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.

Abstract

Three novel moderately anaerobic, thermophilic, rod-shaped bacterial strains, KY38T, KY46T and KA13T, 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 % (KY38T), 96.4 % (KY46T) and 93.3 % (KA13T) 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 KY38T and KA13T formed endospore-like structures in the terminal or subterminal part of their cells at low frequencies. Genomic DNA G+C contents were 68.8 (KY38T), 67.2 (KY46T) and 67.1 (KA13T) 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 KY38T, KY46T and KA13T represent three novel species, for which the names Symbiobacterium ostreiconchae sp. nov. (type strain KY38T = DSM 27624T = KCTC 4567T = JCM 15048T), Symbiobacterium turbinis sp. nov. (type strain KY46T = DSM 27625T = KCTC 4568T = JCM 15996T) and Symbiobacterium terraclitae sp. nov. (type strain KA13T = DSM 27138T = KCTC 4569T = JCM 15997T) 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.