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-AZ5^T) 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-AZ5^T cells were non-spore-forming, non-motile rods, 0.6-0.7 μm wide and 3.0-3.7 μm long. CZ-AZ5^T 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-AZ5^T 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 23119^T (85.7 %) and Lewinella persica T-3^T (85.6 %). DNA G+C content was 40.1 mol%, the major menaquinone was MK-7, and the major cellular fatty acids (>10 %) were C_{16 : 1}ω7c and iso-C_{15 : 0}. Our phenotypic, chemotaxonomic and phylogenetic observations, taken together, led us to conclude that strain CZ-AZ5^T 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-AZ5^T ( = CGMCC 1.13179^T = JCM 18886^T).