Thalassospira tepidiphila sp nov., a polycyclic aromatic hydrocarbon-degrading bacterium isolated from seawater

A Gram-negative, mesophilic bacterial strain, designated 1-1B(T), which degrades polycyclic aromatic hydrocarbons, was isolated from petroleum-contaminated seawater during a bioremediation experiment. A 16S rRNA gene sequence analysis indicated that the isolate was affiliated with the genus Thalassospira in the Alphaproteobacteria; the sequence was found to be most similar to those of Thalassospira profundimaris WP0211(T) (99.8%), Thalassospira xiamenensis M-5(T) (98.2%) and Thalassospira lucentensis DSM 14000(T) (98.1%). However, the levels of DNA-DNA relatedness between strain 1-1B(T) and these type strains were 50.7 +/- 17.2, 35.7 +/- 17.8 and 32.0 +/- 21.1%, respectively. In addition, strain 1-1B(T) was found to be distinct from the other described species of the genus Thalassospira in terms of some taxonomically important traits, including DNA G+C content, optimum growth temperature, salinity tolerance, utilization of carbon sources and fatty acid composition. Furthermore, strain 1-1B(T) and T. profundimaris were also different with regard to motility and denitrification capacities. On the basis of physiological and DNA-DNA hybridization data, strain 1-1B(T) represents a novel species within the genus Thalassospira, for which the name Thalassospira tepidiphila sp. nov. is proposed. The type strain is 1-1B(T) (=JCM 14578(T) = DSM 18888(T)).