Original Research ARTICLE
Prokaryotic genome expansion is facilitated by phages and plasmids but impaired by CRISPR
- 1Huazhong University of Science and Technology, China
- 2Heinrich Heine University of Düsseldorf, Germany
- 3Henan Normal University, China
Bacteriophages 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 phages and plasmids. We found that genomes associated with phages and/or plasmids were significantly larger than those without, indicating that both phages and plasmids contribute to genome expansion. Genomes were increasingly larger with increasing numbers of associated phages 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, bacteriophages 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 phages over plasmids.
Keywords: prokaryotic genome expansion, Bacteriophages, Plasmids, CRISPR, horizontal gene transfer
Received: 28 Apr 2019;
Accepted: 17 Sep 2019.
Copyright: © 2019 Gao, Wang, Lercher and Chen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Prof. Martin J. Lercher, Heinrich Heine University of Düsseldorf, Düsseldorf, 40225, North Rhine-Westphalia, Germany, email@example.com
Prof. Wei-Hua Chen, Huazhong University of Science and Technology, Wuhan, 430074, Hubei Province, China, firstname.lastname@example.org