A novel gram-negative, aerobic, moderate halophilic, and psychrotolerant bacterium, designated as strain H7(T), was isolated from a hypersaline lake located in Skarvsnes, Antarctica. Cells were filaments with varying lengths. Coccoid bodies developed in old cultures. Growth occurred with 0.5-15% (w/v) NaCl (optimum, 5.8-7.0%), at pH 6.0-10.0 (optimum, pH 7.0-8.0), and at 10-28 degrees C (optimum, 25 degrees C). The strain had a G+C content of 34.9 mol%, which is within the range of 32-36 mol% reported for the genus Psychroflexus. Chemotaxonomic data (major respiratory quinone: MK-6; major fatty acids: aC(15:0), iC(16:0) 3-OH, and aC(15: 1) A) supported the classification of strain H7(T) within the genus Psychroflexus. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain H7(T) should be assigned to the genus Psychroflexus and has a homology with Psychroflexus salinarum (98.2%), P. sediminis (96.1%), P. torquis (95.2%), P. tropicus (95.8%), and P. gondwanense (92.2%). Strain H7 is not identified as P. salinarum because that DNA-DNA hybridization data were 8.5% between strain H7(T) and P. salinarum. The combination of phylogenetic analysis, DNA-DNA hybridization data, phenotypic characteristics, and chemotaxonomic differences supported the view that strain H7(T) represents a novel species of the genus Psychroflexus. The name Psychroflexus lacisalsi is proposed, and the type strain is H7(T) (=JCM 16231(T) =KACC 14089(T)).