Baek Inwoo, Lee Kihyun, Goodfellow Michael, Chun Jongsik
School of Biological Sciences, Seoul National University, Seoul, South Korea.
Institute of Molecular Biology and Genetics, Seoul National University, Seoul, South Korea.
Front Microbiol. 2019 Aug 23;10:1978. doi: 10.3389/fmicb.2019.01978. eCollection 2019.
The present study was designed to clarify the taxonomic status of two species classified as , namely and . To this end, nearly 900 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 and formed a well-supported monophyletic clade that was clearly separated from corresponding clades composed of the remaining validly published species classified as . However, since average nucleotide identity and digital DNA-DNA hybridization similarities between the two types of were slightly higher than the thresholds used to distinguish between closely related species we conclude that and should continue to be recognized as validly published species. The strains were assigned to two genomically distinct groups, we propose that these taxa be recognized as genomovars, that is, as gv. and gv. . The extensive comparative genomic data clearly show that the distribution of pesticidal genes is irregular as strains identified as were assigned to several polyphyletic groups/subclades within the - clade. Consequently, we recommend that genomic or equivalent molecular systematic features should be used to identify strains as the presence of pesticidal genes cannot be used as a diagnostic marker for this species. Comparative taxonomic studies are needed to find phenotypic properties that can be used to distinguish between the genomovars and between them and .
本研究旨在阐明被归类为[具体物种1]和[具体物种2]的两个物种的分类地位。为此,近900个归属于这些分类单元的菌株全基因组序列成为了比较基因组学和系统发育基因组学分析的对象。基于核心基因序列构建的系统发育树表明,[具体物种1]和[具体物种2]的模式菌株形成了一个得到充分支持的单系分支,该分支与由其余被归类为[相关属名]的有效发表物种组成的相应分支明显分开。然而,由于这两种[具体物种]之间的平均核苷酸同一性和数字DNA-DNA杂交相似性略高于用于区分密切相关物种的阈值,我们得出结论,[具体物种1]和[具体物种2]应继续被视为有效发表的物种。[具体物种]菌株被分为两个基因组上不同的组,我们建议将这些分类单元识别为基因组变种,即[具体物种1]基因组变种[变种1名称]和[具体物种2]基因组变种[变种2名称]。广泛的比较基因组数据清楚地表明,由于被鉴定为[具体物种]的菌株被分配到[相关属名]分支内的几个多系群/亚分支中,杀虫基因的分布是不规则的。因此,我们建议应使用基因组或等效的分子系统特征来鉴定[具体物种]菌株,因为杀虫基因的存在不能用作该物种的诊断标记。需要进行比较分类学研究,以找到可用于区分[具体物种]基因组变种以及它们与[其他相关物种]之间的表型特征。