Original Research ARTICLE
Comparative genomic and phylogenomic analyses clarify relationships within and between Bacillus cereus and Bacillus thuringiensis: proposal for the recognition of two Bacillus thuringiensis genomovars
- 1Seoul National University, South Korea
- 2Chung-Ang University, South Korea
- 3Newcastle University, United Kingdom
The present study was designed to clarify the taxonomic status of two species classified as Bacillus cereus sensu lato, namely Bacillus cereus sensu stricto and Bacillus thuringiensis. To this end, nearly nine hundred whole genome sequences of strains assigned to these taxa were the subject of comparative genomic and phylogenomic analyses. A phylogenomic tree based on core gene sequences showed that the type strains of Bacillus cereus and Bacillus thuringiensis formed a well-supported subclade separated from subclades composed of the remaining validly published Bacillus cereus sensu lato species. Comprehensive comparative genomics clearly showed that the distribution of pesticidal genes is irregular, which means that the strains identified as Bacillus thuringiensis formed polyphyletic clades. These results when taken together with those from a host of previous studies clearly show that B. cereus sensu stricto and B. thuringiensis stains should be classified in the same species. Consequently, it is proposed that Bacillus thuringiensis Berliner 1918 be recognized as a heterotypic synonym of Bacillus cereus Frankland and Frankland 1887; an emended description is given for the latter. The constituent strains assigned to the emended species were recovered in three subclades which were designated as Bacillus cereus genomovar cereus, Bacillus cereus genomovar nebrakensis and Bacillus cereus genomovar thuringiensis based on overall genome sequence similarities.
Keywords: Bacillus cereus, Bacillus thuringiensis, Bt toxin, Cry toxin, phylogenomic analysis
Received: 16 Apr 2019;
Accepted: 12 Aug 2019.
Edited by:David W. Ussery, University of Arkansas for Medical Sciences, United States
Reviewed by:Mohammad Ali Amoozegar, University of Tehran, Iran
David W. Dyer, University of Oklahoma Health Sciences Center, United States
Christopher Dunlap, Agricultural Research Service, United States Department of Agriculture, United States
Copyright: © 2019 Baek, Lee, Goodfellow and Chun. 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. Michael Goodfellow, Newcastle University, Newcastle upon Tyne, NE1 7RU, North East England, United Kingdom, email@example.com
Prof. Jongsik Chun, Seoul National University, Seoul, 151-742, South Korea, firstname.lastname@example.org