An aggregate-attached bacterium, strain 88/2-7, was isolated from samples of the Southern Ocean and investigated in a polyphasic approach. The novel marine isolate is an aerobic, Gram-negative, oxidase- and catalase-positive, non-motile short rod and grows in form of cream-colored colonies. Growth was observed at 5-35 degrees C. The bacterium tolerated concentrations of 0-13% (w/v) NaCl and utilized a relatively restricted spectrum of carbon sources. The analysis of the fatty acids revealed 18:1 cis 9 (18:1omega9c) as main fatty acid. The G+C content of the DNA was approximately 42 mol%. The sequence of the 16S rDNA assigned strain 88/2-7 to the gamma-subclass of Proteobacteria with a similarity of 99.65% to Psychrobacter proteolyticus (DSM 13887T). A DNA-DNA-hybridization study showed only 26.8% renaturation to the respective strain. Based on the morphological, physiological and molecular properties of the new isolate, the name Psychrobacter nivimaris sp. nov. (type strain 88/2-7T) is proposed.