Description of Symbiobacterium ostreiconchae sp. nov., Symbiobacterium turbinis sp. nov. and Symbiobacterium terraclitae sp. nov., isolated from shellfish, emended description of the genus Symbiobacterium and proposal of Symbiobacteriaceae fam. nov.

Three novel moderately anaerobic, thermophilic, rod-shaped bacterial strains, KY38(T), KY46(T) and KA13(T), were isolated from shellfish collected on the Pacific coastline of Enoshima, Japan. Phylogenetic analysis of the 16S rRNA gene sequences indicated that these bacteria belong to the genus Symbiobacterium, sharing sequence similarities of 97.8% (KY38(T)), 96.4% (KY46(T)) and 93.3% (KA13(T)) with the type strain of Symbiobacterium thermophilum, the only species of the genus with a validly published name. These isolates reduced nitrate and grew optimally at 55-60 °C. Strains KY38(T) and KA13(T) formed endospore-like structures in the terminal or subterminal part of their cells at low frequencies. Genomic DNA G+C contents were 68.8 (KY38(T)), 67.2 (KY46(T)) and 67.1 (KA13(T)) mol%. The isolates all presented the predominant menaquinone MK-6, major fatty acids iso-C15:0, C16:0 and iso-C17:0 and the major polar lipids phosphatidylglycerol, phosphatidylethanolamine and unknown glycol-containing phospholipids. On the basis of their morphological, physiological and phylogenetic properties, strains KY38(T), KY46(T) and KA13(T) represent three novel species, for which the names Symbiobacterium ostreiconchae sp. nov. (type strain KY38(T) = DSM 27624(T) = KCTC 4567(T) = JCM 15048(T)), Symbiobacterium turbinis sp. nov. (type strain KY46(T) = DSM 27625(T) = KCTC 4568(T) = JCM 15996(T)) and Symbiobacterium terraclitae sp. nov. (type strain KA13(T) = DSM 27138(T) = KCTC 4569(T) = JCM 15997(T)) are proposed. An emended description of the genus Symbiobacterium is also presented. The phylogenetic distinctiveness of the genus Symbiobacterium indicates its affiliation with a novel family, for which the name Symbiobacteriaceae fam. nov. is proposed.