A Gram-negative, rod-shaped bacterium (designated strain UST030701-295(T)) with fast gliding motility was isolated from the surface of the sponge Lissodendoryx isodictyalis in the Bahamas. Colonies of UST030701-295(T) were yellow in colour, 2-4 mm in diameter, convex with a smooth surface and entire margins. UST030701-295(T) was heterotrophic, strictly aerobic and required NaCl for growth (1.0-4.0%). Growth was observed at pH 6.0-10.0 and at 12-44 degrees C. Phylogenetic analysis of the 16S rRNA gene sequence placed UST030701-295(T) within the genus Winogradskyella of the family Flavobacteriaceae, sharing 94.7-95.8% similarity with the three recognized members of the genus. The G+C content of the DNA was 32.8 mol% and the predominant fatty acids were iso-C(15:1), iso-C(15:0), iso-C(15:0) 2-OH, iso-C(15:0) 3-OH, iso-C(16:0) 3-OH, C(16:1)omega7 and iso-C(17:0) 3-OH (together representing 75.4% of the total); these data supported the affiliation of UST030701-295(T) to the genus Winogradskyella. UST030701-295(T) differed from the three recognized species of Winogradskyella in 7-17 traits. Molecular evidence together with phenotypic characteristics suggests that UST030701-295(T) represents a novel species within the genus Winogradskyella, for which the name Winogradskyella poriferorum sp. nov. is proposed. The type strain is UST030701-295(T) (=NRRL B-41101(T)=JCM 12885(T)).