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Mancilla-Rojano J, Flores V, Cevallos MA, Ochoa SA, Parra-Flores J, Arellano-Galindo J, Xicohtencatl-Cortes J, Cruz-Córdova A. A bioinformatic approach to identify confirmed and probable CRISPR-Cas systems in the Acinetobacter calcoaceticus- Acinetobacter baumannii complex genomes. Front Microbiol 2024; 15:1335997. [PMID: 38655087 PMCID: PMC11035748 DOI: 10.3389/fmicb.2024.1335997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 03/26/2024] [Indexed: 04/26/2024] Open
Abstract
Introduction The Acinetobacter calcoaceticus-Acinetobacter baumannii complex, or Acb complex, consists of six species: Acinetobacter baumannii, Acinetobacter calcoaceticus, Acinetobacter nosocomialis, Acinetobacter pittii, Acinetobacter seifertii, and Acinetobacter lactucae. A. baumannii is the most clinically significant of these species and is frequently related to healthcare-associated infections (HCAIs). Clustered regularly interspaced short palindromic repeat (CRISPR) arrays and associated genes (cas) constitute bacterial adaptive immune systems and function as variable genetic elements. This study aimed to conduct a genomic analysis of Acb complex genomes available in databases to describe and characterize CRISPR systems and cas genes. Methods Acb complex genomes available in the NCBI and BV-BRC databases, the identification and characterization of CRISPR-Cas systems were performed using CRISPRCasFinder, CRISPRminer, and CRISPRDetect. Sequence types (STs) were determined using the Oxford scheme and ribosomal multilocus sequence typing (rMLST). Prophages were identified using PHASTER and Prophage Hunter. Results A total of 293 genomes representing six Acb species exhibited CRISPR-related sequences. These genomes originate from various sources, including clinical specimens, animals, medical devices, and environmental samples. Sequence typing identified 145 ribosomal multilocus sequence types (rSTs). CRISPR-Cas systems were confirmed in 26.3% of the genomes, classified as subtypes I-Fa, I-Fb and I-Fv. Probable CRISPR arrays and cas genes associated with CRISPR-Cas subtypes III-A, I-B, and III-B were also detected. Some of the CRISPR-Cas systems are associated with genomic regions related to Cap4 proteins, and toxin-antitoxin systems. Moreover, prophage sequences were prevalent in 68.9% of the genomes. Analysis revealed a connection between these prophages and CRISPR-Cas systems, indicating an ongoing arms race between the bacteria and their bacteriophages. Furthermore, proteins associated with anti-CRISPR systems, such as AcrF11 and AcrF7, were identified in the A. baumannii and A. pittii genomes. Discussion This study elucidates CRISPR-Cas systems and defense mechanisms within the Acb complex, highlighting their diverse distribution and interactions with prophages and other genetic elements. This study also provides valuable insights into the evolution and adaptation of these microorganisms in various environments and clinical settings.
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Affiliation(s)
- Jetsi Mancilla-Rojano
- Posgrado en Ciencias Biológicas, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico, Mexico
- Laboratorio de Investigación en Bacteriología Intestinal, Unidad de Enfermedades Infecciosas, Hospital Infantil de México Federico Gómez, Secretaría de Salud, Mexico, Mexico
| | - Víctor Flores
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Miguel A. Cevallos
- Centro de Ciencias Genómicas, Programa de Genómica Evolutiva, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Sara A. Ochoa
- Laboratorio de Investigación en Bacteriología Intestinal, Unidad de Enfermedades Infecciosas, Hospital Infantil de México Federico Gómez, Secretaría de Salud, Mexico, Mexico
| | - Julio Parra-Flores
- Department of Nutrition and Public Health, Universidad del Bío-Bío, Chillán, Chile
| | - José Arellano-Galindo
- Unidad de Investigación en Enfermedades Infecciosas, Hospital Infantil de México Federico Gomez, Mexico, Mexico
| | - Juan Xicohtencatl-Cortes
- Laboratorio de Investigación en Bacteriología Intestinal, Unidad de Enfermedades Infecciosas, Hospital Infantil de México Federico Gómez, Secretaría de Salud, Mexico, Mexico
| | - Ariadnna Cruz-Córdova
- Posgrado en Ciencias Biológicas, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico, Mexico
- Laboratorio de Investigación en Bacteriología Intestinal, Unidad de Enfermedades Infecciosas, Hospital Infantil de México Federico Gómez, Secretaría de Salud, Mexico, Mexico
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Wimmer F, Englert F, Wandera KG, Alkhnbashi O, Collins S, Backofen R, Beisel C. Interrogating two extensively self-targeting Type I CRISPR-Cas systems in Xanthomonas albilineans reveals distinct anti-CRISPR proteins that block DNA degradation. Nucleic Acids Res 2024; 52:769-783. [PMID: 38015466 PMCID: PMC10810201 DOI: 10.1093/nar/gkad1097] [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: 04/15/2023] [Revised: 10/25/2023] [Accepted: 10/31/2023] [Indexed: 11/29/2023] Open
Abstract
CRISPR-Cas systems store fragments of invader DNA as spacers to recognize and clear those same invaders in the future. Spacers can also be acquired from the host's genomic DNA, leading to lethal self-targeting. While self-targeting can be circumvented through different mechanisms, natural examples remain poorly explored. Here, we investigate extensive self-targeting by two CRISPR-Cas systems encoding 24 self-targeting spacers in the plant pathogen Xanthomonas albilineans. We show that the native I-C and I-F1 systems are actively expressed and that CRISPR RNAs are properly processed. When expressed in Escherichia coli, each Cascade complex binds its PAM-flanked DNA target to block transcription, while the addition of Cas3 paired with genome targeting induces cell killing. While exploring how X. albilineans survives self-targeting, we predicted putative anti-CRISPR proteins (Acrs) encoded within the bacterium's genome. Screening of identified candidates with cell-free transcription-translation systems and in E. coli revealed two Acrs, which we named AcrIC11 and AcrIF12Xal, that inhibit the activity of Cas3 but not Cascade of the respective system. While AcrF12Xal is homologous to AcrIF12, AcrIC11 shares sequence and structural homology with the anti-restriction protein KlcA. These findings help explain tolerance of self-targeting through two CRISPR-Cas systems and expand the known suite of DNA degradation-inhibiting Acrs.
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Affiliation(s)
- Franziska Wimmer
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), 97080 Würzburg, Germany
| | - Frank Englert
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), 97080 Würzburg, Germany
| | - Katharina G Wandera
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), 97080 Würzburg, Germany
| | - Omer S Alkhnbashi
- Information and Computer Science Department, King Fahd University of Petroleum and Minerals (KFUPM), Dhahran 31261, Saudi Arabia
- Interdisciplinary Research Center for Intelligent Secure Systems (IRC-ISS), King Fahd University of Petroleum and Minerals (KFUPM), Dhahran 31261, Saudi Arabia
| | - Scott P Collins
- Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Rolf Backofen
- Bioinformatics group, Department of Computer Science, University of Freiburg, Freiburg, Germany
- Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany
| | - Chase L Beisel
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), 97080 Würzburg, Germany
- Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
- Medical Faculty, University of Würzburg, 97080 Würzburg, Germany
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3
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Huo W, Price VJ, Sharifi A, Zhang MQ, Palmer KL. Enterococcus faecalis Strains with Compromised CRISPR-Cas Defense Emerge under Antibiotic Selection for a CRISPR-Targeted Plasmid. Appl Environ Microbiol 2023; 89:e0012423. [PMID: 37278656 PMCID: PMC10304774 DOI: 10.1128/aem.00124-23] [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: 01/31/2023] [Accepted: 05/12/2023] [Indexed: 06/07/2023] Open
Abstract
Enterococcus faecalis is a Gram-positive bacterium that natively colonizes the human gastrointestinal tract and opportunistically causes life-threatening infections. Multidrug-resistant (MDR) E. faecalis strains have emerged that are replete with mobile genetic elements (MGEs). Non-MDR E. faecalis strains frequently possess CRISPR-Cas systems, which reduce the frequency of MGE acquisition. We demonstrated in previous studies that E. faecalis populations can transiently maintain both a functional CRISPR-Cas system and a CRISPR-Cas target. In this study, we used serial passage and deep sequencing to analyze these populations. In the presence of antibiotic selection for the plasmid, mutants with compromised CRISPR-Cas defense and enhanced ability to acquire a second antibiotic resistance plasmid emerged. Conversely, in the absence of selection, the plasmid was lost from wild-type E. faecalis populations but not E. faecalis populations that lacked the cas9 gene. Our results indicate that E. faecalis CRISPR-Cas can become compromised under antibiotic selection, generating populations with enhanced abilities to undergo horizontal gene transfer. IMPORTANCE Enterococcus faecalis is a leading cause of hospital-acquired infections and disseminator of antibiotic resistance plasmids among Gram-positive bacteria. We have previously shown that E. faecalis strains with an active CRISPR-Cas system can prevent plasmid acquisition and thus limit the transmission of antibiotic resistance determinants. However, CRISPR-Cas is not a perfect barrier. In this study, we observed populations of E. faecalis with transient coexistence of CRISPR-Cas and one of its plasmid targets. Our experimental data demonstrate that antibiotic selection results in compromised E. faecalis CRISPR-Cas function, thereby facilitating the acquisition of additional resistance plasmids by E. faecalis.
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Affiliation(s)
- Wenwen Huo
- Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas, USA
| | - Valerie J. Price
- Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas, USA
| | - Ardalan Sharifi
- Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas, USA
| | - Michael Q. Zhang
- Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas, USA
| | - Kelli L. Palmer
- Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas, USA
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Devi V, Harjai K, Chhibber S. Self-targeting spacers in CRISPR-array: Accidental occurrence or evolutionarily conserved phenomenon. J Basic Microbiol 2021; 62:4-12. [PMID: 34904260 DOI: 10.1002/jobm.202100514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 11/18/2021] [Accepted: 11/27/2021] [Indexed: 11/12/2022]
Abstract
In recent years, a tremendous amount of inquisitiveness among scientists in the clustered regularly interspaced short palindrome repeats (CRISPR)-CRISPR-associated proteins (Cas) has led to many studies to delineate their exact role in prokaryotes. CRISPR-Cas is an adaptive immune system that protects prokaryotes from phages and mobile genetic elements. It incorporates small DNA fragment of the invader in the CRISPR-array and protects the host from future invasion by them. In a few instances, the CRISPR-array also incorporates self-targeting spacers, most likely by accident or leaky incorporation. A significant number of spacers are found to match with the host genes across the species; however, self-targeting spacers have not been investigated in detail in most of the organisms. The presence of self-targeting spacers in the CRISPR-array led to speculation that the CRISPR-Cas system has a lot more to offer than just being the conventional adaptive immune system. It has been implicated in gene regulation and autoimmunity more or less equally. In this review, an attempt has been made to understand self-targeting spacers in the context of gene regulation, autoimmunity, and its avoidance strategies.
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Affiliation(s)
- Veena Devi
- Department of Microbiology, Panjab University, Chandigarh, India
| | - Kusum Harjai
- Department of Microbiology, Panjab University, Chandigarh, India
| | - Sanjay Chhibber
- Department of Microbiology, Panjab University, Chandigarh, India
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Correlation between type IIIA CRISPR-Cas system and SCCmec in Staphylococcus epidermidis. Arch Microbiol 2021; 203:6275-6286. [PMID: 34668031 DOI: 10.1007/s00203-021-02595-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 09/21/2021] [Accepted: 09/22/2021] [Indexed: 12/25/2022]
Abstract
A subculture of S.epidermidis strain ATCC35984 that is amenable to genetically manipulate was occasionally found in our laboratory. This mutant exhibited susceptibility to methicillin in contrast to its parent strain. To unveil the underlying mechanism, whole-genome sequencing of the mutant was performed. A comparative analysis revealed that a large DNA fragment encompassing the CRISPR-Cas system, type I R-M system and the SCCmec element was deleted from the mutant. The large chromosomal deletion associated with CRISPR-Cas system was also observed to occur spontaneously in S. epidermidis in another independent laboratory, or artificially induced by introducing engineering crRNAs in other bacterial species. These findings imply the CRISPR-Cas systems can affect bacterial genome remodeling through deletion of the integrated MGEs (mobile genetic elements). Further bioinformatics analysis identified a higher carriage rate of SCCmec element in the S. epidermidis strains harboring the CRISPR-Cas system. MLST typing and phylogenetic analysis of those CRIPSR-Cas-positive S. epidermidis strains revealed multiple origins. In addition, distinct types of SCCmec carried in those strains suggested that acquisition of this MGE originated from multiple independent recombination events. Intriguingly, CRISPR-Cas systems are found to be always located in the vicinity of orfX gene among staphylococci. Allelic analysis of CRISPR loci flanking cas genes disclosed that the loci distal to the orfX gene are considerably stable and conserved, which probably serve as recombination hotspot between CRISPR-Cas system and phage or plasmid. Therefore, the findings generally support the notion that incomplete immune protection of CRISPR-Cas system can promote dissemination of its neighboring SCCmec element.
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Wimmer F, Beisel CL. CRISPR-Cas Systems and the Paradox of Self-Targeting Spacers. Front Microbiol 2020; 10:3078. [PMID: 32038537 PMCID: PMC6990116 DOI: 10.3389/fmicb.2019.03078] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Accepted: 12/19/2019] [Indexed: 12/26/2022] Open
Abstract
CRISPR-Cas immune systems in bacteria and archaea record prior infections as spacers within each system’s CRISPR arrays. Spacers are normally derived from invasive genetic material and direct the immune system to complementary targets as part of future infections. However, not all spacers appear to be derived from foreign genetic material and instead can originate from the host genome. Their presence poses a paradox, as self-targeting spacers would be expected to induce an autoimmune response and cell death. In this review, we discuss the known frequency of self-targeting spacers in natural CRISPR-Cas systems, how these spacers can be incorporated into CRISPR arrays, and how the host can evade lethal attack. We also discuss how self-targeting spacers can become the basis for alternative functions performed by CRISPR-Cas systems that extend beyond adaptive immunity. Overall, the acquisition of genome-targeting spacers poses a substantial risk but can aid in the host’s evolution and potentially lead to or support new functionalities.
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Affiliation(s)
- Franziska Wimmer
- Helmholtz Institute for RNA-Based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), Würzburg, Germany
| | - Chase L Beisel
- Helmholtz Institute for RNA-Based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI), Würzburg, Germany.,Medical Faculty, University of Würzburg, Würzburg, Germany
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7
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Fineran PC. Resistance is not futile: bacterial 'innate' and CRISPR-Cas 'adaptive' immune systems. MICROBIOLOGY-SGM 2019; 165:834-841. [PMID: 30958259 DOI: 10.1099/mic.0.000802] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Bacteria are under a constant pressure from their viruses (phages) and other mobile genetic elements. They protect themselves through a range of defence strategies, which can be broadly classified as 'innate' and 'adaptive'. The bacterial innate immune systems include defences provided by restriction modification and abortive infection, among others. Bacterial adaptive immunity is elicited by a diverse range of CRISPR-Cas systems. Here, I discuss our research on both innate and adaptive phage resistance mechanisms and some of the evasion strategies employed by phages.
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Affiliation(s)
- Peter C Fineran
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
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Maier LK, Stachler AE, Brendel J, Stoll B, Fischer S, Haas KA, Schwarz TS, Alkhnbashi OS, Sharma K, Urlaub H, Backofen R, Gophna U, Marchfelder A. The nuts and bolts of the Haloferax CRISPR-Cas system I-B. RNA Biol 2018; 16:469-480. [PMID: 29649958 PMCID: PMC6546412 DOI: 10.1080/15476286.2018.1460994] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Invading genetic elements pose a constant threat to prokaryotic survival, requiring an effective defence. Eleven years ago, the arsenal of known defence mechanisms was expanded by the discovery of the CRISPR-Cas system. Although CRISPR-Cas is present in the majority of archaea, research often focuses on bacterial models. Here, we provide a perspective based on insights gained studying CRISPR-Cas system I-B of the archaeon Haloferax volcanii. The system relies on more than 50 different crRNAs, whose stability and maintenance critically depend on the proteins Cas5 and Cas7, which bind the crRNA and form the Cascade complex. The interference machinery requires a seed sequence and can interact with multiple PAM sequences. H. volcanii stands out as the first example of an organism that can tolerate autoimmunity via the CRISPR-Cas system while maintaining a constitutively active system. In addition, the H. volcanii system was successfully developed into a tool for gene regulation.
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Affiliation(s)
| | | | | | | | | | - Karina A Haas
- a Biology II, Ulm University , Ulm , Germany.,b Microbiology and Biotechnology, Ulm University , Ulm , Germany
| | | | - Omer S Alkhnbashi
- c Freiburg Bioinformatics Group, Department of Computer Science , University of Freiburg , Georges-Köhler-Allee 106, Freiburg , Germany
| | - Kundan Sharma
- e Max Planck Institute of Biophysical Chemistry , Am Faßberg 11, Göttingen , Germany.,f Ludwig Institute for Cancer Research, University of Oxford , Oxford , United Kingdom
| | - Henning Urlaub
- e Max Planck Institute of Biophysical Chemistry , Am Faßberg 11, Göttingen , Germany.,g Institute for Clinical Chemistry, University Medical Center Göttingen , Robert Koch Straße 10, Göttingen , Germany
| | - Rolf Backofen
- c Freiburg Bioinformatics Group, Department of Computer Science , University of Freiburg , Georges-Köhler-Allee 106, Freiburg , Germany.,d Centre for Biological Signalling Studies (BIOSS), Cluster of Excellence, University of Freiburg , Germany
| | - Uri Gophna
- h School of Molecular Cell Biology & Biotechnology, George S. Wise, Faculty of Life Sciences, Tel Aviv University , Tel Aviv , Israel
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Abstract
Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas) constitute a multi-functional, constantly evolving immune system in bacteria and archaea cells. A heritable, molecular memory is generated of phage, plasmids, or other mobile genetic elements that attempt to attack the cell. This memory is used to recognize and interfere with subsequent invasions from the same genetic elements. This versatile prokaryotic tool has also been used to advance applications in biotechnology. Here we review a large body of CRISPR-Cas research to explore themes of evolution and selection, population dynamics, horizontal gene transfer, specific and cross-reactive interactions, cost and regulation, non-immunological CRISPR functions that boost host cell robustness, as well as applicable mechanisms for efficient and specific genetic engineering. We offer future directions that can be addressed by the physics community. Physical understanding of the CRISPR-Cas system will advance uses in biotechnology, such as developing cell lines and animal models, cell labeling and information storage, combatting antibiotic resistance, and human therapeutics.
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Affiliation(s)
- Melia E Bonomo
- Department of Physics and Astronomy, Rice University, Houston, TX 77005, United States of America. Center for Theoretical Biological Physics, Rice University, Houston, TX 77005, United States of America
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van der Els S, James JK, Kleerebezem M, Bron PA. Versatile Cas9-Driven Subpopulation Selection Toolbox for Lactococcus lactis. Appl Environ Microbiol 2018; 84:e02752-17. [PMID: 29453254 PMCID: PMC5881059 DOI: 10.1128/aem.02752-17] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 02/08/2018] [Indexed: 12/26/2022] Open
Abstract
CRISPR-Cas9 technology has been exploited for the removal or replacement of genetic elements in a wide range of prokaryotes and eukaryotes. Here, we describe the extension of the Cas9 application toolbox to the industrially important dairy species Lactococcus lactis The Cas9 expression vector pLABTarget, encoding the Streptocccus pyogenes Cas9 under the control of a constitutive promoter, was constructed, allowing plug and play introduction of short guide RNA (sgRNA) sequences to target specific genetic loci. Introduction of a pepN-targeting derivative of pLABTarget into L. lactis strain MG1363 led to a strong reduction in the number of transformants obtained, which did not occur in a pepN deletion derivative of the same strain, demonstrating the specificity and lethality of the Cas9-mediated double-strand breaks in the lactococcal chromosome. Moreover, the same pLABTarget derivative allowed the selection of a pepN deletion subpopulation from its corresponding single-crossover plasmid integrant precursor, accelerating the construction and selection of gene-specific deletion derivatives in L. lactis Finally, pLABTarget, which contained sgRNAs designed to target mobile genetic elements, allowed the effective curing of plasmids, prophages, and integrative conjugative elements (ICEs). These results establish that pLABTarget enables the effective exploitation of Cas9 targeting in L. lactis, while the broad-host-range vector used suggests that this toolbox could readily be expanded to other Gram-positive bacteria.IMPORTANCE Mobile genetic elements in Lactococcus lactis and other lactic acid bacteria (LAB) play an important role in dairy fermentation, having both positive and detrimental effects during the production of fermented dairy products. The pLABTarget vector offers an efficient cloning platform for Cas9 application in lactic acid bacteria. Targeting Cas9 toward mobile genetic elements enabled their effective curing, which is of particular interest in the context of potentially problematic prophages present in a strain. Moreover, Cas9 targeting of other mobile genetic elements enables the deciphering of their contribution to dairy fermentation processes and further establishment of their importance for product characteristics.
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Affiliation(s)
- Simon van der Els
- Host-Microbe Interactomics Group, Animal Sciences, Wageningen University & Research, Wageningen, The Netherlands
- NIZO B.V., Ede, The Netherlands
- BE-Basic Foundation, Delft, The Netherlands
| | | | - Michiel Kleerebezem
- Host-Microbe Interactomics Group, Animal Sciences, Wageningen University & Research, Wageningen, The Netherlands
- BE-Basic Foundation, Delft, The Netherlands
| | - Peter A Bron
- NIZO B.V., Ede, The Netherlands
- BE-Basic Foundation, Delft, The Netherlands
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Immune loss as a driver of coexistence during host-phage coevolution. ISME JOURNAL 2018; 12:585-597. [PMID: 29328063 PMCID: PMC5776473 DOI: 10.1038/ismej.2017.194] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 09/18/2017] [Accepted: 10/09/2017] [Indexed: 12/26/2022]
Abstract
Bacteria and their viral pathogens face constant pressure for augmented immune and
infective capabilities, respectively. Under this reciprocally imposed selective regime, we
expect to see a runaway evolutionary arms race, ultimately leading to the extinction of
one species. Despite this prediction, in many systems host and pathogen coexist with
minimal coevolution even when well-mixed. Previous work explained this puzzling phenomenon
by invoking fitness tradeoffs, which can diminish an arms race dynamic. Here we propose
that the regular loss of immunity by the bacterial host can also produce host-phage
coexistence. We pair a general model of immunity with an experimental and theoretical case
study of the CRISPR-Cas immune system to contrast the behavior of tradeoff and loss
mechanisms in well-mixed systems. We find that, while both mechanisms can produce stable
coexistence, only immune loss does so robustly within realistic parameter ranges.
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Panda P, Vanga BR, Lu A, Fiers M, Fineran PC, Butler R, Armstrong K, Ronson CW, Pitman AR. Pectobacterium atrosepticum and Pectobacterium carotovorum Harbor Distinct, Independently Acquired Integrative and Conjugative Elements Encoding Coronafacic Acid that Enhance Virulence on Potato Stems. Front Microbiol 2016; 7:397. [PMID: 27065965 PMCID: PMC4814525 DOI: 10.3389/fmicb.2016.00397] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 03/14/2016] [Indexed: 12/25/2022] Open
Abstract
Integrative and conjugative elements (ICEs) play a central role in the evolution of bacterial virulence, their transmission between bacteria often leading to the acquisition of virulence factors that alter host range or aggressiveness. Much is known about the functions of the virulence determinants that ICEs harbor, but little is understood about the cryptic effects of ICEs on their host cell. In this study, the importance of horizontally acquired island 2 (HAI2), an ICE in the genome of Pectobacterium atrosepticum SCRI1043, was studied using a strain in which the entire ICE had been removed by CRISPR-Cas-mediated genome editing. HAI2 encodes coronafacic acid, a virulence factor that enhances blackleg disease of potato stems caused by P. atrosepticum SCRI1043. As expected, deletion of HAI2 resulted in reduced blackleg symptoms in potato stems. A subsequent screen for HAI2-related ICEs in other strains of the Pectobacterium genus revealed their ubiquitous nature in P. atrosepticum. Yet, HAI2-related ICEs were only detected in the genomes of a few P. carotovorum strains. These strains were notable as blackleg causing strains belonging to two different subspecies of P. carotovorum. Sequence analysis of the ICEs in different strains of both P. atrosepticum and P. carotovorum confirmed that they were diverse and were present in different locations on the genomes of their bacterial host, suggesting that the cfa cluster was probably acquired independently on a number of occasions via chromosomal insertion of related ICEs. Excision assays also demonstrated that the ICEs in both P. atrosepticum and P. carotovorum are mobilized from the host chromosome. Thus, the future spread of these ICEs via lateral gene transfer might contribute to an increase in the prevalence of blackleg-causing strains of P. carotovorum.
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Affiliation(s)
- Preetinanda Panda
- The Bio-Protection Research CentreLincoln, New Zealand
- Plant Pathology, The New Zealand Institute for Plant and Food Research LimitedLincoln, New Zealand
| | - Bhanupratap R. Vanga
- Plant Pathology, The New Zealand Institute for Plant and Food Research LimitedLincoln, New Zealand
- Department of Microbiology and Immunology, University of OtagoDunedin, New Zealand
| | - Ashley Lu
- Plant Pathology, The New Zealand Institute for Plant and Food Research LimitedLincoln, New Zealand
| | - Mark Fiers
- Plant Pathology, The New Zealand Institute for Plant and Food Research LimitedLincoln, New Zealand
| | - Peter C. Fineran
- The Bio-Protection Research CentreLincoln, New Zealand
- Department of Microbiology and Immunology, University of OtagoDunedin, New Zealand
| | - Ruth Butler
- Plant Pathology, The New Zealand Institute for Plant and Food Research LimitedLincoln, New Zealand
| | | | - Clive W. Ronson
- Department of Microbiology and Immunology, University of OtagoDunedin, New Zealand
| | - Andrew R. Pitman
- The Bio-Protection Research CentreLincoln, New Zealand
- Plant Pathology, The New Zealand Institute for Plant and Food Research LimitedLincoln, New Zealand
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Hampton HG, McNeil MB, Paterson TJ, Ney B, Williamson NR, Easingwood RA, Bostina M, Salmond GPC, Fineran PC. CRISPR-Cas gene-editing reveals RsmA and RsmC act through FlhDC to repress the SdhE flavinylation factor and control motility and prodigiosin production in Serratia. MICROBIOLOGY-SGM 2016; 162:1047-1058. [PMID: 27010574 PMCID: PMC5042078 DOI: 10.1099/mic.0.000283] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
SdhE is required for the flavinylation and activation of succinate dehydrogenase and fumarate reductase (FRD). In addition, SdhE is conserved in proteobacteria (α, β and γ) and eukaryotes. Although the function of this recently characterized family of proteins has been determined, almost nothing is known about how their genes are regulated. Here, the RsmA (CsrA) and RsmC (HexY) post-transcriptional and post-translational regulators have been identified and shown to repress sdhEygfX expression in Serratia sp. ATCC 39006. Conversely, the flagella master regulator complex, FlhDC, activated sdhEygfX transcription. To investigate the hierarchy of control, we developed a novel approach that utilized endogenous CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR associated) genome-editing by a type I-F system to generate a chromosomal point mutation in flhC. Mutation of flhC alleviated the ability of RsmC to repress sdhEygfX expression, whereas RsmA acted in both an FlhDC-dependent and -independent manner to inhibit sdhEygfX. Mutation of rsmA or rsmC, or overexpression of FlhDC, led to increased prodigiosin, biosurfactant, swimming and swarming. Consistent with the modulation of sdhE by motility regulators, we have demonstrated that SdhE and FRD are required for maximal flagella-dependent swimming. Together, these results demonstrate that regulators of both metabolism and motility (RsmA, RsmC and FlhDC) control the transcription of the sdhEygfX operon.
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Affiliation(s)
- Hannah G Hampton
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Matthew B McNeil
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Thomas J Paterson
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Blair Ney
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Neil R Williamson
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Richard A Easingwood
- Otago Centre for Electron Microscopy, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Mihnea Bostina
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand.,Otago Centre for Electron Microscopy, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - George P C Salmond
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Peter C Fineran
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
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14
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Kumar MS, Plotkin JB, Hannenhalli S. Regulated CRISPR Modules Exploit a Dual Defense Strategy of Restriction and Abortive Infection in a Model of Prokaryote-Phage Coevolution. PLoS Comput Biol 2015; 11:e1004603. [PMID: 26544847 PMCID: PMC4636164 DOI: 10.1371/journal.pcbi.1004603] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 10/14/2015] [Indexed: 11/23/2022] Open
Abstract
CRISPRs offer adaptive immunity in prokaryotes by acquiring genomic fragments from infecting phage and subsequently exploiting them for phage restriction via an RNAi-like mechanism. Here, we develop and analyze a dynamical model of CRISPR-mediated prokaryote-phage coevolution that incorporates classical CRISPR kinetics along with the recently discovered infection-induced activation and autoimmunity side effects. Our analyses reveal two striking characteristics of the CRISPR defense strategy: that both restriction and abortive infections operate during coevolution with phages, driving phages to much lower densities than possible with restriction alone, and that CRISPR maintenance is determined by a key dimensionless combination of parameters, which upper bounds the activation level of CRISPRs in uninfected populations. We contrast these qualitative observations with experimental data on CRISPR kinetics, which offer insight into the spacer deletion mechanism and the observed low CRISPR prevalence in clinical isolates. More generally, we exploit numerical simulations to delineate four regimes of CRISPR dynamics in terms of its host, kinetic, and regulatory parameters. To counteract viral infections, bacteria and archaea have evolved a variety of defense systems. These can broadly be classified into either restriction or suicide mechanisms. The former enforces nicks in the invading DNA making it unusable for production of further infectious particles; the latter, by contrast, induces cell death whereby an infected cell activates specific host suicidal pathways that are otherwise strongly repressed, thus inhibiting further infection. Examples of the former class include restriction-modification (R-M) and the recently discovered CRISPR systems, while the latter class includes a variety of toxin/anti-toxin systems. CRISPRs, in contrast to R-Ms, adapt to target viral genomes by updating the database of target sites they recognize. The adverse side effect of such a mechanism, however, is that CRISPRs can target the host genome itself resulting in undesirable cell death (autoimmunity). The recent discovery of infection-induced activation of CRISPR systems suggests that these negative side effects may be limited to periods of infection. This led us to hypothesize that such regulatory control—similar to abortive infection mechanisms—can be advantageous by limiting viral spread through suicide of infected cells. To test this hypothesis, we mathematically model CRISPR induced prokaryote-phage coevolutionary dynamics in the presence of infection-regulated CRISPR activity. Our results indicate that, except in limited growth rates, regulated CRISPRs exploit both autoimmunity and target restriction and can therefore be considered a hybrid class that leverages both restriction and suicide mechanisms to limit phage infection.
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Affiliation(s)
- M. Senthil Kumar
- Graduate Program in Bioinformatics, University of Maryland, College Park, Maryland, United States of America
- Center for Bioinformatics and Computational Biology, University of Maryland, College Park, Maryland, United States of America
- * E-mail: (MSK); (JBP); (SH)
| | - Joshua B. Plotkin
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail: (MSK); (JBP); (SH)
| | - Sridhar Hannenhalli
- Center for Bioinformatics and Computational Biology, University of Maryland, College Park, Maryland, United States of America
- * E-mail: (MSK); (JBP); (SH)
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15
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Yang C, Li P, Su W, Li H, Liu H, Yang G, Xie J, Yi S, Wang J, Cui X, Wu Z, Wang L, Hao R, Jia L, Qiu S, Song H. Polymorphism of CRISPR shows separated natural groupings of Shigella subtypes and evidence of horizontal transfer of CRISPR. RNA Biol 2015; 12:1109-20. [PMID: 26327282 PMCID: PMC4829275 DOI: 10.1080/15476286.2015.1085150] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Revised: 07/30/2015] [Accepted: 08/15/2015] [Indexed: 10/23/2022] Open
Abstract
Clustered, regularly interspaced, short palindromic repeats (CRISPR) act as an adaptive RNA-mediated immune mechanism in bacteria. They can also be used for identification and evolutionary studies based on polymorphisms within the CRISPR locus. We amplified and analyzed 6 CRISPR loci from 237 Shigella strains belonging to the 4 species groups, as well as 13 Escherichia coli strains. The CRISPR-associated (cas) gene sequence arrays of these strains were screened and compared. The CRISPR sequences from Shigella were conserved among subtypes, suggesting that CRISPR may represent a new identification tool for the detection and discrimination of Shigella species. Secondary structure analysis showed a different stem-loop structure at the terminal repeat, suggesting a distinct recognition mechanism in the formation of crRNA. In addition, the presence of "self-target" spacers and polymorphisms within CRISPR in Shigella indicated a selective pressure for inhibition of this system, which has the potential to damage "self DNA." Homology analysis of spacers showed that CRISPR might be involved in the regulation of virulence transmission. Phylogenetic analysis based on CRISPR sequences from Shigella and E. coli indicated that although phenotypic properties maintain convergent evolution, the 4 Shigella species do not represent natural groupings. Surprisingly, comparative analysis of Shigella repeats with other species provided new evidence for CRISPR horizontal transfer. Our results suggested that CRISPR analysis is applicable for the detection of Shigella species and for investigation of evolutionary relationships.
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Affiliation(s)
- Chaojie Yang
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Peng Li
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Wenli Su
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Hao Li
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Hongbo Liu
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Guang Yang
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Jing Xie
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Shengjie Yi
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Jian Wang
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Xianyan Cui
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Zhihao Wu
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Ligui Wang
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Rongzhang Hao
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Leili Jia
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Shaofu Qiu
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
| | - Hongbin Song
- Institute of Disease Control and Prevention; Academy of Military Medical Sciences; Beijing, China
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16
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Richter C, Dy RL, McKenzie RE, Watson BNJ, Taylor C, Chang JT, McNeil MB, Staals RHJ, Fineran PC. Priming in the Type I-F CRISPR-Cas system triggers strand-independent spacer acquisition, bi-directionally from the primed protospacer. Nucleic Acids Res 2014; 42:8516-26. [PMID: 24990370 PMCID: PMC4117759 DOI: 10.1093/nar/gku527] [Citation(s) in RCA: 146] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 05/27/2014] [Accepted: 05/28/2014] [Indexed: 12/23/2022] Open
Abstract
Clustered regularly interspaced short palindromic repeats (CRISPR), in combination with CRISPR associated (cas) genes, constitute CRISPR-Cas bacterial adaptive immune systems. To generate immunity, these systems acquire short sequences of nucleic acids from foreign invaders and incorporate these into their CRISPR arrays as spacers. This adaptation process is the least characterized step in CRISPR-Cas immunity. Here, we used Pectobacterium atrosepticum to investigate adaptation in Type I-F CRISPR-Cas systems. Pre-existing spacers that matched plasmids stimulated hyperactive primed acquisition and resulted in the incorporation of up to nine new spacers across all three native CRISPR arrays. Endogenous expression of the cas genes was sufficient, yet required, for priming. The new spacers inhibited conjugation and transformation, and interference was enhanced with increasing numbers of new spacers. We analyzed ∼ 350 new spacers acquired in priming events and identified a 5'-protospacer-GG-3' protospacer adjacent motif. In contrast to priming in Type I-E systems, new spacers matched either plasmid strand and a biased distribution, including clustering near the primed protospacer, suggested a bi-directional translocation model for the Cas1:Cas2-3 adaptation machinery. Taken together these results indicate priming adaptation occurs in different CRISPR-Cas systems, that it can be highly active in wild-type strains and that the underlying mechanisms vary.
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Affiliation(s)
- Corinna Richter
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Ron L Dy
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Rebecca E McKenzie
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Bridget N J Watson
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Corinda Taylor
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - James T Chang
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Matthew B McNeil
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Raymond H J Staals
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Peter C Fineran
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
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17
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Makarova KS, Anantharaman V, Grishin NV, Koonin EV, Aravind L. CARF and WYL domains: ligand-binding regulators of prokaryotic defense systems. Front Genet 2014; 5:102. [PMID: 24817877 PMCID: PMC4012209 DOI: 10.3389/fgene.2014.00102] [Citation(s) in RCA: 140] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 04/08/2014] [Indexed: 12/26/2022] Open
Abstract
CRISPR-Cas adaptive immunity systems of bacteria and archaea insert fragments of virus or plasmid DNA as spacer sequences into CRISPR repeat loci. Processed transcripts encompassing these spacers guide the cleavage of the cognate foreign DNA or RNA. Most CRISPR-Cas loci, in addition to recognized cas genes, also include genes that are not directly implicated in spacer acquisition, CRISPR transcript processing or interference. Here we comprehensively analyze sequences, structures and genomic neighborhoods of one of the most widespread groups of such genes that encode proteins containing a predicted nucleotide-binding domain with a Rossmann-like fold, which we denote CARF (CRISPR-associated Rossmann fold). Several CARF protein structures have been determined but functional characterization of these proteins is lacking. The CARF domain is most frequently combined with a C-terminal winged helix-turn-helix DNA-binding domain and “effector” domains most of which are predicted to possess DNase or RNase activity. Divergent CARF domains are also found in RtcR proteins, sigma-54 dependent regulators of the rtc RNA repair operon. CARF genes frequently co-occur with those coding for proteins containing the WYL domain with the Sm-like SH3 β-barrel fold, which is also predicted to bind ligands. CRISPR-Cas and possibly other defense systems are predicted to be transcriptionally regulated by multiple ligand-binding proteins containing WYL and CARF domains which sense modified nucleotides and nucleotide derivatives generated during virus infection. We hypothesize that CARF domains also transmit the signal from the bound ligand to the fused effector domains which attack either alien or self nucleic acids, resulting, respectively, in immunity complementing the CRISPR-Cas action or in dormancy/programmed cell death.
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Affiliation(s)
- Kira S Makarova
- National Library of Medicine, National Center for Biotechnology Information, National Institutes of Health Bethesda, MD, USA
| | - Vivek Anantharaman
- National Library of Medicine, National Center for Biotechnology Information, National Institutes of Health Bethesda, MD, USA
| | - Nick V Grishin
- Departments of Biophysics and Biochemistry, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center Dallas, TX, USA
| | - Eugene V Koonin
- National Library of Medicine, National Center for Biotechnology Information, National Institutes of Health Bethesda, MD, USA
| | - L Aravind
- National Library of Medicine, National Center for Biotechnology Information, National Institutes of Health Bethesda, MD, USA
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18
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Sampson TR, Weiss DS. CRISPR-Cas systems: new players in gene regulation and bacterial physiology. Front Cell Infect Microbiol 2014; 4:37. [PMID: 24772391 PMCID: PMC3983513 DOI: 10.3389/fcimb.2014.00037] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Accepted: 02/24/2014] [Indexed: 12/26/2022] Open
Abstract
CRISPR-Cas systems are bacterial defenses against foreign nucleic acids derived from bacteriophages, plasmids or other sources. These systems are targeted in an RNA-dependent, sequence-specific manner, and are also adaptive, providing protection against previously encountered foreign elements. In addition to their canonical function in defense against foreign nucleic acid, their roles in various aspects of bacterial physiology are now being uncovered. We recently revealed a role for a Cas9-based Type II CRISPR-Cas system in the control of endogenous gene expression, a novel form of prokaryotic gene regulation. Cas9 functions in association with two small RNAs to target and alter the stability of an endogenous transcript encoding a bacterial lipoprotein (BLP). Since BLPs are recognized by the host innate immune protein Toll-like Receptor 2 (TLR2), CRISPR-Cas-mediated repression of BLP expression facilitates evasion of TLR2 by the intracellular bacterial pathogen Francisella novicida, and is essential for its virulence. Here we describe the Cas9 regulatory system in detail, as well as data on its role in controlling virulence traits of Neisseria meningitidis and Campylobacter jejuni. We also discuss potential roles of CRISPR-Cas systems in the response to envelope stress and other aspects of bacterial physiology. Since ~45% of bacteria and ~83% of Archaea encode these machineries, the newly appreciated regulatory functions of CRISPR-Cas systems are likely to play broad roles in controlling the pathogenesis and physiology of diverse prokaryotes.
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Affiliation(s)
- Timothy R Sampson
- Department of Microbiology and Immunology, Microbiology and Molecular Genetics Program, Emory University School of Medicine Atlanta, GA, USA ; Emory Vaccine Center, Emory University School of Medicine Atlanta, GA, USA ; Yerkes National Primate Research Center, Emory University School of Medicine Atlanta, GA, USA
| | - David S Weiss
- Emory Vaccine Center, Emory University School of Medicine Atlanta, GA, USA ; Yerkes National Primate Research Center, Emory University School of Medicine Atlanta, GA, USA ; Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine Atlanta, GA, USA
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