Francisella halioticida sp. nov., a pathogen of farmed giant abalone (Haliotis gigantea) in Japan

Aims: In 2005, a Francisella sp. was isolated from diseased cultured giant abalone (Haliotis gigantea) in Japan. The aim of this study was to clarify the taxonomic status of this Francisella sp. Shimane‐1 isolate in relation to the four described Francisella species. Methods and Results: The 16S rRNA gene and several housekeeping genes of the Shimane‐1 were compared to isolates of the four recognized species within the Francisella genus. DNA–DNA hybridization (DDH) and biochemical profile comparison were performed with the two phylogenetically closely related species, Francisella philomiragia and Francisella noatunensis. Results show that the Shimane‐1 is genetically different from all described Francisella species and differs phenotypically from F. philomiragia and F. noatunensis. The average DDH similarity of Francisella sp. Shimane‐1 to F. noatunensis ssp. noatunensis (NCIMB14265T) and to F. philomiragia (DSM7535T) was 49·2 and 61%, respectably, clearly supporting the establishment of Shimane‐1 as a new species within the Francisella genus. Conclusions: The phenotypic and genetic results presented in this study suggest the establishment of Shimane‐1 as a novel species, for which the name Francisella halioticida sp. nov. (=LMG26062T, =DSM23729T) is proposed. Significance and Impact of the Study: This study clarifies the taxonomic position and characteristics of a novel mollusc pathogenic Francisella species.