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Mutations of Francisella novicida that Alter the Mechanism of Its Phagocytosis by Murine Macrophages
Infection with the bacterial pathogen Francisella tularensis tularensis (F. tularensis) causes tularemia, a serious and debilitating disease. Francisella tularensis novicida strain U112 (abbreviated F. novicida), which is closely related to F. tularensis, is pathogenic for mice but not for man, maki...
Autores principales: | , , , , , , , , |
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Formato: | Texto |
Lenguaje: | English |
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Public Library of Science
2010
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2912274/ https://www.ncbi.nlm.nih.gov/pubmed/20686600 http://dx.doi.org/10.1371/journal.pone.0011857 |
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author | Lai, Xin-He Shirley, Renee L. Crosa, Lidia Kanistanon, Duangjit Tempel, Rebecca Ernst, Robert K. Gallagher, Larry A. Manoil, Colin Heffron, Fred |
author_facet | Lai, Xin-He Shirley, Renee L. Crosa, Lidia Kanistanon, Duangjit Tempel, Rebecca Ernst, Robert K. Gallagher, Larry A. Manoil, Colin Heffron, Fred |
author_sort | Lai, Xin-He |
collection | PubMed |
description | Infection with the bacterial pathogen Francisella tularensis tularensis (F. tularensis) causes tularemia, a serious and debilitating disease. Francisella tularensis novicida strain U112 (abbreviated F. novicida), which is closely related to F. tularensis, is pathogenic for mice but not for man, making it an ideal model system for tularemia. Intracellular pathogens like Francisella inhibit the innate immune response, thereby avoiding immune recognition and death of the infected cell. Because activation of inflammatory pathways may lead to cell death, we reasoned that we could identify bacterial genes involved in inhibiting inflammation by isolating mutants that killed infected cells faster than the wild-type parent. We screened a comprehensive transposon library of F. novicida for mutant strains that increased the rate of cell death following infection in J774 macrophage-like cells, as compared to wild-type F. novicida. Mutations in 28 genes were identified as being hypercytotoxic to both J774 and primary macrophages of which 12 were less virulent in a mouse infection model. Surprisingly, we found that F. novicida with mutations in four genes (lpcC, manB, manC and kdtA) were taken up by and killed macrophages at a much higher rate than the parent strain, even upon treatment with cytochalasin D (cytD), a classic inhibitor of macrophage phagocytosis. At least 10-fold more mutant bacteria were internalized by macrophages as compared to the parent strain if the bacteria were first fixed with formaldehyde, suggesting a surface structure is required for the high phagocytosis rate. However, bacteria were required to be viable for macrophage toxicity. The four mutant strains do not make a complete LPS but instead have an exposed lipid A. Interestingly, other mutations that result in an exposed LPS core were not taken up at increased frequency nor did they kill host cells more than the parent. These results suggest an alternative, more efficient macrophage uptake mechanism for Francisella that requires exposure of a specific bacterial surface structure(s) but results in increased cell death following internalization of live bacteria. |
format | Text |
id | pubmed-2912274 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2010 |
publisher | Public Library of Science |
record_format | MEDLINE/PubMed |
spelling | pubmed-29122742010-08-03 Mutations of Francisella novicida that Alter the Mechanism of Its Phagocytosis by Murine Macrophages Lai, Xin-He Shirley, Renee L. Crosa, Lidia Kanistanon, Duangjit Tempel, Rebecca Ernst, Robert K. Gallagher, Larry A. Manoil, Colin Heffron, Fred PLoS One Research Article Infection with the bacterial pathogen Francisella tularensis tularensis (F. tularensis) causes tularemia, a serious and debilitating disease. Francisella tularensis novicida strain U112 (abbreviated F. novicida), which is closely related to F. tularensis, is pathogenic for mice but not for man, making it an ideal model system for tularemia. Intracellular pathogens like Francisella inhibit the innate immune response, thereby avoiding immune recognition and death of the infected cell. Because activation of inflammatory pathways may lead to cell death, we reasoned that we could identify bacterial genes involved in inhibiting inflammation by isolating mutants that killed infected cells faster than the wild-type parent. We screened a comprehensive transposon library of F. novicida for mutant strains that increased the rate of cell death following infection in J774 macrophage-like cells, as compared to wild-type F. novicida. Mutations in 28 genes were identified as being hypercytotoxic to both J774 and primary macrophages of which 12 were less virulent in a mouse infection model. Surprisingly, we found that F. novicida with mutations in four genes (lpcC, manB, manC and kdtA) were taken up by and killed macrophages at a much higher rate than the parent strain, even upon treatment with cytochalasin D (cytD), a classic inhibitor of macrophage phagocytosis. At least 10-fold more mutant bacteria were internalized by macrophages as compared to the parent strain if the bacteria were first fixed with formaldehyde, suggesting a surface structure is required for the high phagocytosis rate. However, bacteria were required to be viable for macrophage toxicity. The four mutant strains do not make a complete LPS but instead have an exposed lipid A. Interestingly, other mutations that result in an exposed LPS core were not taken up at increased frequency nor did they kill host cells more than the parent. These results suggest an alternative, more efficient macrophage uptake mechanism for Francisella that requires exposure of a specific bacterial surface structure(s) but results in increased cell death following internalization of live bacteria. Public Library of Science 2010-07-29 /pmc/articles/PMC2912274/ /pubmed/20686600 http://dx.doi.org/10.1371/journal.pone.0011857 Text en Lai et al. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited. |
spellingShingle | Research Article Lai, Xin-He Shirley, Renee L. Crosa, Lidia Kanistanon, Duangjit Tempel, Rebecca Ernst, Robert K. Gallagher, Larry A. Manoil, Colin Heffron, Fred Mutations of Francisella novicida that Alter the Mechanism of Its Phagocytosis by Murine Macrophages |
title | Mutations of Francisella novicida that Alter the Mechanism of Its Phagocytosis by Murine Macrophages |
title_full | Mutations of Francisella novicida that Alter the Mechanism of Its Phagocytosis by Murine Macrophages |
title_fullStr | Mutations of Francisella novicida that Alter the Mechanism of Its Phagocytosis by Murine Macrophages |
title_full_unstemmed | Mutations of Francisella novicida that Alter the Mechanism of Its Phagocytosis by Murine Macrophages |
title_short | Mutations of Francisella novicida that Alter the Mechanism of Its Phagocytosis by Murine Macrophages |
title_sort | mutations of francisella novicida that alter the mechanism of its phagocytosis by murine macrophages |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2912274/ https://www.ncbi.nlm.nih.gov/pubmed/20686600 http://dx.doi.org/10.1371/journal.pone.0011857 |
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