Journal of Applied Microbiology, Vol.106, No.4, 1231-1243, 2009
Elevation of Francisella philomiragia subsp noatunensis Mikalsen et al. (2007) to Francisella noatunensis comb. nov [syn. Francisella piscicida Ottem et al. (2008) syn. nov.] and characterization of Francisella noatunensis subsp. orientalis subsp nov., two important fish pathogens
This study was conducted to clarify the taxonomic status of Francisella sp. strain Ehime-1, a fish pathogen, in relation to the fish pathogens F. piscicida and F. philomiragia subsp. noatunensis and to F. philomiragia subsp. philomiragia. Francisella sp. Ehime-1 was compared to F. piscicida, F. philomiragia subsp. noatunensis and several F. philomiragia subsp. philomiragia isolates through sequencing of the 16S rRNA-gene and several house-keeping genes and determination of biochemical and phenotypic properties. Results show that F. piscicida is indistinguishable from F. philomiragia subsp. noatunensis by sequence and phenotypic traits. Francisella sp. Ehime-1 and F. philomiragia subsp. noatunensis are clearly separated from F. philomiragia. Francisella sp. Ehime-1 is biochemically, phenotypically and genetically different from F. philomiragia subsp. noatunensis (=F. piscicida), but DNA-DNA hybridization does not clearly support establishment as a separate species (level of relatedness 64% and 73.4%, mean 68.7%). We propose to elevate F. philomiragia subsp. noatunensis to species rank as F. noatunensis comb. nov., while F. piscicida is considered a heterotypic synonym of F. noatunensis comb. nov. Evidence suggests that Francisella sp. Ehime-1 represents a novel subspecies of F. noatunensis, for which the name F. noatunensis subsp. orientalis subsp. nov. is proposed (=DSM21254(T), = LMG24544(T)). This study contributes to the taxonomy and characteristics of fish-pathogenic Francisella spp.
Keywords:16S rRNA-genes;fish pathogens;Francisella noatunensis comb;nov;Francisella noatunensis subsp;orientalis subsp;nov;Francisella piscicida;housekeeping genes;synonymy