AUTHOR=Liu Jun-Ying , Zhang Jian-Feng , Wu Han-Lian , Chen Zhen , Li Shu-Ying , Li Hong-Mei , Zhang Cui-Ping , Zhou Yuan-Qing , Lu Can-Hua 

TITLE=Proposal to classify Ralstonia solanacearum phylotype I strains as Ralstonia nicotianae sp. nov., and a genomic comparison between members of the genus Ralstonia

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1135872

DOI=10.3389/fmicb.2023.1135872

ISSN=1664-302X

ABSTRACT=<p>A Gram-negative, aerobic, rod-shaped, motile bacterium with multi-flagella, strain RS<sup>T</sup>, was isolated from bacterial wilt of tobacco in Yuxi city of Yunnan province, China. The strain contains the major fatty acids of C<sub>16:0</sub>, summed feature 3 (C<sub>16:1</sub><italic>ω</italic>7<italic>c</italic> and/or C<sub>16:1</sub><italic>ω</italic>6<italic>c</italic>), and summed feature 8 (C<sub>18:1</sub><italic>ω</italic>7<italic>c</italic> and/or C<sub>18:1</sub><italic>ω</italic>6<italic>c</italic>). The polar lipid profile of strain RS<sup>T</sup> consists of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and unidentified aminophospholipid. Strain RS<sup>T</sup> contains ubiquinones Q-7 and Q-8. 16S rRNA gene sequence (1,407 bp) analysis showed that strain RS<sup>T</sup> is closely related to members of the genus <italic>Ralstonia</italic> and shares the highest sequence identities with <italic>R. pseudosolanacearum</italic> LMG 9673<sup>T</sup> (99.50%), <italic>R. syzygii</italic> subsp. <italic>indonesiensis</italic> LMG 27703<sup>T</sup> (99.50%), <italic>R. solanacearum</italic> LMG 2299<sup>T</sup> (99.28%), and <italic>R. syzygii</italic> subsp. <italic>celebesensis</italic> LMG 27706<sup>T</sup> (99.21%). The 16S rRNA gene sequence identities between strain RS<sup>T</sup> and other members of the genus <italic>Ralstonia</italic> were below 98.00%. Genome sequencing yielded a genome size of 5.61 Mbp and a G + C content of 67.1 mol%. The genomic comparison showed average nucleotide identity (ANIb) values between strain RS<sup>T</sup> and <italic>R. pseudosolanacearum</italic> LMG 9673<sup>T</sup>, <italic>R. solanacearum</italic> LMG 2299<sup>T</sup>, and <italic>R. syzygii</italic> subsp. <italic>indonesiensis</italic> UQRS 627<sup>T</sup> of 95.23, 89.43, and 91.41%, respectively, and the corresponding digital DNA–DNA hybridization (dDDH) values (yielded by formula 2) were 66.20, 44.80, and 47.50%, respectively. In addition, strains belonging to <italic>R. solanacearum</italic> phylotype I shared both ANIb and dDDH with strain RS<sup>T</sup> above the species cut-off values of 96 and 70%, respectively. The ANIb and dDDH values between the genome sequences from 12 strains of <italic>R. solanacearum</italic> phylotype III (Current <italic>R. pseudosolanacearum</italic>) and those of strain RS<sup>T</sup> were below the species cut-off values. Based on these data, we concluded that strains of phylotype I, including RS<sup>T</sup>, represent a novel species of the genus <italic>Ralstonia</italic>, for which the name <italic>Ralstonia nicotianae</italic> sp. nov. is proposed. The type strain of <italic>Ralstonia nicotianae</italic> sp. nov. is RS<sup>T</sup> (=GDMCC 1.3533<sup>T</sup> = JCM 35814<sup>T</sup>).</p>