Duganella hordei sp. nov., Duganella kodaimurasaki sp. nov., and Duganella rhizosphaerae sp. nov., isolated from barley rhizosphere

Duganella sp. strains R1 ^T , R57 ^T , and R64 ^T , isolated from barley roots in Japan, are Gram-stain-negative, motile, rod-shaped bacteria. Duganella species abundantly colonized the barley roots. Strains R1 ^T , R57 ^T , and R64 ^T were capable of growth at 4°C, suggesting adaptation to colonize winter barley roots. Strains R57 ^T and R64 ^T formed purple colonies, indicating violacein production, while strain R1 ^T did not. Based on 16S rRNA gene sequence similarities, strains R1 ^T , R57 ^T , and R64 ^T were most closely related to D. violaceipulchra HSC-15S17 ^T (99.10%), D. vulcania FT81W ^T (99.45%), and D. violaceipulchra HSC-15S17 ^T (99.86%), respectively. Their genome sizes ranged from 7.05 to 7.38 Mbp, and their genomic G+C contents were 64.2 to 64.7%. The average nucleotide identity and digital DNA–DNA hybridization values between R1 ^T and D. violaceipulchra HSC-15S17 ^T , R57 ^T and D. vulcania FT81W ^T , R64 ^T and D. violaceipulchra HSC-15S17 ^T were 86.0% and 33.2%, 95.7% and 67.9%, and 92.7% and 52.6%, respectively. Their fatty acids were predominantly composed of C16:0, C17:0 cyclo, and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c). Based on their distinct genetic and phenotypic characteristics, and supported by chemotaxonomic analyses, we propose that strains R1 ^T , R57 ^T , and R64 ^T represent novel species within the Duganella genus, for which the names Duganella hordei (type strain R1 ^T = NBRC 115982 ^T = DSMZ 115069 ^T ), Duganella kodaimurasaki (type strain R57 ^T = NBRC 115983 ^T = DSMZ 115070 ^T ), and Duganella rhizosphaerae (type strain R64 ^T = NBRC 115984 ^T = DSMZ 115071 ^T ) are suggested.