A bacterial strain designated PtRA-8T was isolated from the trunk surface of a Japanese aspen tree (Populus tremula var. sieboldii). Cells of strain PtRA-8T were aerobic, non-motile, non-spore forming, Gram-stain-negative rods, 1.0‒2.0 µm in width and 3.0‒10.0 µm in length. The pH range for growth was between 5.5 and 7.5, with an optimum at 6.5. The temperature range for growth was between 10 and 37 °C, with an optimum at around 25‒30 °C. Strain PtRA-8T was highly resistant to UV irradiation, similar to its Deinococcus relatives. The respiratory quinone was menaquinone MK-8. The major cellular fatty acids (> 10% of the total fatty acid content) were iso-C15:0 (17.8%), C16:0 (15.0%), iso-C17:0 (10.4%), and iso-C17:1 ω9c/C16:010-methyl (22.2%). The polar lipids consisted of four unidentified glycolipids, two unidentified aminolipids, two unidentified phospholipids, and three unidentified polar lipids. The peptidoglycan was A3β-type containing glutamic acid, glycine, alanine, and ornithine. The DNA G + C content of strain PtRA-8T was 68.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain PtRA-8T was closely related to "Deinococcus radioresistens" 8AT (97.4%), Deinococcus metalli DSM 27521T (95.7%), and Deinococcus yunweiensis YIM 007T (94.5%). The DNA-DNA hybridization experiments between strain PtRA-8T and its relatives yielded relatedness values below 70%. Based on the polyphasic evidence, we concluded that strain PtRA-8T represents a novel species within the genus Deinococcus, for which the name Deinococcus populi is proposed. The type strain of D. populi is PtRA-8T (= DSM 29820T= NBRC 110763T; DPD TaxonNumber TA00271).
Keywords: Deinococcus; Japanese aspen tree; Phyllosphere; Populus tremula var. sieboldii.