Arthrobacter rhizophilus sp. nov., an Organic Phosphate Solubilizing Bacterium Isolated from Rhizosphere Soil of...

A Gram-stain-positive, rod-shaped, non-motile bacterium, designated strain MI7-26^T, with organic phosphate solubilizing ability was isolated from rhizosphere soil of Meconopsis integrifolia, Nyingchi, Xizang, China. Optimal growth conditions were observed at 30 ℃, pH 7.0 and 0.5% (w/v) NaCl. A comparative analysis of 16 S rRNA gene sequences revealed that strain MI7-26^T showed the highest similarity to Arthrobacter bambusae JCM 19,335^T (98.6% sequence similarity); Arthrobacter gyeryongensis DCY72^T (98.5%); Pseudarthrobacter enclensis NIO-1008^T (97.5%). The genome size was 4.81 Mb and the G + C content was 63.1%. Whole genome-based analysis revealed that strain MI7-26^T is more closely related to Arthrobacter ramosus, Arthrobacter bambusae, and Arthrobacter gyeryongensis, with both the Average Nucleotide Identity (ANI) and digital DNA-DNA hybridization (dDDH) values below the thresholds used for species delineation (ANI < 90%, dDDH < 40%). The major fatty acids were anteiso-C_15:0 and anteiso-C_17:0. The predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, two unidentified phospholipids, one unidentified aminolipid and two unidentified glycolipids. The major quinone was menaquinone MK-9(H₂). The cell-wall peptidoglycan was A3α type, containing lysine and alanine. Phenotypically, strain MI7-26^T differed from its close relatives by being positive for the Voges-Proskauer reaction, methyl red test, and hydrolysis of Tween 80, as well as for enzyme activities of β-glucuronidase and N-acetyl-β-glucosaminidase. On the basis of phenotypic, phylogenetic and genotypic data, strain MI7-26^T is considered to represent a novel species of the genus Arthrobacter, for which the name Arthrobacter rhizophilus sp. nov. is proposed. The type strain is MI7-26^T (= GDMCC 1.3254^T = JCM 35693^T).