ABSTRACT
Two marine bacteria, designated strains MBE#61(T) and MBE#74(T), 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#61(T) was spiral, whereas MBE#74(T) was rod-shaped. The temperature, pH and salt concentration ranges for growth of strain MBE#61(T) were 4-38 °C (optimal at 32 °C), pH 4.5-11.0 (optimal at pH 7.0-8.0) and 1-11â% (optimal at 2â%) NaCl, whereas those of strain MBE#74(T) were 4-36 °C (optimal at 30 °C), pH 4.0-10.5 (optimal at pH 7.0-8.0) and 1-12â% (optimal at 4â%) 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#61(T) and those of the type strains of species of the genus Thalassospira was 97.5-99.0â%, and that of strain MBE#74(T) was 96.9-98.6â%; these two isolates were most closely related to Thalassospira lucentensis QMT2(T). However, the DNA-DNA hybridization values between T. lucentensis QMT2(T) and strain MBE#61(T) or MBE#74(T) were only 16.0â% and 7.1â%, respectively. The DNA G+C content of strain MBE#61(T) was 54.4 mol%, and that of strain MBE#74(T) was 55.9 mol%. The predominant isoprenoid quinone of the two strains was Q-10 (MBE#61(T), 97.3â%; MBE#74(T), 93.5â%). The major cellular fatty acids of strain MBE#61(T) were C18â:â1ω7c (31.1â%), summed feature 3 comprising C16â:â0ω7c/iso-C15â:â0 2-OH (26.1â%) and C16â:â0 (20.9â%); those of strain MBE#74(T) were C16â:â0 (26.2â%), C17â:â0 cyclo (19.9â%) and C18â:â1ω7c (12.1â%). On the basis of these results, strain MBE#61(T) and strain MBE#74(T) 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#61(T) (â=âJCM 18968(T)â=âCECT 8273(T)) and MBE#74(T) (â=âJCM 18969(T)â=âCECT 8274(T)), respectively. An emended description of the genus Thalassospira is also proposed.