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 TBZ2T 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 C18:1ω7C, C16:1ω7C/ C15:0 iso 2-OH, C16:0, C12:0, C10:0 3-OH, C12:0 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 TBZ2T is a member of the genus Pseudomonas with the highest similarity to P. oleovorans subsp. oleovorans DSM 1045T (98.83%), P. mendocina NBRC 14162T (98.63%), P. oleovorans subsp. lubricantis RS1T (98.61%) and P. alcaliphila JCM 10630T (98.49%) based on EzBioCloud server. Phylogenetic analyses using housekeeping genes (16S rRNA, rpoD, gyrB and rpoB) and genome sequences demonstrated that the strain TBZ2T 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 TBZ2T and its closest relatives, P. mendocina NBRC 14162T (25.3%, 81.5%) and P. guguanensis JCM 18146T (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 TBZ2T is a novel species of the genus Pseudomonas, for which the name Pseudomonas khazarica sp. nov., is proposed. The type strain is TBZ2T (= LMG 29674T = KCTC 52410T).