A rod-shaped, Gram-negative, chemo-organotrophic, heterotrophic, strictly aerobic, gliding bacterial strain, SW5(T), capable of degrading sulphated fucans from brown algae was isolated from a water-treatment facility that recycles the effluent of an alginate-extraction plant in Landerneau (Brittany, France). Its taxonomic position was investigated by a polyphasic approach. Strain SW5(T) formed dark-yellow colonies, was oxidase-negative and catalase-positive and grew optimally at 25 degrees C and pH 7.5 and in the presence of 2.5% (w/v) NaCl. The DNA G+C content was 34.5 mol%. Phylogenetic analysis based on the sequence of the 16S rRNA gene allocated strain SW5(T) to the genus Mariniflexile in the family Flavobacteriaceae, with a similarity of 98.4 % to the type strain of Mariniflexile gromovii, the only recognized Mariniflexile species. Its low level of DNA-DNA relatedness (<25%) with the type strain of this species and differentiating phenotypic characteristics demonstrated that strain SW5(T) constitutes a novel Mariniflexile species, for which the name Mariniflexile fucanivorans sp. nov. is proposed. Strain SW5(T) (=CIP 109502(T) =DSM 18792(T)) is the type strain.