Labrys okinawensis sp nov and Labrys miyagiensis sp nov., budding bacteria isolated from rhizosphere habitats in Japan, and emended descriptions of the genus Labrys and Labrys monachus

Three strains, MAFF 210191(T), G24103(T) and G24116, assumed to be members of two novel species, were isolated from several rhizosphere habitats in different parts of Japan. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolates formed a distinct monophyletic group together with the two known species of the genus Labrys, suggesting that the isolates have a close affiliation with this genus. In this study, a polyphasic approach was used to characterize and compare the three isolates with the two species of the genus Labrys, Labrys monachus and Labrys methylaminiphilus. All three isolates were aerobic, Gram-negative, motile and non-sporulating and they ranged in shape from spherical to short rods. The cells multiplied by budding and utilized a wide variety of monosaccharides, disaccharicles and sugar alcohols as sole carbon and energy sources, but they did not utilize C, compounds, salicin or D-melezitose. The strains were inhibited by DL-alpha-alanine and glycine (both at 10 mM). The major cellular fatty acids were C-19:0 cyclo w8c, C-16:0, C-18:0 and C(18:1)w7c. The three isolates shared < 12% and < 11% DNA-DNA relatedness with L. monachus DSM 5896(T) and L. methylaminiphilus DSM 16812(T) respectively. The G+C content of the isolates (61-62 mol%) was also significantly lower than those of the two previously characterized species. In spite of many morphological, physiological and chemotaxonomic similarities among the three isolates, strain MAFF 210191 T could be differentiated from strains G24103(T) and G24116 on the basis of 16S rRNA gene sequence divergence, DNA-DNA relatedness (< 46%) and gelatin hydrolysis. Two novel species are therefore proposed, namely Labrys okinawensis sp. nov., with the type strain MAFF 210191(T) (=DSM 18385T), and Labrys miyagiensis sp. nov., with the type strain G24103(T) (= NBRC 101365(T) =NCIMB 14143(T)) and also including strain G24116 (= NBRC 101366 = NCMB 14144). Emended descriptions of the genus Labrys and Labrys monachus are also presented.