ISPsa2, the first mobile genetic element to be described and characterized in the bacterial facultative intracellular pathogen Piscirickettsia salmonis

• Published in: FEMS microbiology letters 2011, Vol.314 (1), p.18-24
• Main Authors: Marshall, Sergio H, Henríquez, Vitalia, Gómez, Fernando A, Cárdenas, Constanza
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacteriology; Base Sequence; Biological and medical sciences; Deoxyribonucleic acid; DNA; DNA Transposable Elements; Epidemiology; Epizootics; Fish Diseases - microbiology; Fundamental and applied biological sciences. Psychology; Genetics; Genomes; Insertion; insertion sequence; Intracellular; inverted repeats; Microbiology; Miscellaneous; Molecular Sequence Data; Nucleotide sequence; Open reading frames; Piscirickettsia - chemistry; Piscirickettsia - enzymology; Piscirickettsia - genetics; Piscirickettsia - physiology; Piscirickettsia salmonis; Piscirickettsiaceae Infections - microbiology; Piscirickettsiaceae Infections - veterinary; Promoter Regions, Genetic; Salmon; Salmon - microbiology; Sequence Alignment; Transposase; Transposases - chemistry; Transposases - genetics
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1111/j.1574-6968.2010.02132.x

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 16/16 bp 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.