Pseudomonas khazarica sp. nov., a polycyclic aromatic hydrocarbon-degrading bacterium isolated from Khazar Sea sediments

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 °C (optimum, 30 °C). The major fatty acids are C 18:1 ω 7C, C 16:1 ω 7C/ C 15:0 iso 2-OH, C 16:0 , C 12:0, 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, rpo D, gyr B and rpo B) 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 ).