AUTHOR=Jiang Lingmin , Seo Jiyoon , Peng Yuxin , Jeon Doeun , Lee Ju Huck , Kim Cha Young , Lee Jiyoung 

TITLE=A nostoxanthin-producing bacterium, Sphingomonas nostoxanthinifaciens sp. nov., alleviates the salt stress of Arabidopsis seedlings by scavenging of reactive oxygen species

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1101150

DOI=10.3389/fmicb.2023.1101150

ISSN=1664-302X

ABSTRACT=<p>A novel, nostoxanthin-producing, endophytic bacterium, designated as AK-PDB1-5<sup>T</sup>, was isolated from the needle-like leaves of the Korean fir (<italic>Abies koreana</italic> Wilson) collected from Mt. Halla in Jeju, South Korea. A 16S rRNA sequence comparison indicated that the closest phylogenetic neighbors were <italic>Sphingomonas crusticola</italic> MIMD3<sup>T</sup> (95.6%) and <italic>Sphingomonas jatrophae</italic> S5-249<sup>T</sup> (95.3%) of the family <italic>Sphingomonadaceae</italic>. Strain AK-PDB1-5<sup>T</sup> had a genome size of 4,298,284 bp with a 67.8% G + C content, and digital DNA–DNA hybridization and OrthoANI values with the most closely related species of only 19.5–21% and 75.1–76.8%, respectively. Cells of the strain AK-PDB1-5<sup>T</sup> were Gram-negative, short rods, oxidase- and catalase-positive. Growth occurred at pH 5.0–9.0 (optimum pH 8.0) in the absence of NaCl at 4–37°C (optimum 25–30°C). Strain AK-PDB1-5<sup>T</sup> contained C<sub>14:0</sub> 2OH<sub>,</sub> C<sub>16:0</sub> and summed feature 8 as the major cellular fatty acids (&gt; 10%), while sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, phospholipids and lipids were found to be the major polar lipids. The strain produces a yellow carotenoid pigment; natural products prediction <italic>via</italic> AntiSMASH tool found zeaxanthin biosynthesis clusters in the entire genome. Biophysical characterization by ultraviolet–visible absorption spectroscopy and ESI-MS studies confirmed the yellow pigment was nostoxanthin. In addition, strain AK-PDB1-5<sup>T</sup> was found significantly promote Arabidopsis seedling growth under salt conditions by reducing reactive oxygen species (ROS). Based on the polyphasic taxonomic analysis results, strain AK-PDB1-5<sup>T</sup> was determined to be a novel species in the genus <italic>Sphingomonas</italic> with the proposed name <italic>Sphingomonas nostoxanthinifaciens</italic> sp. nov. The type strain is AK-PDB1-5<sup>T</sup> (= KCTC 82822<sup>T</sup> = CCTCC AB 2021150<sup>T</sup>).</p>