Research Article

Complete genome sequence of Francisella noatunensis subsp. orientalis strain F1 and prediction of vaccine candidates against warm and cold-water fish francisellosis


Francisella noatunensis subsp. orientalis (Fno) is a Gram-negative bacterium that causes granulomatous infections in fish reared at low water temperatures; it has been responsible for a large number of deaths in tilapia fish farms. Fno has been reported in many countries in the last decade. Studies on phylogenomic relationships among isolates are needed because of the increasing importance of this disease. Here, we present the complete genome of the Fno F1 strain isolated in 2015 from a tilapia farm in São Paulo state, Brazil. The genome is a circular chromosome with a length of 1,854,333 bp, containing 32.26% G+C DNA content, 1,448 protein-coding genes and 393 pseudogenes. In addition, a prediction of conserved vaccine targets was made between the two subspecies of F. noatunensis that cause disease in tropical and cold-water fish species. Five proteins conserved between Fno and Francisella noatunensis subsp. noatunensis were predicted to be good vaccine candidates for the development of a recombinant vaccine against francisellosis. This genome also provides useful data to help understand the pathogen evolution and epidemiology of this disease in Brazil.