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

Abstract

A novel, nostoxanthin-producing, endophytic bacterium, designated as AK-PDB1-5T, 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 MIMD3T (95.6%) and Sphingomonas jatrophae S5-249T (95.3%) of the family Sphingomonadaceae. Strain AK-PDB1-5T 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-PDB1-5T 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-PDB1-5T contained C14:0 2OH, C16:0 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-PDB1-5T 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-PDB1-5T was determined to be a novel species in the genus Sphingomonas with the proposed name Sphingomonas nostoxanthinifaciens sp. nov. The type strain is AK-PDB1-5T (= KCTC 82822T = CCTCC AB 2021150T).

Jeongeuplla avenae gen. nov., sp. nov., a novel β-carotene-producing bacterium that alleviates salinity stress in Arabidopsis

“…Similar previous studies showed that, when externally applied via foliar spray, β-carotene can alleviate salt stress by reducing the amount of hydrogen peroxide (H 2 O 2 ) which can increase the ROS contents ( Babaei et al, 2022 ). Additionally, bacteria that produce nostoxanthin have been found to reduce ROS-induced stress in plants and facilitate plant growth when exposed to salinity stress ( Jiang et al, 2023 ). β-carotene is a member of the carotenoid family, a well-known group of isoprenoid pigments extensively researched for their ability to quench ROS and plant self-defense mechanisms, ultimately mitigating oxidative stress-induced damage ( Li et al, 2019 ).…”

“…ROS in plant roots were detected using DCFH-DA (Sigma, Korea) as previously described ( Jiang et al, 2023 ), but with a minor modification. Briefly, the seedlings were exposed to 5 μM DCFH-DA in 50 mM sodium phosphate buffer (pH 7.0) for 30 min in the dark.…”

“…Briefly, the seedlings were exposed to 5 μM DCFH-DA in 50 mM sodium phosphate buffer (pH 7.0) for 30 min in the dark. Subsequently, the roots were rinsed three times with water and imaged under a fluorescence microscope (Zeiss Imager.A2) equipped with a FITC filter as described by Jiang et al (2023) . The means of the sum intensities of fluorescence in the roots were determined using ImageJ software (National Institute of Health, MD, USA).…”

Characterization of carotenoid-producingMuricaudasp. strains isolated from the reef-building coralGalaxea fascicularisand subtropical seawater

“…Despite their potential usefulness, coral-associated carotenoid-producing bacteria have not been deposited in public repositories, and their general unavailability hinders progress in coral conservation research. Although carotenoid-producing bacteria have been isolated from seawater (Hameed et al 2012; Yokoyama et al 1994; Jiang et al 2023), it remains unclear whether seawater-derived bacteria can be used as probiotics.…”

Validation List no. 216. Valid publication of new names and new combinations effectively published outside the IJSEM

“…59 The effective publication states that the type strain was also deposited as CIP 109896, but no documentation was supplied. 60 The effective publication states that the type strain was also deposited as CIP 110370, but no documentation was supplied.…”