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Beamud B, Benz F, Bikard D. Going viral: The role of mobile genetic elements in bacterial immunity. Cell Host Microbe 2024; 32:804-819. [PMID: 38870898 DOI: 10.1016/j.chom.2024.05.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 05/17/2024] [Accepted: 05/20/2024] [Indexed: 06/15/2024]
Abstract
Bacteriophages and other mobile genetic elements (MGEs) pose a significant threat to bacteria, subjecting them to constant attacks. In response, bacteria have evolved a sophisticated immune system that employs diverse defensive strategies and mechanisms. Remarkably, a growing body of evidence suggests that most of these defenses are encoded by MGEs themselves. This realization challenges our traditional understanding of bacterial immunity and raises intriguing questions about the evolutionary forces at play. Our review provides a comprehensive overview of the latest findings on the main families of MGEs and the defense systems they encode. We also highlight how a vast diversity of defense systems remains to be discovered and their mechanism of mobility understood. Altogether, the composition and distribution of defense systems in bacterial genomes only makes sense in the light of the ecological and evolutionary interactions of a complex network of MGEs.
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Affiliation(s)
- Beatriz Beamud
- Institut Pasteur, Université de Paris, Synthetic Biology, 75015 Paris, France.
| | - Fabienne Benz
- Institut Pasteur, Université de Paris, Synthetic Biology, 75015 Paris, France; Institut Pasteur, Université Paris Cité, CNRS UMR3525, Microbial Evolutionary Genomics, 75015 Paris, France
| | - David Bikard
- Institut Pasteur, Université de Paris, Synthetic Biology, 75015 Paris, France.
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2
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Domingo-Sananes MR, Meehan CJ. The population genetics of prokaryotic pangenomes. Nat Ecol Evol 2024; 8:190-191. [PMID: 38177691 DOI: 10.1038/s41559-023-02276-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2024]
Affiliation(s)
| | - Conor J Meehan
- Department of Biosciences, Nottingham Trent University, Nottingham, UK
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3
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Martins PMM, Granato LM, Morgan T, Nalin JL, Takita MA, Alfenas-Zerbini P, de Souza AA. Analysis of CRISPR-Cas loci distribution in Xanthomonas citri and its possible control by the quorum sensing system. FEMS Microbiol Lett 2024; 371:fnae005. [PMID: 38244227 DOI: 10.1093/femsle/fnae005] [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: 04/18/2023] [Revised: 10/04/2023] [Accepted: 01/18/2024] [Indexed: 01/22/2024] Open
Abstract
Xanthomonas is an important genus of plant-associated bacteria that causes significant yield losses of economically important crops worldwide. Different approaches have assessed genetic diversity and evolutionary interrelationships among the Xanthomonas species. However, information from clustered regularly interspaced short palindromic repeats (CRISPRs) has yet to be explored. In this work, we analyzed the architecture of CRISPR-Cas loci and presented a sequence similarity-based clustering of conserved Cas proteins in different species of Xanthomonas. Although absent in many investigated genomes, Xanthomonas harbors subtype I-C and I-F CRISPR-Cas systems. The most represented species, Xanthomonas citri, presents a great diversity of genome sequences with an uneven distribution of the CRISPR-Cas systems among the subspecies/pathovars. Only X. citri subsp. citri and X. citri pv. punicae have these systems, exclusively of subtype I-C system. Moreover, the most likely targets of the X. citri CRISPR spacers are viruses (phages). At the same time, few are plasmids, indicating that CRISPR/Cas system is possibly a mechanism to control the invasion of foreign DNA. We also showed in X. citri susbp. citri that the cas genes are regulated by the diffusible signal factor, the quorum sensing (QS) signal molecule, according to cell density increases, and under environmental stress like starvation. These results suggest that the regulation of CRISPR-Cas by QS occurs to activate the gene expression only during phage infection or due to environmental stresses, avoiding a possible reduction in fitness. Although more studies are needed, CRISPR-Cas systems may have been selected in the Xanthomonas genus throughout evolution, according to the cost-benefit of protecting against biological threats and fitness maintenance in challenging conditions.
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Affiliation(s)
| | - Laís Moreira Granato
- Citrus Research Center "Sylvio Moreira", Agronomic Institute (IAC), Cordeiropolis-SP 13490-970, Brazil
| | - Túlio Morgan
- Department of Microbiology, Institute of Biotechnology Applied to Agriculture (BIOAGRO), Federal University of Viçosa, Viçosa-MG 36570-900, Brazil
| | - Julia Lopes Nalin
- Citrus Research Center "Sylvio Moreira", Agronomic Institute (IAC), Cordeiropolis-SP 13490-970, Brazil
| | - Marco Aurélio Takita
- Citrus Research Center "Sylvio Moreira", Agronomic Institute (IAC), Cordeiropolis-SP 13490-970, Brazil
| | - Poliane Alfenas-Zerbini
- Department of Microbiology, Institute of Biotechnology Applied to Agriculture (BIOAGRO), Federal University of Viçosa, Viçosa-MG 36570-900, Brazil
| | - Alessandra Alves de Souza
- Citrus Research Center "Sylvio Moreira", Agronomic Institute (IAC), Cordeiropolis-SP 13490-970, Brazil
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4
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Manzano-Morales S, Liu Y, González-Bodí S, Huerta-Cepas J, Iranzo J. Comparison of gene clustering criteria reveals intrinsic uncertainty in pangenome analyses. Genome Biol 2023; 24:250. [PMID: 37904249 PMCID: PMC10614367 DOI: 10.1186/s13059-023-03089-3] [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: 12/19/2022] [Accepted: 10/16/2023] [Indexed: 11/01/2023] Open
Abstract
BACKGROUND A key step for comparative genomics is to group open reading frames into functionally and evolutionarily meaningful gene clusters. Gene clustering is complicated by intraspecific duplications and horizontal gene transfers that are frequent in prokaryotes. In consequence, gene clustering methods must deal with a trade-off between identifying vertically transmitted representatives of multicopy gene families, which are recognizable by synteny conservation, and retrieving complete sets of species-level orthologs. We studied the implications of adopting homology, orthology, or synteny conservation as formal criteria for gene clustering by performing comparative analyses of 125 prokaryotic pangenomes. RESULTS Clustering criteria affect pangenome functional characterization, core genome inference, and reconstruction of ancestral gene content to different extents. Species-wise estimates of pangenome and core genome sizes change by the same factor when using different clustering criteria, allowing robust cross-species comparisons regardless of the clustering criterion. However, cross-species comparisons of genome plasticity and functional profiles are substantially affected by inconsistencies among clustering criteria. Such inconsistencies are driven not only by mobile genetic elements, but also by genes involved in defense, secondary metabolism, and other accessory functions. In some pangenome features, the variability attributed to methodological inconsistencies can even exceed the effect sizes of ecological and phylogenetic variables. CONCLUSIONS Choosing an appropriate criterion for gene clustering is critical to conduct unbiased pangenome analyses. We provide practical guidelines to choose the right method depending on the research goals and the quality of genome assemblies, and a benchmarking dataset to assess the robustness and reproducibility of future comparative studies.
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Affiliation(s)
- Saioa Manzano-Morales
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-CSIC), Madrid, Spain
- Barcelona Supercomputing Centre (BSC-CNS) - Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Yang Liu
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-CSIC), Madrid, Spain
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
| | - Sara González-Bodí
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-CSIC), Madrid, Spain
| | - Jaime Huerta-Cepas
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-CSIC), Madrid, Spain.
| | - Jaime Iranzo
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-CSIC), Madrid, Spain.
- Institute for Biocomputation and Physics of Complex Systems (BIFI), University of Zaragoza, Zaragoza, Spain.
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5
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Wang R, Shu X, Zhao H, Xue Q, Liu C, Wu A, Cheng F, Wang L, Zhang Y, Feng J, Wu N, Li M. Associate toxin-antitoxin with CRISPR-Cas to kill multidrug-resistant pathogens. Nat Commun 2023; 14:2078. [PMID: 37045931 PMCID: PMC10097628 DOI: 10.1038/s41467-023-37789-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 03/31/2023] [Indexed: 04/14/2023] Open
Abstract
CreTA, CRISPR-regulated toxin-antitoxin (TA), safeguards CRISPR-Cas immune systems by inducing cell dormancy/death upon their inactivation. Here, we characterize a bacterial CreTA associating with the I-F CRISPR-Cas in Acinetobacter. CreT is a distinct bactericidal small RNA likely targeting several essential RNA molecules that are required to initiate protein synthesis. CreA guides the CRISPR effector to transcriptionally repress CreT. We further demonstrate a proof-of-concept antimicrobial strategy named ATTACK, which AssociaTes TA and CRISPR-Cas to Kill multidrug resistant (MDR) pathogens. In this design, CRISPR-Cas is programed to target antibiotic resistance gene(s) to selectively kill MDR pathogens or cure their resistance, and when CRISPR-Cas is inactivated or suppressed by unwanted genetic or non-genetic events/factors, CreTA triggers cell death as the last resort. Our data highlight the diversity of RNA toxins coevolving with CRISPR-Cas, and illuminate a combined strategy of CRISPR and TA antimicrobials to 'ATTACK' MDR pathogens.
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Affiliation(s)
- Rui Wang
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Non-coding RNA and Drug Discovery Key Laboratory of Sichuan Province, Chengdu Medical College, Chengdu, Sichuan, China
| | - Xian Shu
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- College of Life Science, University of Chinese Academy of Sciences, Beijing, China
| | - Huiwei Zhao
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Qiong Xue
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Chao Liu
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- College of Life Science, University of Chinese Academy of Sciences, Beijing, China
| | - Aici Wu
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- College of Life Science, University of Chinese Academy of Sciences, Beijing, China
| | - Feiyue Cheng
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Lingyun Wang
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- College of Plant Protection, Shandong Agricultural University, Taian, Shandong, China
| | - Yihan Zhang
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- School of life Sciences, Hebei University, Baoding, Hebei, China
| | - Jie Feng
- College of Life Science, University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Nannan Wu
- Shanghai Institute of Phage, Shanghai Public Health Clinical Center, Fudan University, Shanghai, China
| | - Ming Li
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
- College of Life Science, University of Chinese Academy of Sciences, Beijing, China.
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6
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Haudiquet M, de Sousa JM, Touchon M, Rocha EPC. Selfish, promiscuous and sometimes useful: how mobile genetic elements drive horizontal gene transfer in microbial populations. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210234. [PMID: 35989606 PMCID: PMC9393566 DOI: 10.1098/rstb.2021.0234] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Horizontal gene transfer (HGT) drives microbial adaptation but is often under the control of mobile genetic elements (MGEs) whose interests are not necessarily aligned with those of their hosts. In general, transfer is costly to the donor cell while potentially beneficial to the recipients. The diversity and plasticity of cell–MGEs interactions, and those among MGEs, result in complex evolutionary processes where the source, or even the existence of selection for maintaining a function in the genome, is often unclear. For example, MGE-driven HGT depends on cell envelope structures and defense systems, but many of these are transferred by MGEs themselves. MGEs can spur periods of intense gene transfer by increasing their own rates of horizontal transmission upon communicating, eavesdropping, or sensing the environment and the host physiology. This may result in high-frequency transfer of host genes unrelated to the MGE. Here, we review how MGEs drive HGT and how their transfer mechanisms, selective pressures and genomic traits affect gene flow, and therefore adaptation, in microbial populations. The encoding of many adaptive niche-defining microbial traits in MGEs means that intragenomic conflicts and alliances between cells and their MGEs are key to microbial functional diversification. This article is part of a discussion meeting issue ‘Genomic population structures of microbial pathogens’.
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Affiliation(s)
- Matthieu Haudiquet
- Institut Pasteur, Université de Paris Cité, CNRS UMR3525, Microbial Evolutionary Genomics, Paris 75015, France
| | - Jorge Moura de Sousa
- Institut Pasteur, Université de Paris Cité, CNRS UMR3525, Microbial Evolutionary Genomics, Paris 75015, France
| | - Marie Touchon
- Institut Pasteur, Université de Paris Cité, CNRS UMR3525, Microbial Evolutionary Genomics, Paris 75015, France
| | - Eduardo P C Rocha
- Institut Pasteur, Université de Paris Cité, CNRS UMR3525, Microbial Evolutionary Genomics, Paris 75015, France
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7
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A PDE Model for Protocell Evolution and the Origin of Chromosomes via Multilevel Selection. Bull Math Biol 2022; 84:109. [PMID: 36030325 DOI: 10.1007/s11538-022-01062-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Accepted: 07/28/2022] [Indexed: 11/02/2022]
Abstract
The evolution of complex cellular life involved two major transitions: the encapsulation of self-replicating genetic entities into cellular units and the aggregation of individual genes into a collectively replicating genome. In this paper, we formulate a minimal model of the evolution of proto-chromosomes within protocells. We model a simple protocell composed of two types of genes: a "fast gene" with an advantage for gene-level self-replication and a "slow gene" that replicates more slowly at the gene level, but which confers an advantage for protocell-level reproduction. Protocell-level replication capacity depends on cellular composition of fast and slow genes. We use a partial differential equation to describe how the composition of genes within protocells evolves over time under within-cell and between-cell competition, considering an infinite population of protocells that each contain infinitely many genes. We find that the gene-level advantage of fast replicators casts a long shadow on the multilevel dynamics of protocell evolution: no level of between-protocell competition can produce coexistence of the fast and slow replicators when the two genes are equally needed for protocell-level reproduction. By introducing a "dimer replicator" consisting of a linked pair of the slow and fast genes, we show analytically that coexistence between the two genes can be promoted in pairwise multilevel competition between fast and dimer replicators, and provide numerical evidence for coexistence in trimorphic competition between fast, slow, and dimer replicators. Our results suggest that dimerization, or the formation of a simple chromosome-like dimer replicator, can help to overcome the shadow of lower-level selection and work in concert with deterministic multilevel selection in protocells featuring high gene copy number to allow for the coexistence of two genes that are complementary at the protocell level but compete at the level of individual gene-level replication. These results for the PDE model complement existing results on the benefits of dimerization in the case of low genetic copy number, for which it has been shown that genetic linkage can help to overcome the stochastic loss of necessary genetic templates.
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8
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Zaayman M, Wheatley RM. Fitness costs of CRISPR-Cas systems in bacteria. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35849532 DOI: 10.1099/mic.0.001209] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
CRISPR-Cas systems provide bacteria with both specificity and adaptability in defence against invading genetic elements. From a theoretical perspective, CRISPR-Cas systems confer many benefits. However, they are observed at an unexpectedly low prevalence across the bacterial domain. While these defence systems can be gained horizontally, fitness costs may lead to selection against their carriage. Understanding the source of CRISPR-related fitness costs will help us to understand the evolutionary dynamics of CRISPR-Cas systems and their role in shaping bacterial genome evolution. Here, we review our current understanding of the potential fitness costs associated with CRISPR-Cas systems. In addition to potentially restricting the acquisition of genetic material that could confer fitness benefits, we explore five alternative biological factors that from a theoretical perspective may influence the fitness costs associated with CRISPR-Cas system carriage: (1) the repertoire of defence mechanisms a bacterium has available to it, (2) the potential for a metabolic burden, (3) larger-scale population and environmental factors, (4) the phenomenon of self-targeting spacers, and (5) alternative non-defence roles for CRISPR-Cas.
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9
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Bowers RM, Nayfach S, Schulz F, Jungbluth SP, Ruhl IA, Sheremet A, Lee J, Goudeau D, Eloe-Fadrosh EA, Stepanauskas R, Malmstrom RR, Kyrpides NC, Dunfield PF, Woyke T. Dissecting the dominant hot spring microbial populations based on community-wide sampling at single-cell genomic resolution. THE ISME JOURNAL 2022; 16:1337-1347. [PMID: 34969995 PMCID: PMC9039060 DOI: 10.1038/s41396-021-01178-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Revised: 11/29/2021] [Accepted: 12/10/2021] [Indexed: 02/07/2023]
Abstract
With advances in DNA sequencing and miniaturized molecular biology workflows, rapid and affordable sequencing of single-cell genomes has become a reality. Compared to 16S rRNA gene surveys and shotgun metagenomics, large-scale application of single-cell genomics to whole microbial communities provides an integrated snapshot of community composition and function, directly links mobile elements to their hosts, and enables analysis of population heterogeneity of the dominant community members. To that end, we sequenced nearly 500 single-cell genomes from a low diversity hot spring sediment sample from Dewar Creek, British Columbia, and compared this approach to 16S rRNA gene amplicon and shotgun metagenomics applied to the same sample. We found that the broad taxonomic profiles were similar across the three sequencing approaches, though several lineages were missing from the 16S rRNA gene amplicon dataset, likely the result of primer mismatches. At the functional level, we detected a large array of mobile genetic elements present in the single-cell genomes but absent from the corresponding same species metagenome-assembled genomes. Moreover, we performed a single-cell population genomic analysis of the three most abundant community members, revealing differences in population structure based on mutation and recombination profiles. While the average pairwise nucleotide identities were similar across the dominant species-level lineages, we observed differences in the extent of recombination between these dominant populations. Most intriguingly, the creek's Hydrogenobacter sp. population appeared to be so recombinogenic that it more closely resembled a sexual species than a clonally evolving microbe. Together, this work demonstrates that a randomized single-cell approach can be useful for the exploration of previously uncultivated microbes from community composition to population structure.
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Affiliation(s)
- Robert M. Bowers
- grid.451309.a0000 0004 0449 479XU.S. Department of Energy, Joint Genome Institute, Berkeley, CA USA
| | - Stephen Nayfach
- grid.451309.a0000 0004 0449 479XU.S. Department of Energy, Joint Genome Institute, Berkeley, CA USA
| | - Frederik Schulz
- grid.451309.a0000 0004 0449 479XU.S. Department of Energy, Joint Genome Institute, Berkeley, CA USA
| | - Sean P. Jungbluth
- grid.184769.50000 0001 2231 4551Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA USA
| | - Ilona A. Ruhl
- grid.22072.350000 0004 1936 7697Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4 Canada ,grid.419357.d0000 0001 2199 3636National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO USA
| | - Andriy Sheremet
- grid.22072.350000 0004 1936 7697Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4 Canada
| | - Janey Lee
- grid.451309.a0000 0004 0449 479XU.S. Department of Energy, Joint Genome Institute, Berkeley, CA USA
| | - Danielle Goudeau
- grid.451309.a0000 0004 0449 479XU.S. Department of Energy, Joint Genome Institute, Berkeley, CA USA
| | - Emiley A. Eloe-Fadrosh
- grid.451309.a0000 0004 0449 479XU.S. Department of Energy, Joint Genome Institute, Berkeley, CA USA
| | - Ramunas Stepanauskas
- grid.296275.d0000 0000 9516 4913Bigelow Laboratory for Ocean Sciences, 60 Bigelow Drive, East Boothbay, ME USA
| | - Rex R. Malmstrom
- grid.451309.a0000 0004 0449 479XU.S. Department of Energy, Joint Genome Institute, Berkeley, CA USA
| | - Nikos C. Kyrpides
- grid.451309.a0000 0004 0449 479XU.S. Department of Energy, Joint Genome Institute, Berkeley, CA USA
| | - Peter F. Dunfield
- grid.22072.350000 0004 1936 7697Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4 Canada
| | - Tanja Woyke
- U.S. Department of Energy, Joint Genome Institute, Berkeley, CA, USA.
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10
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Benler S, Koonin EV. Recruitment of Mobile Genetic Elements for Diverse Cellular Functions in Prokaryotes. Front Mol Biosci 2022; 9:821197. [PMID: 35402511 PMCID: PMC8987985 DOI: 10.3389/fmolb.2022.821197] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 02/08/2022] [Indexed: 12/15/2022] Open
Abstract
Prokaryotic genomes are replete with mobile genetic elements (MGE) that span a continuum of replication autonomy. On numerous occasions during microbial evolution, diverse MGE lose their autonomy altogether but, rather than being quickly purged from the host genome, assume a new function that benefits the host, rendering the immobilized MGE subject to purifying selection, and resulting in its vertical inheritance. This mini-review highlights the diversity of the repurposed (exapted) MGE as well as the plethora of cellular functions that they perform. The principal contribution of the exaptation of MGE and their components is to the prokaryotic functional systems involved in biological conflicts, and in particular, defense against viruses and other MGE. This evolutionary entanglement between MGE and defense systems appears to stem both from mechanistic similarities and from similar evolutionary predicaments whereby both MGEs and defense systems tend to incur fitness costs to the hosts and thereby evolve mechanisms for survival including horizontal mobility, causing host addiction, and exaptation for functions beneficial to the host. The examples discussed demonstrate that the identity of an MGE, overall mobility and relationship with the host cell (mutualistic, symbiotic, commensal, or parasitic) are all factors that affect exaptation.
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Affiliation(s)
| | - Eugene V. Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, United States
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11
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Abstract
We apply the theory of learning to physically renormalizable systems in an attempt to outline a theory of biological evolution, including the origin of life, as multilevel learning. We formulate seven fundamental principles of evolution that appear to be necessary and sufficient to render a universe observable and show that they entail the major features of biological evolution, including replication and natural selection. It is shown that these cornerstone phenomena of biology emerge from the fundamental features of learning dynamics such as the existence of a loss function, which is minimized during learning. We then sketch the theory of evolution using the mathematical framework of neural networks, which provides for detailed analysis of evolutionary phenomena. To demonstrate the potential of the proposed theoretical framework, we derive a generalized version of the Central Dogma of molecular biology by analyzing the flow of information during learning (back propagation) and predicting (forward propagation) the environment by evolving organisms. The more complex evolutionary phenomena, such as major transitions in evolution (in particular, the origin of life), have to be analyzed in the thermodynamic limit, which is described in detail in the paper by Vanchurin et al. [V. Vanchurin, Y. I. Wolf, E. V. Koonin, M. I. Katsnelson, Proc. Natl. Acad. Sci. U.S.A. 119, 10.1073/pnas.2120042119 (2022)].
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12
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Vanchurin V, Wolf YI, Katsnelson MI, Koonin EV. Toward a theory of evolution as multilevel learning. Proc Natl Acad Sci U S A 2022; 119:e2120037119. [PMID: 35121666 PMCID: PMC8833143 DOI: 10.1073/pnas.2120037119] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 01/03/2022] [Indexed: 12/28/2022] Open
Abstract
We apply the theory of learning to physically renormalizable systems in an attempt to outline a theory of biological evolution, including the origin of life, as multilevel learning. We formulate seven fundamental principles of evolution that appear to be necessary and sufficient to render a universe observable and show that they entail the major features of biological evolution, including replication and natural selection. It is shown that these cornerstone phenomena of biology emerge from the fundamental features of learning dynamics such as the existence of a loss function, which is minimized during learning. We then sketch the theory of evolution using the mathematical framework of neural networks, which provides for detailed analysis of evolutionary phenomena. To demonstrate the potential of the proposed theoretical framework, we derive a generalized version of the Central Dogma of molecular biology by analyzing the flow of information during learning (back propagation) and predicting (forward propagation) the environment by evolving organisms. The more complex evolutionary phenomena, such as major transitions in evolution (in particular, the origin of life), have to be analyzed in the thermodynamic limit, which is described in detail in the paper by Vanchurin et al. [V. Vanchurin, Y. I. Wolf, E. V. Koonin, M. I. Katsnelson, Proc. Natl. Acad. Sci. U.S.A. 119, 10.1073/pnas.2120042119 (2022)].
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Affiliation(s)
- Vitaly Vanchurin
- National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD 20894;
- Duluth Institute for Advanced Study, Duluth, MN 55804
| | - Yuri I Wolf
- National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD 20894
| | - Mikhail I Katsnelson
- Institute for Molecules and Materials, Radboud University, Nijmegen 6525AJ, The Netherlands
| | - Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD 20894;
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13
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Coelho LP, Alves R, del Río ÁR, Myers PN, Cantalapiedra CP, Giner-Lamia J, Schmidt TS, Mende DR, Orakov A, Letunic I, Hildebrand F, Van Rossum T, Forslund SK, Khedkar S, Maistrenko OM, Pan S, Jia L, Ferretti P, Sunagawa S, Zhao XM, Nielsen HB, Huerta-Cepas J, Bork P. Towards the biogeography of prokaryotic genes. Nature 2022; 601:252-256. [PMID: 34912116 PMCID: PMC7613196 DOI: 10.1038/s41586-021-04233-4] [Citation(s) in RCA: 70] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Accepted: 11/12/2021] [Indexed: 12/19/2022]
Abstract
Microbial genes encode the majority of the functional repertoire of life on earth. However, despite increasing efforts in metagenomic sequencing of various habitats1-3, little is known about the distribution of genes across the global biosphere, with implications for human and planetary health. Here we constructed a non-redundant gene catalogue of 303 million species-level genes (clustered at 95% nucleotide identity) from 13,174 publicly available metagenomes across 14 major habitats and use it to show that most genes are specific to a single habitat. The small fraction of genes found in multiple habitats is enriched in antibiotic-resistance genes and markers for mobile genetic elements. By further clustering these species-level genes into 32 million protein families, we observed that a small fraction of these families contain the majority of the genes (0.6% of families account for 50% of the genes). The majority of species-level genes and protein families are rare. Furthermore, species-level genes, and in particular the rare ones, show low rates of positive (adaptive) selection, supporting a model in which most genetic variability observed within each protein family is neutral or nearly neutral.
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Affiliation(s)
- Luis Pedro Coelho
- Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China. .,MOE Key Laboratory of Computational Neuroscience and Brain-Inspired Intelligence, and MOE Frontiers Center for Brain Science, Shanghai, China. .,Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.
| | - Renato Alves
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Álvaro Rodríguez del Río
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-CSIC), Madrid, Spain
| | - Pernille Neve Myers
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Carlos P. Cantalapiedra
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-CSIC), Madrid, Spain
| | - Joaquín Giner-Lamia
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-CSIC), Madrid, Spain,Departamento de Biotecnología-Biología Vegetal, Escuela Técnica Superior de Ingeniería Agronómica, Alimentaria y de Biosistemas, Universidad Politécnica de Madrid (UPM), Madrid, Spain
| | - Thomas Sebastian Schmidt
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Daniel R. Mende
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany,Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawai’i at Mānoa, Honolulu, HI, USA
| | - Askarbek Orakov
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | | | - Falk Hildebrand
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany,Earlham Institute, Norwich Research Park, Norwich, UK,Gut Health and Microbes Programme, Quadram Institute, Norwich Research Park, Norwich, UK
| | - Thea Van Rossum
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Sofia K. Forslund
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany,Experimental and Clinical Research Center (ECRC), a joint venture of the Max Delbrück Centre (MDC) and Charité University Hospital, Berlin, Germany,Berlin Initiative of Health, Berlin, Germany
| | - Supriya Khedkar
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Oleksandr M. Maistrenko
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Shaojun Pan
- Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China,MOE Key Laboratory of Computational Neuroscience and Brain-Inspired Intelligence, and MOE Frontiers Center for Brain Science, Shanghai, China
| | - Longhao Jia
- Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China,MOE Key Laboratory of Computational Neuroscience and Brain-Inspired Intelligence, and MOE Frontiers Center for Brain Science, Shanghai, China
| | - Pamela Ferretti
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Shinichi Sunagawa
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany,Department of Biology, Institute of Microbiology and Swiss Institute of Bioinformatics, ETH Zürich, Zürich, Switzerland
| | - Xing-Ming Zhao
- Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China,MOE Key Laboratory of Computational Neuroscience and Brain-Inspired Intelligence, and MOE Frontiers Center for Brain Science, Shanghai, China
| | | | - Jaime Huerta-Cepas
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany. .,Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-CSIC), Madrid, Spain.
| | - Peer Bork
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany. .,Max Delbrück Centre for Molecular Medicine, Berlin, Germany. .,Yonsei Frontier Lab (YFL), Yonsei University, Seoul, South Korea. .,Department of Bioinformatics, Biocenter, University of Würzburg, Würzburg, Germany.
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14
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Cargo Genes of Tn 7-Like Transposons Comprise an Enormous Diversity of Defense Systems, Mobile Genetic Elements, and Antibiotic Resistance Genes. mBio 2021; 12:e0293821. [PMID: 34872347 PMCID: PMC8649781 DOI: 10.1128/mbio.02938-21] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Transposition is a major mechanism of horizontal gene mobility in prokaryotes. However, exploration of the genes mobilized by transposons (cargo) is hampered by the difficulty in delineating integrated transposons from their surrounding genetic context. Here, we present a computational approach that allowed us to identify the boundaries of 6,549 Tn7-like transposons. We found that 96% of these transposons carry at least one cargo gene. Delineation of distinct communities in a gene-sharing network demonstrates how transposons function as a conduit of genes between phylogenetically distant hosts. Comparative analysis of the cargo genes reveals significant enrichment of mobile genetic elements (MGEs) nested within Tn7-like transposons, such as insertion sequences and toxin-antitoxin modules, and of genes involved in recombination, anti-MGE defense, and antibiotic resistance. More unexpectedly, cargo also includes genes encoding central carbon metabolism enzymes. Twenty-two Tn7-like transposons carry both an anti-MGE defense system and antibiotic resistance genes, illustrating how bacteria can overcome these combined pressures upon acquisition of a single transposon. This work substantially expands the distribution of Tn7-like transposons, defines their evolutionary relationships, and provides a large-scale functional classification of prokaryotic genes mobilized by transposition.
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15
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González-Delgado A, Mestre MR, Martínez-Abarca F, Toro N. Prokaryotic reverse transcriptases: from retroelements to specialized defense systems. FEMS Microbiol Rev 2021; 45:fuab025. [PMID: 33983378 PMCID: PMC8632793 DOI: 10.1093/femsre/fuab025] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 05/07/2021] [Indexed: 12/30/2022] Open
Abstract
Reverse transcriptases (RTs) catalyze the polymerization of DNA from an RNA template. These enzymes were first discovered in RNA tumor viruses in 1970, but it was not until 1989 that they were found in prokaryotes as a key component of retrons. Apart from RTs encoded by the 'selfish' mobile retroelements known as group II introns, prokaryotic RTs are extraordinarily diverse, but their function has remained elusive. However, recent studies have revealed that different lineages of prokaryotic RTs, including retrons, those associated with CRISPR-Cas systems, Abi-like RTs and other yet uncharacterized RTs, are key components of different lines of defense against phages and other mobile genetic elements. Prokaryotic RTs participate in various antiviral strategies, including abortive infection (Abi), in which the infected cell is induced to commit suicide to protect the host population, adaptive immunity, in which a memory of previous infection is used to build an efficient defense, and other as yet unidentified mechanisms. These prokaryotic enzymes are attracting considerable attention, both for use in cutting-edge technologies, such as genome editing, and as an emerging research topic. In this review, we discuss what is known about prokaryotic RTs, and the exciting evidence for their domestication from retroelements to create specialized defense systems.
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Affiliation(s)
- Alejandro González-Delgado
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Structure, Dynamics and Function of Rhizobacterial Genomes, Grupo de Ecología Genética de la Rizosfera, C/ Profesor Albareda 1, 18008 Granada, Spain
| | - Mario Rodríguez Mestre
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Structure, Dynamics and Function of Rhizobacterial Genomes, Grupo de Ecología Genética de la Rizosfera, C/ Profesor Albareda 1, 18008 Granada, Spain
- Department of Biochemistry, Universidad Autónoma de Madrid and Instituto de Investigaciones Biomédicas “Alberto Sols”, CSIC-UAM, Madrid, Spain
| | - Francisco Martínez-Abarca
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Structure, Dynamics and Function of Rhizobacterial Genomes, Grupo de Ecología Genética de la Rizosfera, C/ Profesor Albareda 1, 18008 Granada, Spain
| | - Nicolás Toro
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Structure, Dynamics and Function of Rhizobacterial Genomes, Grupo de Ecología Genética de la Rizosfera, C/ Profesor Albareda 1, 18008 Granada, Spain
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16
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Lee IPA, Eldakar OT, Gogarten JP, Andam CP. Bacterial cooperation through horizontal gene transfer. Trends Ecol Evol 2021; 37:223-232. [PMID: 34815098 DOI: 10.1016/j.tree.2021.11.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 10/27/2021] [Accepted: 11/01/2021] [Indexed: 11/16/2022]
Abstract
Cooperation exists across all scales of biological organization, from genetic elements to complex human societies. Bacteria cooperate by secreting molecules that benefit all individuals in the population (i.e., public goods). Genes associated with cooperation can spread among strains through horizontal gene transfer (HGT). We discuss recent findings on how HGT mediated by mobile genetic elements promotes bacterial cooperation, how cooperation in turn can facilitate more frequent HGT, and how the act of HGT itself may be considered as a form of cooperation. We propose that HGT is an important enforcement mechanism in bacterial populations, thus creating a positive feedback loop that further maintains cooperation. To enforce cooperation, HGT serves as a homogenizing force by transferring the cooperative trait, effectively eliminating cheaters.
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Affiliation(s)
- Isaiah Paolo A Lee
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Omar Tonsi Eldakar
- Department of Biological Sciences, Nova Southeastern University, Fort Lauderdale, FL 33314, USA
| | - J Peter Gogarten
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA.
| | - Cheryl P Andam
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY 12222, USA.
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17
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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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18
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Sklyar T, Kurahina N, Lavrentieva K, Burlaka V, Lykholat T, Lykholat O. Autonomic (Mobile) Genetic Elements of Bacteria and Their Hierarchy. CYTOL GENET+ 2021. [DOI: 10.3103/s0095452721030099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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19
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Nutrient Loading and Viral Memory Drive Accumulation of Restriction Modification Systems in Bloom-Forming Cyanobacteria. mBio 2021; 12:e0087321. [PMID: 34060332 PMCID: PMC8262939 DOI: 10.1128/mbio.00873-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The mechanisms driving cyanobacterial harmful algal blooms (HABs) like those caused by Microcystis aeruginosa remain elusive, but improved defense against viral predation has been implicated for success in eutrophic environments. Our genus-level analyses of 139,023 genomes revealed that HAB-forming cyanobacteria carry vastly more restriction modification systems per genome (RMPG) than nearly all other prokaryotic genera, suggesting that viral defense is a cornerstone of their ecological success. In contrast, picocyanobacteria that numerically dominate nutrient-poor systems have the fewest RMPG within the phylum Cyanobacteria. We used classic resource competition models to explore the hypothesis that nutrient enrichments drive ecological selection for high RMPG due to increased host-phage contact rate. These classic models, agnostic to the mechanism of defense, explain how nutrient loading can select for increased RMPG but, importantly, fail to explain the extreme accumulation of these defense systems. However, extreme accumulation of RMPG can be achieved in a novel “memory” model that accounts for a unique activity of restriction modification systems: the accidental methylation of viral DNA by the methyltransferase. The methylated virus “remembers” the RM defenses of its former host and can evade these defenses if they are present in the next host. This viral memory leads to continual RM system devaluation; RMs accumulate extensively because the benefit of each addition is diminished. Our modeling leads to the hypothesis that nutrient loading and virion methylation drive the extreme accumulation of RMPG in HAB-forming cyanobacteria. Finally, our models suggest that hosts with different RMPG values can coexist when hosts have unique sets of RM systems.
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20
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Li M, Gong L, Cheng F, Yu H, Zhao D, Wang R, Wang T, Zhang S, Zhou J, Shmakov SA, Koonin EV, Xiang H. Toxin-antitoxin RNA pairs safeguard CRISPR-Cas systems. Science 2021; 372:372/6541/eabe5601. [PMID: 33926924 DOI: 10.1126/science.abe5601] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 12/29/2020] [Accepted: 03/10/2021] [Indexed: 12/18/2022]
Abstract
CRISPR-Cas systems provide RNA-guided adaptive immunity in prokaryotes. We report that the multisubunit CRISPR effector Cascade transcriptionally regulates a toxin-antitoxin RNA pair, CreTA. CreT (Cascade-repressed toxin) is a bacteriostatic RNA that sequesters the rare arginine tRNAUCU (transfer RNA with anticodon UCU). CreA is a CRISPR RNA-resembling antitoxin RNA, which requires Cas6 for maturation. The partial complementarity between CreA and the creT promoter directs Cascade to repress toxin transcription. Thus, CreA becomes antitoxic only in the presence of Cascade. In CreTA-deleted cells, cascade genes become susceptible to disruption by transposable elements. We uncover several CreTA analogs associated with diverse archaeal and bacterial CRISPR-cas loci. Thus, toxin-antitoxin RNA pairs can safeguard CRISPR immunity by making cells addicted to CRISPR-Cas, which highlights the multifunctionality of Cas proteins and the intricate mechanisms of CRISPR-Cas regulation.
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Affiliation(s)
- Ming Li
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China. .,CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Chinese Academy of Sciences, Beijing, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing, China
| | - Luyao Gong
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing, China
| | - Feiyue Cheng
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing, China
| | - Haiying Yu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Dahe Zhao
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Rui Wang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing, China
| | - Tian Wang
- College of Life Sciences, Sichuan Normal University, Chengdu, China
| | - Shengjie Zhang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,College of Life Science, University of Chinese Academy of Sciences, Beijing, China
| | - Jian Zhou
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Sergey A Shmakov
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - Hua Xiang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China. .,College of Life Science, University of Chinese Academy of Sciences, Beijing, China.,Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
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21
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Koonin EV, Makarova KS, Wolf YI. Evolution of Microbial Genomics: Conceptual Shifts over a Quarter Century. Trends Microbiol 2021; 29:582-592. [PMID: 33541841 DOI: 10.1016/j.tim.2021.01.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/07/2021] [Accepted: 01/08/2021] [Indexed: 12/20/2022]
Abstract
Prokaryote genomics started in earnest in 1995, with the complete sequences of two small bacterial genomes, those of Haemophilus influenzae and Mycoplasma genitalium. During the next quarter century, the prokaryote genome database has been growing exponentially, with no saturation in sight. For most of these 25 years, genome sequencing remained limited to cultivable microbes. Together with next-generation sequencing methods, advances in metagenomics and single-cell genomics have lifted this limitation, providing for an increasingly unbiased characterization of the global prokaryote diversity. Advances in computational genomics followed the progress of genome sequencing, even if occasionally lagging behind. Several major new branches of bacteria and archaea were discovered, including Asgard archaea, the apparent closest relatives of eukaryotes and expansive groups of bacteria and archaea with small genomes thought to be symbionts of other prokaryotes. Comparative analysis of numerous prokaryote genomes spanning a wide range of evolutionary distances changed the conceptual foundations of microbiology, supplanting the notion of species genomes with fixed gene sets with that of dynamic pangenomes and the notion of a single Tree of Life (ToL) with a statistical tree-like trend among individual gene trees. Strides were also made towards a theory and quantitative laws of prokaryote genome evolution.
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Affiliation(s)
- Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD 20894, USA.
| | - Kira S Makarova
- National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD 20894, USA
| | - Yuri I Wolf
- National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD 20894, USA
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22
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Domingo-Sananes MR, McInerney JO. Mechanisms That Shape Microbial Pangenomes. Trends Microbiol 2021; 29:493-503. [PMID: 33423895 DOI: 10.1016/j.tim.2020.12.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 12/09/2020] [Accepted: 12/10/2020] [Indexed: 01/02/2023]
Abstract
Analyses of multiple whole-genome sequences from the same species have revealed that differences in gene content can be substantial, particularly in prokaryotes. Such variation has led to the recognition of pangenomes, the complete set of genes present in a species - consisting of core genes, present in all individuals, and accessory genes whose presence is variable. Questions now arise about how pangenomes originate and evolve. We describe how gene content variation can arise as a result of the combination of several processes, including random drift, selection, gain/loss balance, and the influence of ecological and epistatic interactions. We believe that identifying the contributions of these processes to pangenomes will need novel theoretical approaches and empirical data.
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Affiliation(s)
- Maria Rosa Domingo-Sananes
- School of Life Sciences, University of Nottingham, Nottingham, UK; School of Science and Technology, Nottingham Trent University, Nottingham, UK.
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23
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van Dijk B. Can mobile genetic elements rescue genes from extinction? Curr Genet 2020; 66:1069-1071. [PMID: 32880674 PMCID: PMC7599165 DOI: 10.1007/s00294-020-01104-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 08/19/2020] [Accepted: 08/24/2020] [Indexed: 01/04/2023]
Abstract
Bacteria and other prokaryotes evolve primarily through rapid changes in their gene content by quickly losing and gaining genes whenever an ecological opportunity emerges. As gene loss and horizontal gene transfer (HGT) appear to be the most common events across the prokaryotic tree of life, we need to think beyond gradual sequence evolution if we wish to understand the microbial world. Especially genes that reside on mobile genetic elements (MGEs) may spread much more rapidly through a microbial population than genes that reside on the bacterial chromosome. This raises the question: why are some genes associated with MGEs, while others are not? Here, I briefly review a recently proposed class of genes for which we have coined the term "rescuable genes". The fitness effect of carrying these genes is so small, either constantly or on average, that they are prone to be lost from a microbial population. I argue that HGT, even when costly to the individual cells, may play an important role in maintaining these rescuable genes in microbial communities.
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Affiliation(s)
- Bram van Dijk
- Max Planck Institute for Evolutionary Biology, Plön, Germany.
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24
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Koonin EV, Dolja VV, Krupovic M, Varsani A, Wolf YI, Yutin N, Zerbini FM, Kuhn JH. Global Organization and Proposed Megataxonomy of the Virus World. Microbiol Mol Biol Rev 2020; 84:e00061-19. [PMID: 32132243 PMCID: PMC7062200 DOI: 10.1128/mmbr.00061-19] [Citation(s) in RCA: 324] [Impact Index Per Article: 81.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Viruses and mobile genetic elements are molecular parasites or symbionts that coevolve with nearly all forms of cellular life. The route of virus replication and protein expression is determined by the viral genome type. Comparison of these routes led to the classification of viruses into seven "Baltimore classes" (BCs) that define the major features of virus reproduction. However, recent phylogenomic studies identified multiple evolutionary connections among viruses within each of the BCs as well as between different classes. Due to the modular organization of virus genomes, these relationships defy simple representation as lines of descent but rather form complex networks. Phylogenetic analyses of virus hallmark genes combined with analyses of gene-sharing networks show that replication modules of five BCs (three classes of RNA viruses and two classes of reverse-transcribing viruses) evolved from a common ancestor that encoded an RNA-directed RNA polymerase or a reverse transcriptase. Bona fide viruses evolved from this ancestor on multiple, independent occasions via the recruitment of distinct cellular proteins as capsid subunits and other structural components of virions. The single-stranded DNA (ssDNA) viruses are a polyphyletic class, with different groups evolving by recombination between rolling-circle-replicating plasmids, which contributed the replication protein, and positive-sense RNA viruses, which contributed the capsid protein. The double-stranded DNA (dsDNA) viruses are distributed among several large monophyletic groups and arose via the combination of distinct structural modules with equally diverse replication modules. Phylogenomic analyses reveal the finer structure of evolutionary connections among RNA viruses and reverse-transcribing viruses, ssDNA viruses, and large subsets of dsDNA viruses. Taken together, these analyses allow us to outline the global organization of the virus world. Here, we describe the key aspects of this organization and propose a comprehensive hierarchical taxonomy of viruses.
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Affiliation(s)
- Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
| | - Valerian V Dolja
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA
| | - Mart Krupovic
- Institut Pasteur, Archaeal Virology Unit, Department of Microbiology, Paris, France
| | - Arvind Varsani
- The Biodesign Center for Fundamental and Applied Microbiomics, Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Tempe, Arizona, USA
- Structural Biology Research Unit, Department of Clinical Laboratory Sciences, University of Cape Town, Observatory, Cape Town, South Africa
| | - Yuri I Wolf
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
| | - Natalya Yutin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
| | - F Murilo Zerbini
- Departamento de Fitopatologia/Bioagro, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil
| | - Jens H Kuhn
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Frederick, Maryland, USA
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25
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Iranzo J, Wolf YI, Koonin EV, Sela I. Gene gain and loss push prokaryotes beyond the homologous recombination barrier and accelerate genome sequence divergence. Nat Commun 2019; 10:5376. [PMID: 31772262 PMCID: PMC6879757 DOI: 10.1038/s41467-019-13429-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 11/07/2019] [Indexed: 02/05/2023] Open
Abstract
Bacterial and archaeal evolution involve extensive gene gain and loss. Thus, phylogenetic trees of prokaryotes can be constructed both by traditional sequence-based methods (gene trees) and by comparison of gene compositions (genome trees). Comparing the branch lengths in gene and genome trees with identical topologies for 34 clusters of closely related bacterial and archaeal genomes, we show here that terminal branches of gene trees are systematically compressed compared to those of genome trees. Thus, sequence evolution is delayed compared to genome evolution by gene gain and loss. The extent of this delay differs widely among bacteria and archaea. Mathematical modeling shows that the divergence delay can result from sequence homogenization by homologous recombination. The model explains how homologous recombination maintains the cohesiveness of the core genome of a species while allowing extensive gene gain and loss within the accessory genome. Once evolving genomes become isolated by barriers impeding homologous recombination, gene and genome evolution processes settle into parallel trajectories, and genomes diverge, resulting in speciation. A significant proportion of the molecular evolution of bacteria and archaea occurs through gene gain and loss. Here Iranzo et al. develop a mathematical model that explains observed differential patterns of sequence evolution vs. gene content evolution as a consequence of homologous recombination.
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Affiliation(s)
- Jaime Iranzo
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, 20894, USA.,Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM)-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Campus de Montegancedo-UPM, Pozuelo de Alarcón, 28223, Madrid, Spain
| | - Yuri I Wolf
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, 20894, USA
| | - Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, 20894, USA.
| | - Itamar Sela
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, 20894, USA.
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26
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Koonin EV, Makarova KS, Wolf YI, Krupovic M. Evolutionary entanglement of mobile genetic elements and host defence systems: guns for hire. Nat Rev Genet 2019; 21:119-131. [PMID: 31611667 DOI: 10.1038/s41576-019-0172-9] [Citation(s) in RCA: 114] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/02/2019] [Indexed: 12/12/2022]
Abstract
All cellular life forms are afflicted by diverse genetic parasites, including viruses and other types of mobile genetic elements (MGEs), and have evolved multiple, diverse defence systems that protect them from MGE assault via different mechanisms. Here, we provide our perspectives on how recent evidence points to tight evolutionary connections between MGEs and defence systems that reach far beyond the proverbial arms race. Defence systems incur a fitness cost for the hosts; therefore, at least in prokaryotes, horizontal mobility of defence systems, mediated primarily by MGEs, is essential for their persistence. Moreover, defence systems themselves possess certain features of selfish elements. Common components of MGEs, such as site-specific nucleases, are 'guns for hire' that can also function as parts of defence mechanisms and are often shuttled between MGEs and defence systems. Thus, evolutionary and molecular factors converge to mould the multifaceted, inextricable connection between MGEs and anti-MGE defence systems.
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Affiliation(s)
- Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD, USA.
| | - Kira S Makarova
- National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD, USA
| | - Yuri I Wolf
- National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD, USA
| | - Mart Krupovic
- Department of Microbiology, Institut Pasteur, Paris, France.
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27
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Broecker F, Moelling K. Evolution of Immune Systems From Viruses and Transposable Elements. Front Microbiol 2019; 10:51. [PMID: 30761103 PMCID: PMC6361761 DOI: 10.3389/fmicb.2019.00051] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Accepted: 01/14/2019] [Indexed: 12/20/2022] Open
Abstract
Virus-derived sequences and transposable elements constitute a substantial portion of many cellular genomes. Recent insights reveal the intimate evolutionary relationship between these sequences and various cellular immune pathways. At the most basic level, superinfection exclusion may be considered a prototypical virus-mediated immune system that has been described in both prokaryotes and eukaryotes. More complex immune mechanisms fully or partially derived from mobile genetic elements include CRISPR-Cas of prokaryotes and the RAG1/2 system of vertebrates, which provide immunological memory of foreign genetic elements and generate antibody and T cell receptor diversity, respectively. In this review, we summarize the current knowledge on the contribution of mobile genetic elements to the evolution of cellular immune pathways. A picture is emerging in which the various cellular immune systems originate from and are spread by viruses and transposable elements. Immune systems likely evolved from simple superinfection exclusion to highly complex defense strategies.
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Affiliation(s)
- Felix Broecker
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Karin Moelling
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.,Max Planck Institute for Molecular Genetics, Berlin, Germany
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28
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Testing the retroelement invasion hypothesis for the emergence of the ancestral eukaryotic cell. Proc Natl Acad Sci U S A 2018; 115:12465-12470. [PMID: 30455297 PMCID: PMC6298092 DOI: 10.1073/pnas.1807709115] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Phylogenetic evidence suggests that the invasion and proliferation of retroelements, selfish mobile genetic elements that copy and paste themselves within a host genome, was one of the early evolutionary events in the emergence of eukaryotes. Here we test the effects of this event by determining the pressures retroelements exert on simple genomes. We transferred two retroelements, human LINE-1 and the bacterial group II intron Ll.LtrB, into bacteria, and find that both are functional and detrimental to growth. We find, surprisingly, that retroelement lethality and proliferation are enhanced by the ability to perform eukaryotic-like nonhomologous end-joining (NHEJ) DNA repair. We show that the only stable evolutionary consequence in simple cells is maintenance of retroelements in low numbers, suggesting how retrotransposition rates and costs in early eukaryotes could have been constrained to allow proliferation. Our results suggest that the interplay between NHEJ and retroelements may have played a fundamental and previously unappreciated role in facilitating the proliferation of retroelements, elements of which became the ancestors of the spliceosome components in eukaryotes.
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29
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Abstract
Biological systems reach hierarchical complexity that has no counterpart outside the realm of biology. Undoubtedly, biological entities obey the fundamental physical laws. Can today's physics provide an explanatory framework for understanding the evolution of biological complexity? We argue that the physical foundation for understanding the origin and evolution of complexity can be gleaned at the interface between the theory of frustrated states resulting in pattern formation in glass-like media and the theory of self-organized criticality (SOC). On the one hand, SOC has been shown to emerge in spin-glass systems of high dimensionality. On the other hand, SOC is often viewed as the most appropriate physical description of evolutionary transitions in biology. We unify these two faces of SOC by showing that emergence of complex features in biological evolution typically, if not always, is triggered by frustration that is caused by competing interactions at different organizational levels. Such competing interactions lead to SOC, which represents the optimal conditions for the emergence of complexity. Competing interactions and frustrated states permeate biology at all organizational levels and are tightly linked to the ubiquitous competition for limiting resources. This perspective extends from the comparatively simple phenomena occurring in glasses to large-scale events of biological evolution, such as major evolutionary transitions. Frustration caused by competing interactions in multidimensional systems could be the general driving force behind the emergence of complexity, within and beyond the domain of biology.
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30
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Koonin EV, Krupovic M. The depths of virus exaptation. Curr Opin Virol 2018; 31:1-8. [PMID: 30071360 DOI: 10.1016/j.coviro.2018.07.011] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 07/13/2018] [Accepted: 07/19/2018] [Indexed: 02/07/2023]
Abstract
Viruses are ubiquitous parasites of cellular life forms and the most abundant biological entities on earth. The relationships between viruses and their hosts involve the continuous arms race but are by no account limited to it. Growing evidence shows that, in the course of evolution, viruses and their components are repeatedly recruited (exapted) for host functions. The functions of exapted viruses typically involve either defense from other viruses or cellular competitors or transfer of nucleic acids between cells, or storage functions. Virus exaptation can reach different depths, from recruitment of a fully functional virus to exploitation of defective, partially degraded viruses, to utilization of individual virus proteins.
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Affiliation(s)
- Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, United States.
| | - Mart Krupovic
- Unité Biologie Moléculaire du Gène chez les Extrêmophiles, Department of Microbiology, Institut Pasteur, 25 rue du Docteur Roux, Paris 75015, France.
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31
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Aguirre J, Catalán P, Cuesta JA, Manrubia S. On the networked architecture of genotype spaces and its critical effects on molecular evolution. Open Biol 2018; 8:180069. [PMID: 29973397 PMCID: PMC6070719 DOI: 10.1098/rsob.180069] [Citation(s) in RCA: 27] [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: 04/18/2018] [Accepted: 06/12/2018] [Indexed: 12/26/2022] Open
Abstract
Evolutionary dynamics is often viewed as a subtle process of change accumulation that causes a divergence among organisms and their genomes. However, this interpretation is an inheritance of a gradualistic view that has been challenged at the macroevolutionary, ecological and molecular level. Actually, when the complex architecture of genotype spaces is taken into account, the evolutionary dynamics of molecular populations becomes intrinsically non-uniform, sharing deep qualitative and quantitative similarities with slowly driven physical systems: nonlinear responses analogous to critical transitions, sudden state changes or hysteresis, among others. Furthermore, the phenotypic plasticity inherent to genotypes transforms classical fitness landscapes into multiscapes where adaptation in response to an environmental change may be very fast. The quantitative nature of adaptive molecular processes is deeply dependent on a network-of-networks multilayered structure of the map from genotype to function that we begin to unveil.
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Affiliation(s)
- Jacobo Aguirre
- Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain
- Programa de Biología de Sistemas, Centro Nacional de Biotecnología (CSIC), Madrid, Spain
| | - Pablo Catalán
- Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain
- Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Madrid, Spain
| | - José A Cuesta
- Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain
- Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Madrid, Spain
- Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, Zaragoza, Spain
- UC3M-BS Institute of Financial Big Data (IFiBiD), Universidad Carlos III de Madrid, Getafe, Madrid, Spain
| | - Susanna Manrubia
- Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain
- Programa de Biología de Sistemas, Centro Nacional de Biotecnología (CSIC), Madrid, Spain
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Estimation of universal and taxon-specific parameters of prokaryotic genome evolution. PLoS One 2018; 13:e0195571. [PMID: 29652909 PMCID: PMC5898727 DOI: 10.1371/journal.pone.0195571] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 03/23/2018] [Indexed: 01/13/2023] Open
Abstract
The results of our recent study on mathematical modeling of microbial genome evolution indicate that, on average, genomes of bacteria and archaea evolve in the regime of mutation-selection balance defined by positive selection coefficients associated with gene acquisition that is counter-acted by the intrinsic deletion bias. This analysis was based on the strong assumption that parameters of genome evolution are universal across the diversity of bacteria and archaea, and yielded extremely low values of the selection coefficient. Here we further refine the modeling approach by taking into account evolutionary factors specific for individual groups of microbes using two independent fitting strategies, an ad hoc hard fitting scheme and a mixture model. The resulting estimate of the mean selection coefficient of s∼10−10 associated with the gain of one gene implies that, on average, acquisition of a gene is beneficial, and that microbial genomes typically evolve under a weak selection regime that might transition to strong selection in highly abundant organisms with large effective population sizes. The apparent selective pressure towards larger genomes is balanced by the deletion bias, which is estimated to be consistently greater than unity for all analyzed groups of microbes. The estimated values of s are more realistic than the lower values obtained previously, indicating that global and group-specific evolutionary factors synergistically affect microbial genome evolution that seems to be driven primarily by adaptation to existence in diverse niches.
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Koonin EV, Wolf YI, Katsnelson MI. Inevitability of the emergence and persistence of genetic parasites caused by evolutionary instability of parasite-free states. Biol Direct 2017; 12:31. [PMID: 29202832 PMCID: PMC5715634 DOI: 10.1186/s13062-017-0202-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 11/22/2017] [Indexed: 01/02/2023] Open
Abstract
Genetic parasites, including viruses and mobile genetic elements, are ubiquitous among cellular life forms, and moreover, are the most abundant biological entities on earth that harbor the bulk of the genetic diversity. Here we examine simple thought experiments to demonstrate that both the emergence of parasites in simple replicator systems and their persistence in evolving life forms are inevitable because the putative parasite-free states are evolutionarily unstable. REVIEWERS This article has been reviewed by Yitzhak Pilpel, Bojan Zagrovic, and Eric van Nimwegen.
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Affiliation(s)
- Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, 20894, USA.
| | - Yuri I Wolf
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, 20894, USA
| | - Mikhail I Katsnelson
- Institute for Molecules and Materials, Radboud University, 6525AJ, Nijmegen, Netherlands
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