1
|
Wagner TM, Janice J, Sivertsen A, Sjögren I, Sundsfjord A, Hegstad K. Alternative vanHAX promoters and increased vanA-plasmid copy number resurrect silenced glycopeptide resistance in Enterococcus faecium. J Antimicrob Chemother 2021; 76:876-882. [PMID: 33367710 PMCID: PMC7953315 DOI: 10.1093/jac/dkaa541] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 12/04/2020] [Indexed: 11/30/2022] Open
Abstract
Background Vancomycin variable enterococci (VVE) are van-positive isolates with a susceptible phenotype that can convert to a resistant phenotype during vancomycin selection. Objectives To describe a vancomycin-susceptible vanA-PCR positive ST203 VVE Enterococcus faecium isolate (VVESwe-S) from a liver transplantation patient in Sweden which reverted to resistant (VVESwe-R) during in vitro vancomycin exposure. Methods WGS analysis revealed the genetic differences between the isolates. Expression of the van-operon was investigated by qPCR. Fitness and stability of the revertant were investigated by growth measurements, competition and serial transfer. Results The VVESwe-R isolate gained high-level vancomycin (MIC >256 mg/L) and teicoplanin resistance (MIC = 8 mg/L). VVESwe-S has a 5′-truncated vanR activator sequence and the VVESwe-R has in addition acquired a 44 bp deletion upstream of vanHAX in a region containing alternative putative constitutive promoters. In VVESwe-R the vanHAX-operon is constitutively expressed at a level comparable to the non-induced prototype E. faecium BM4147 strain. The vanHAX operon of VVESwe is located on an Inc18-like plasmid, which has a 3–4-fold higher copy number in VVESwe-R compared with VVESwe-S. Resistance has a low fitness cost and the vancomycin MIC of VVESwe-R decreased during in vitro serial culture without selection. The reduction in MIC was associated with a decreased vanA-plasmid copy number. Conclusions Our data support a mechanism by which vancomycin-susceptible VVE strains may revert to a resistant phenotype through the use of an alternative, constitutive, vanR-activator-independent promoter and a vanA-plasmid copy number increase.
Collapse
Affiliation(s)
- Theresa Maria Wagner
- Research group for Host-Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Norway
| | - Jessin Janice
- Research group for Host-Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Norway.,Norwegian National Advisory Unit on Detection of Antimicrobial Resistance, Department of Microbiology and Infection Control, University Hospital of North-Norway, Tromsø, Norway
| | - Audun Sivertsen
- Norwegian National Advisory Unit on Detection of Antimicrobial Resistance, Department of Microbiology and Infection Control, University Hospital of North-Norway, Tromsø, Norway
| | - Ingegerd Sjögren
- Department of Clinical Microbiology and Infection Control, Hospital of Halland, Halmstad, Sweden
| | - Arnfinn Sundsfjord
- Research group for Host-Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Norway.,Norwegian National Advisory Unit on Detection of Antimicrobial Resistance, Department of Microbiology and Infection Control, University Hospital of North-Norway, Tromsø, Norway
| | - Kristin Hegstad
- Research group for Host-Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Norway.,Norwegian National Advisory Unit on Detection of Antimicrobial Resistance, Department of Microbiology and Infection Control, University Hospital of North-Norway, Tromsø, Norway
| |
Collapse
|
2
|
Santos-Garcia D, Mestre-Rincon N, Ouvrard D, Zchori-Fein E, Morin S. Portiera Gets Wild: Genome Instability Provides Insights into the Evolution of Both Whiteflies and Their Endosymbionts. Genome Biol Evol 2020; 12:2107-2124. [PMID: 33049039 PMCID: PMC7821994 DOI: 10.1093/gbe/evaa216] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/09/2020] [Indexed: 12/12/2022] Open
Abstract
Whiteflies (Hemiptera: Sternorrhyncha: Aleyrodidae) are a superfamily of small phloem-feeding insects. They rely on their primary endosymbionts "Candidatus Portiera aleyrodidarum" to produce essential amino acids not present in their diet. Portiera has been codiverging with whiteflies since their origin and therefore reflects its host's evolutionary history. Like in most primary endosymbionts, the genome of Portiera stays stable across the Aleyrodidae superfamily after millions of years of codivergence. However, Portiera of the whitefly Bemisia tabaci has lost the ancestral genome order, reflecting a rare event in the endosymbiont evolution: the appearance of genome instability. To gain a better understanding of Portiera genome evolution, identify the time point in which genome instability appeared and contribute to the reconstruction of whitefly phylogeny, we developed a new phylogenetic framework. It targeted five Portiera genes and determined the presence of the DNA polymerase proofreading subunit (dnaQ) gene, previously associated with genome instability, and two alternative gene rearrangements. Our results indicated that Portiera gene sequences provide a robust tool for studying intergenera phylogenetic relationships in whiteflies. Using these new framework, we found that whitefly species from the Singhiella, Aleurolobus, and Bemisia genera form a monophyletic tribe, the Aleurolobini, and that their Portiera exhibit genome instability. This instability likely arose once in the common ancestor of the Aleurolobini tribe (at least 70 Ma), drawing a link between the appearance of genome instability in Portiera and the switch from multibacteriocyte to a single-bacteriocyte mode of inheritance in this tribe.
Collapse
Affiliation(s)
- Diego Santos-Garcia
- Department of Entomology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Natividad Mestre-Rincon
- Department of Entomology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - David Ouvrard
- Department of Life Sciences, Natural History Museum, London, United Kingdom.,Entomology and Invasive Plants Unit, Plant Health Laboratory, ANSES, Montferrier-sur-Lez, France
| | - Einat Zchori-Fein
- Department of Entomology, Newe-Ya'ar Research Center, ARO, Ramat-Yishai, Israel
| | - Shai Morin
- Department of Entomology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| |
Collapse
|
3
|
Russell SL, Pepper-Tunick E, Svedberg J, Byrne A, Ruelas Castillo J, Vollmers C, Beinart RA, Corbett-Detig R. Horizontal transmission and recombination maintain forever young bacterial symbiont genomes. PLoS Genet 2020; 16:e1008935. [PMID: 32841233 PMCID: PMC7473567 DOI: 10.1371/journal.pgen.1008935] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 09/04/2020] [Accepted: 06/16/2020] [Indexed: 12/30/2022] Open
Abstract
Bacterial symbionts bring a wealth of functions to the associations they participate in, but by doing so, they endanger the genes and genomes underlying these abilities. When bacterial symbionts become obligately associated with their hosts, their genomes are thought to decay towards an organelle-like fate due to decreased homologous recombination and inefficient selection. However, numerous associations exist that counter these expectations, especially in marine environments, possibly due to ongoing horizontal gene flow. Despite extensive theoretical treatment, no empirical study thus far has connected these underlying population genetic processes with long-term evolutionary outcomes. By sampling marine chemosynthetic bacterial-bivalve endosymbioses that range from primarily vertical to strictly horizontal transmission, we tested this canonical theory. We found that transmission mode strongly predicts homologous recombination rates, and that exceedingly low recombination rates are associated with moderate genome degradation in the marine symbionts with nearly strict vertical transmission. Nonetheless, even the most degraded marine endosymbiont genomes are occasionally horizontally transmitted and are much larger than their terrestrial insect symbiont counterparts. Therefore, horizontal transmission and recombination enable efficient natural selection to maintain intermediate symbiont genome sizes and substantial functional genetic variation.
Collapse
Affiliation(s)
- Shelbi L. Russell
- Department of Molecular Cellular and Developmental Biology. University of California Santa Cruz, Santa Cruz, California, United States of America
- Department of Biomolecular Engineering. University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Evan Pepper-Tunick
- Department of Biomolecular Engineering. University of California Santa Cruz, Santa Cruz, California, United States of America
- Genomics Institute, University of California, Santa Cruz, California, United States of America
| | - Jesper Svedberg
- Department of Biomolecular Engineering. University of California Santa Cruz, Santa Cruz, California, United States of America
- Genomics Institute, University of California, Santa Cruz, California, United States of America
| | - Ashley Byrne
- Department of Molecular Cellular and Developmental Biology. University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Jennie Ruelas Castillo
- Department of Molecular Cellular and Developmental Biology. University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Christopher Vollmers
- Department of Biomolecular Engineering. University of California Santa Cruz, Santa Cruz, California, United States of America
- Genomics Institute, University of California, Santa Cruz, California, United States of America
| | - Roxanne A. Beinart
- Graduate School of Oceanography. University of Rhode Island, Narragansett, Rhode Island, United States of America
| | - Russell Corbett-Detig
- Department of Biomolecular Engineering. University of California Santa Cruz, Santa Cruz, California, United States of America
- Genomics Institute, University of California, Santa Cruz, California, United States of America
| |
Collapse
|
4
|
Eraso JM, Kachroo P, Olsen RJ, Beres SB, Zhu L, Badu T, Shannon S, Cantu CC, Saavedra MO, Kubiak SL, Porter AR, DeLeo FR, Musser JM. Genetic heterogeneity of the Spy1336/R28-Spy1337 virulence axis in Streptococcus pyogenes and effect on gene transcript levels and pathogenesis. PLoS One 2020; 15:e0229064. [PMID: 32214338 PMCID: PMC7098570 DOI: 10.1371/journal.pone.0229064] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 01/28/2020] [Indexed: 12/20/2022] Open
Abstract
Streptococcus pyogenes is a strict human pathogen responsible for more than 700 million infections annually worldwide. Strains of serotype M28 S. pyogenes are typically among the five more abundant types causing invasive infections and pharyngitis in adults and children. Type M28 strains also have an unusual propensity to cause puerperal sepsis and neonatal disease. We recently discovered that a one-nucleotide indel in an intergenic homopolymeric tract located between genes Spy1336/R28 and Spy1337 altered virulence in a mouse model of infection. In the present study, we analyzed size variation in this homopolymeric tract and determined the extent of heterogeneity in the number of tandemly-repeated 79-amino acid domains in the coding region of Spy1336/R28 in large samples of strains recovered from humans with invasive infections. Both repeat sequence elements are highly polymorphic in natural populations of M28 strains. Variation in the homopolymeric tract results in (i) changes in transcript levels of Spy1336/R28 and Spy1337 in vitro, (ii) differences in virulence in a mouse model of necrotizing myositis, and (iii) global transcriptome changes as shown by RNAseq analysis of isogenic mutant strains. Variation in the number of tandem repeats in the coding sequence of Spy1336/R28 is responsible for size variation of R28 protein in natural populations. Isogenic mutant strains in which genes encoding R28 or transcriptional regulator Spy1337 are inactivated are significantly less virulent in a nonhuman primate model of necrotizing myositis. Our findings provide impetus for additional studies addressing the role of R28 and Spy1337 variation in pathogen-host interactions.
Collapse
Affiliation(s)
- Jesus M. Eraso
- Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Houston Methodist Hospital, Houston, Texas, United States of America
| | - Priyanka Kachroo
- Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Houston Methodist Hospital, Houston, Texas, United States of America
| | - Randall J. Olsen
- Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Houston Methodist Hospital, Houston, Texas, United States of America
- Departments of Pathology and Laboratory Medicine and Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
| | - Stephen B. Beres
- Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Houston Methodist Hospital, Houston, Texas, United States of America
| | - Luchang Zhu
- Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Houston Methodist Hospital, Houston, Texas, United States of America
| | - Traci Badu
- Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Houston Methodist Hospital, Houston, Texas, United States of America
| | - Sydney Shannon
- Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Houston Methodist Hospital, Houston, Texas, United States of America
| | - Concepcion C. Cantu
- Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Houston Methodist Hospital, Houston, Texas, United States of America
| | - Matthew Ojeda Saavedra
- Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Houston Methodist Hospital, Houston, Texas, United States of America
| | - Samantha L. Kubiak
- Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Houston Methodist Hospital, Houston, Texas, United States of America
| | - Adeline R. Porter
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Frank R. DeLeo
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - James M. Musser
- Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Houston Methodist Hospital, Houston, Texas, United States of America
- Departments of Pathology and Laboratory Medicine and Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
| |
Collapse
|
5
|
Orlov M, Garanina I, Fisunov GY, Sorokin A. Comparative Analysis of Mycoplasma gallisepticum vlhA Promoters. Front Genet 2018; 9:569. [PMID: 30519256 PMCID: PMC6258824 DOI: 10.3389/fgene.2018.00569] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 11/06/2018] [Indexed: 12/15/2022] Open
Abstract
Mycoplasma gallisepticum is an intracellular parasite affecting respiratory tract of poultry that belongs to class Mollicutes. M. gallisepticum features numerous variable lipoprotein hemagglutinin genes (vlhA) that play a role in immune escape. The vlhA promoters have a set of distinct properties in comparison to promoters of the other genes. The vlhA promoters carry a variable GAA repeats region at approximately 40 nts upstream of transcription start site. The promoters have been considered active only in the presence of exactly 12 GAA repeats. The mechanisms of vlhA expression regulation and GAA number variation are not described. Here we tried to understand these mechanisms using different computational methods. We conducted a comparative analysis among several M. gallisepticum strains. Nucleotide sequences analysis showed the presence of highly conserved regions flanking repeated trinucleotides that are not linked to GAA number variation. VlhA genes with 12 GAA repeats and their orthologs in 12 M. gallisepticum strains are more conserved than other vlhA genes and have narrower GAA number distribution. We conducted comparative analysis of physicochemical profiles of M. gallisepticum vlhA and sigma-70 promoters. Stress-induced duplex destabilization (SIDD) profiles showed that sigma-70 group is characterized by the common to prokaryotic promoters sharp maxima while vlhA promoters are hardly destabilized with the region between GAA repeats and transcription start site having zero opening probability. Electrostatic potential profiles of vlhA promoters indicate the presence of the distinct patterns that appear to govern initial stages of specific DNA-protein recognition. Open state dynamics profiles of vlhA demonstrate the pattern that might facilitate transcription bubble formation. Obtained data could be the basis for experimental identification of mechanisms of phase variation in M. gallisepticum.
Collapse
Affiliation(s)
- Mikhail Orlov
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia
| | - Irina Garanina
- Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical-Biological Agency, Moscow, Russia
| | - Gleb Y Fisunov
- Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical-Biological Agency, Moscow, Russia
| | - Anatoly Sorokin
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia
| |
Collapse
|
6
|
Wang W, Chen S, Zhang X. Whole-Genome Comparison Reveals Heterogeneous Divergence and Mutation Hotspots in Chloroplast Genome of Eucommia ulmoides Oliver. Int J Mol Sci 2018; 19:E1037. [PMID: 29601491 PMCID: PMC5979487 DOI: 10.3390/ijms19041037] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 03/24/2018] [Accepted: 03/25/2018] [Indexed: 11/16/2022] Open
Abstract
Eucommia ulmoides (E. ulmoides), the sole species of Eucommiaceae with high importance of medicinal and industrial values, is a Tertiary relic plant that is endemic to China. However, the population genetics study of E. ulmoides lags far behind largely due to the scarcity of genomic data. In this study, one complete chloroplast (cp) genome of E. ulmoides was generated via the genome skimming approach and compared to another available E. ulmoides cp genome comprehensively at the genome scale. We found that the structure of the cp genome in E. ulmoides was highly consistent with genome size variation which might result from DNA repeat variations in the two E. ulmoides cp genomes. Heterogeneous sequence divergence patterns were revealed in different regions of the E. ulmoides cp genomes, with most (59 out of 75) of the detected SNPs (single nucleotide polymorphisms) located in the gene regions, whereas most (50 out of 80) of the indels (insertions/deletions) were distributed in the intergenic spacers. In addition, we also found that all the 40 putative coding-region-located SNPs were synonymous mutations. A total of 71 polymorphic cpDNA fragments were further identified, among which 20 loci were selected as potential molecular markers for subsequent population genetics studies of E. ulmoides. Moreover, eight polymorphic cpSSR loci were also developed. The sister relationship between E. ulmoides and Aucuba japonica in Garryales was also confirmed based on the cp phylogenomic analyses. Overall, this study will shed new light on the conservation genomics of this endangered plant in the future.
Collapse
Affiliation(s)
- Wencai Wang
- Institute of Clinical Pharmacology, Guangzhou University of Chinese Medicine, Guangzhou 510000, China.
| | - Siyun Chen
- Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China.
| | - Xianzhi Zhang
- College of Forestry, Northwest A&F University, Yangling 712100, China.
| |
Collapse
|
7
|
Das G, Das S, Dutta S, Ghosh I. In silico identification and characterization of stress and virulence associated repeats in Salmonella. Genomics 2017; 110:23-34. [PMID: 28827093 DOI: 10.1016/j.ygeno.2017.08.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 05/09/2017] [Accepted: 08/03/2017] [Indexed: 01/05/2023]
Abstract
So much genomic similarities yet causing different diseases, is like a paradox in Salmonella biology. Repeat is one of the probes that can explain such differences. Here, a comparative genomics approach is followed to identify and characterize repeats that might play role in adaptation and pathogenesis. Repeats are non-randomly distributed in the genomes except few typhoid causing strains. Perfect long repeats are rare compare to polymorphic ones and both are statistically consistent. Significant differences in repeat densities in stress related genes manifest its probable participation in survival and virulence. 573 and 1053 repeat loci have been identified which are exclusively associated with stress and virulent genes respectively. In Salmonella Typhi, an octameric VNTR locus is found in between acrD and yffB genes having more than 25 perfect copies across Salmonella Typhi but possesses only single copy in other serovars. This repeat can be used as a diagnostic probe for typhoid.
Collapse
Affiliation(s)
- Gourab Das
- School of Computational and Integrative Sciences, Jawaharlal Nehru University (JNU), New Mehrauli Road, Munirka, New Delhi, Delhi 110067, India
| | - Surojit Das
- National Institute of Cholera and Enteric Diseases (NICED), P-33, C.I.T. Road, Scheme XM, Beleghata, Kolkata 700010, India
| | - Shanta Dutta
- National Institute of Cholera and Enteric Diseases (NICED), P-33, C.I.T. Road, Scheme XM, Beleghata, Kolkata 700010, India
| | - Indira Ghosh
- School of Computational and Integrative Sciences, Jawaharlal Nehru University (JNU), New Mehrauli Road, Munirka, New Delhi, Delhi 110067, India.
| |
Collapse
|
8
|
Gratia JP. Genetic recombinational events in prokaryotes and their viruses: insight into the study of evolution and biodiversity. Antonie van Leeuwenhoek 2017; 110:1493-1514. [DOI: 10.1007/s10482-017-0916-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 07/20/2017] [Indexed: 01/21/2023]
|
9
|
Touchon M, Moura de Sousa JA, Rocha EP. Embracing the enemy: the diversification of microbial gene repertoires by phage-mediated horizontal gene transfer. Curr Opin Microbiol 2017; 38:66-73. [PMID: 28527384 DOI: 10.1016/j.mib.2017.04.010] [Citation(s) in RCA: 161] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 04/20/2017] [Accepted: 04/21/2017] [Indexed: 01/21/2023]
Abstract
Bacteriophages and archaeal viruses contribute, through lysogenic conversion or transduction, to the horizontal transfer of genetic material between microbial genomes. Recent genomics, metagenomics, and single cell studies have shown that lysogenic conversion is widespread and provides hosts with adaptive traits often associated with biotic interactions. The quantification of the evolutionary impact of transduction has lagged behind and requires further theoretical and experimental work. Nevertheless, recent studies suggested that generalized transduction plays a role in the transfer of antibiotic resistance genes and in the acquisition of novel genes during intra-specific bacterial competition. The characteristics of transduction and lysogenic conversion complement those of other mechanisms of transfer, and could play a key role in the spread of adaptive genes between communities.
Collapse
Affiliation(s)
- Marie Touchon
- Microbial Evolutionary Genomics, Institut Pasteur, 25-28 rue Dr Roux, Paris, 75015, France; CNRS, UMR3525, 25-28 rue Dr. Roux, Paris, 75015, France
| | - Jorge A Moura de Sousa
- Microbial Evolutionary Genomics, Institut Pasteur, 25-28 rue Dr Roux, Paris, 75015, France; CNRS, UMR3525, 25-28 rue Dr. Roux, Paris, 75015, France
| | - Eduardo Pc Rocha
- Microbial Evolutionary Genomics, Institut Pasteur, 25-28 rue Dr Roux, Paris, 75015, France; CNRS, UMR3525, 25-28 rue Dr. Roux, Paris, 75015, France.
| |
Collapse
|
10
|
Shimamura S, Kaneko T, Ozawa G, Matsumoto MN, Koshiishi T, Takaki Y, Kato C, Takai K, Yoshida T, Fujikura K, Barry JP, Maruyama T. Loss of genes related to Nucleotide Excision Repair (NER) and implications for reductive genome evolution in symbionts of deep-sea vesicomyid clams. PLoS One 2017; 12:e0171274. [PMID: 28199404 PMCID: PMC5310779 DOI: 10.1371/journal.pone.0171274] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 01/17/2017] [Indexed: 01/08/2023] Open
Abstract
Intracellular thioautotrophic symbionts of deep-sea vesicomyid clams lack some DNA repair genes and are thought to be undergoing reductive genome evolution (RGE). In this study, we addressed two questions, 1) how these symbionts lost their DNA repair genes and 2) how such losses affect RGE. For the first question, we examined genes associated with nucleotide excision repair (NER; uvrA, uvrB, uvrC, uvrD, uvrD paralog [uvrDp] and mfd) in 12 symbionts of vesicomyid clams belonging to two clades (5 clade I and 7 clade II symbionts). While uvrA, uvrDp and mfd were conserved in all symbionts, uvrB and uvrC were degraded in all clade I symbionts but were apparently intact in clade II symbionts. UvrD was disrupted in two clade II symbionts. Among the intact genes in Ca. Vesicomyosocius okutanii (clade I), expressions of uvrD and mfd were detected by reverse transcription-polymerase chain reaction (RT-PCR), but those of uvrA and uvrDp were not. In contrast, all intact genes were expressed in the symbiont of Calyptogena pacifica (clade II). To assess how gene losses affect RGE (question 2), genetic distances of the examined genes in symbionts from Bathymodiolus septemdierum were shown to be larger in clade I than clade II symbionts. In addition, these genes had lower guanine+cytosine (GC) content and higher repeat sequence densities in clade I than measured in clade II. Our results suggest that NER genes are currently being lost from the extant lineages of vesicomyid clam symbionts. The loss of NER genes and mutY in these symbionts is likely to promote increases in genetic distance and repeat sequence density as well as reduced GC content in genomic genes, and may have facilitated reductive evolution of the genome.
Collapse
Affiliation(s)
- Shigeru Shimamura
- Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology, 2–15, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
- Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
| | - Takashi Kaneko
- Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology, 2–15, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
- Tokyo College of Biotechnology, Kitakoujiya, Ota-ku,Tokyo, Japan
| | - Genki Ozawa
- Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology, 2–15, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
- Kitasato University, School of Marine Biosciences, Kitasato Minami-ku Sagamihara-shi Kanagawa, Japan
| | - Mamiko Nishino Matsumoto
- Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology, 2–15, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
| | - Takeru Koshiishi
- Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology, 2–15, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
| | - Yoshihiro Takaki
- Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
| | - Chiaki Kato
- Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology, 2–15, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
| | - Ken Takai
- Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
| | - Takao Yoshida
- Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology, 2–15, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
- Kitasato University, School of Marine Biosciences, Kitasato Minami-ku Sagamihara-shi Kanagawa, Japan
| | - Katsunori Fujikura
- Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology, 2–15, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
| | - James P. Barry
- Monterey Bay Aquarium Research Institute, Moss Landing, California, United States of America
| | - Tadashi Maruyama
- Kitasato University, School of Marine Biosciences, Kitasato Minami-ku Sagamihara-shi Kanagawa, Japan
- Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology, Natsushima-cho, Yokosuka-shi, Kanagawa, Japan
- * E-mail:
| |
Collapse
|
11
|
Logacheva MD, Schelkunov MI, Shtratnikova VY, Matveeva MV, Penin AA. Comparative analysis of plastid genomes of non-photosynthetic Ericaceae and their photosynthetic relatives. Sci Rep 2016; 6:30042. [PMID: 27452401 PMCID: PMC4958920 DOI: 10.1038/srep30042] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 06/27/2016] [Indexed: 12/24/2022] Open
Abstract
Although plastid genomes of flowering plants are typically highly conserved regarding their size, gene content and order, there are some exceptions. Ericaceae, a large and diverse family of flowering plants, warrants special attention within the context of plastid genome evolution because it includes both non-photosynthetic and photosynthetic species with rearranged plastomes and putative losses of "essential" genes. We characterized plastid genomes of three species of Ericaceae, non-photosynthetic Monotropa uniflora and Hypopitys monotropa and photosynthetic Pyrola rotundifolia, using high-throughput sequencing. As expected for non-photosynthetic plants, M. uniflora and H. monotropa have small plastid genomes (46 kb and 35 kb, respectively) lacking genes related to photosynthesis, whereas P. rotundifolia has a larger genome (169 kb) with a gene set similar to other photosynthetic plants. The examined genomes contain an unusually high number of repeats and translocations. Comparative analysis of the expanded set of Ericaceae plastomes suggests that the genes clpP and accD that are present in the plastid genomes of almost all plants have not been lost in this family (as was previously thought) but rather persist in these genomes in unusual forms. Also we found a new gene in P. rotundifolia that emerged as a result of duplication of rps4 gene.
Collapse
Affiliation(s)
- Maria D. Logacheva
- Lomonosov Moscow State University, A.N Belozersky Institute of Physico-Chemical Biology, Moscow, Russia
- Kazan Federal University, Institute of Fundamental Biology and Medicine, Kazan, Russia
| | - Mikhail I. Schelkunov
- Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia
| | - Victoria Y. Shtratnikova
- Lomonosov Moscow State University, Department of Bioengineering and Bioinformatics, Moscow, Russia
| | - Maria V. Matveeva
- Kazan Federal University, Institute of Fundamental Biology and Medicine, Kazan, Russia
| | - Aleksey A. Penin
- Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia
- Lomonosov Moscow State University, Department of Genetics, Moscow, Russia
| |
Collapse
|
12
|
Clayton AL, Jackson DG, Weiss RB, Dale C. Adaptation by Deletogenic Replication Slippage in a Nascent Symbiont. Mol Biol Evol 2016; 33:1957-66. [PMID: 27189544 PMCID: PMC4948707 DOI: 10.1093/molbev/msw071] [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] [Indexed: 01/04/2023] Open
Abstract
As a consequence of population level constraints in the obligate, host-associated lifestyle, intracellular symbiotic bacteria typically exhibit high rates of molecular sequence evolution and extensive genome degeneration over the course of their host association. While the rationale for genome degeneration is well understood, little is known about the molecular mechanisms driving this change. To understand these mechanisms we compared the genome of Sodalis praecaptivus, a nonhost associated bacterium that is closely related to members of the Sodalis-allied clade of insect endosymbionts, with the very recently derived insect symbiont Candidatus Sodalis pierantonius. The characterization of indel mutations in the genome of Ca. Sodalis pierantonius shows that the replication system in this organism is highly prone to deletions resulting from polymerase slippage events in regions encoding G+C-rich repetitive sequences. This slippage-prone phenotype is mechanistically associated with the loss of certain components of the bacterial DNA recombination machinery at an early stage in symbiotic life and is expected to facilitate rapid adaptation to the novel host environment. This is analogous to the emergence of mutator strains in both natural and laboratory populations of bacteria, which tend to reach high frequencies in clonal populations due to linkage between the mutator allele and the resulting adaptive mutations.
Collapse
Affiliation(s)
| | | | | | - Colin Dale
- Department of Biology, University of Utah
| |
Collapse
|
13
|
Chlamydia trachomatis In Vivo to In Vitro Transition Reveals Mechanisms of Phase Variation and Down-Regulation of Virulence Factors. PLoS One 2015. [PMID: 26207372 PMCID: PMC4514472 DOI: 10.1371/journal.pone.0133420] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Research on the obligate intracellular bacterium Chlamydia trachomatis demands culture in cell-lines, but the adaptive process behind the in vivo to in vitro transition is not understood. We assessed the genomic and transcriptomic dynamics underlying C. trachomatis in vitro adaptation of strains representing the three disease groups (ocular, epithelial-genital and lymphogranuloma venereum) propagated in epithelial cells over multiple passages. We found genetic features potentially underlying phase variation mechanisms mediating the regulation of a lipid A biosynthesis enzyme (CT533/LpxC), and the functionality of the cytotoxin (CT166) through an ON/OFF mechanism. We detected inactivating mutations in CT713/porB, a scenario suggesting metabolic adaptation to the available carbon source. CT135 was inactivated in a tropism-specific manner, with CT135-negative clones emerging for all epithelial-genital populations (but not for LGV and ocular populations) and rapidly increasing in frequency (~23% mutants per 10 passages). RNA-sequencing analyses revealed that a deletion event involving CT135 impacted the expression of multiple virulence factors, namely effectors known to play a role in the C. trachomatis host-cell invasion or subversion (e.g., CT456/Tarp, CT694, CT875/TepP and CT868/ChlaDub1). This reflects a scenario of attenuation of C. trachomatis virulence in vitro, which may take place independently or in a cumulative fashion with the also observed down-regulation of plasmid-related virulence factors. This issue may be relevant on behalf of the recent advances in Chlamydia mutagenesis and transformation where culture propagation for selecting mutants/transformants is mandatory. Finally, there was an increase in the growth rate for all strains, reflecting gradual fitness enhancement over time. In general, these data shed light on the adaptive process underlying the C. trachomatis in vivo to in vitro transition, and indicates that it would be prudent to restrict culture propagation to minimal passages and check the status of the CT135 genotype in order to avoid the selection of CT135-negative mutants, likely originating less virulent strains.
Collapse
|
14
|
Larson MA, Nalbantoglu U, Sayood K, Zentz EB, Bartling AM, Francesconi SC, Fey PD, Dempsey MP, Hinrichs SH. Francisella tularensis Subtype A.II Genomic Plasticity in Comparison with Subtype A.I. PLoS One 2015; 10:e0124906. [PMID: 25918839 PMCID: PMC4412822 DOI: 10.1371/journal.pone.0124906] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 03/09/2015] [Indexed: 11/26/2022] Open
Abstract
Although Francisella tularensis is considered a monomorphic intracellular pathogen, molecular genotyping and virulence studies have demonstrated important differences within the tularensis subspecies (type A). To evaluate genetic variation within type A strains, sequencing and assembly of a new subtype A.II genome was achieved for comparison to other completed F. tularensis type A genomes. In contrast with the F. tularensis A.I strains (SCHU S4, FSC198, NE061598, and TI0902), substantial genomic variation was observed between the newly sequenced F. tularensis A.II strain (WY-00W4114) and the only other publically available A.II strain (WY96-3418). Genome differences between WY-00W4114 and WY96-3418 included three major chromosomal translocations, 1580 indels, and 286 nucleotide substitutions of which 159 were observed in predicted open reading frames and 127 were located in intergenic regions. The majority of WY-00W4114 nucleotide deletions occurred in intergenic regions, whereas most of the insertions and substitutions occurred in predicted genes. Of the nucleotide substitutions, 48 (30%) were synonymous and 111 (70%) were nonsynonymous. WY-00W4114 and WY96-3418 nucleotide polymorphisms were predominantly G/C to A/T allelic mutations, with WY-00W4114 having more A+T enrichment. In addition, the A.II genomes contained a considerably higher number of intact genes and longer repetitive sequences, including transposon remnants than the A.I genomes. Together these findings support the premise that F. tularensis A.II may have a fitness advantage compared to the A.I subtype due to the higher abundance of functional genes and repeated chromosomal sequences. A better understanding of the selective forces driving F. tularensis genetic diversity and plasticity is needed.
Collapse
Affiliation(s)
- Marilynn A. Larson
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
- * E-mail:
| | - Ufuk Nalbantoglu
- Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Khalid Sayood
- Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Emily B. Zentz
- OpGen Inc., Gaithersburg, Maryland, United States of America
| | - Amanda M. Bartling
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | | | - Paul D. Fey
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Michael P. Dempsey
- United States Air Force School of Aerospace Medicine, Wright-Patterson Air Force Base, Ohio, United States of America
| | - Steven H. Hinrichs
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| |
Collapse
|
15
|
Genome wide survey of microsatellites in ssDNA viruses infecting vertebrates. Gene 2014; 552:209-18. [DOI: 10.1016/j.gene.2014.09.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 08/15/2014] [Accepted: 09/15/2014] [Indexed: 01/26/2023]
|
16
|
Abstract
Bacterial genomes are remarkably stable from one generation to the next but are plastic on an evolutionary time scale, substantially shaped by horizontal gene transfer, genome rearrangement, and the activities of mobile DNA elements. This implies the existence of a delicate balance between the maintenance of genome stability and the tolerance of genome instability. In this review, we describe the specialized genetic elements and the endogenous processes that contribute to genome instability. We then discuss the consequences of genome instability at the physiological level, where cells have harnessed instability to mediate phase and antigenic variation, and at the evolutionary level, where horizontal gene transfer has played an important role. Indeed, this ability to share DNA sequences has played a major part in the evolution of life on Earth. The evolutionary plasticity of bacterial genomes, coupled with the vast numbers of bacteria on the planet, substantially limits our ability to control disease.
Collapse
|
17
|
Zhou K, Aertsen A, Michiels CW. The role of variable DNA tandem repeats in bacterial adaptation. FEMS Microbiol Rev 2013; 38:119-41. [PMID: 23927439 DOI: 10.1111/1574-6976.12036] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 07/13/2013] [Accepted: 07/26/2013] [Indexed: 01/05/2023] Open
Abstract
DNA tandem repeats (TRs), also designated as satellite DNA, are inter- or intragenic nucleotide sequences that are repeated two or more times in a head-to-tail manner. Because TR tracts are prone to strand-slippage replication and recombination events that cause the TR copy number to increase or decrease, loci containing TRs are hypermutable. An increasing number of examples illustrate that bacteria can exploit this instability of TRs to reversibly shut down or modulate the function of specific genes, allowing them to adapt to changing environments on short evolutionary time scales without an increased overall mutation rate. In this review, we discuss the prevalence and distribution of inter- and intragenic TRs in bacteria and the mechanisms of their instability. In addition, we review evidence demonstrating a role of TR variations in bacterial adaptation strategies, ranging from immune evasion and tissue tropism to the modulation of environmental stress tolerance. Nevertheless, while bioinformatic analysis reveals that most bacterial genomes contain a few up to several dozens of intra- and intergenic TRs, only a small fraction of these have been functionally studied to date.
Collapse
Affiliation(s)
- Kai Zhou
- Department of Microbial and Molecular Systems (M²S), Faculty of Bioscience Engineering, Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | | | | |
Collapse
|
18
|
Siozios S, Ioannidis P, Klasson L, Andersson SGE, Braig HR, Bourtzis K. The diversity and evolution of Wolbachia ankyrin repeat domain genes. PLoS One 2013; 8:e55390. [PMID: 23390535 PMCID: PMC3563639 DOI: 10.1371/journal.pone.0055390] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 12/21/2012] [Indexed: 11/25/2022] Open
Abstract
Ankyrin repeat domain-encoding genes are common in the eukaryotic and viral domains of life, but they are rare in bacteria, the exception being a few obligate or facultative intracellular Proteobacteria species. Despite having a reduced genome, the arthropod strains of the alphaproteobacterium Wolbachia contain an unusually high number of ankyrin repeat domain-encoding genes ranging from 23 in wMel to 60 in wPip strain. This group of genes has attracted considerable attention for their astonishing large number as well as for the fact that ankyrin proteins are known to participate in protein-protein interactions, suggesting that they play a critical role in the molecular mechanism that determines host-Wolbachia symbiotic interactions. We present a comparative evolutionary analysis of the wMel-related ankyrin repeat domain-encoding genes present in different Drosophila-Wolbachia associations. Our results show that the ankyrin repeat domain-encoding genes change in size by expansion and contraction mediated by short directly repeated sequences. We provide examples of intra-genic recombination events and show that these genes are likely to be horizontally transferred between strains with the aid of bacteriophages. These results confirm previous findings that the Wolbachia genomes are evolutionary mosaics and illustrate the potential that these bacteria have to generate diversity in proteins potentially involved in the symbiotic interactions.
Collapse
Affiliation(s)
- Stefanos Siozios
- Department of Environmental and Natural Resources Management, University of Western Greece, Agrinio, Greece
| | - Panagiotis Ioannidis
- Department of Environmental and Natural Resources Management, University of Western Greece, Agrinio, Greece
| | - Lisa Klasson
- Department of Molecular Evolution, Uppsala University, Uppsala, Sweden
| | | | - Henk R. Braig
- School of Biological Sciences Bangor University, Bangor Gwynedd, United Kingdom
| | - Kostas Bourtzis
- Department of Environmental and Natural Resources Management, University of Western Greece, Agrinio, Greece
- Biomedical Sciences Research Center Al. Fleming, Vari, Greece
- Insect Pest Control Laboratory, Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, Vienna, Austria
| |
Collapse
|
19
|
Abstract
Proteins secreted to the extracellular environment or to the periphery of the cell envelope, the secretome, play essential roles in foraging, antagonistic and mutualistic interactions. We hypothesize that arms races, genetic conflicts and varying selective pressures should lead to the rapid change of sequences and gene repertoires of the secretome. The analysis of 42 bacterial pan-genomes shows that secreted, and especially extracellular proteins, are predominantly encoded in the accessory genome, i.e. among genes not ubiquitous within the clade. Genes encoding outer membrane proteins might engage more frequently in intra-chromosomal gene conversion because they are more often in multi-genic families. The gene sequences encoding the secretome evolve faster than the rest of the genome and in particular at non-synonymous positions. Cell wall proteins in Firmicutes evolve particularly fast when compared with outer membrane proteins of Proteobacteria. Virulence factors are over-represented in the secretome, notably in outer membrane proteins, but cell localization explains more of the variance in substitution rates and gene repertoires than sequence homology to known virulence factors. Accordingly, the repertoires and sequences of the genes encoding the secretome change fast in the clades of obligatory and facultative pathogens and also in the clades of mutualists and free-living bacteria. Our study shows that cell localization shapes genome evolution. In agreement with our hypothesis, the repertoires and the sequences of genes encoding secreted proteins evolve fast. The particularly rapid change of extracellular proteins suggests that these public goods are key players in bacterial adaptation.
Collapse
Affiliation(s)
- Teresa Nogueira
- Centro de Biologia Ambiental, Evolutionary Ecology of Microorganisms, Faculdade de Ciências da Universidade de Lisboa, Lisboa, Portugal
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
- Centro de Investigação em Saúde e Ambiente, Escola Superior de Tecnologia da Saúde do Porto, Instituto Politécnico do Porto, Vila Nova de Gaia, Portugal
| | - Marie Touchon
- Institut Pasteur, Microbial Evolutionary Genomics, Département Génomes et Génétique, Paris, France
- CNRS, UMR3525, Paris, France
| | - Eduardo P. C. Rocha
- Institut Pasteur, Microbial Evolutionary Genomics, Département Génomes et Génétique, Paris, France
- CNRS, UMR3525, Paris, France
- * E-mail:
| |
Collapse
|
20
|
Zhao X, Tian Y, Yang R, Feng H, Ouyang Q, Tian Y, Tan Z, Li M, Niu Y, Jiang J, Shen G, Yu R. Coevolution between simple sequence repeats (SSRs) and virus genome size. BMC Genomics 2012; 13:435. [PMID: 22931422 PMCID: PMC3585866 DOI: 10.1186/1471-2164-13-435] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Accepted: 08/18/2012] [Indexed: 12/26/2022] Open
Abstract
Background Relationship between the level of repetitiveness in genomic sequence and genome size has been investigated by making use of complete prokaryotic and eukaryotic genomes, but relevant studies have been rarely made in virus genomes. Results In this study, a total of 257 viruses were examined, which cover 90% of genera. The results showed that simple sequence repeats (SSRs) is strongly, positively and significantly correlated with genome size. Certain repeat class is distributed in a certain range of genome sequence length. Mono-, di- and tri- repeats are widely distributed in all virus genomes, tetra- SSRs as a common component consist in genomes which more than 100 kb in size; in the range of genome < 100 kb, genomes containing penta- and hexa- SSRs are not more than 50%. Principal components analysis (PCA) indicated that dinucleotide repeat affects the differences of SSRs most strongly among virus genomes. Results showed that SSRs tend to accumulate in larger virus genomes; and the longer genome sequence, the longer repeat units. Conclusions We conducted this research standing on the height of the whole virus. We concluded that genome size is an important factor in affecting the occurrence of SSRs; hosts are also responsible for the variances of SSRs content to a certain degree.
Collapse
Affiliation(s)
- Xiangyan Zhao
- Chinese Academy of Inspection and Quarantine, Beijing, 100029, China
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Altered patterns of fractionation and exon deletions in Brassica rapa support a two-step model of paleohexaploidy. Genetics 2012; 190:1563-74. [PMID: 22308264 DOI: 10.1534/genetics.111.137349] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The genome sequence of the paleohexaploid Brassica rapa shows that fractionation is biased among the three subgenomes and that the least fractionated subgenome has approximately twice as many orthologs as its close (and relatively unduplicated) relative Arabidopsis than had either of the other two subgenomes. One evolutionary scenario is that the two subgenomes with heavy gene losses (I and II) were in the same nucleus for a longer period of time than the third subgenome (III) with the fewest gene losses. This "two-step" hypothesis is essentially the same as that proposed previously for the eudicot paleohexaploidy; however, the more recent nature of the B. rapa paleohexaploidy makes this model more testable. We found that subgenome II suffered recent small deletions within exons more frequently than subgenome I, as would be expected if the genes in subgenome I had already been near maximally fractionated before subgenome III was introduced. We observed that some sequences, before these deletions, were flanked by short direct repeats, a unique signature of intrachromosomal illegitimate recombination. We also found, through simulations, that short--single or two-gene--deletions appear to dominate the fractionation patterns in B. rapa. We conclude that the observed patterns of the triplicated regions in the Brassica genome are best explained by a two-step fractionation model. The triplication and subsequent mode of fractionation could influence the potential to generate morphological diversity--a hallmark of the Brassica genus.
Collapse
|
22
|
Kuwahara H, Takaki Y, Shimamura S, Yoshida T, Maeda T, Kunieda T, Maruyama T. Loss of genes for DNA recombination and repair in the reductive genome evolution of thioautotrophic symbionts of Calyptogena clams. BMC Evol Biol 2011; 11:285. [PMID: 21966992 PMCID: PMC3202245 DOI: 10.1186/1471-2148-11-285] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 10/03/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Two Calyptogena clam intracellular obligate symbionts, Ca. Vesicomyosocius okutanii (Vok; C. okutanii symbiont) and Ca. Ruthia magnifica (Rma; C. magnifica symbiont), have small genomes (1.02 and 1.16 Mb, respectively) with low G+C contents (31.6% and 34.0%, respectively) and are thought to be in an ongoing stage of reductive genome evolution (RGE). They lack recA and some genes for DNA repair, including mutY. The loss of recA and mutY is thought to contribute to the stabilization of their genome architectures and GC bias, respectively. To understand how these genes were lost from the symbiont genomes, we surveyed these genes in the genomes from 10 other Calyptogena clam symbionts using the polymerase chain reaction (PCR). RESULTS Phylogenetic trees reconstructed using concatenated 16S and 23S rRNA gene sequences showed that the symbionts formed two clades, clade I (symbionts of C. kawamurai, C. laubieri, C. kilmeri, C. okutanii and C. soyoae) and clade II (those of C. pacifica, C. fausta, C. nautilei, C. stearnsii, C. magnifica, C. fossajaponica and C. phaseoliformis). recA was detected by PCR with consensus primers for recA in the symbiont of C. phaseoliformis. A detailed homology search revealed a remnant recA in the Rma genome. Using PCR with a newly designed primer set, intact recA or its remnant was detected in clade II symbionts. In clade I symbionts, the recA coding region was found to be mostly deleted.In the Rma genome, a pseudogene of mutY was found. Using PCR with newly designed primer sets, mutY was not found in clade I symbionts but was found in clade II symbionts. The G+C content of 16S and 23S rRNA genes in symbionts lacking mutY was significantly lower than in those with mutY. CONCLUSIONS The extant Calyptogena clam symbionts in clade II were shown to have recA and mutY or their remnants, while those in clade I did not. The present results indicate that the extant symbionts are losing these genes in RGE, and that the loss of mutY contributed to the GC bias of the genomes during their evolution.
Collapse
Affiliation(s)
- Hirokazu Kuwahara
- Marine Biodiversity Research Program, Japan Agency for Marine-Earth Science and Technology, Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan
| | | | | | | | | | | | | |
Collapse
|
23
|
Smirnov GB. Repeats in bacterial genome: Evolutionary considerations. MOLECULAR GENETICS, MICROBIOLOGY AND VIROLOGY 2010. [DOI: 10.3103/s0891416810020023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
|
24
|
Touchon M, Rocha EPC. The small, slow and specialized CRISPR and anti-CRISPR of Escherichia and Salmonella. PLoS One 2010; 5:e11126. [PMID: 20559554 PMCID: PMC2886076 DOI: 10.1371/journal.pone.0011126] [Citation(s) in RCA: 174] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Accepted: 05/25/2010] [Indexed: 11/30/2022] Open
Abstract
Prokaryotes thrive in spite of the vast number and diversity of their viruses. This partly results from the evolution of mechanisms to inactivate or silence the action of exogenous DNA. Among these, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) are unique in providing adaptive immunity against elements with high local resemblance to genomes of previously infecting agents. Here, we analyze the CRISPR loci of 51 complete genomes of Escherichia and Salmonella. CRISPR are in two pairs of loci in Escherichia, one single pair in Salmonella, each pair showing a similar turnover rate, repeat sequence and putative linkage to a common set of cas genes. Yet, phylogeny shows that CRISPR and associated cas genes have different evolutionary histories, the latter being frequently exchanged or lost. In our set, one CRISPR pair seems specialized in plasmids often matching genes coding for the replication, conjugation and antirestriction machinery. Strikingly, this pair also matches the cognate cas genes in which case these genes are absent. The unexpectedly high conservation of this anti-CRISPR suggests selection to counteract the invasion of mobile elements containing functional CRISPR/cas systems. There are few spacers in most CRISPR, which rarely match genomes of known phages. Furthermore, we found that strains divergent less than 250 thousand years ago show virtually identical CRISPR. The lack of congruence between cas, CRISPR and the species phylogeny and the slow pace of CRISPR change make CRISPR poor epidemiological markers in enterobacteria. All these observations are at odds with the expectedly abundant and dynamic repertoire of spacers in an immune system aiming at protecting bacteria from phages. Since we observe purifying selection for the maintenance of CRISPR these results suggest that alternative evolutionary roles for CRISPR remain to be uncovered.
Collapse
Affiliation(s)
- Marie Touchon
- Département Génomes et Génétique, Institut Pasteur, Microbial Evolutionary Genomics, Paris, France.
| | | |
Collapse
|
25
|
Analysis of DNA repeats in bacterial plasmids reveals the potential for recurrent instability events. Appl Microbiol Biotechnol 2010; 87:2157-67. [PMID: 20496146 DOI: 10.1007/s00253-010-2671-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Revised: 04/05/2010] [Accepted: 05/05/2010] [Indexed: 12/17/2022]
Abstract
Structural instability has been frequently observed in natural plasmids and vectors used for protein expression or DNA vaccine development. However, there is a lack of information concerning hotspot mapping, namely, DNA repeats or sequences identical to the host genome. This led us to evaluate the abundance and distribution of direct, inverted, and tandem repeats with high recombination potential in 36 natural plasmids from ten bacterial genera, as well as in several widely used bacterial and mammalian expression vectors. In natural plasmids, we observed an overrepresentation of close direct repeats in comparison to inverted ones and a preferential location of repeats with high recombination potential in intergenic regions, suggesting a highly plastic and dynamic behavior. In plasmid vectors, we found a high density of repeats within eukaryotic promoters and non-coding sequences. As a result of this in silico analysis, we detected a spontaneous recombination between two 21-bp direct repeats present in the human cytomegalovirus early enhancer/promoter (huCMV EEP) of the pCIneo plasmid. This finding is of particular importance, as the huCMV EEP is one of the most frequently used regulatory elements in plasmid vectors. Because pDNA integration into host gDNA can have adverse consequences in terms of plasmid processing and host safety, we also mapped several regions with high probability to mediate integration into the Escherichia coli or human genomes. Like repeated regions, some of these were located in non-coding regions of the plasmids, thus being preferential targets to be removed.
Collapse
|
26
|
Abraham AL, Pothier J, Rocha EPC. Alternative to homo-oligomerisation: the creation of local symmetry in proteins by internal amplification. J Mol Biol 2009; 394:522-34. [PMID: 19769988 DOI: 10.1016/j.jmb.2009.09.031] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2009] [Revised: 09/11/2009] [Accepted: 09/15/2009] [Indexed: 11/18/2022]
Abstract
The biologically active state of many proteins requires their prior homo-oligomerisation. Such complexes are typically symmetrical, a feature that has been proposed to increase their stability and facilitate the evolution of allosteric regulation. We wished to examine the possibility that similar structures and properties could arise from genetic amplifications leading to internal symmetrical repeats. For this, we identified internal structural repeats in a nonredundant Protein Data Bank subset. While testing if repeats in proteins tend to be symmetrical, we found that about half of the large internal repeats are symmetrical, most frequently around a rotation axis of 180 degrees . These repeats were most likely created by genetic amplification processes because they show significant sequence similarity. Symmetrical repeats tend to have a fixed number of copies corresponding to their rotational symmetry order, that is, two for 180 degrees rotation axis, whereas asymmetrical repeats are in longer proteins and show copy number variability. When possible, we confirmed that proteins with symmetrical repeats folding as an n-mer have homologues lacking the repeat with a higher oligomerisation number corresponding to the rotation symmetry order of the repeat. Phylogenetic analyses of these protein families suggest that typically, but not always, symmetrical repeats arise in one single event from proteins that are homo-oligomers. These results suggest that oligomerisation and amplification of internal sequences can interplay in evolutionary terms because they result in functional analogues when the latter exhibit rotational symmetry.
Collapse
Affiliation(s)
- Anne-Laure Abraham
- Atelier de BioInformatique, Université Pierre et Marie Curie-Paris 06, Paris, France.
| | | | | |
Collapse
|
27
|
Gómez-Valero L, Latorre A, Gil R, Gadau J, Feldhaar H, Silva FJ. Patterns and rates of nucleotide substitution, insertion and deletion in the endosymbiont of ants Blochmannia floridanus. Mol Ecol 2009; 17:4382-92. [PMID: 19378410 DOI: 10.1111/j.1365-294x.2008.03912.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Genome reduction is a general process that has been studied in numerous symbiotic bacteria associated with insects. We investigated the last stages of genome degradation in Blochmannia floridanus, a mutualistic bacterial endosymbiont of the ant Camponotus floridanus. We determined the tempo (rates of insertion and deletion) and mode (size and number of insertion-deletion events) of the process in the last 200,000 years by analysing a total of 16 intergenic regions in several strains of this endosymbiont from different ant populations. We provide the first calculation of the reduction rate for noncoding DNA in this endosymbiont (2.2 x 10(-8) lost nucleotides/site/year) and compare it with the rate of loss in other species. Our results confirm, as it has been observed in other organisms like Buchnera aphidicola or Rickettsia spp., that deletions larger than one nucleotide can still appear in advanced stages of genome reduction and that a substitutional deletion bias exists. However, this bias is not due to a higher proportion of deletion over insertion events but to a few deletion events being larger than the rest. Moreover, we detected a substitutional AT bias that is probably responsible for the increase in the number of the small and moderate indel events in the last stages of genome reduction. Accordingly, we found intrapopulational polymorphisms for the detected microsatellites in contrast to the stability associated with these in free-living bacteria such as Escherichia coli.
Collapse
Affiliation(s)
- L Gómez-Valero
- Biologie des bactéries intracellulaires, Institute Pasteur, 28 Rue du Dr Roux, 75724 Paris, France.
| | | | | | | | | | | |
Collapse
|
28
|
Treangen TJ, Abraham AL, Touchon M, Rocha EPC. Genesis, effects and fates of repeats in prokaryotic genomes. FEMS Microbiol Rev 2009; 33:539-71. [PMID: 19396957 DOI: 10.1111/j.1574-6976.2009.00169.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
DNA repeats are causes and consequences of genome plasticity. Repeats are created by intrachromosomal recombination or horizontal transfer. They are targeted by recombination processes leading to amplifications, deletions and rearrangements of genetic material. The identification and analysis of repeats in nearly 700 genomes of bacteria and archaea is facilitated by the existence of sequence data and adequate bioinformatic tools. These have revealed the immense diversity of repeats in genomes, from those created by selfish elements to the ones used for protection against selfish elements, from those arising from transient gene amplifications to the ones leading to stable duplications. Experimental works have shown that some repeats do not carry any adaptive value, while others allow functional diversification and increased expression. All repeats carry some potential to disorganize and destabilize genomes. Because recombination and selection for repeats vary between genomes, the number and types of repeats are also quite diverse and in line with ecological variables, such as host-dependent associations or population sizes, and with genetic variables, such as the recombination machinery. From an evolutionary point of view, repeats represent both opportunities and problems. We describe how repeats are created and how they can be found in genomes. We then focus on the functional and genomic consequences of repeats that dictate their fate.
Collapse
|
29
|
Transcription of clpP is enhanced by a unique tandem repeat sequence in Streptococcus mutans. J Bacteriol 2008; 191:1056-65. [PMID: 19047352 DOI: 10.1128/jb.01436-08] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Streptococcus mutans, the primary causative agent of human dental caries, contains a single copy of the gene encoding ClpP, the chief intracellular protease responsible for tolerance to various environmental stresses. To better understand the role of ClpP in stress response, we investigated the regulation of clpP expression in S. mutans. Using semiquantitative reverse transcription-PCR analysis, we observed that, under nonstressed conditions, clpP expression is somewhat constant throughout the growth phases, although it gradually decreases as cells enter the late stationary phase. The half-life of the clpP transcript was found to be less than 1 minute. Sequence analysis of the clpP locus reveals the presence of a 50-bp tandem repeat sequence located immediately upstream of the clpP promoter (PclpP). PCR and DNA sequence analyses suggest that the number of tandem repeat units can vary from as few as two to as many as nine, depending on the particular S. mutans isolate. Further analysis, using a transcriptional reporter fusion consisting of PclpP fused to a promoterless gusA gene, indicates that the presence of the repeat sequence region within PclpP results in an approximately fivefold increase in expression from PclpP compared to the repeat-free transcriptional reporter fusion. CtsR, a transcriptional repressor that negatively regulates clpP expression, has no effect on this repeat-mediated induction of clpP transcription. Furthermore, the repeat sequence is not necessary for the induction of clpP under stress conditions. Database searches indicate that the region containing the tandem repeats is absent in the clpP loci in other bacteria, including other closely related Streptococcus spp., suggesting that the repeat sequences are specific for the induction of clpP expression in S. mutans. We speculate that a host-specific transcriptional activator might be involved in the upregulation of clpP expression in S. mutans.
Collapse
|
30
|
López-Sánchez MJ, Neef A, Patiño-Navarrete R, Navarro L, Jiménez R, Latorre A, Moya A. Blattabacteria, the endosymbionts of cockroaches, have small genome sizes and high genome copy numbers. Environ Microbiol 2008; 10:3417-22. [PMID: 19025557 DOI: 10.1111/j.1462-2920.2008.01776.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Blattabacteria are intracellular endosymbionts of cockroaches and primitive termites that belong to the class Flavobacteria and live only in specialized cells in the abdominal fat body of their hosts. In the present study we determined genome sizes as well as genome copy numbers for the endosymbionts of three cockroach species, Blattella germanica, Periplaneta americana and Blatta orientalis. The sole presence of blattabacteria in the fat body was demonstrated by rRNA-targeting techniques. The genome sizes of the three blattabacteria were determined by pulsed field gel electrophoresis. The resulting total genome sizes for the three symbionts were all approximately 650 +/- 15 kb. Comparison of the genome sizes with those of free-living Bacteroidetes shows extended reduction, as occurs in other obligatory insect endosymbionts. Genome copy numbers were determined based on cell counts and determination of DNA amounts via quantitative PCR. Values between 10.2 and 18.3 and between 323 and 353 were found for the symbionts of P. americana and B. orientalis respectively. Polyploidy in intracellular bacteria may play a significant role in the genome reduction process.
Collapse
Affiliation(s)
- María José López-Sánchez
- Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Universitat de València, Apartado Postal 2085, 46071 Valencia, Spain
| | | | | | | | | | | | | |
Collapse
|
31
|
Guo X, Mrázek J. Long simple sequence repeats in host-adapted pathogens localize near genes encoding antigens, housekeeping genes, and pseudogenes. J Mol Evol 2008; 67:497-509. [PMID: 18925380 DOI: 10.1007/s00239-008-9166-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Revised: 09/03/2008] [Accepted: 09/03/2008] [Indexed: 10/21/2022]
Abstract
Simple sequence repeats (SSRs) in DNA sequences are tandem iterations of a single nucleotide or a short oligonucleotide. SSRs are subject to slipped-strand mutations and a common source of phase variation in bacteria and antigenic variation in pathogens. Significantly long SSRs are generally rare in prokaryotic genomes, and long SSRs composed of iterations of mono-, di-, tri-, and tetranucleotides are mostly restricted to host-adapted pathogens. We present new results concerning associations between long SSRs and genes related to different cellular functions in genomes of host-adapted pathogens. We found that in the majority of the analyzed genomes, at least some of the genes associated with SSRs encode potential antigens, which is expected if the primary function of SSRs is their contribution to antigenic variation. However, we also found a number of long SSRs associated with housekeeping genes, including rRNA and tRNA genes, genes encoding ribosomal proteins, amino acyl-tRNA synthetases, chaperones, and important metabolic enzymes. Many of these genes are probably essential and it is unlikely that they are phase-variable. Few statistically significant associations between SSRs and gene functional classifications were detected, suggesting that most long SSRs are not related to a particular cellular function or process. Long SSRs in Mycobacterium leprae are mostly associated with pseudogenes and may be contributing to gene loss following the adaptation to an obligate pathogenic lifestyle. We speculate that LSSRs may have played a similar role in genome reduction of other host-adapted pathogens.
Collapse
Affiliation(s)
- Xiangxue Guo
- Department of Microbiology, University of Georgia, Athens, GA 30602-2605, USA
| | | |
Collapse
|
32
|
Recombination frequency in plasmid DNA containing direct repeats—predictive correlation with repeat and intervening sequence length. Plasmid 2008; 60:159-65. [DOI: 10.1016/j.plasmid.2008.06.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Revised: 06/09/2008] [Accepted: 06/24/2008] [Indexed: 11/19/2022]
|
33
|
Kuwahara H, Takaki Y, Yoshida T, Shimamura S, Takishita K, Reimer JD, Kato C, Maruyama T. Reductive genome evolution in chemoautotrophic intracellular symbionts of deep-sea Calyptogena clams. Extremophiles 2008; 12:365-74. [PMID: 18305898 DOI: 10.1007/s00792-008-0141-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Accepted: 01/07/2008] [Indexed: 10/22/2022]
Abstract
To understand reductive genome evolution (RGE), we comparatively analyzed the recently reported small genomes of two chemoautotrophic, intracellular symbionts of deep-sea clams, Calyptogena okutanii and C. magnifica. Both genomes lack most genes for DNA recombination and repair such as recA and mutY. Their genome architectures were highly conserved except one inversion. Many deletions from small (<100 bp) to large (1-11 kbp) sizes were detected and the deletion numbers decreased exponentially with size. Densities of deletions and short-repeats, as well as A+T content were higher in non-coding regions than in coding regions. Because Calyptogena symbiont genomes lack recA, we propose that deletions and the single inversion occurred by RecA-independent recombination (RIR) at short-repeats with simultaneous consumption of repeats, and that short-repeats were regenerated by accelerated mutations with enhanced A+T bias due to the absence of mutY. We further propose that extant Calyptogena symbiont genomes are in an actively reducing stage of RGE consisting of small and large deletions, and the deletions are caused by short-repeat dependent RIR along with regeneration of short-repeats. In future, the RGE rate will slowdown when the gene repertoires approach the minimum gene set necessary for intracellular symbiotic life.
Collapse
Affiliation(s)
- Hirokazu Kuwahara
- Extremobiosphere Research Center, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan
| | | | | | | | | | | | | | | |
Collapse
|
34
|
Knibbe C, Coulon A, Mazet O, Fayard JM, Beslon G. A Long-Term Evolutionary Pressure on the Amount of Noncoding DNA. Mol Biol Evol 2007; 24:2344-53. [PMID: 17709335 DOI: 10.1093/molbev/msm165] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
A significant part of eukaryotic noncoding DNA is viewed as the passive result of mutational processes, such as the proliferation of mobile elements. However, sequences lacking an immediate utility can nonetheless play a major role in the long-term evolvability of a lineage, for instance by promoting genomic rearrangements. They could thus be subject to an indirect selection. Yet, such a long-term effect is difficult to isolate either in vivo or in vitro. Here, by performing in silico experimental evolution, we demonstrate that, under low mutation rates, the indirect selection of variability promotes the accumulation of noncoding sequences: Even in the absence of self-replicating elements and mutational bias, noncoding sequences constituted an important fraction of the evolved genome because the indirectly selected genomes were those that were variable enough to discover beneficial mutations. On the other hand, high mutation rates lead to compact genomes, much like the viral ones, although no selective cost of genome size was applied: The indirectly selected genomes were those that were small enough for the genetic information to be reliably transmitted. Thus, the spontaneous evolution of the amount of noncoding DNA strongly depends on the mutation rate. Our results suggest the existence of an additional pressure on the amount of noncoding DNA, namely the indirect selection of an appropriate trade-off between the fidelity of the transmission of the genetic information and the exploration of the mutational neighborhood. Interestingly, this trade-off resulted robustly in the accumulation of noncoding DNA so that the best individual leaves one offspring without mutation (or only neutral ones) per generation.
Collapse
|
35
|
Mrázek J, Guo X, Shah A. Simple sequence repeats in prokaryotic genomes. Proc Natl Acad Sci U S A 2007; 104:8472-7. [PMID: 17485665 PMCID: PMC1895974 DOI: 10.1073/pnas.0702412104] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Indexed: 11/18/2022] Open
Abstract
Simple sequence repeats (SSRs) in DNA sequences are composed of tandem iterations of short oligonucleotides and may have functional and/or structural properties that distinguish them from general DNA sequences. They are variable in length because of slip-strand mutations and may also affect local structure of the DNA molecule or the encoded proteins. Long SSRs (LSSRs) are common in eukaryotes but rare in most prokaryotes. In pathogens, SSRs can enhance antigenic variance of the pathogen population in a strategy that counteracts the host immune response. We analyze representations of SSRs in >300 prokaryotic genomes and report significant differences among different prokaryotes as well as among different types of SSRs. LSSRs composed of short oligonucleotides (1-4 bp length, designated LSSR(1-4)) are often found in host-adapted pathogens with reduced genomes that are not known to readily survive in a natural environment outside the host. In contrast, LSSRs composed of longer oligonucleotides (5-11 bp length, designated LSSR(5-11)) are found mostly in nonpathogens and opportunistic pathogens with large genomes. Comparisons among SSRs of different lengths suggest that LSSR(1-4) are likely maintained by selection. This is consistent with the established role of some LSSR(1-4) in enhancing antigenic variance. By contrast, abundance of LSSR(5-11) in some genomes may reflect the SSRs' general tendency to expand rather than their specific role in the organisms' physiology. Differences among genomes in terms of SSR representations and their possible interpretations are discussed.
Collapse
Affiliation(s)
- Jan Mrázek
- Department of Microbiology, University of Georgia, Athens, GA 30602, USA.
| | | | | |
Collapse
|
36
|
Swidan F, Ziv-Ukelson M, Pinter RY. On the repeat-annotated phylogenetic tree reconstruction problem. J Comput Biol 2007; 13:1397-418. [PMID: 17061918 DOI: 10.1089/cmb.2006.13.1397] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
A new problem in phylogenetic inference is presented, based on recent biological findings indicating a strong association between reversals (i.e., inversions) and repeats. These biological findings are formalized here in a new mathematical model, called repeat-annotated phylogenetic trees (RAPT). We show that, under RAPT, the evolutionary process--including both the tree-topology as well as internal node genome orders--is uniquely determined, a property that is of major significance both in theory and in practice. Furthermore, the repeats are employed to provide linear-time algorithms for reconstructing both the genomic orders and the phylogeny, which are NP-hard problems under the classical model of sorting by reversals (SBR).
Collapse
Affiliation(s)
- Firas Swidan
- Department of Computer Science, Technion-Israel Institute of Technology, Haifa, Israel.
| | | | | |
Collapse
|
37
|
Abstract
Insertion sequences (ISs) are the smallest and most frequent transposable elements in prokaryotes where they play an important evolutionary role by promoting gene inactivation and genome plasticity. Their genomic abundance varies by several orders of magnitude for reasons largely unknown and widely speculated. The current availability of hundreds of genomes renders testable many of these hypotheses, notably that IS abundance correlates positively with the frequency of horizontal gene transfer (HGT), genome size, pathogenicity, nonobligatory ecological associations, and human association. We thus reannotated ISs in 262 prokaryotic genomes and tested these hypotheses showing that when using appropriate controls, there is no empirical basis for IS family specificity, pathogenicity, or human association to influence IS abundance or density. HGT seems necessary for the presence of ISs, but cannot alone explain the absence of ISs in more than 20% of the organisms, some of which showing high rates of HGT. Gene transfer is also not a significant determinant of the abundance of IS elements in genomes, suggesting that IS abundance is controlled at the level of transposition and ensuing natural selection and not at the level of infection. Prokaryotes engaging in obligatory associations have fewer ISs when controlled for genome size, but this may be caused by some being sexually isolated. Surprisingly, genome size is the only significant predictor of IS numbers and density. Alone, it explains over 40% of the variance of IS abundance. Because we find that genome size and IS abundance correlate negatively with minimal doubling times, we conclude that selection for rapid replication cannot account for the few ISs found in small genomes. Instead, we show evidence that IS numbers are controlled by the frequency of highly deleterious insertion targets. Indeed, IS abundance increases quickly with genome size, which is the exact inverse trend found for the density of genes under strong selection such as essential genes. Hence, for ISs, the bigger the genome the better.
Collapse
Affiliation(s)
- Marie Touchon
- Génétique des Génomes Bactériens, CNRS URA2171, Institut Pasteur, Paris, France.
| | | |
Collapse
|
38
|
Szekeres S, Dauti M, Wilde C, Mazel D, Rowe-Magnus DA. Chromosomal toxin-antitoxin loci can diminish large-scale genome reductions in the absence of selection. Mol Microbiol 2007; 63:1588-605. [PMID: 17367382 DOI: 10.1111/j.1365-2958.2007.05613.x] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Superintegrons (SIs) are chromosomal genetic elements containing assemblies of genes, each flanked by a recombination sequence (attC site) targeted by the integron integrase. SIs may contain hundreds of attC sites and intrinsic instability is anticipated; yet SIs are remarkably stable. This implies that either selective pressure maintains the genes or mechanisms exist which favour their persistence in the absence of selection. Toxin/antitoxin (TA) systems encode a stable toxin and a specific, unstable antitoxin. Once activated, the continued synthesis of the unstable antitoxin is necessary for cell survival. A bioinformatic search of accessible microbial genomes for SIs and TA systems revealed that large SIs harboured TA gene cassettes while smaller SIs did not. We demonstrated the function of TA loci in different genomic contexts where large-scale deletions can occur; in SIs and in a 165 kb dispensable region of the Escherichia coli genome. When devoid of TA loci, large-scale genome loss was evident in both environments. The inclusion of two TA loci, relBE1 and parDE1, which we identified in the Vibrio vulnificus SI rendered these environments refractory to gene loss. Thus, chromosomal TA loci can stabilize massive SI arrays and limit the extensive gene loss that is a hallmark of reductive evolution.
Collapse
Affiliation(s)
- Silvia Szekeres
- Division of Clinical Integrative Biology, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, S1-26A, Toronto, Ontario, M4N 3N5, Canada
| | | | | | | | | |
Collapse
|
39
|
Wang W, Pearson MM, Attia AS, Blick RJ, Hansen EJ. A UspA2H-negative variant of Moraxella catarrhalis strain O46E has a deletion in a homopolymeric nucleotide repeat common to uspA2H genes. Infect Immun 2007; 75:2035-45. [PMID: 17220316 PMCID: PMC1865690 DOI: 10.1128/iai.00609-06] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Moraxella catarrhalis strains can express either a UspA2 protein or a UspA2H protein. The latter protein is encoded by a gene that possesses a homopolymeric nucleotide tract containing eight adenine (A) residues [i.e., a poly(A) tract] which is located near the 5' end. A spontaneous UspA2H-negative variant of M. catarrhalis strain O46E, designated O46E.U2V, was found to have a uspA2H poly(A) tract that contained seven A residues. Northern blot analysis of total RNA from the O46E parent strain revealed a readily detectable uspA2H mRNA transcript, whereas little or no uspA2H transcript was detectable in total RNA from the UspA2H-negative variant O46E.U2V. The 5' end of the uspA2H genes from both the O46E parent strain and the O46E.U2V variant were ligated to a promoterless lacZ gene to prepare translational fusions for use as reporter constructs. The level of beta-galactosidase activity expressed by the fusion construct containing eight A residues in its poly(A) tract was 200-fold greater than that obtained with the construct that had seven A residues. Site-directed mutagenesis of the 5' end of the uspA2H gene confirmed that translation was initiated at a GTG codon located 21 nucleotides (nt) upstream of the poly(A) tract. Primer extension analysis determined that the transcriptional start site of the uspA2H gene was located 291 nt upstream from the GTG translational start codon. This poly(A) tract was also found to be present in the uspA2H genes of other M. catarrhalis strains.
Collapse
MESH Headings
- Amino Acid Sequence
- Artificial Gene Fusion
- Bacterial Outer Membrane Proteins/chemistry
- Bacterial Outer Membrane Proteins/genetics
- Base Sequence
- Blotting, Northern
- Codon, Initiator
- Gene Expression
- Genes, Reporter
- Molecular Sequence Data
- Moraxella catarrhalis/genetics
- Mutagenesis, Site-Directed
- Open Reading Frames
- Poly A/genetics
- RNA, Bacterial/analysis
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Repetitive Sequences, Nucleic Acid/genetics
- Sequence Deletion
- Transcription Initiation Site
- Transcription, Genetic
- beta-Galactosidase/analysis
- beta-Galactosidase/genetics
Collapse
Affiliation(s)
- Wei Wang
- Department of Microbiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
| | | | | | | | | |
Collapse
|
40
|
Rocha EPC, Touchon M, Feil EJ. Similar compositional biases are caused by very different mutational effects. Genome Res 2006; 16:1537-47. [PMID: 17068325 PMCID: PMC1665637 DOI: 10.1101/gr.5525106] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Compositional replication strand bias, commonly referred to as GC skew, is present in many genomes of prokaryotes, eukaryotes, and viruses. Although cytosine deamination in ssDNA (resulting in C-->T changes on the leading strand) is often invoked as its major cause, the precise contributions of this and other substitution types are currently unknown. It is also unclear if the underlying mutational asymmetries are the same among taxa, are stable over time, or how closely the observed biases are to mutational equilibrium. We analyzed nearly neutral sites of seven taxa each with between three and six complete bacterial genomes, and inferred the substitution spectra of fourfold degenerate positions in nonhighly expressed genes. Using a bootstrap procedure, we extracted compositional biases associated with replication and identified the significant asymmetries. Although all taxa showed an overrepresentation of G relative to C on the leading strand (and imbalances between A and T), widely variable substitution asymmetries are noted. Surprisingly, all substitution types show significant asymmetry in at least one taxon, but none were universally biased in all taxa. Notably, in the two most biased genomes, A-->G, rather than C-->T, shapes the compositional bias. Given the variability in these biases, we propose that the process is multifactorial. Finally, we also find that most genomes are not at compositional equilibrium, and suggest that mutational-based heterotachy is deeply imprinted in the history of biological macromolecules. This shows that similar compositional biases associated with the same essential well-conserved process, replication, do not reflect similar mutational processes in different genomes, and that caution is required in inferring the roles of specific mutational biases on the basis of contemporary patterns of sequence composition.
Collapse
Affiliation(s)
- Eduardo P C Rocha
- Unité Génétique des Génomes Bactériens, URA 2171, Institut Pasteur, 75015 Paris, France.
| | | | | |
Collapse
|
41
|
Gómez-Valero L, Silva FJ, Christophe Simon J, Latorre A. Genome reduction of the aphid endosymbiont Buchnera aphidicola in a recent evolutionary time scale. Gene 2006; 389:87-95. [PMID: 17098378 DOI: 10.1016/j.gene.2006.10.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 09/27/2006] [Accepted: 10/01/2006] [Indexed: 10/24/2022]
Abstract
Genome reduction, a typical feature of symbiotic bacteria, was analyzed in the last stages of evolution of Buchnera aphidicola, the primary aphid endosymbiont, in two neutrally evolving regions: the pseudogene cmk and an intergenic region. These two regions were examined in endosymbionts from several lineages of their aphid host Rhopalosiphum padi, and different species of the same genus, whose divergence times ranged from 0.62 to 19.51 million years. Estimates of nucleotide substitution rates were between 4.3 and 6.7x10(-9) substitution/site/year, with G or C nucleotides being substituted around four times more frequently than A or T. Two different types of indel events were detected, of which many were small (1-10 nt) but one was large (about 200 nucleotides). With respect to the large one and considering the proportion and size of the deletions and insertions, the reduction rate was 1.3x10(-8) lost nucleotides/site/year. We propose a stepwise scenario for the last stages of evolution in B. aphidicola: together with a very slow and gradual degradation, considerable indels would punctually emerge. The only restriction to large deletion fixation is that the lost fragment does not contain essential genes.
Collapse
Affiliation(s)
- Laura Gómez-Valero
- Institut Cavanilles de Biodiversitat i Biologia Evolutiva and Departament de Genètica, Universitat de València, Apartat 22085, 46071 Valencia, Spain
| | | | | | | |
Collapse
|
42
|
Knibbe C, Mazet O, Chaudier F, Fayard JM, Beslon G. Evolutionary coupling between the deleteriousness of gene mutations and the amount of non-coding sequences. J Theor Biol 2006; 244:621-30. [PMID: 17055537 DOI: 10.1016/j.jtbi.2006.09.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2006] [Revised: 07/20/2006] [Accepted: 09/06/2006] [Indexed: 11/17/2022]
Abstract
The phenotypic effects of random mutations depend on both the architecture of the genome and the gene-trait relationships. Both levels thus play a key role in the mutational variability of the phenotype, and hence in the long-term evolutionary success of the lineage. Here, by simulating the evolution of organisms with flexible genomes, we show that the need for an appropriate phenotypic variability induces a relationship between the deleteriousness of gene mutations and the quantity of non-coding sequences maintained in the genome. The more deleterious the gene mutations, the shorter the intergenic sequences. Indeed, in a shorter genome, fewer genes are affected by rearrangements (duplications, deletions, inversions, translocations) at each replication, which compensates for the higher impact of each gene mutation. This spontaneous adjustment of genome structure allows the organisms to retain the same average fitness loss per replication, despite the higher impact of single gene mutations. These results show how evolution can generate unexpected couplings between distinct organization levels.
Collapse
Affiliation(s)
- Carole Knibbe
- Computer Science Department, INSA Lyon, Bat. Blaise Pascal, 69621 Villeurbanne Cedex, France.
| | | | | | | | | |
Collapse
|
43
|
Gomes JP, Nunes A, Bruno WJ, Borrego MJ, Florindo C, Dean D. Polymorphisms in the nine polymorphic membrane proteins of Chlamydia trachomatis across all serovars: evidence for serovar Da recombination and correlation with tissue tropism. J Bacteriol 2006; 188:275-86. [PMID: 16352844 PMCID: PMC1317584 DOI: 10.1128/jb.188.1.275-286.2006] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chlamydia trachomatis is an intracellular bacterium responsible for ocular, respiratory, and sexually transmitted diseases. The genome contains a nine-member polymorphic membrane protein (Pmp) family unique to members of the order Chlamydiales. Genomic and molecular analyses were performed for the entire pmp gene family for the 18 reference serological variants (serovars) and genovariant Ja to identify specific gene and protein regions that differentiate chlamydial disease groups. The mean genetic distance among all serovars varied from 0.1% for pmpA to 7.0% for pmpF. Lymphogranuloma venereum (LGV) serovars were the most closely related for the pmp genes and were also the most divergent, compared to ocular and non-LGV urogenital disease groups. Phylogenetic reconstructions showed that for six of nine pmp genes (not pmpA, pmpD, or pmpE), the serovars clustered based on tissue tropism. The most globally successful serovars, E and F, clustered distantly from the urogenital group for five pmp genes. These pmp genes may confer a biologic advantage that may facilitate infection and transmission for E and F. Surprisingly, serovar Da clustered with the ocular group from pmpE to pmpI, which are located together in the chromosome, providing statistically significant evidence for intergenomic recombination and acquisition of a genetic composition that could hypothetically expand the host cell range of serovar Da. We also identified distinct domains for pmpE, pmpF, and pmpH where substitutions were concentrated and associated with a specific disease group. Thus, our data suggest a possible structural or functional role that may vary among pmp genes in promoting antigenic polymorphisms and/or diverse adhesions-receptors that may be involved in immune evasion and differential tissue tropism.
Collapse
Affiliation(s)
- João P Gomes
- Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609, USA
| | | | | | | | | | | |
Collapse
|
44
|
Abstract
The stability of genomes is highly variable, both in terms of gene content and gene order. Here I calibrate the loss of gene order conservation (GOC) through time by fitting a simple probabilistic model on pairwise comparisons involving 126 bacterial genomes. The model computes the probability of separation of pairs of contiguous genes per unit of time and fits the data better than previous ones while allowing a mechanistic interpretation for the loss of GOC with time. Although the information on operons is not used in the model, I observe, as expected, that most highly conserved pairs of genes are indeed within operons. However, even the other pairs are much more conserved than expected given the observed experimental rearrangement rates. After 500 Myr, about 50% of the originally contiguous orthologues remain so in the average genome. Hence, the large majority of rearrangements must be deleterious and random genome rearrangements are unlikely to provide for positively selected structural changes. I then use the deviations from the model to define an intrinsic measure of genome stability that allowed the comparison of distantly related genomes and the inference of ancestral states. This shows that clades differ in genome stability, with cyanobacteria being the least stable and gamma-proteobacteria the most stable. Without correction for phylogeny, free-living bacteria are the least stable group of genomes, followed by pathogens, and then endomutualists. However, after correction for phylogenetic inertia (or the removal of cyanobacteria from the analysis), there is no significant association between genome stability and lifestyle or genome size. Hence, although this method has allowed uncovering some of mechanisms leading to rearrangements, we still ignore the forces that differentially shape selection upon genome stability in different species.
Collapse
Affiliation(s)
- Eduardo P C Rocha
- Unité Génétique des Génomes Bactériens, Institut Pasteur, Paris, France and Atelier de BioInformatique, Université Pierre et Marie Curie (Paris VI), Paris, France.
| |
Collapse
|
45
|
Nilsson AI, Koskiniemi S, Eriksson S, Kugelberg E, Hinton JCD, Andersson DI. Bacterial genome size reduction by experimental evolution. Proc Natl Acad Sci U S A 2005; 102:12112-6. [PMID: 16099836 PMCID: PMC1189319 DOI: 10.1073/pnas.0503654102] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacterial evolution toward endosymbiosis with eukaryotic cells is associated with extensive bacterial genome reduction and loss of metabolic and regulatory capabilities. Here we examined the rate and process of genome reduction in the bacterium Salmonella enterica by a serial passage experimental evolution procedure. The initial rate of DNA loss was estimated to be 0.05 bp per chromosome per generation for a WT bacterium and approximately 50-fold higher for a mutS mutant defective in methyl-directed DNA mismatch repair. The endpoints were identified for seven chromosomal deletions isolated during serial passage and in two separate genetic selections. Deletions ranged in size from 1 to 202 kb, and most of them were not associated with DNA repeats, indicating that they were formed via RecA-independent recombination events. These results suggest that extensive genome reduction can occur on a short evolutionary time scale and that RecA-dependent homologous recombination only plays a limited role in this process of jettisoning superfluous DNA.
Collapse
Affiliation(s)
- A I Nilsson
- Microbiology and Tumor Biology Center, Karolinska Institute, SE-171 77 Stockholm, Sweden
| | | | | | | | | | | |
Collapse
|
46
|
Svensson K, Larsson P, Johansson D, Byström M, Forsman M, Johansson A. Evolution of subspecies of Francisella tularensis. J Bacteriol 2005; 187:3903-8. [PMID: 15901721 PMCID: PMC1112057 DOI: 10.1128/jb.187.11.3903-3908.2005] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Analysis of unidirectional genomic deletion events and single nucleotide variations suggested that the four subspecies of Francisella tularensis have evolved by vertical descent. The analysis indicated an evolutionary scenario where the highly virulent F. tularensis subsp. tularensis (type A) appeared before the less virulent F. tularensis subsp. holarctica (type B). Compared to their virulent progenitors, attenuated strains of F. tularensis exhibited specific unidirectional gene losses.
Collapse
Affiliation(s)
- Kerstin Svensson
- Department of NBC-Analysis, Swedish Defence Research Agency, SE-901 82 Umeå, Sweden
| | | | | | | | | | | |
Collapse
|
47
|
Collins NE, Liebenberg J, de Villiers EP, Brayton KA, Louw E, Pretorius A, Faber FE, van Heerden H, Josemans A, van Kleef M, Steyn HC, van Strijp MF, Zweygarth E, Jongejan F, Maillard JC, Berthier D, Botha M, Joubert F, Corton CH, Thomson NR, Allsopp MT, Allsopp BA. The genome of the heartwater agent Ehrlichia ruminantium contains multiple tandem repeats of actively variable copy number. Proc Natl Acad Sci U S A 2005; 102:838-43. [PMID: 15637156 PMCID: PMC545511 DOI: 10.1073/pnas.0406633102] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Heartwater, a tick-borne disease of domestic and wild ruminants, is caused by the intracellular rickettsia Ehrlichia ruminantium (previously known as Cowdria ruminantium). It is a major constraint to livestock production throughout subSaharan Africa, and it threatens to invade the Americas, yet there is no immediate prospect of an effective vaccine. A shotgun genome sequencing project was undertaken in the expectation that access to the complete protein coding repertoire of the organism will facilitate the search for vaccine candidate genes. We report here the complete 1,516,355-bp sequence of the type strain, the stock derived from the South African Welgevonden isolate. Only 62% of the genome is predicted to be coding sequence, encoding 888 proteins and 41 stable RNA species. The most striking feature is the large number of tandemly repeated and duplicated sequences, some of continuously variable copy number, which contributes to the low proportion of coding sequence. These repeats have mediated numerous translocation and inversion events that have resulted in the duplication and truncation of some genes and have also given rise to new genes. There are 32 predicted pseudogenes, most of which are truncated fragments of genes associated with repeats. Rather then being the result of the reductive evolution seen in other intracellular bacteria, these pseudogenes appear to be the product of ongoing sequence duplication events.
Collapse
Affiliation(s)
- Nicola E Collins
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Abstract
In prokaryotic genomes, related genes are frequently clustered in operons and higher-order arrangements that reflect functional context. Organization emerges despite rearrangements that constantly shuffle gene and operon order. Evidence is presented that the tandem duplication of related genes acts as a driving evolutionary force in the origin and maintenance of clusters. Gene amplification can be viewed as a dynamic and reversible regulatory mechanism that facilitates adaptation to variable environments. Clustered genes confer selective benefits via their ability to be coamplified. During evolution, rearrangements that bring together related genes can be selected if they increase the fitness of the organism in which they reside. Similarly, the benefits of gene amplification can prevent the dispersal of existing clusters. Examples of frequent and spontaneous amplification of large genomic fragments are provided. The possibility is raised that tandem gene duplication works in concert with horizontal gene transfer as interrelated evolutionary forces for gene clustering.
Collapse
Affiliation(s)
- Andrew B Reams
- Section of Microbiology, University of California, Davis, California 95616, USA.
| | | |
Collapse
|
49
|
Gevers D, Vandepoele K, Simillon C, Van de Peer Y. Gene duplication and biased functional retention of paralogs in bacterial genomes. Trends Microbiol 2004; 12:148-54. [PMID: 15116722 DOI: 10.1016/j.tim.2004.02.007] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Dirk Gevers
- Bioinformatics and Evolutionary Genomics, Ghent University/Flanders Interuniversity Institute for Biotechnology (VIB), Technologiepark 927, B-9052 Ghent, Belgium
| | | | | | | |
Collapse
|
50
|
Affiliation(s)
- David C Samuels
- Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
| |
Collapse
|