Dataset Information

Prokaryotic Genome Expansion Is Facilitated by Phages and Plasmids but Impaired by CRISPR.

ABSTRACT: Viruses and plasmids can introduce novel DNA into bacterial cells, thereby creating an opportunity for genome expansion; conversely, CRISPR, the prokaryotic adaptive immune system, which targets and eliminates foreign DNAs, may impair genome expansions. Recent studies presented conflicting results over the impact of CRISPR on genome expansion. In this study, we constructed a comprehensive dataset of prokaryotic genomes and identified their associations with viruses and plasmids. We found that genomes associated with viruses and/or plasmids were significantly larger than those without, indicating that both viruses and plasmids contribute to genome expansion. Genomes were increasingly larger with increasing numbers of associated viruses or plasmids. Conversely, genomes with CRISPR systems were significantly smaller than those without, indicating that CRISPR has a negative impact on genome size. These results confirmed that on evolutionary timescales, viruses and plasmids facilitate genome expansion, while CRISPR impairs such a process in prokaryotes. Furthermore, our results also revealed that CRISPR systems show a preference for targeting viruses over plasmids.

SUBMITTER: Gao NL

PROVIDER: S-EPMC6805729 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Prokaryotic Genome Expansion Is Facilitated by Phages and Plasmids but Impaired by CRISPR.

Gao Na L NL Chen Jingchao J Wang Teng T Lercher Martin J MJ Chen Wei-Hua WH

Frontiers in microbiology 20191016

Viruses and plasmids can introduce novel DNA into bacterial cells, thereby creating an opportunity for genome expansion; conversely, CRISPR, the prokaryotic adaptive immune system, which targets and eliminates foreign DNAs, may impair genome expansions. Recent studies presented conflicting results over the impact of CRISPR on genome expansion. In this study, we constructed a comprehensive dataset of prokaryotic genomes and identified their associations with viruses and plasmids. We found that ge ...[more]

PMID: 31681190

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Project description:Staphylococcus epidermidis is a leading opportunistic pathogen causing nosocomial infections that is notable for its ability to form a biofilm and for its high rates of antibiotic resistance. It serves as a reservoir of multiple antimicrobial resistance genes that spread among the staphylococcal population by horizontal gene transfer such as transduction. While phage-mediated transduction is well studied in Staphylococcus aureus, S. epidermidis transducing phages have not been described in detail yet. Here, we report the characteristics of four phages, 27, 48, 456, and 459, previously used for S. epidermidis phage typing, and the newly isolated phage E72, from a clinical S. epidermidis strain. The phages, classified in the family Siphoviridae and genus Phietavirus, exhibited an S. epidermidis-specific host range, and together they infected 49% of the 35 strains tested. A whole-genome comparison revealed evolutionary relatedness to transducing S. aureus phietaviruses. In accordance with this, all the tested phages were capable of transduction with high frequencies up to 10-4 among S. epidermidis strains from different clonal complexes. Plasmids with sizes from 4 to 19 kb encoding resistance to streptomycin, tetracycline, and chloramphenicol were transferred. We provide here the first evidence of a phage-inducible chromosomal island transfer in S. epidermidis Similarly to S. aureus pathogenicity islands, the transfer was accompanied by phage capsid remodeling; however, the interfering protein encoded by the island was distinct. Our findings underline the role of S. epidermidis temperate phages in the evolution of S. epidermidis strains by horizontal gene transfer, which can also be utilized for S. epidermidis genetic studies.IMPORTANCE Multidrug-resistant strains of S. epidermidis emerge in both nosocomial and livestock environments as the most important pathogens among coagulase-negative staphylococcal species. The study of transduction by phages is essential to understanding how virulence and antimicrobial resistance genes spread in originally commensal bacterial populations. In this work, we provide a detailed description of transducing S. epidermidis phages. The high transduction frequencies of antimicrobial resistance plasmids and the first evidence of chromosomal island transfer emphasize the decisive role of S. epidermidis phages in attaining a higher pathogenic potential of host strains. To date, such importance has been attributed only to S. aureus phages, not to those of coagulase-negative staphylococci. This study also proved that the described transducing bacteriophages represent valuable genetic modification tools in S. epidermidis strains where other methods for gene transfer fail.

Dataset Information

Prokaryotic Genome Expansion Is Facilitated by Phages and Plasmids but Impaired by CRISPR.

Publications

Prokaryotic Genome Expansion Is Facilitated by Phages and Plasmids but Impaired by CRISPR.

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