title: ISPsa2, the first mobile genetic element to be described and characterized in the bacterial facultative intracellular pathogen Piscirickettsia salmonis.
abstract: Piscirickettsia salmonis is a novel, aggressive, facultative Gram-negative bacterium that drastically affects salmon production at different latitudes, with particular impact in southern Chile. Initially, P. salmonis was described as a Rickettsia-like, obligate, intracellular Alphaproteobacteria, but it was reclassified recently as a facultative intracellular Gammaproteobacteria. This designation has prompted the independent growth of the bacterium to a pure state for detailed study of its biology, genetics and epidemiology, properties that are still relatively poorly characterized. The preliminary sequence analysis of a 992-bp fragment of pure P. salmonis DNA allowed us to characterize a novel and complete 863-bp insertion sequence in the bacterial genome (named ISPsa2), which has a novel 16/16bp perfectly inverted terminal repeat flanking a 726-bp ORF that encodes a putative transposase (Tnp-Psa). The coding sequence of the enzyme shares similarities to that described in some Bacillus species and particularly to those of the IS6 family. ISPsa2 carries its own promoter with standard -10 and -35 sequences, suggesting an interesting potential for plasticity in this pathogenic bacterium. Additionally, the presence of ISPsa2 was confirmed from three isolates of P. salmonis collected from different epizootics in Chile in 2010.
authors.affiliation: Laboratorio de Genética e Inmunología Molecular, Instituto de Biología, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile. smarshal@ucv.cl
authors.forename: Sergio H
authors.initials: SH
authors.lastname: Marshall
authors.forename: Vitalia
authors.initials: V
authors.lastname: Henríquez
authors.forename: Fernando A
authors.initials: FA
authors.lastname: Gómez
authors.forename: Constanza
authors.initials: C
authors.lastname: Cárdenas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D001483:Base Sequence; D004251:DNA Transposable Elements; D005393:Fish Diseases / Q000382:microbiology*; D008969:Molecular Sequence Data; D053522:Piscirickettsia / Q000737:chemistry / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D044225:Piscirickettsiaceae Infections / Q000382:microbiology / Q000662:veterinary*; D011401:Promoter Regions, Genetic; D012474:Salmon / Q000382:microbiology*; D016415:Sequence Alignment; D019895:Transposases / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D019895:Transposases