the infection process independently of any other component encoded within the CRISPR-Cas locus. Finally, a cas2 mutant was impaired for infection of Willaertia magna but not Naegleria lovaniensis, suggesting that Cas2 promotes infection of most but not all amoebal hosts.
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21
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Tyson JY, Vargas P, Cianciotto NP. The novel Legionella pneumophila type II secretion substrate NttC contributes to infection of amoebae Hartmannella vermiformis and Willaertia magna. MICROBIOLOGY-SGM 2014; 160:2732-2744. [PMID: 25253612 DOI: 10.1099/mic.0.082750-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The type II protein secretion (T2S) system of Legionella pneumophila secretes over 25 proteins, including novel proteins that have no similarity to proteins of known function. T2S is also critical for the ability of L. pneumophila to grow within its natural amoebal hosts, including Acanthamoeba castellanii, Hartmannella vermiformis and Naegleria lovaniensis. Thus, T2S has an important role in the natural history of legionnaires' disease. Our previous work demonstrated that the novel T2S substrate NttA promotes intracellular infection of A. castellanii, whereas the secreted RNase SrnA, acyltransferase PlaC, and metalloprotease ProA all promote infection of H. vermiformis and N. lovaniensis. In this study, we determined that another novel T2S substrate that is specific to Legionella, designated NttC, is unique in being required for intracellular infection of H. vermiformis but not for infection of N. lovaniensis or A. castellanii. Expanding our repertoire of amoebal hosts, we determined that Willaertia magna is susceptible to infection by L. pneumophila strains 130b, Philadelphia-1 and Paris. Furthermore, T2S and, more specifically, NttA, NttC and PlaC were required for infection of W. magna. Taken together, these data demonstrate that the T2S system of L. pneumophila is critical for infection of at least four types of aquatic amoebae and that the importance of the individual T2S substrates varies in a host cell-specific fashion. Finally, it is now clear that novel T2S-dependent proteins that are specific to the genus Legionella are particularly important for L. pneumophila infection of key, environmental hosts.
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Affiliation(s)
- Jessica Y Tyson
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, IL 60611, USA
| | - Paloma Vargas
- 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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Free-living amoebae (FLA) co-occurring with legionellae in industrial waters. Eur J Protistol 2014; 50:422-9. [PMID: 25062389 PMCID: PMC4155075 DOI: 10.1016/j.ejop.2014.04.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 04/30/2014] [Accepted: 04/30/2014] [Indexed: 11/23/2022]
Abstract
Legionella pneumophila is known as the causative agent of Legionnaires’ disease and free-living amoebae (FLA) can serve as vehicles for legionellae. The aim of this study was to screen industrial waters for the occurrence of FLA and their co-occurrence with legionellae. A total of 201 water samples, including 129 cooling waters and 72 process waters, and 30 cooling lubricants were included in the study. Treated waters were screened periodically, pre and post treatment. Altogether, 72.6% of the water samples were positive for FLA, acanthamoebae being most prevalent (in 23.9% of the samples) followed by Vermamoeba vermiformis (19.4%). Only one cooling lubricant was positive (Acanthamoeba genotype T4). Legionella spp. were detected in 34.8% of the water samples and in 15% in high concentrations (>1000 CFU/100 ml). Altogether, 81.4% of the Legionella-positive samples were positive for FLA by standard methods. By applying a highly sensitive nested PCR to a representative set of random samples it was revealed that Legionella spp. always co-occurred with Acanthamoeba spp. Although the addition of disinfectants did influence amoebal density and diversity, treated waters showed no difference concerning FLA in the interphases of disinfection. It appears that FLA can re-colonize treated waters within a short period of time.
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23
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Pagnier I, Reteno DGI, Saadi H, Boughalmi M, Gaia M, Slimani M, Ngounga T, Bekliz M, Colson P, Raoult D, La Scola B. A decade of improvements in Mimiviridae and Marseilleviridae isolation from amoeba. Intervirology 2013; 56:354-63. [PMID: 24157882 DOI: 10.1159/000354556] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Since the isolation of the first giant virus, the Mimivirus, by T.J. Rowbotham in a cooling tower in Bradford, UK, and after its characterisation by our group in 2003, we have continued to develop novel strategies to isolate additional strains. By first focusing on cooling towers using our original time-consuming procedure, we were able to isolate a new lineage of giant virus called Marseillevirus and a new Mimivirus strain called Mamavirus. In the following years, we have accumulated the world's largest unique collection of giant viruses by improving the use of antibiotic combinations to avoid bacterial contamination of amoeba, developing strategies of preliminary screening of samples by molecular methods, and using a high-throughput isolation method developed by our group. Based on the inoculation of nearly 7,000 samples, our collection currently contains 43 strains of Mimiviridae (14 in lineage A, 6 in lineage B, and 23 in lineage C) and 17 strains of Marseilleviridae isolated from various environments, including 3 of human origin. This study details the procedures used to build this collection and paves the way for the high-throughput isolation of new isolates to improve the record of giant virus distribution in the environment and the determination of their pangenome.
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Affiliation(s)
- Isabelle Pagnier
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), Aix-Marseille Université, Marseille, France
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24
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Chang CW, Lu LW, Kuo CL, Hung NT. Density of environmental Acanthamoeba and their responses to superheating disinfection. Parasitol Res 2013; 112:3687-96. [PMID: 23933810 DOI: 10.1007/s00436-013-3556-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 07/22/2013] [Indexed: 10/26/2022]
Abstract
Exposure to viable Acanthamoeba may cause fatal encephalitis and blinding keratitis in humans. Quantification of environmental Acanthamoeba by a reliable analytical assay is essential to assess the risk of human exposure and efficacy of control measures (e.g., superheating). Two DNA binding dyes (ethidium monoazide (EMA) and propidium monoazide) coupled with real-time quantitative PCR (qPCR) were tested for the ability in selectively quantifying viable Acanthamoeba castellanii. This newly developed qPCR assay was applied to determine the density of environmental Acanthamoeba and disinfection efficacy of superheating. Results showed qPCR with 2.3 μg/mL EMA performed optimal with a great linearity (R (2) = 0.98) and a wide range of detection (5-1.5 × 10(5) cells). EMA-qPCR analyses on water samples collected from cooling towers, eyewash stations, irrigated farmlands, and various wastewater treatment stages further showed viable Acanthamoeba density from nondetectable level to 6.3 × 10(5) cells/L. Superheating A. castellanii at 75-95 °C for 20 min revealed significant reductions in both EMA-qPCR and qPCR detectable Acanthamoeba target sequences with an adverse association between heating temperature and qPCR-determined DNA quantity (r = -0.76 to -0.93, p < 0.0001). Moreover, A. castellanii trophozoites were more sensitive to superheat stress than the cells being encysted for 6 and 13 d (p < 0.05). This is the first study to quantify environmental Acanthamoeba and characterize their responses to superheating by EMA-qPCR. The quantitative data provided in this study facilitate to understand better the relative risk for human exposed to viable Acanthamoeba and the efficacy of superheating against Acanthamoeba.
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Affiliation(s)
- Ching-Wen Chang
- Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei, 100, Taiwan, Republic of China,
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25
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Multiple Legionella pneumophila Type II secretion substrates, including a novel protein, contribute to differential infection of the amoebae Acanthamoeba castellanii, Hartmannella vermiformis, and Naegleria lovaniensis. Infect Immun 2013; 81:1399-410. [PMID: 23429532 DOI: 10.1128/iai.00045-13] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Type II protein secretion (T2S) by Legionella pneumophila is required for intracellular infection of host cells, including macrophages and the amoebae Acanthamoeba castellanii and Hartmannella vermiformis. Previous proteomic analysis revealed that T2S by L. pneumophila 130b mediates the export of >25 proteins, including several that appeared to be novel. Following confirmation that they are unlike known proteins, T2S substrates NttA, NttB, and LegP were targeted for mutation. nttA mutants were impaired for intracellular multiplication in A. castellanii but not H. vermiformis or macrophages, suggesting that novel exoproteins which are specific to Legionella are especially important for infection. Because the importance of NttA was host cell dependent, we examined a panel of T2S substrate mutants that had not been tested before in more than one amoeba. As a result, RNase SrnA, acyltransferase PlaC, and metalloprotease ProA all proved to be required for optimal intracellular multiplication in H. vermiformis but not A. castellanii. Further examination of an lspF mutant lacking the T2S apparatus documented that T2S is also critical for infection of the amoeba Naegleria lovaniensis. Mutants lacking SrnA, PlaC, or ProA, but not those deficient for NttA, were defective in N. lovaniensis. Based upon analysis of a double mutant lacking PlaC and ProA, the role of ProA in H. vermiformis was connected to its ability to activate PlaC, whereas in N. lovaniensis, ProA appeared to have multiple functions. Together, these data document that the T2S system exports multiple effectors, including a novel one, which contribute in different ways to the broad host range of L. pneumophila.
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Kao PM, Tung MC, Hsu BM, Tsai HL, She CY, Shen SM, Huang WC. Real-time PCR method for the detection and quantification of Acanthamoeba species in various types of water samples. Parasitol Res 2013; 112:1131-6. [DOI: 10.1007/s00436-012-3242-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 12/10/2012] [Indexed: 10/27/2022]
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Lamrabet O, Merhej V, Pontarotti P, Raoult D, Drancourt M. The genealogic tree of mycobacteria reveals a long-standing sympatric life into free-living protozoa. PLoS One 2012; 7:e34754. [PMID: 22511965 PMCID: PMC3325273 DOI: 10.1371/journal.pone.0034754] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 03/08/2012] [Indexed: 02/07/2023] Open
Abstract
Free-living protozoa allow horizontal gene transfer with and between the microorganisms that they host. They host mycobacteria for which the sources of transferred genes remain unknown. Using BLASTp, we searched within the genomes of 15 mycobacteria for homologous genes with 34 amoeba-resistant bacteria and the free-living protozoa Dictyostelium discoideum. Subsequent phylogenetic analysis of these sequences revealed that eight mycobacterial open-reading frames (ORFs) were probably acquired via horizontal transfer from beta- and gamma-Proteobacteria and from Firmicutes, but the transfer histories could not be reliably established in details. One further ORF encoding a pyridine nucleotide disulfide oxidoreductase (pyr-redox) placed non-tuberculous mycobacteria in a clade with Legionella spp., Francisella spp., Coxiella burnetii, the ciliate Tetrahymena thermophila and D. discoideum with a high reliability. Co-culturing Mycobacterium avium and Legionella pneumophila with the amoeba Acanthamoeba polyphaga demonstrated that these two bacteria could live together in amoebae for five days, indicating the biological relevance of intra-amoebal transfer of the pyr-redox gene. In conclusion, the results of this study support the hypothesis that protists can serve as a source and a place for gene transfer in mycobacteria.
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Affiliation(s)
- Otmane Lamrabet
- URMITE CNRS-IRD UMR 6236, IFR48, Méditerranée Infection, Aix-Marseille Université, Marseille, France
| | - Vicky Merhej
- URMITE CNRS-IRD UMR 6236, IFR48, Méditerranée Infection, Aix-Marseille Université, Marseille, France
| | - Pierre Pontarotti
- Equipe Evolution Biologique et Modélisation UMR 6632, IRF48, Aix-Marseille Université/CNRS, Marseille, France
| | - Didier Raoult
- URMITE CNRS-IRD UMR 6236, IFR48, Méditerranée Infection, Aix-Marseille Université, Marseille, France
| | - Michel Drancourt
- URMITE CNRS-IRD UMR 6236, IFR48, Méditerranée Infection, Aix-Marseille Université, Marseille, France
- * E-mail:
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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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The surfactant of Legionella pneumophila Is secreted in a TolC-dependent manner and is antagonistic toward other Legionella species. J Bacteriol 2011; 193:5971-84. [PMID: 21890700 DOI: 10.1128/jb.05405-11] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
When Legionella pneumophila grows on agar plates, it secretes a surfactant that promotes flagellum- and pilus-independent "sliding" motility. We isolated three mutants that were defective for surfactant. The first two had mutations in genes predicted to encode cytoplasmic enzymes involved in lipid metabolism. These genes mapped to two adjacent operons that we designated bbcABCDEF and bbcGHIJK. Backcrossing and complementation confirmed the importance of the bbc genes and suggested that the Legionella surfactant is lipid containing. The third mutant had an insertion in tolC. TolC is the outer membrane part of various trimolecular complexes involved in multidrug efflux and type I protein secretion. Complementation of the tolC mutant restored sliding motility. Mutants defective for an inner membrane partner of TolC also lacked a surfactant, confirming that TolC promotes surfactant secretion. L. pneumophila (lspF) mutants lacking type II protein secretion (T2S) are also impaired for a surfactant. When the tolC and lspF mutants were grown next to each other, the lsp mutant secreted surfactant, suggesting that TolC and T2S conjoin to mediate surfactant secretion, with one being the conduit for surfactant export and the other the exporter of a molecule that is required for induction or maturation of surfactant synthesis/secretion. Although the surfactant was not required for the extracellular growth, intracellular infection, and intrapulmonary survival of L. pneumophila, it exhibited antimicrobial activity toward seven other species of Legionella but not toward various non-Legionella species. These data suggest that the surfactant provides L. pneumophila with a selective advantage over other legionellae in the natural environment.
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FITTIPALDI MARIANA, PINO RODRIGUEZ NANCYJ, ADRADOS BÁRBARA, AGUSTÍ GEMMA, PEÑUELA GUSTAVO, MORATÓ JORDI, CODONY FRANCESC. Discrimination of Viable Acanthamoeba castellani Trophozoites and Cysts by Propidium Monoazide Real-Time Polymerase Chain Reaction. J Eukaryot Microbiol 2011; 58:359-64. [DOI: 10.1111/j.1550-7408.2011.00557.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Buse HY, Brehm A, Santo Domingo JW, Ashbolt NJ. Screening-level assays for potentially human-infectious environmental Legionella spp. J Microbiol 2011; 49:200-7. [DOI: 10.1007/s12275-011-0233-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Accepted: 12/08/2010] [Indexed: 10/18/2022]
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Chang CW, Wu YC, Ming KW. Evaluation of real-time PCR methods for quantification of Acanthamoeba in anthropogenic water and biofilms. J Appl Microbiol 2011; 109:799-807. [PMID: 20233260 DOI: 10.1111/j.1365-2672.2010.04708.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS To assess two real-time PCR methods (the Riviere and Qvarnstrom assays) for environmental Acanthamoeba. METHODS AND RESULTS DNA extracted from Acanthamoeba castellanii taken from water and biofilms of cooling towers was analysed by the Riviere and Qvarnstrom assays. To quantify environmental Acanthamoeba, the calibration curves (DNA quantity vs cell number) were constructed with samples spiked with A. castellanii. The calibration curves for both quantitative PCR assays showed low variation (coefficient of variation of C(t) ≤ 5·7%) and high linearity (R(2) ≥ 0·99) over six orders of magnitudes with detection limit of three cells per water sample. DNA quantity determined by Qvarnstrom assay was equivalent between trophozoites and cysts (P=0·49), whereas a significant difference was observed with Riviere assay (P<0·0001). Riviere assay failed to detect Acanthamoeba in 21% (15/71) of the environmental samples which were positively detected by Qvarnstrom assay, while one sample (1·4%) was shown positive by Riviere assay but negative by Qvarnstrom assay. Moreover, Acanthamoeba counts by Qvarnstrom assay were greater than those by Riviere assay (P<0·0001). CONCLUSIONS Qvarnstrom assay performs better than Riviere assay for detection and quantification of Acanthamoeba in anthropogenic water and biofilms. SIGNIFICANCE AND IMPACT OF THE STUDY Qvarnstrom assay may significantly contribute to a better knowledge about the distribution and abundance of Acanthamoeba in environments.
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Affiliation(s)
- C-W Chang
- Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei, Taiwan, China.
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Liu Y, Zhang W, Sileika T, Warta R, Cianciotto NP, Packman AI. Disinfection of bacterial biofilms in pilot-scale cooling tower systems. BIOFOULING 2011; 27:393-402. [PMID: 21547755 PMCID: PMC4507511 DOI: 10.1080/08927014.2011.577525] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The impact of continuous chlorination and periodic glutaraldehyde treatment on planktonic and biofilm microbial communities was evaluated in pilot-scale cooling towers operated continuously for 3 months. The system was operated at a flow rate of 10,080 l day(-1). Experiments were performed with a well-defined microbial consortium containing three heterotrophic bacteria: Pseudomonas aeruginosa, Klebsiella pneumoniae and Flavobacterium sp. The persistence of each species was monitored in the recirculating cooling water loop and in biofilms on steel and PVC coupons in the cooling tower basin. The observed bacterial colonization in cooling towers did not follow trends in growth rates observed under batch conditions and, instead, reflected differences in the ability of each organism to remain attached and form biofilms under the high-through flow conditions in cooling towers. Flavobacterium was the dominant organism in the community, while P. aeruginosa and K. pneumoniae did not attach well to either PVC or steel coupons in cooling towers and were not able to persist in biofilms. As a result, the much greater ability of Flavobacterium to adhere to surfaces protected it from disinfection, whereas P. aeruginosa and K. pneumoniae were subject to rapid disinfection in the planktonic state.
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Affiliation(s)
- Yang Liu
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Wei Zhang
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Tadas Sileika
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Richard Warta
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Nicholas P. Cianciotto
- Department of Microbiology – Immunology, Northwestern University Medical School, Chicago, IL 60611, USA
| | - Aaron I. Packman
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208, USA
- Corresponding author:
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Legionella pneumophila type II secretion dampens the cytokine response of infected macrophages and epithelia. Infect Immun 2011; 79:1984-97. [PMID: 21383054 DOI: 10.1128/iai.01077-10] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The type II secretion (T2S) system of Legionella pneumophila is required for the ability of the bacterium to grow within the lungs of A/J mice. By utilizing mutants lacking T2S (lsp), we now document that T2S promotes the intracellular infection of both multiple types of macrophages and lung epithelia. Following infection of macrophages, lsp mutants (but not a complemented mutant) elicited significantly higher levels of interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), IL-10, IL-8, IL-1β, and MCP-1 within tissue culture supernatants. A similar result was obtained with infected lung epithelial cell lines and the lungs of infected A/J mice. Infection with a mutant specifically lacking the T2S-dependent ProA protease (but not a complemented proA mutant) resulted in partial elevation of cytokine levels. These data demonstrate that the T2S system of L. pneumophila dampens the cytokine/chemokine output of infected host cells. Upon quantitative reverse transcription (RT)-PCR analysis of infected host cells, an lspF mutant, but not the proA mutant, produced significantly higher levels of cytokine transcripts, implying that some T2S-dependent effectors dampen signal transduction and transcription but that others, such as ProA, act at a posttranscriptional step in cytokine expression. In summary, the impact of T2S on lung infection is a combination of at least three factors: the promotion of growth in macrophages, the facilitation of growth in epithelia, and the dampening of the chemokine and cytokine output from infected host cells. To our knowledge, these data are the first to identify a link between a T2S system and the modulation of immune factors following intracellular infection.
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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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Adrados B, Julián E, Codony F, Torrents E, Luquin M, Morató J. Prevalence and concentration of non-tuberculous mycobacteria in cooling towers by means of quantitative PCR: a prospective study. Curr Microbiol 2010; 62:313-9. [PMID: 20640853 DOI: 10.1007/s00284-010-9706-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 06/20/2010] [Indexed: 11/30/2022]
Abstract
There is an increasing level of interest in non-tuberculous mycobacteria (NTM) due to the increasing reported rates of diseases caused by them. Although it is well known that NTM are widely distributed in the environment it is necessary to identify its reservoirs to prevent possible infections. In this study, we aimed to investigate the occurrence and levels of NTM in cooling towers to provide evidences for considering these settings as possible sources of respiratory infections. In the current study, we detected and quantified the presence of NTM by means of a rapid method in water samples taken from 53 cooling towers of an urban area (Barcelona, Spain). A genus-specific quantitative PCR (Q-PCR) assay with a quantification limit (QL) of 500 cells l(-1) was used. 56% (30) of samples were positive with a concentration range from 4.6 × 10(3) to 1.79 × 10(6) cells l(-1). In some cases (9/30), samples were positive but with levels below the QL. The colonization rate confirmed that cooling towers could be considered as a potential reservoir for NTM. This study also evaluated Q-PCR as a useful method to detect and quantify NTM in samples coming from environmental sources.
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Affiliation(s)
- Bárbara Adrados
- Laboratori de Microbiologia Sanitària i Mediambiental, Departament d'Optica i Optometria, Universitat Politècnica de Catalunya, Edifici Gaia - Pg. Ernest Lluch/Rambla Sant Nebridi, 08222, Terrassa, Barcelona, Spain.
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Abstract
Despite using modern microbiological diagnostic approaches, the aetiological agents of pneumonia remain unidentified in about 50% of cases. Some bacteria that grow poorly or not at all in axenic media used in routine clinical bacteriology laboratory but which can develop inside amoebae may be the agents of these lower respiratory tract infections (RTIs) of unexplained aetiology. Such amoebae-resisting bacteria, which coevolved with amoebae to resist their microbicidal machinery, may have developed virulence traits that help them survive within human macrophages, i.e. the first line of innate immune defence in the lung. We review here the current evidence for the emerging pathogenic role of various amoebae-resisting microorganisms as agents of RTIs in humans. Specifically, we discuss the emerging pathogenic roles of Legionella-like amoebal pathogens, novel Chlamydiae (Parachlamydia acanthamoebae, Simkania negevensis), waterborne mycobacteria and Bradyrhizobiaceae (Bosea and Afipia spp.).
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Affiliation(s)
- Frédéric Lamoth
- Infectious Diseases Service, University of Lausanne, Lausanne, Switzerland
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