Abstract

A novel Gram-negative, aerobic, motile and rod-shaped bacterium with the potential to biodegrade polycyclic aromatic hydrocarbons, was isolated from Khazar (Caspian) Sea. Strain TBZ2(T) grows in the absence of NaCl and tolerates up to 8.5% NaCl. Growth occurred at pH 3.0-10.0 (optimum, pH 6.0-7.0) and 10-45 degrees C (optimum, 30 degrees C). The major fatty acids are C-18:1 omega 7C, C-16:1 omega 7C/ C-15:0 iso 2-OH, C-16:0, C-12:0,C- C-10:0 3-OH, C-12:0 3-OH. The major polar lipids include diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and the predominant respiratory quinone is ubiquinone Q-9. The 16S rRNA gene sequence analysis showed that strain TBZ2(T) is a member of the genus Pseudomonas with the highest similarity to P. oleovorans subsp. oleovorans DSM 1045(T) (98.83%), P. mendocina NBRC 14162(T) (98.63%), P. oleovorans subsp. lubricantis RS1(T) (98.61%) and P. alcaliphila JCM 10630(T) (98.49%) based on EzBioCloud server. Phylogenetic analyses using housekeeping genes (16S rRNA, rpoD, gyrB and rpoB) and genome sequences demonstrated that the strain TBZ2(T) formed a distinct branch closely related to the type strains of P. mendocina and P. guguanensis. Digital DNA-DNA hybridisation and average nucleotide identity values between strain TBZ2(T) and its closest relatives, P. mendocina NBRC 14162(T) (25.3%, 81.5%) and P. guguanensis JCM 18146(T) (26.8%, 79.0%), rate well below the designed threshold for assigning prokaryotic strains to the same species. On the basis of phenotypic, chemotaxonomic, genomic and phylogenetic results, it is recommended that strain TBZ2(T) is a novel species of the genus Pseudomonas, for which the name Pseudomonas khazarica sp. nov., is proposed. The type strain is TBZ2(T) (= LMG 29674(T) = KCTC 52410(T)).