The genus Piscirickettsia is part of the Piscirickettsiaceae family, belonging to the Gammaproteobacteria class within the Thiotrichales order. The family contains seven phylogenetically related genera (Cycloclasticus, Hydrogenovibrio, Sulfurivirga, Thioalkalimicrobium, Methylophaga, Thiomicrospira, and Piscirickettsia), with highly diverse characteristics, making them very different from one another. The genus Piscirickettsia comprises a single species called Piscirickettsia salmonis, a Gram-negative facultative intracellular fish pathogen that significantly affects the salmon industry. Since its first isolation in Chile in 1989, the bacterium has been reported in Norway, Scotland, Greece, Canada, and the USA, among others. To date, the complete genome sequence of P. salmonis has not been reported, and relevant aspects of its metabolism, virulence, and life cycle are still poorly understood
