A nostoxanthin-producing bacterium, Sphingomonas nostoxanthinifaciens sp. nov., alleviates the salt stress of Arabidopsis seedlings by scavenging of reactive oxygen species
Lingmin Jiang, Jiyoon Seo, Yuxin Peng, Doeun Jeon, Ju Huck Lee, Ju Huck Lee, Cha Young Kim, Jiyoung Lee, Jiyoung Lee
Abstract
A novel, nostoxanthin-producing, endophytic bacterium, designated as AK-PDB1-5 T , was isolated from the needle-like leaves of the Korean fir ( Abies koreana Wilson) collected from Mt. Halla in Jeju, South Korea. A 16S rRNA sequence comparison indicated that the closest phylogenetic neighbors were Sphingomonas crusticola MIMD3 T (95.6%) and Sphingomonas jatrophae S5-249 T (95.3%) of the family Sphingomonadaceae . Strain AK-PDB1-5 T 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 T 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 T contained C 14:0 2OH , C 16:0 and summed feature 8 as the major cellular fatty acids (> 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 via 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 T 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 T was determined to be a novel species in the genus Sphingomonas with the proposed name Sphingomonas nostoxanthinifaciens sp. nov. The type strain is AK-PDB1-5 T (= KCTC 82822 T = CCTCC AB 2021150 T ).