Phaeobacter porticola sp nov., an antibiotic-producing bacterium isolated from a sea harbour

Three heterotrophic, aerobic, brown-pigmented strains, designated P97(T), P100 and P104, were isolated from a harbour in the southern North Sea. Phylogenetic analysis of 16S rRNA gene sequences revealed that the isolates are affiliated to the genus Phaeobacter. In silico DNA-DNA hybridization of the genome of strain P97(T) against those of existing type species indicated that P97(T) represents a novel species within the genus Phaeobacter, with Phaeobacter inhibens T5(T) as the closest described organism (29.6% DNA-DNA relatedness) followed by P. gallaeciensis CIP 105210(T) (26.4 %). DNA-DNA hybridization demonstrated that the three new strains belong to the same species. The new isolates inhibited Pseudoalteromonas tunicata DSM 14096(T), and were Gram-stain-negative, catalase-and oxidase-positive, chemo-organoheterotrophic and motile. Growth occurred at pH 6.5-9.5 (optimum 7.0-8.0) and at 4-30 degrees C (optimum 20-28 degrees C). The strains required NaCl for growth. The salinity range was 0.5-6.0% (w/v) NaCl for P97(T) and P100, and 0.5-5.0% for P104, lower than values described for Phaeobacter gallaeciensis and Phaeobacter inhibens. The optimum NaCl concentration for strains P97 T and P104 was 2.0-4.0 %, and for P100 was 2.0-3.0 %. Fatty acids (> 1 %) comprised 18 : 1 omega 7c, 16 : 0, 18 : 1 omega 7c 11-methyl, 18 : 0, 12 : 1, 18 : 2 omega 7c, 12, 10 : 0 3-OH and 12 : 0 3-OH. Polar lipids were phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, an aminolipid, one unknown lipid and one additional unknown lipid in strain P97 (T). The major respiratory quinone was Q10. Based on phylogenetic and phenotypic differences, the strains represent a novel species in the genus Phaeobacter, for which the name Phaeobacter porticola sp. nov. is proposed. The type strain is P97(T) (= DSM 103148(T) = LMG 29594(T)).