Spirosoma oryzicola sp. nov., isolated from dried rice husk

Strain RHs26^T is an aerobic, Gram-stain-negative, non-flagellated and rod- or filamentous-shaped (1.0-1.1×2.3-50 µm) bacterium that was isolated from dried rice husk. It was positive for oxidase and catalase, hydrolysed starch and Tween 80, and weakly hydrolysed CM-cellulose. The strain grew at temperatures between 10 and 37 °C (optimum, 28 °C), in 0-1 % NaCl (optimum, 0 %) and at pH 6.0-9.0 (optimum, pH 7.0-8.0). The predominant membrane fatty acids were summed feature 3 (C_16 : 1 ω7c and/or C_16 : 1 ω6c), C_16 : 1 ω5c, iso-C_15 : 0 and iso-C_17 : 0 3-OH. The major polar lipids were phosphatidylethanolamine, an unidentified aminolipid, two unidentified aminophospholipids and two unidentified lipids. The predominant quinone was menaquinone MK-7. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain RHs26^T belongs to the genus Spirosoma, presenting the highest sequence similarity to Spirosoma agri S7-3-3^T (95.8 %). The genomic DNA G+C content of strain RHs26^T was 49.5 %. Strain RHs26^T showed the highest orthologous average nucleotide identity (OrthoANI) and digital DNA-DNA hybridization (dDDH) values of 76.4 % and 20.0 % with S. agri KCTC 52727^T while sharing OrthoANI and dDDH values of 74.6 % and 19.2 % with Spirosoma terrae KCTC 52035^T, the closest relative in the phylogenomic tree. Based on the results of a polyphasic taxonomic study, strain RHs26^T represents a novel species in the genus Spirosoma, for which the name Spirosoma oryzicola sp. nov. is proposed. The type strain is RHs26^T (=JCM 35224^T=KACC 17318^T).