Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Zhejiang Province Key Laboratory of Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China.
Curr Microbiol. 2020 Aug;77(8):1945-1954. doi: 10.1007/s00284-020-02004-4. Epub 2020 Apr 30.
The genus Metakosakonia, as the closest phylogenetic neighbor of the genus Kosakonia within the family Enterobacteriaceae, when proposed in 2017, consisted of M. massiliensis JC163 and Metakosakonia spp. strains CAV1151 and GT-16. The strain CAV1151 was later classified into a novel species Phytobacter ursingii. Here, we show that the strain GT-16 shares a digital DNA-DNA hybridization (DDH) similarity of 91.0% with P. diazotrophicus DSM 17806 and thus also belongs to P. diazotrophicus. M. massiliensis and the strains within the genus Phytobacter formed a monophyletic cluster on a phylogenomic tree based on the core proteins of the family Enterobacteriaceae and on a phylogenetic tree based on the 16S rRNA genes. M. massiliensis and the genus Phytobacter share average amino acid identities of 86.80‒87.41% above the threshold (86%) for genus delimitation within the family Enterobacteriaceae. Moreover, they share conserved signature indels in the intracellular growth protein IgaA and the outer membrane assembly protein AsmA. Therefore, we propose to unite the genus Metakosakonia and the genus Phytobacter to a single genus. Because the genus Phytobacter was validly published earlier in 2017 than the genus Metakosakonia in 2017, the genus name Phytobacter has priority over Metakosakonia. We propose to unite the two genera under the name Phytobacter with the type species P. diazotrophicus and reclassify M. massiliensis as P. massiliensis comb. nov. In addition, the analyses of genome relatedness and phylogenomic relationship identified one potential novel species within the genus Phytobacter and three potential novel species within the genus Kosakonia.
肠杆菌科中的近缘属梅托考沙酮氏菌属（Metakosakonia）于 2017 年被提出时，包含 M. massiliensis JC163 和梅托考沙酮氏菌属菌株 CAV1151 和 GT-16。后来，CAV1151 菌株被归类为一个新物种植物杆菌（Phytobacter）ursin-gii。在这里，我们表明 GT-16 菌株与 P. diazotrophicus DSM 17806 的数字 DNA-DNA 杂交（DDH）相似度为 91.0%，因此也属于 P. diazotrophicus。M. massiliensis 和植物杆菌属内的菌株在基于肠杆菌科核心蛋白的系统发育树上和基于 16S rRNA 基因的系统发育树上形成了一个单系群。M. massiliensis 和植物杆菌属的平均氨基酸同一性为 86.80-87.41%，高于肠杆菌科属内的 86%的属界定阈值。此外，它们在细胞内生长蛋白 IgaA 和外膜组装蛋白 AsmA 中共享保守的特征缺失。因此，我们建议将梅托考沙酮氏菌属和植物杆菌属合并为一个属。由于植物杆菌属于 2017 年比梅托考沙酮氏菌属更早有效发表，因此植物杆菌属的名称优先于梅托考沙酮氏菌属。我们建议将这两个属合并为一个属，名称为 Phytobacter，模式种为 P. diazotrophicus，并将 M. massiliensis 重新分类为 P. massiliensis comb. nov. 此外，基因组相关性和系统发育关系分析确定了植物杆菌属内的一个潜在新种和科斯考沙酮氏菌属内的三个潜在新种。
