1
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Kim H, Marraffini LA. Cas9 interaction with the tracrRNA nexus modulates the repression of type II-A CRISPR-cas genes. Nucleic Acids Res 2024:gkae597. [PMID: 38994567 DOI: 10.1093/nar/gkae597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 06/22/2024] [Accepted: 07/10/2024] [Indexed: 07/13/2024] Open
Abstract
Immune responses need to be regulated to prevent autoimmunity. CRISPR-Cas systems provide adaptive immunity in prokaryotes through the acquisition of short DNA sequences from invading viruses (bacteriophages), known as spacers. Spacers are inserted into the CRISPR locus and serve as templates for the transcription of guides used by RNA-guided nucleases to recognize complementary nucleic acids of the invaders and start the CRISPR immune response. In type II-A CRISPR systems, Cas9 uses the guide RNA to cleave target DNA sequences in the genome of infecting phages, and the tracrRNA to bind the promoter of cas genes and repress their transcription. We previously isolated a Cas9 mutant carrying the I473F substitution that increased the frequency of spacer acquisition by 2-3 orders of magnitude, leading to a fitness cost due to higher levels of autoimmunity. Here, we investigated the molecular basis underlying these findings. We found that the I473F mutation decreases the association of Cas9 to tracrRNA, limiting its repressor function, leading to high levels of expression of cas genes, which in turn increase the strength of the type II-A CRISPR-Cas immune response. We obtained similar results for a related type II-A system, and therefore our findings highlight the importance of the interaction between Cas9 and its tracrRNA cofactor in tuning the immune response to balanced levels that enable phage defense but avoid autoimmunity.
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Affiliation(s)
- Hyejin Kim
- Laboratory of Bacteriology, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
- Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY, USA
| | - Luciano A Marraffini
- Laboratory of Bacteriology, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
- Howard Hughes Medical Institute, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
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2
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Stoltzfus MJ, Workman RE, Keith NC, Modell JW. A dynamic subpopulation of CRISPR-Cas overexpressers allows Streptococcus pyogenes to rapidly respond to phage. Nat Microbiol 2024:10.1038/s41564-024-01748-0. [PMID: 38997519 DOI: 10.1038/s41564-024-01748-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Accepted: 06/03/2024] [Indexed: 07/14/2024]
Abstract
Many CRISPR-Cas (clustered regularly interspaced short palindromic repeats and CRISPR-associated protein) systems, which provide bacteria with adaptive immunity against phages, are transcriptionally repressed in their native hosts. How CRISPR-Cas expression is induced as needed, for example, during a bacteriophage infection, remains poorly understood. In Streptococcus pyogenes, a non-canonical guide RNA tracr-L directs Cas9 to autorepress its own promoter. Here we describe a dynamic subpopulation of cells harbouring single mutations that disrupt Cas9 binding and cause CRISPR-Cas overexpression. Cas9 actively expands this population by elevating mutation rates at the tracr-L target site. Overexpressers show higher rates of memory formation, stronger potency of old memories and a larger memory storage capacity relative to wild-type cells, which are surprisingly vulnerable to phage infection. However, in the absence of phage, CRISPR-Cas overexpression reduces fitness. We propose that CRISPR-Cas overexpressers are critical players in phage defence, enabling bacterial populations to mount rapid transcriptional responses to phage without requiring transient changes in any one cell.
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Affiliation(s)
- Marie J Stoltzfus
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Rachael E Workman
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Nicholas C Keith
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Joshua W Modell
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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3
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Wilbanks B, Pearson K, Maher LJ. A non-rational approach to optimized targeting of CRISPR-Cas9 complexes. Cell Chem Biol 2023; 30:855-857. [PMID: 37595547 PMCID: PMC10787275 DOI: 10.1016/j.chembiol.2023.07.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 07/21/2023] [Accepted: 07/22/2023] [Indexed: 08/20/2023]
Abstract
In this issue of Cell Chemical Biology, Bush et al.1 report an in vitro selection method for optimizing CRISPR-Cas9 single-guide RNAs. This approach may be useful in targeting previously intractable genomic sequences. The results also provide insights into which positions in single-guide RNAs are most amenable to modification.
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Affiliation(s)
- Brandon Wilbanks
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
| | - Keenan Pearson
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA
| | - L James Maher
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine and Science, Rochester, MN 55905, USA.
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4
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Kenney CT, Marraffini LA. Rarely acquired type II-A CRISPR-Cas spacers mediate anti-viral immunity through the targeting of a non-canonical PAM sequence. Nucleic Acids Res 2023; 51:7438-7450. [PMID: 37293964 PMCID: PMC10415147 DOI: 10.1093/nar/gkad501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 05/23/2023] [Accepted: 06/07/2023] [Indexed: 06/10/2023] Open
Abstract
The Streptococcus pyogenes type II-A CRISPR-Cas systems provides adaptive immunity through the acquisition of short DNA sequences from invading viral genomes, called spacers. Spacers are transcribed into short RNA guides that match regions of the viral genome followed by a conserved NGG DNA motif, known as the PAM. These RNA guides, in turn, are used by the Cas9 nuclease to find and destroy complementary DNA targets within the viral genome. While most of the spacers present in bacterial populations that survive phage infection target protospacers flanked by NGG sequences, there is a small fraction that target non-canonical PAMs. Whether these spacers originate through accidental acquisition of phage sequences and/or provide efficient defense is unknown. Here we found that many of them match phage target regions flanked by an NAGG PAM. Despite being scarcely present in bacterial populations, NAGG spacers provide substantial immunity in vivo and generate RNA guides that support robust DNA cleavage by Cas9 in vitro; with both activities comparable to spacers that target sequences followed by the canonical AGG PAM. In contrast, acquisition experiments showed that NAGG spacers are acquired at very low frequencies. We therefore conclude that discrimination against these sequences occurs during immunization of the host. Our results reveal unexpected differences in PAM recognition during the spacer acquisition and targeting stages of the type II-A CRISPR-Cas immune response.
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Affiliation(s)
- Claire T Kenney
- Laboratory of Bacteriology, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
| | - Luciano A Marraffini
- Laboratory of Bacteriology, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
- Howard Hughes Medical Institute, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
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5
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Huang D, Yuan MM, Chen J, Zheng X, Wong D, Alvarez PJJ, Yu P. The association of prokaryotic antiviral systems and symbiotic phage communities in drinking water microbiomes. ISME COMMUNICATIONS 2023; 3:46. [PMID: 37142716 PMCID: PMC10160068 DOI: 10.1038/s43705-023-00249-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 04/11/2023] [Accepted: 04/18/2023] [Indexed: 05/06/2023]
Abstract
Prokaryotic antiviral systems are important mediators for prokaryote-phage interactions, which have significant implications for the survival of prokaryotic community. However, the prokaryotic antiviral systems under environmental stress are poorly understood, limiting the understanding of microbial adaptability. Here, we systematically investigated the profile of the prokaryotic antiviral systems at the community level and prokaryote-phage interactions in the drinking water microbiome. Chlorine disinfectant was revealed as the main ecological driver for the difference in prokaryotic antiviral systems and prokaryote-phage interactions. Specifically, the prokaryotic antiviral systems in the microbiome exhibited a higher abundance, broader antiviral spectrum, and lower metabolic burden under disinfectant stress. Moreover, significant positive correlations were observed between phage lysogenicity and enrichment of antiviral systems (e.g., Type IIG and IV restriction-modification (RM) systems, and Type II CRISPR-Cas system) in the presence of disinfection, indicating these antiviral systems might be more compatible with lysogenic phages and prophages. Accordingly, there was a stronger prokaryote-phage symbiosis in disinfected microbiome, and the symbiotic phages carried more auxiliary metabolic genes (AMGs) related to prokaryotic adaptability as well as antiviral systems, which might further enhance prokaryote survival in drinking water distribution systems. Overall, this study demonstrates that the prokaryotic antiviral systems had a close association with their symbiotic phages, which provides novel insights into prokaryote-phage interactions and microbial environmental adaptation.
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Affiliation(s)
- Dan Huang
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Mengting Maggie Yuan
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, USA
| | - Juhong Chen
- Department of Biological Systems Engineering, Virginia Tech, Blacksburg, VA, USA
| | - Xiaoxuan Zheng
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Dongsheng Wong
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Pedro J J Alvarez
- Department of Civil and Environmental Engineering, Rice University, Houston, TX, USA
| | - Pingfeng Yu
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.
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6
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Abstract
CRISPR-Cas is a widespread adaptive immune system in bacteria and archaea that protects against viral infection by targeting specific invading nucleic acid sequences. Whereas some CRISPR-Cas systems sense and cleave viral DNA, type III and type VI CRISPR-Cas systems sense RNA that results from viral transcription and perhaps invasion by RNA viruses. The sequence-specific detection of viral RNA evokes a cell-wide response that typically involves global damage to halt the infection. How can one make sense of an immune strategy that encompasses broad, collateral effects rather than specific, targeted destruction? In this Review, we summarize the current understanding of RNA-targeting CRISPR-Cas systems. We detail the composition and properties of type III and type VI systems, outline the cellular defence processes that are instigated upon viral RNA sensing and describe the biological rationale behind the broad RNA-activated immune responses as an effective strategy to combat viral infection.
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7
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Flusche T, Rajan R. Molecular Details of DNA Integration by CRISPR-Associated Proteins During Adaptation in Bacteria and Archaea. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1414:27-43. [PMID: 35852729 DOI: 10.1007/5584_2022_730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) proteins constitute an adaptive immune system in bacteria and archaea, where immunological memory is retained in the CRISPR locus as short pieces of the intruding nucleic acid, termed spacers. The adaptation to new infections occurs through the integration of a new spacer into the CRISPR array. For immune protection, spacers are transcribed into CRISPR RNAs (crRNA) that are used to guide the effector nuclease of the system in sequence-dependent target cleavage. Spacers originate as a prespacer from either DNA or RNA depending on the CRISPR-Cas system being observed, and the nearly universal Cas proteins, Cas1 and Cas2, insert the prespacer into the CRISPR locus during adaptation in all systems that contain them. The mechanism of site-specific prespacer integration varies across CRISPR classes and types, and distinct differences can even be found within the same subtype. In this review, the current knowledge on the mechanisms of prespacer integration in type II-A CRISPR-Cas systems will be described. Comparisons of the currently characterized type II-A systems show that distinct mechanisms exist within different members of this subtype and are correlated to sequence-specific interactions of Cas proteins and the DNA elements present in the CRISPR array. These observations indicate that nature has fine-tuned the mechanistic details while performing the basic step of DNA integration by Cas proteins, which offers unique advantages to develop Cas1-Cas2-based biotechnology.
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Affiliation(s)
- Tamara Flusche
- Department of Chemistry and Biochemistry, Price Family Foundation Institute of Structural Biology, Stephenson Life Sciences Research Center, University of Oklahoma, Norman, OK, USA
| | - Rakhi Rajan
- Department of Chemistry and Biochemistry, Price Family Foundation Institute of Structural Biology, Stephenson Life Sciences Research Center, University of Oklahoma, Norman, OK, USA.
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8
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Wang JY, Pausch P, Doudna JA. Structural biology of CRISPR-Cas immunity and genome editing enzymes. Nat Rev Microbiol 2022; 20:641-656. [PMID: 35562427 DOI: 10.1038/s41579-022-00739-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/11/2022] [Indexed: 12/20/2022]
Abstract
CRISPR-Cas systems provide resistance against foreign mobile genetic elements and have a wide range of genome editing and biotechnological applications. In this Review, we examine recent advances in understanding the molecular structures and mechanisms of enzymes comprising bacterial RNA-guided CRISPR-Cas immune systems and deployed for wide-ranging genome editing applications. We explore the adaptive and interference aspects of CRISPR-Cas function as well as open questions about the molecular mechanisms responsible for genome targeting. These structural insights reflect close evolutionary links between CRISPR-Cas systems and mobile genetic elements, including the origins and evolution of CRISPR-Cas systems from DNA transposons, retrotransposons and toxin-antitoxin modules. We discuss how the evolution and structural diversity of CRISPR-Cas systems explain their functional complexity and utility as genome editing tools.
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Affiliation(s)
- Joy Y Wang
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA
- Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA, USA
| | - Patrick Pausch
- VU LSC-EMBL Partnership for Genome Editing Technologies, Life Sciences Center, Vilnius University, Vilnius, Lithuania.
| | - Jennifer A Doudna
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA.
- Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA, USA.
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA, USA.
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, Berkeley, CA, USA.
- MBIB Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
- Gladstone Institutes, University of California, San Francisco, San Francisco, CA, USA.
- Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA.
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9
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Chabas H, Müller V, Bonhoeffer S, Regoes RR. Epidemiological and evolutionary consequences of different types of CRISPR-Cas systems. PLoS Comput Biol 2022; 18:e1010329. [PMID: 35881633 PMCID: PMC9355216 DOI: 10.1371/journal.pcbi.1010329] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 08/05/2022] [Accepted: 06/27/2022] [Indexed: 11/19/2022] Open
Abstract
Bacteria have adaptive immunity against viruses (phages) in the form of CRISPR-Cas immune systems. Currently, 6 types of CRISPR-Cas systems are known and the molecular study of three of these has revealed important molecular differences. It is unknown if and how these molecular differences change the outcome of phage infection and the evolutionary pressure the CRISPR-Cas systems faces. To determine the importance of these molecular differences, we model a phage outbreak entering a population defending exclusively with a type I/II or a type III CRISPR-Cas system. We show that for type III CRISPR-Cas systems, rapid phage extinction is driven by the probability to acquire at least one resistance spacer. However, for type I/II CRISPR-Cas systems, rapid phage extinction is characterized by an a threshold-like behaviour: any acquisition probability below this threshold leads to phage survival whereas any acquisition probability above it, results in phage extinction. We also show that in the absence of autoimmunity, high acquisition rates evolve. However, when CRISPR-Cas systems are prone to autoimmunity, intermediate levels of acquisition are optimal during a phage outbreak. As we predict an optimal probability of spacer acquisition 2 factors of magnitude above the one that has been measured, we discuss the origin of such a discrepancy. Finally, we show that in a biologically relevant parameter range, a type III CRISPR-Cas system can outcompete a type I/II CRISPR-Cas system with a slightly higher probability of acquisition. CRISPR-Cas systems are adaptive immune systems that use a complex 3-step molecular mechanism to defend prokaryotes against phages. Viral infections of populations defending themselves with CRISPR-Cas can result in rapid phage extinction or in medium-term phage maintenance. To investigate what controls the fate of the phage population, we use mathematical modeling of type I/II and type III CRISPR-Cas systems, and show that two parameters control the epidemiological short-term outcome: the type of CRISPR-Cas systems and CRISPR-Cas probability of resistance acquisition. Furthermore, the latter impacts host fitness. From this, we derive that 1) for both types, CRISPR-Cas acquisition probability is a key predictor of the efficiency and of the cost of a CRISPR-Cas system, 2) during an outbreak, there is an optimal probability of resistance acquisition balancing the cost of autoimmunity and immune efficiency and 3) type I/II CRISPR-Cas systems are likely to evolve higher acquisition probability than type III.
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Affiliation(s)
- Hélène Chabas
- Institute for Integrative Biology, ETH Zürich, Zürich, Switzerland
- * E-mail:
| | - Viktor Müller
- Institute of Biology, Eötvös Loránd University, Budapest, Hungary
| | | | - Roland R. Regoes
- Institute for Integrative Biology, ETH Zürich, Zürich, Switzerland
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10
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Wu WY, Jackson SA, Almendros C, Haagsma AC, Yilmaz S, Gort G, van der Oost J, Brouns SJJ, Staals RHJ. Adaptation by Type V-A and V-B CRISPR-Cas Systems Demonstrates Conserved Protospacer Selection Mechanisms Between Diverse CRISPR-Cas Types. CRISPR J 2022; 5:536-547. [PMID: 35833800 PMCID: PMC9419969 DOI: 10.1089/crispr.2021.0150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Adaptation of clustered regularly interspaced short palindromic repeats (CRISPR) arrays is a crucial process responsible for the unique, adaptive nature of CRISPR-Cas immune systems. The acquisition of new CRISPR spacers from mobile genetic elements has previously been studied for several types of CRISPR-Cas systems. In this study, we used a high-throughput sequencing approach to characterize CRISPR adaptation of the type V-A system from Francisella novicida and the type V-B system from Alicyclobacillus acidoterrestris. In contrast to other class 2 CRISPR-Cas systems, we found that for the type V-A and V-B systems, the Cas12 nucleases are dispensable for spacer acquisition, with only Cas1 and Cas2 (type V-A) or Cas4/1 and Cas2 (type V-B) being necessary and sufficient. Whereas the catalytic activity of Cas4 is not essential for adaptation, Cas4 activity is required for correct protospacer adjacent motif selection in both systems and for prespacer trimming in type V-A. In addition, we provide evidence for acquisition of RecBCD-produced DNA fragments by both systems, but with spacers derived from foreign DNA being incorporated preferentially over those derived from the host chromosome. Our work shows that several spacer acquisition mechanisms are conserved between diverse CRISPR-Cas systems, but also highlights unexpected nuances between similar systems that generally contribute to a bias of gaining immunity against invading genetic elements.
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Affiliation(s)
- Wen Y Wu
- Laboratory of Microbiology, Wageningen University and Research, Wageningen, The Netherlands
| | - Simon A Jackson
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Cristóbal Almendros
- Department of Bionanoscience, Delft University of Technology, Delft, The Netherlands.,Kavli Institute of Nanoscience, Delft, The Netherlands
| | - Anna C Haagsma
- Department of Bionanoscience, Delft University of Technology, Delft, The Netherlands.,Kavli Institute of Nanoscience, Delft, The Netherlands
| | - Suzan Yilmaz
- Laboratory of Microbiology, Wageningen University and Research, Wageningen, The Netherlands
| | - Gerrit Gort
- Biometris, Wageningen University and Research, Wageningen, The Netherlands
| | - John van der Oost
- Laboratory of Microbiology, Wageningen University and Research, Wageningen, The Netherlands
| | - Stan J J Brouns
- Department of Bionanoscience, Delft University of Technology, Delft, The Netherlands.,Kavli Institute of Nanoscience, Delft, The Netherlands
| | - Raymond H J Staals
- Laboratory of Microbiology, Wageningen University and Research, Wageningen, The Netherlands
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11
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Zhang X, An X. Adaptation by Type III CRISPR-Cas Systems: Breakthrough Findings and Open Questions. Front Microbiol 2022; 13:876174. [PMID: 35495695 PMCID: PMC9048733 DOI: 10.3389/fmicb.2022.876174] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 03/03/2022] [Indexed: 12/26/2022] Open
Abstract
CRISPR-Cas systems acquire heritable defense memory against invading nucleic acids through adaptation. Type III CRISPR-Cas systems have unique and intriguing features of defense and are important in method development for Genetics research. We started to understand the common and unique properties of type III CRISPR-Cas adaptation in recent years. This review summarizes our knowledge regarding CRISPR-Cas adaptation with the emphasis on type III systems and discusses open questions for type III adaptation studies.
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Affiliation(s)
- Xinfu Zhang
- Department of Biochemistry and Molecular Biology, The University of Georgia, Athens, GA, United States
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, National Engineering Research Center of Tree breeding and Ecological Remediation, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
- *Correspondence: Xinfu Zhang,
| | - Xinmin An
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, National Engineering Research Center of Tree breeding and Ecological Remediation, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
- Xinmin An,
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12
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Cury J, Bernheim A. CRISPR-Cas and restriction–modification team up to achieve long-term immunity. Trends Microbiol 2022; 30:513-514. [DOI: 10.1016/j.tim.2022.04.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 04/01/2022] [Accepted: 04/05/2022] [Indexed: 11/30/2022]
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13
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Maguin P, Varble A, Modell JW, Marraffini LA. Cleavage of viral DNA by restriction endonucleases stimulates the type II CRISPR-Cas immune response. Mol Cell 2022; 82:907-919.e7. [PMID: 35134339 PMCID: PMC8900293 DOI: 10.1016/j.molcel.2022.01.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 12/03/2021] [Accepted: 01/14/2022] [Indexed: 12/26/2022]
Abstract
Prokaryotic organisms have developed multiple defense systems against phages; however, little is known about whether and how these interact with each other. Here, we studied the connection between two of the most prominent prokaryotic immune systems: restriction-modification and CRISPR. While both systems employ enzymes that cleave a specific DNA sequence of the invader, CRISPR nucleases are programmed with phage-derived spacer sequences, which are integrated into the CRISPR locus upon infection. We found that restriction endonucleases provide a short-term defense, which is rapidly overcome through methylation of the phage genome. In a small fraction of the cells, however, restriction results in the acquisition of spacer sequences from the cleavage site, which mediates a robust type II-A CRISPR-Cas immune response against the methylated phage. This mechanism is reminiscent of eukaryotic immunity in which the innate response offers a first temporary line of defense and also activates a second and more robust adaptive response.
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Affiliation(s)
- Pascal Maguin
- Laboratory of Bacteriology, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
| | - Andrew Varble
- Laboratory of Bacteriology, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA
| | - Joshua W. Modell
- Laboratory of Bacteriology, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA.,Present address: Department of Molecular Biology & Genetics, Johns Hopkins University School of Medicine, 725 N. Wolfe St., PCTB 803, Baltimore, MD 21205, USA
| | - Luciano A. Marraffini
- Laboratory of Bacteriology, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA.,Howard Hughes Medical Institute, The Rockefeller University, 1230 York Ave, New York, NY 10065, USA.,Correspondence to:
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14
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Lee H, Sashital DG. Creating memories: molecular mechanisms of CRISPR adaptation. Trends Biochem Sci 2022; 47:464-476. [DOI: 10.1016/j.tibs.2022.02.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 02/06/2022] [Accepted: 02/07/2022] [Indexed: 12/22/2022]
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15
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Barrangou R, Marraffini LA. Turning CRISPR on with antibiotics. Cell Host Microbe 2022; 30:12-14. [PMID: 35026132 DOI: 10.1016/j.chom.2021.12.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
CRISPR-Cas systems have the ability to integrate invasive DNA sequences to build adaptive immunity in bacteria. In this issue Dimitriu et al. show bacteriostatic antibiotics prompt CRISPR acquisition events, illustrating how environmental conditions affect complex dynamics between host and virus and the corresponding biological and genetic arms race.
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Affiliation(s)
| | - Luciano A Marraffini
- Laboratory of Bacteriology, The Rockefeller University, New York, NY, USA; Howard Hughes Medical Institute, The Rockefeller University, New York, NY, USA.
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16
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Bacteriostatic antibiotics promote CRISPR-Cas adaptive immunity by enabling increased spacer acquisition. Cell Host Microbe 2021; 30:31-40.e5. [PMID: 34932986 DOI: 10.1016/j.chom.2021.11.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 10/12/2021] [Accepted: 11/24/2021] [Indexed: 01/21/2023]
Abstract
Phages impose strong selection on bacteria to evolve resistance against viral predation. Bacteria can rapidly evolve phage resistance via receptor mutation or using their CRISPR-Cas adaptive immune systems. Acquisition of CRISPR immunity relies on the insertion of a phage-derived sequence into CRISPR arrays in the bacterial genome. Using Pseudomonas aeruginosa and its phage DMS3vir as a model, we demonstrate that conditions that reduce bacterial growth rates, such as exposure to bacteriostatic antibiotics (which inhibit cell growth without killing), promote the evolution of CRISPR immunity. We demonstrate that this is due to slower phage development under these conditions, which provides more time for cells to acquire phage-derived sequences and mount an immune response. Our data reveal that the speed of phage development is a key determinant of the evolution of CRISPR immunity and suggest that use of bacteriostatic antibiotics can trigger elevated levels of CRISPR immunity in human-associated and natural environments.
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17
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Prophage integration into CRISPR loci enables evasion of antiviral immunity in Streptococcus pyogenes. Nat Microbiol 2021; 6:1516-1525. [PMID: 34819640 DOI: 10.1038/s41564-021-00996-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 10/15/2021] [Indexed: 12/26/2022]
Abstract
CRISPR loci are composed of short DNA repeats separated by sequences, known as spacers, that match the genomes of invaders such as phages and plasmids. Spacers are transcribed and processed to generate RNA guides used by CRISPR-associated nucleases to recognize and destroy the complementary nucleic acids of invaders. To counteract this defence, phages can produce small proteins that inhibit these nucleases, termed anti-CRISPRs (Acrs). Here we demonstrate that the ΦAP1.1 temperate phage utilizes an alternative approach to antagonize the type II-A CRISPR response in Streptococcus pyogenes. Immediately after infection, this phage expresses a small anti-CRISPR protein, AcrIIA23, that prevents Cas9 function, allowing ΦAP1.1 to integrate into the direct repeats of the CRISPR locus, neutralizing immunity. However, acrIIA23 is not transcribed during lysogeny and phage integration/excision cycles can result in the deletion and/or transduction of spacers, enabling a complex modulation of the type II-A CRISPR immune response. A bioinformatic search identified prophages integrated not only in the CRISPR repeats, but also the cas genes, of diverse bacterial species, suggesting that prophage disruption of the CRISPR-cas locus is a recurrent mechanism to counteract immunity.
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18
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Viral recombination systems limit CRISPR-Cas targeting through the generation of escape mutations. Cell Host Microbe 2021; 29:1482-1495.e12. [PMID: 34582782 DOI: 10.1016/j.chom.2021.09.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 06/24/2021] [Accepted: 09/02/2021] [Indexed: 12/26/2022]
Abstract
CRISPR-Cas systems provide immunity to bacteria by programing Cas nucleases with RNA guides that recognize and cleave infecting viral genomes. Bacteria and their viruses each encode recombination systems that could repair the cleaved viral DNA. However, it is unknown whether and how these systems can affect CRISPR immunity. Bacteriophage λ uses the Red system (gam-exo-bet) to promote recombination between related phages. Here, we show that λ Red also mediates evasion of CRISPR-Cas targeting. Gam inhibits the host E. coli RecBCD recombination system, allowing recombination and repair of the cleaved DNA by phage Exo-Beta, which promotes the generation of mutations within the CRISPR target sequence. Red recombination is strikingly more efficient than the host's RecBCD-RecA in the production of large numbers of phages that escape CRISPR targeting. These results reveal a role for Red-like systems in the protection of bacteriophages against sequence-specific nucleases, which may facilitate their spread across viral genomes.
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19
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Guzmán NM, Esquerra-Ruvira B, Mojica FJM. Digging into the lesser-known aspects of CRISPR biology. Int Microbiol 2021; 24:473-498. [PMID: 34487299 PMCID: PMC8616872 DOI: 10.1007/s10123-021-00208-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/30/2021] [Accepted: 08/31/2021] [Indexed: 12/26/2022]
Abstract
A long time has passed since regularly interspaced DNA repeats were discovered in prokaryotes. Today, those enigmatic repetitive elements termed clustered regularly interspaced short palindromic repeats (CRISPR) are acknowledged as an emblematic part of multicomponent CRISPR-Cas (CRISPR associated) systems. These systems are involved in a variety of roles in bacteria and archaea, notably, that of conferring protection against transmissible genetic elements through an adaptive immune-like response. This review summarises the present knowledge on the diversity, molecular mechanisms and biology of CRISPR-Cas. We pay special attention to the most recent findings related to the determinants and consequences of CRISPR-Cas activity. Research on the basic features of these systems illustrates how instrumental the study of prokaryotes is for understanding biology in general, ultimately providing valuable tools for diverse fields and fuelling research beyond the mainstream.
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Affiliation(s)
- Noemí M Guzmán
- Dpto. Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain
| | - Belén Esquerra-Ruvira
- Dpto. Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain
| | - Francisco J M Mojica
- Dpto. Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain. .,Instituto Multidisciplinar para el Estudio del Medio, Universidad de Alicante, Alicante, Spain.
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20
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Dimitriu T, Szczelkun MD, Westra ER. Evolutionary Ecology and Interplay of Prokaryotic Innate and Adaptive Immune Systems. Curr Biol 2021; 30:R1189-R1202. [PMID: 33022264 DOI: 10.1016/j.cub.2020.08.028] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Like many organisms, bacteria and archaea have both innate and adaptive immune systems to defend against infection by viruses and other parasites. Innate immunity most commonly relies on the endonuclease-mediated cleavage of any incoming DNA that lacks a specific epigenetic modification, through a system known as restriction-modification. CRISPR-Cas-mediated adaptive immunity relies on the insertion of short DNA sequences from parasite genomes into CRISPR arrays on the host genome to provide sequence-specific protection. The discovery of each of these systems has revolutionised our ability to carry out genetic manipulations, and, as a consequence, the enzymes involved have been characterised in exquisite detail. In comparison, much less is known about the importance of these two arms of the defence for the ecology and evolution of prokaryotes and their parasites. Here, we review our current ecological and evolutionary understanding of these systems in isolation, and discuss the need to study how innate and adaptive immune responses are integrated when they coexist in the same cell.
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Affiliation(s)
- Tatiana Dimitriu
- Environment and Sustainability Institute, Biosciences, University of Exeter, Penryn TR10 9FE, UK.
| | - Mark D Szczelkun
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK.
| | - Edze R Westra
- Environment and Sustainability Institute, Biosciences, University of Exeter, Penryn TR10 9FE, UK.
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21
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Isaev AB, Musharova OS, Severinov KV. Microbial Arsenal of Antiviral Defenses. Part II. BIOCHEMISTRY (MOSCOW) 2021; 86:449-470. [PMID: 33941066 DOI: 10.1134/s0006297921040064] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Bacteriophages or phages are viruses that infect bacterial cells (for the scope of this review we will also consider viruses that infect Archaea). The constant threat of phage infection is a major force that shapes evolution of microbial genomes. To withstand infection, bacteria had evolved numerous strategies to avoid recognition by phages or to directly interfere with phage propagation inside the cell. Classical molecular biology and genetic engineering had been deeply intertwined with the study of phages and host defenses. Nowadays, owing to the rise of phage therapy, broad application of CRISPR-Cas technologies, and development of bioinformatics approaches that facilitate discovery of new systems, phage biology experiences a revival. This review describes variety of strategies employed by microbes to counter phage infection. In the first part defense associated with cell surface, roles of small molecules, and innate immunity systems relying on DNA modification were discussed. The second part focuses on adaptive immunity systems, abortive infection mechanisms, defenses associated with mobile genetic elements, and novel systems discovered in recent years through metagenomic mining.
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Affiliation(s)
- Artem B Isaev
- Skolkovo Institute of Science and Technology, Skolkovo, Moscow, 143028, Russia.
| | - Olga S Musharova
- Skolkovo Institute of Science and Technology, Skolkovo, Moscow, 143028, Russia. .,Institute of Molecular Genetics, Moscow, 119334, Russia
| | - Konstantin V Severinov
- Skolkovo Institute of Science and Technology, Skolkovo, Moscow, 143028, Russia. .,Waksman Institute of Microbiology, Piscataway, NJ 08854, USA
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22
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Prespacers formed during primed adaptation associate with the Cas1-Cas2 adaptation complex and the Cas3 interference nuclease-helicase. Proc Natl Acad Sci U S A 2021; 118:2021291118. [PMID: 34035168 PMCID: PMC8179228 DOI: 10.1073/pnas.2021291118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Primed adaptation allows rapid acquisition of protective spacers derived from foreign mobile genetic elements into CRISPR arrays of the host. Primed adaptation requires ongoing CRISPR interference that destroys foreign genetic elements, but the nature of this requirement is unknown. Using the Escherichia coli I-E CRISPR-Cas as a model, we show that prespacers, short fragments of foreign DNA on their way to become incorporated into CRISPR arrays as spacers, are associated with both the adaptation integrase Cas1 and the interference nuclease Cas3, implying physical association of the interference and adaptation machineries during priming. For Type I CRISPR-Cas systems, a mode of CRISPR adaptation named priming has been described. Priming allows specific and highly efficient acquisition of new spacers from DNA recognized (primed) by the Cascade-crRNA (CRISPR RNA) effector complex. Recognition of the priming protospacer by Cascade-crRNA serves as a signal for engaging the Cas3 nuclease–helicase required for both interference and primed adaptation, suggesting the existence of a primed adaptation complex (PAC) containing the Cas1–Cas2 adaptation integrase and Cas3. To detect this complex in vivo, we here performed chromatin immunoprecipitation with Cas3-specific and Cas1-specific antibodies using cells undergoing primed adaptation. We found that prespacers are bound by both Cas1 (presumably, as part of the Cas1–Cas2 integrase) and Cas3, implying direct physical association of the interference and adaptation machineries as part of PAC.
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23
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Abstract
Streptococcus mutans strain P42S possesses a type II-A CRISPR-Cas system that protects against phage infection and plasmid transformation. The analysis of 293 bacteriophage-insensitive mutants (BIMs) obtained upon exposure to the virulent phage M102AD revealed the acquisition of 399 unique spacers, including several ectopic spacer acquisitions and a few cases of native spacer deletions. The acquisition of multiple spacers was also observed and appears to be mostly due to priming, which has been rarely reported for type II-A systems. Analyses of the acquired spacers indicated that 88% of them are identical to a region of the phage M102AD genome. The remaining 12% of spacers had mismatches with the phage genome, primarily at the 5′ end of the spacer, leaving the seed sequence at the 3′ end largely intact. When a high multiplicity of infection (MOI) was used in the phage challenge assays, we also observed the emergence of CRISPR BIMs that, in addition to the acquisition of new spacers, displayed a reduced phage adsorption phenotype. While CRISPR-Cas and adsorption resistance work in tandem to protect S. mutans P42S against phage M102AD, nonidentified antiviral mechanisms are also likely at play in this strain. IMPORTANCE Bacteria are under the constant threat of viral predation and have therefore developed several defense mechanisms, including CRISPR-Cas systems. While studies on the mode of action of CRISPR-Cas systems have already provided great insights into phage-bacterium interactions, still more information is needed on the biology of these systems. The additional characterization of the type II-A CRISPR-Cas system of Streptococcus mutans P42S in this study provides novel information on the spacer acquisition step, especially regarding protospacer-adjacent motif (PAM) recognition, multiple-spacer acquisition, and priming.
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24
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Jakhanwal S, Cress BF, Maguin P, Lobba MJ, Marraffini LA, Doudna JA. A CRISPR-Cas9-integrase complex generates precise DNA fragments for genome integration. Nucleic Acids Res 2021; 49:3546-3556. [PMID: 33693715 PMCID: PMC8034620 DOI: 10.1093/nar/gkab123] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 02/04/2021] [Accepted: 02/26/2021] [Indexed: 01/24/2023] Open
Abstract
CRISPR-Cas9 is an RNA-guided DNA endonuclease involved in bacterial adaptive immunity and widely repurposed for genome editing in human cells, animals and plants. In bacteria, RNA molecules that guide Cas9's activity derive from foreign DNA fragments that are captured and integrated into the host CRISPR genomic locus by the Cas1-Cas2 CRISPR integrase. How cells generate the specific lengths of DNA required for integrase capture is a central unanswered question of type II-A CRISPR-based adaptive immunity. Here, we show that an integrase supercomplex comprising guide RNA and the proteins Cas1, Cas2, Csn2 and Cas9 generates precisely trimmed 30-base pair DNA molecules required for genome integration. The HNH active site of Cas9 catalyzes exonucleolytic DNA trimming by a mechanism that is independent of the guide RNA sequence. These results show that Cas9 possesses a distinct catalytic capacity for generating immunological memory in prokaryotes.
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Affiliation(s)
- Shrutee Jakhanwal
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.,California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA.,Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Brady F Cress
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.,California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA.,Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Pascal Maguin
- Laboratory of Bacteriology, The Rockefeller University, New York, NY 10065, USA
| | - Marco J Lobba
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.,California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA.,Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | | | - Jennifer A Doudna
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.,California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA.,Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA.,Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA.,Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720, USA.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.,Gladstone Institute of Data Science and Biotechnology, Gladstone Institutes, San Francisco, CA 94158, USA
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25
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Abstract
CRISPR-Cas systems provide bacteria and archaea with adaptive, heritable immunity against their viruses (bacteriophages and phages) and other parasitic genetic elements. CRISPR-Cas systems are highly diverse, and we are only beginning to understand their relative importance in phage defense. In this review, we will discuss when and why CRISPR-Cas immunity against phages evolves, and how this, in turn, selects for the evolution of immune evasion by phages. Finally, we will discuss our current understanding of if, and when, we observe coevolution between CRISPR-Cas systems and phages, and how this may be influenced by the mechanism of CRISPR-Cas immunity.
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26
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Tenea GN, Ortega C. Genome Characterization of Lactiplantibacillus plantarum Strain UTNGt2 Originated from Theobroma grandiflorum (White Cacao) of Ecuadorian Amazon: Antimicrobial Peptides from Safety to Potential Applications. Antibiotics (Basel) 2021; 10:antibiotics10040383. [PMID: 33916842 PMCID: PMC8066128 DOI: 10.3390/antibiotics10040383] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Revised: 03/31/2021] [Accepted: 04/01/2021] [Indexed: 12/31/2022] Open
Abstract
The genome characterization of the Lactiplantibacillus plantarum strain UTNGt2, isolated from wild copoazu or white cacao (Theobroma grandiflorum), is described. A total of 31 contigs is assembled with a total length of 3,264,448 bases, with all contigs matching the core genome of different groups in the database. The genome size is 3,540,752 bases with GC content of 44.53% and the genome repeat sequences constitute around 457,386 bases of the assembly. The UTNGt2 matches the Lactiplantibacillus plantarum genome with 99% identity. The genome contains 3115 genes, 3052 protein-coding genes, assigned with the EggNOG database. On the basis of the results, 745 proteins are classified with an unknown function, from which 128 proteins have no match in the BLASTN database. It also contains 57 tRNAs, 5 copies of 5S rRNA, and 1 copy of tmRNA. Based on gene prediction and annotation results, 9.4% of proteins are involved in carbohydrate transport and metabolism and 8.46% in transcription, 2.36% are responsible for defense mechanisms, 0.5% are responsible for the biosynthesis of secondary metabolites, transport, and catabolism, while 25.11% have an unknown function. The genome revealed the presence of genes involved in riboflavin and folate production, the presence of CRISPR/Cas genes, phage sequences, the absence of acquired antibiotics resistance genes, virulence, and pathogenic factors, suggesting that UTNGt2 is a safe strain. Its highly antimicrobial capacity is related to the presence of two bacteriocin clusters (class IIc) of the sactipeptide class (contig 4) and plantaricin E class (contig 22), as detected by the BAGEL 4 webserver. Several RiPP-like peptides (non-bactericidal ribosomally produced and post-translationally modified peptides), polyketides (PKs), and terpenes were predicted. Whole-genome sequencing analysis revealed that the UTNGt2 strain has diverse bacteriocins with a high inhibitory capacity, thus it is a bacteriocinogenic strain. Considering the safety profile, UTNGt2 is a nonpathogenic, nonvirulent strain with valuable biotechnological traits and can be further exploited for its probiotic and antimicrobial potential in the food industry or as a potential producer strain of antimicrobial peptides as an alternative to conventional antibiotics.
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27
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Abstract
CRISPR-Cas systems are immune systems that protect bacteria and archaea against their viruses, bacteriophages. Immunity is achieved through the acquisition of short DNA fragments from the viral invader’s genome. CRISPR-Cas immune systems adapt to new threats by acquiring new spacers from invading nucleic acids such as phage genomes. However, some CRISPR-Cas loci lack genes necessary for spacer acquisition despite variation in spacer content between microbial strains. It has been suggested that such loci may use acquisition machinery from cooccurring CRISPR-Cas systems within the same strain. Here, following infection by a virulent phage with a double-stranded DNA (dsDNA) genome, we observed spacer acquisition in the native host Flavobacterium columnare that carries an acquisition-deficient CRISPR-Cas subtype VI-B system and a complete subtype II-C system. We show that the VI-B locus acquires spacers from both the bacterial and phage genomes, while the newly acquired II-C spacers mainly target the viral genome. Both loci preferably target the terminal end of the phage genome, with priming-like patterns around a preexisting II-C protospacer. Through gene deletion, we show that the RNA-cleaving VI-B system acquires spacers in trans using acquisition machinery from the DNA-cleaving II-C system. Our observations support the concept of cross talk between CRISPR-Cas systems and raise further questions regarding the plasticity of adaptation modules.
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28
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Diversity of molecular mechanisms used by anti-CRISPR proteins: the tip of an iceberg? Biochem Soc Trans 2021; 48:507-516. [PMID: 32196554 DOI: 10.1042/bst20190638] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 02/27/2020] [Accepted: 02/28/2020] [Indexed: 12/14/2022]
Abstract
Bacteriophages (phages) and their preys are engaged in an evolutionary arms race driving the co-adaptation of their attack and defense mechanisms. In this context, phages have evolved diverse anti-CRISPR proteins to evade the bacterial CRISPR-Cas immune system, and propagate. Anti-CRISPR proteins do not share much resemblance with each other and with proteins of known function, which raises intriguing questions particularly relating to their modes of action. In recent years, there have been many structure-function studies shedding light on different CRISPR-Cas inhibition strategies. As the anti-CRISPR field of research is rapidly growing, it is opportune to review the current knowledge on these proteins, with particular emphasis on the molecular strategies deployed to inactivate distinct steps of CRISPR-Cas immunity. Anti-CRISPR proteins can be orthosteric or allosteric inhibitors of CRISPR-Cas machineries, as well as enzymes that irreversibly modify CRISPR-Cas components. This repertoire of CRISPR-Cas inhibition mechanisms will likely expand in the future, providing fundamental knowledge on phage-bacteria interactions and offering great perspectives for the development of biotechnological tools to fine-tune CRISPR-Cas-based gene edition.
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29
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Goldberg GW, Spencer JM, Giganti DO, Camellato BR, Agmon N, Ichikawa DM, Boeke JD, Noyes MB. Engineered dual selection for directed evolution of SpCas9 PAM specificity. Nat Commun 2021; 12:349. [PMID: 33441553 PMCID: PMC7807044 DOI: 10.1038/s41467-020-20650-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 11/18/2020] [Indexed: 12/26/2022] Open
Abstract
The widely used Streptococcus pyogenes Cas9 (SpCas9) nuclease derives its DNA targeting specificity from protein-DNA contacts with protospacer adjacent motif (PAM) sequences, in addition to base-pairing interactions between its guide RNA and target DNA. Previous reports have established that the PAM specificity of SpCas9 can be altered via positive selection procedures for directed evolution or other protein engineering strategies. Here we exploit in vivo directed evolution systems that incorporate simultaneous positive and negative selection to evolve SpCas9 variants with commensurate or improved activity on NAG PAMs relative to wild type and reduced activity on NGG PAMs, particularly YGG PAMs. We also show that the PAM preferences of available evolutionary intermediates effectively determine whether similar counterselection PAMs elicit different selection stringencies, and demonstrate that negative selection can be specifically increased in a yeast selection system through the fusion of compensatory zinc fingers to SpCas9.
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Affiliation(s)
- Gregory W Goldberg
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA.
| | - Jeffrey M Spencer
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
| | - David O Giganti
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
| | - Brendan R Camellato
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
| | - Neta Agmon
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
- Neochromosome, Inc., Alexandria Center for Life Science, New York, NY, 10016, USA
| | - David M Ichikawa
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
| | - Jef D Boeke
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA
- Department of Biomedical Engineering, NYU Tandon School of Engineering, Brooklyn, NY, 11201, USA
| | - Marcus B Noyes
- Institute for Systems Genetics, NYU Langone Health, New York, NY, 10016, USA.
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30
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Abstract
Prokaryotes have developed numerous defense strategies to combat the constant threat posed by the diverse genetic parasites that endanger them. Clustered regularly interspaced short palindromic repeat (CRISPR)-Cas loci guard their hosts with an adaptive immune system against foreign nucleic acids. Protection starts with an immunization phase, in which short pieces of the invader's genome, known as spacers, are captured and integrated into the CRISPR locus after infection. Next, during the targeting phase, spacers are transcribed into CRISPR RNAs (crRNAs) that guide CRISPR-associated (Cas) nucleases to destroy the invader's DNA or RNA. Here we describe the many different molecular mechanisms of CRISPR targeting and how they are interconnected with the immunization phase through a third phase of the CRISPR-Cas immune response: primed spacer acquisition. In this phase, Cas proteins direct the crRNA-guided acquisition of additional spacers to achieve a more rapid and robust immunization of the population.
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Affiliation(s)
- Philip M. Nussenzweig
- Laboratory of Bacteriology, The Rockefeller University, New York, NY 10065, USA
- Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY 10065, USA
| | - Luciano A. Marraffini
- Laboratory of Bacteriology, The Rockefeller University, New York, NY 10065, USA
- Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10065, USA
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31
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Westra ER, Levin BR. It is unclear how important CRISPR-Cas systems are for protecting natural populations of bacteria against infections by mobile genetic elements. Proc Natl Acad Sci U S A 2020; 117:27777-27785. [PMID: 33122438 PMCID: PMC7668106 DOI: 10.1073/pnas.1915966117] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Articles on CRISPR commonly open with some variant of the phrase "these short palindromic repeats and their associated endonucleases (Cas) are an adaptive immune system that exists to protect bacteria and archaea from viruses and infections with other mobile genetic elements." There is an abundance of genomic data consistent with the hypothesis that CRISPR plays this role in natural populations of bacteria and archaea, and experimental demonstrations with a few species of bacteria and their phage and plasmids show that CRISPR-Cas systems can play this role in vitro. Not at all clear are the ubiquity, magnitude, and nature of the contribution of CRISPR-Cas systems to the ecology and evolution of natural populations of microbes and the strength of selection mediated by different types of phage and plasmids to the evolution and maintenance of CRISPR-Cas systems. In this perspective, with the aid of heuristic mathematical-computer simulation models, we explore the a priori conditions under which exposure to lytic and temperate phage and conjugative plasmids will select for and maintain CRISPR-Cas systems in populations of bacteria and archaea. We review the existing literature addressing these ecological and evolutionary questions and highlight the experimental and other evidence needed to fully understand the conditions responsible for the evolution and maintenance of CRISPR-Cas systems and the contribution of these systems to the ecology and evolution of bacteria, archaea, and the mobile genetic elements that infect them.
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Affiliation(s)
- Edze R Westra
- Environment and Sustainability Institute, Biosciences, University of Exeter, Penryn, TR10 9FE Cornwall, United Kingdom;
| | - Bruce R Levin
- Department of Biology, Emory University, Atlanta, GA 30307
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32
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Garrett S, Shiimori M, Watts EA, Clark L, Graveley BR, Terns MP. Primed CRISPR DNA uptake in Pyrococcus furiosus. Nucleic Acids Res 2020; 48:6120-6135. [PMID: 32421777 PMCID: PMC7293040 DOI: 10.1093/nar/gkaa381] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 04/15/2020] [Accepted: 05/11/2020] [Indexed: 12/19/2022] Open
Abstract
CRISPR-Cas adaptive immune systems are used by prokaryotes to defend against invaders like viruses and other mobile genetic elements. Immune memories are stored in the form of 'spacers' which are short DNA sequences that are captured from invaders and added to the CRISPR array during a process called 'adaptation'. Spacers are transcribed and the resulting CRISPR (cr)RNAs assemble with different Cas proteins to form effector complexes that recognize matching nucleic acid and destroy it ('interference'). Adaptation can be 'naïve', i.e. independent of any existing spacer matches, or it can be 'primed', i.e. spurred by the crRNA-mediated detection of a complete or partial match to an invader sequence. Here we show that primed adaptation occurs in Pyrococcus furiosus. Although P. furiosus has three distinct CRISPR-Cas interference systems (I-B, I-A and III-B), only the I-B system and Cas3 were necessary for priming. Cas4, which is important for selection and processing of new spacers in naïve adaptation, was also essential for priming. Loss of either the I-B effector proteins or Cas3 reduced naïve adaptation. However, when Cas3 and all crRNP genes were deleted, uptake of correctly processed spacers was observed, indicating that none of these interference proteins are necessary for naïve adaptation.
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Affiliation(s)
- Sandra Garrett
- Department of Genetics and Genome Sciences, Institute for Systems Genomics, UConn Stem Cell Institute, UConn Health, Farmington, CT 06030, USA
| | - Masami Shiimori
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Elizabeth A Watts
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Landon Clark
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Brenton R Graveley
- Department of Genetics and Genome Sciences, Institute for Systems Genomics, UConn Stem Cell Institute, UConn Health, Farmington, CT 06030, USA
| | - Michael P Terns
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.,Department of Microbiology, University of Georgia, Athens, GA 30602, USA.,Department of Genetics, University of Georgia, Athens, GA 30602, USA
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33
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Abstract
CRISPR research began over 30 years ago with the incidental discovery of an unusual nucleotide arrangement in the Escherichia coli genome. It took 20 years to find the main function of CRISPR-Cas systems as an adaptive defence mechanism against invading nucleic acids, and our knowledge of their biology has steadily increased ever since. In parallel, the number of applications derived from CRISPR-Cas systems has risen spectacularly. The CRISPR-based genome editing tool is arguably the most exciting application in both basic and applied research. Lately, CRISPR-Cas research has partially shifted to the least understood aspect of its biology: the ability of CRISPR-Cas systems to acquire new immunities during the so-called adaptation step. To date, the most efficient natural system to readily acquire new spacers is the type II-A system of the gram-positive dairy bacterium Streptococcus thermophilus. The discovery of additional systems able to acquire new spacers will hopefully draw more attention to this step of CRISPR-Cas biology. This review focuses on the breakthroughs that have helped to unravel the adaptation phase and on questions that remain to be answered.
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Affiliation(s)
- Cas Mosterd
- Département de biochimie, de microbiologie et de bio-informatique, Faculté des sciences et de génie, Université Laval, QC G1V 0A6, Canada.,Groupe de recherche en écologie buccale, Faculté de médecine dentaire, Université Laval, QC G1V 0A6, Canada
| | - Geneviève M Rousseau
- Département de biochimie, de microbiologie et de bio-informatique, Faculté des sciences et de génie, Université Laval, QC G1V 0A6, Canada.,Groupe de recherche en écologie buccale, Faculté de médecine dentaire, Université Laval, QC G1V 0A6, Canada
| | - Sylvain Moineau
- Département de biochimie, de microbiologie et de bio-informatique, Faculté des sciences et de génie, Université Laval, QC G1V 0A6, Canada.,Groupe de recherche en écologie buccale, Faculté de médecine dentaire, Université Laval, QC G1V 0A6, Canada.,Félix d'Hérelle Reference Center for Bacterial Viruses, Faculté de médecine dentaire, Université Laval, QC G1V 0A6, Canada
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34
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Roberts A, Barrangou R. Applications of CRISPR-Cas systems in lactic acid bacteria. FEMS Microbiol Rev 2020; 44:523-537. [DOI: 10.1093/femsre/fuaa016] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 05/18/2020] [Indexed: 12/26/2022] Open
Abstract
ABSTRACT
As a phenotypically and phylogenetically diverse group, lactic acid bacteria are found in a variety of natural environments and occupy important roles in medicine, biotechnology, food and agriculture. The widespread use of lactic acid bacteria across these industries fuels the need for new and functionally diverse strains that may be utilized as starter cultures or probiotics. Originally characterized in lactic acid bacteria, CRISPR-Cas systems and derived molecular machines can be used natively or exogenously to engineer new strains with enhanced functional attributes. Research on CRISPR-Cas biology and its applications has exploded over the past decade with studies spanning from the initial characterization of CRISPR-Cas immunity in Streptococcus thermophilus to the use of CRISPR-Cas for clinical gene therapies. Here, we discuss CRISPR-Cas classification, overview CRISPR biology and mechanism of action, and discuss current and future applications in lactic acid bacteria, opening new avenues for their industrial exploitation and manipulation of microbiomes.
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Affiliation(s)
- Avery Roberts
- Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Campus Box 7624, Raleigh, NC 27695, USA
- Genomic Sciences Graduate Program, North Carolina State University, Campus Box 7566, Raleigh, NC 27695, USA
| | - Rodolphe Barrangou
- Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Campus Box 7624, Raleigh, NC 27695, USA
- Genomic Sciences Graduate Program, North Carolina State University, Campus Box 7566, Raleigh, NC 27695, USA
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35
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Weissman JL, Stoltzfus A, Westra ER, Johnson PLF. Avoidance of Self during CRISPR Immunization. Trends Microbiol 2020; 28:543-553. [PMID: 32544441 DOI: 10.1016/j.tim.2020.02.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 02/05/2020] [Accepted: 02/25/2020] [Indexed: 02/07/2023]
Abstract
The battle between microbes and their viruses is ancient and ongoing. Clustered regularly interspaced short palindromic repeat (CRISPR) immunity, the first and, to date, only form of adaptive immunity found in prokaryotes, represents a flexible mechanism to recall past infections while also adapting to a changing pathogenic environment. Critical to the role of CRISPR as an adaptive immune mechanism is its capacity for self versus non-self recognition when acquiring novel immune memories. Yet, CRISPR systems vary widely in both how and to what degree they can distinguish foreign from self-derived genetic material. We document known and hypothesized mechanisms that bias the acquisition of immune memory towards non-self targets. We demonstrate that diversity is the rule, with many widespread but no universal mechanisms for self versus non-self recognition.
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Affiliation(s)
- Jake L Weissman
- Department of Biology, University of Maryland, College Park, MD, USA
| | - Arlin Stoltzfus
- Office of Data and Informatics, Material Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA; Institute for Bioscience and Biotechnology Research, 9600 Gudelsky Drive, Rockville, MD 20850, USA
| | - Edze R Westra
- Environment and Sustainability Institute, Centre for Ecology and Conservation, University of Exeter, Biosciences, Penryn, Cornwall, UK
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Abstract
The response of bacteria to the threat posed by phages depends on their local environment.
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Affiliation(s)
- Michael A Schelling
- Roy J Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State UniversityAmesUnited States
| | - Dipali G Sashital
- Roy J Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State UniversityAmesUnited States
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Pyenson NC, Marraffini LA. Co-evolution within structured bacterial communities results in multiple expansion of CRISPR loci and enhanced immunity. eLife 2020; 9:e53078. [PMID: 32223887 PMCID: PMC7105378 DOI: 10.7554/elife.53078] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2019] [Accepted: 02/12/2020] [Indexed: 12/26/2022] Open
Abstract
Type II CRISPR-Cas systems provide immunity against phages and plasmids that infect bacteria through the insertion of a short sequence from the invader's genome, known as the 'spacer', into the CRISPR locus. Spacers are transcribed into guide RNAs that direct the Cas9 nuclease to its target on the invader. In liquid cultures, most bacteria acquire a single spacer. Multiple spacer integration is a rare event which significance for immunity is poorly understood. Here, we found that when phage infections occur on solid media, a high proportion of the surviving colonies display complex morphologies that contain cells with multiple spacers. This is the result of the viral-host co-evolution, in which the immunity provided by the initial acquired spacer is easily overcome by escaper phages. Our results reveal the versatility of CRISPR-Cas immunity, which can respond with both single or multiple spacer acquisition schemes to solve challenges presented by different environments.
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Affiliation(s)
- Nora C Pyenson
- Laboratory of Bacteriology, The Rockefeller UniversityNew YorkUnited States
| | - Luciano A Marraffini
- Laboratory of Bacteriology, The Rockefeller UniversityNew YorkUnited States
- Howard Hughes Medical Institute, The Rockefeller UniversityNew YorkUnited States
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38
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The arms race between bacteria and their phage foes. Nature 2020; 577:327-336. [PMID: 31942051 DOI: 10.1038/s41586-019-1894-8] [Citation(s) in RCA: 415] [Impact Index Per Article: 103.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 11/13/2019] [Indexed: 12/26/2022]
Abstract
Bacteria are under immense evolutionary pressure from their viral invaders-bacteriophages. Bacteria have evolved numerous immune mechanisms, both innate and adaptive, to cope with this pressure. The discovery and exploitation of CRISPR-Cas systems have stimulated a resurgence in the identification and characterization of anti-phage mechanisms. Bacteriophages use an extensive battery of counter-defence strategies to co-exist in the presence of these diverse phage defence mechanisms. Understanding the dynamics of the interactions between these microorganisms has implications for phage-based therapies, microbial ecology and evolution, and the development of new biotechnological tools. Here we review the spectrum of anti-phage systems and highlight their evasion by bacteriophages.
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