Eleven phthalate-degrading bacterial strains were isolated from seawater collected off the coast of Japan. The isolates were found to be most closely related to the marine bacterial genera Alteromonas, Citreicella, Marinomonas, Marinovum, Pelagibaca, Rhodovulum, Sulfitobacter, Thalassobius, Thalassococcus, Thalassospira, and Tropicibacter. For the first time, members of these genera were shown to be capable of growth on phthalate. The plate assay for visual detection of phthalate dioxygenase activity and PCR detection of a possible gene encoding 4,5-dihydroxyphthalate decarboxylase indicated that phthalate is degraded via 4,5-dihydroxyphthalate to protocatechuate in all the isolates.

An aerobic, Gram-negative bacterial strain, designated KU27E1(T), which degrades phthalate and dimethylphthalate, was isolated from seawater obtained from the coastal region of Ishigaki Island, Japan. Cells are motile rods with polar flagella. Strain KU27E1(T) grew at 15-30°C, pH 6.0-8.0, in the presence of 1.0-2.0% (w/v) NaCl. The 16S rRNA gene sequence analysis revealed that this strain was affiliated with the family Rhodobacteraceae in the class Alphaproteobacteria, and was most closely related to Tropicibacter naphthalenivorans (96.8%). The predominant respiratory lipoquinone was ubiquinone-10, and the major cellular fatty acid was C(18:1)ω7c (88.5%). The G+C content of genomic DNA was 58.7 mol%. Based on the physiological, chemotaxonomic, and phylogenetic data, strain KU27E1(T) is suggested to represent a novel species of the genus Tropicibacter, for which the name Tropicibacter phthalicus sp. nov. is proposed. The type strain of Tropicibacter phthalicus is designated as KU27E1(T) (=JCM 17793(T) = KCTC 23703(T)).