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PiscirickettsiaRANK: GenusTAXONOMY: cellular organisms -> Bacteria -> Proteobacteria -> Gammaproteobacteria -> Thiotrichales -> Piscirickettsiaceae -> Piscirickettsia OVERVIEW: Pleomorphic, but predominantly coccoid organisms, ~0.5–1.5 μm in diameter. Gram negative, Gimenez negative, and stain dark blue with Giemsa's stain. Nonmotile. Aerobic. Characteristically replicate within cytoplasmic vacuoles in susceptible fish host cells. Cultivable in fish cell cultures but not on any known host-cell-free medium. Direct host-to-host transmission occurs in the aquatic environment without the requirement of a vector. The 16S rRNA gene sequence conforms to the secondary structural models for the Gammaproteobacteria. No signature sequence has been identified. The etiological agent of the disease piscirickettsiosis in fishes. Type species: Piscirickettsia salmonis |