Thalassospira alkalitolerans sp. nov. and Thalassospira mesophila sp. nov., isolated from a decaying bamboo sunken in the marine environment, and emended description of the genus Thalassospira.

Two marine bacteria, designated strains MBE#61T and MBE#74T, were isolated from a piece of sunken bamboo in the marine environment in Japan. Both of these strains were Gram-stain-negative, but had different cell shapes: MBE#61T was spiral, whereas MBE#74T was rod-shaped. The temperature, pH and salt concentration ranges for growth of strain MBE#61T were 4–38 °C (optimal at 32 °C), pH 4.5–11.0 (optimal at pH 7.0–8.0) and 1–11 % (optimal at 2 %) NaCl, whereas those of strain MBE#74T were 4–36 °C (optimal at 30 °C), pH 4.0–10.5 (optimal at pH 7.0–8.0) and 1–12 % (optimal at 4 %) NaCl. Phylogenetic analysis based on partial 16S rRNA gene sequences revealed that both strains belong to the genus Thalassospira within the class Alphaproteobacteria . Similarity between the 16S rRNA gene sequence of strain MBE#61T and those of the type strains of species of the genus Thalassospira was 97.5–99.0 %, and that of strain MBE#74T was 96.9–98.6 %; these two isolates were most closely related to Thalassospira lucentensis QMT2T. However, the DNA–DNA hybridization values between T. lucentensis QMT2T and strain MBE#61T or MBE#74T were only 16.0 % and 7.1 %, respectively. The DNA G+C content of strain MBE#61T was 54.4 mol%, and that of strain MBE#74T was 55.9 mol%. The predominant isoprenoid quinone of the two strains was Q-10 (MBE#61T, 97.3 %; MBE#74T, 93.5 %). The major cellular fatty acids of strain MBE#61T were C18 : 1ω7c (31.1 %), summed feature 3 comprising C16 : 0ω7c/iso-C15 : 0 2-OH (26.1 %) and C16 : 0 (20.9 %); those of strain MBE#74T were C16 : 0 (26.2 %), C17 : 0 cyclo (19.9 %) and C18 : 1ω7c (12.1 %). On the basis of these results, strain MBE#61T and strain MBE#74T are considered to represent novel species of the genus Thalassospira , for which names Thalassospira alkalitolerans sp. nov. and Thalassospira mesophila sp. nov. are proposed. The type strains are MBE#61T ( = JCM 18968T = CECT 8273T) and MBE#74T ( = JCM 18969T = CECT 8274T), respectively. An emended description of the genus Thalassospira is also proposed.