Membranicola marinus gen. nov., sp. nov., a new member of the family Saprospiraceae isolated from a biofilter in a recirculating aquaculture system.

A Gram-staining-negative bacterial strain (termed CZ-AZ5T) was isolated from a biological filter in a marine recirculating aquaculture system in Tianjin, China. Its taxonomic status was determined using a polyphasic approach. CZ-AZ5T cells were non-spore-forming, non-motile rods, 0.6-0.7 μm wide and 3.0-3.7 μm long. CZ-AZ5T was strictly heterotrophic, aerobic, oxidase-negative and catalase-positive. Growth occurred in the temperature range 20-40 °C (optimal: 30 °C), pH range 6.0-8.5 (optimal: pH 7.5) and salinity range 0-5 % (w/v) NaCl (optimal: 1 %). In phylogenetic analyses based on 16S rRNA gene sequences, CZ-AZ5T was assigned to the family Saprospiraceae (phylum Bacteroidetes) and was clustered with the genera Saprospira and Aureispira within this family. It showed highest sequence similarity to 'Candidatus Haliscomenobacter calcifugiens' (86.2 %), followed by Saprospira grandis ATCC 23119T (85.7 %) and Lewinella persica T-3T (85.6 %). DNA G+C content was 40.1 mol%, the major menaquinone was MK-7, and the major cellular fatty acids (>10 %) were C16 : 1ω7c and iso-C15 : 0. Our phenotypic, chemotaxonomic and phylogenetic observations, taken together, led us to conclude that strain CZ-AZ5T represents a novel species and genus of the family Saprospiraceae, for which the name Membranicola marinus gen. nov., sp. nov. is proposed. The type strain is CZ-AZ5T ( = CGMCC 1.13179T = JCM 18886T).