Active and adaptive Legionella CRISPR‐Cas reveals a recurrent challenge to the pathogen
| Autor: | Ken Dewar, Jessica Wasserscheid, Carmen Pelaz, Alexander W. Ensminger, Joseph Bondy-Denomy, Chitong Rao, Cyril Guyard |
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| Přispěvatelé: | University of Toronto, Canadian Institutes of Health Research, Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, Ontario Research Fund, University of Toronto (Cánada), Natural Sciences and Engineering Research Council (Canada), Ontario Research Fund - Research Excellence (ORF-RE) |
| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
030106 microbiology Immunology Genomics Microbiology Legionella pneumophila Genome Conserved sequence Evolution Molecular Bacteriophage 03 medical and health sciences Plasmid Virology CRISPR Clustered Regularly Interspaced Short Palindromic Repeats Gene Conserved Sequence Genetics Acanthamoeba castellanii Microbial Viability Base Sequence biology Sequence Analysis DNA biology.organism_classification Editor's Choice Genes Bacterial Host-Pathogen Interactions |
| Zdroj: | Repisalud Instituto de Salud Carlos III (ISCIII) Cellular Microbiology |
| ISSN: | 1462-5822 1462-5814 |
| DOI: | 10.1111/cmi.12586 |
| Popis: | Clustered regularly interspaced short palindromic repeats with CRISPR-associated gene (CRISPR-Cas) systems are widely recognized as critical genome defense systems that protect microbes from external threats such as bacteriophage infection. Several isolates of the intracellular pathogen Legionella pneumophila possess multiple CRISPR-Cas systems (type I-C, type I-F and type II-B), yet the targets of these systems remain unknown. With the recent observation that at least one of these systems (II-B) plays a non-canonical role in supporting intracellular replication, the possibility remained that these systems are vestigial genome defense systems co-opted for other purposes. Our data indicate that this is not the case. Using an established plasmid transformation assay, we demonstrate that type I-C, I-F and II-B CRISPR-Cas provide protection against spacer targets. We observe efficient laboratory acquisition of new spacers under 'priming' conditions, in which initially incomplete target elimination leads to the generation of new spacers and ultimate loss of the invasive DNA. Critically, we identify the first known target of L. pneumophila CRISPR-Cas: a 30 kb episome of unknown function whose interbacterial transfer is guarded against by CRISPR-Cas. We provide evidence that the element can subvert CRISPR-Cas by mutating its targeted sequences - but that primed spacer acquisition may limit this mechanism of escape. Rather than generally impinging on bacterial fitness, this element drives a host specialization event - with improved fitness in Acanthamoeba but a reduced ability to replicate in other hosts and conditions. These observations add to a growing body of evidence that host range restriction can serve as an existential threat to L. pneumophila in the wild. This work was supported by the University of Toronto and operating grants awarded to AWE by the Canadian Institutes of Health Research (MOP‐133406) and the Natural Sciences and Engineering Research Council of Canada (RGPIN‐2014‐03641), along with an infrastructure grant awarded to AWE from the Canada Foundation for Innovation and the Ontario Research Fund (30364). The authors have no conflict of interest to declare. Sí |
| Databáze: | OpenAIRE |
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