tRNA genes were found in Piscirickettsia salmonis 16S–23S rDNA spacer region (ITS)

Abstract

Piscirickettsia salmonis is the etiological agent of Salmonid Rickettsial Septicemia, a disease affecting salmon aquaculture industry. We analyzed the 16S^23S rDNA spacer region (internal transcribed spacer, ITS) of Chilean P. salmonis isolates LF-89 and EM-90. Two main ITS amplification products were obtained by PCR using L1 and G1 primers, differing from that described where only one ITS region was found. By Southern blot, it was established that these two amplification products contained sequences related to P. salmonis ITS. Sequence analysis confirmed that P. salmonis had two ITS regions: ITS A and ITS B. In both isolates, the smaller (ITS B) corresponded to ITS sequences previously described for each one, and the larger (ITS A) were almost the same as their respective ITS B sequences interrupted by an insert which contained two tRNAs genes: tRNA-Ile and tRNA-Ala. ß

Confirmation of Piscirickettsia salmonis as a pathogen in European sea bass Dicentrarchus labrax and phylogenetic comparison with salmonid strains

“…They established that these strains formed a monophyletic group within the Gammaproteobacteria, although 1 Chilean isolate, EM-90, had diverged sufficiently to allow differentiation from the other isolates based on restriction fragment length polymorphism (RFLP) (Mauel et al 1996). This group found only 1 ITS sequence in the isolates examined but, following polyacrylamide gel analysis of amplified ITS regions, Casanova et al (2001) have suggested that P. salmonis may contain at least 2 rRNA (rrn) operons, as is commonly the case for other Gram-negative bacteria (Gürtler & Stanisich 1996, Crosby & Criddle 2003. More recently, have extended the information on regional variation of P. salmonis isolates through their comparison of 16S rDNA and ITS sequences from Scottish and Irish isolates.…”

Isolates of Piscirickettsia salmonis from Scotland and Ireland Show Evidence of Clonal Diversity

“…Salmonid rickettsial septicemia (SRS), or piscirickettsiosis, is a systemic disease of cultured salmonids initially recognized in coho salmon in Chile (1), where it causes significant losses in aquaculture (4). Subsequently, disease has been recorded in Canada (3), Norway (19), Ireland (21), and Scotland (A. N. Grant, A. G. Brown, D. I. Cox, T. H. Birkbeck, and A.…”

“…Both 16S rDNA and ITS data can be complicated by the presence of multiple rDNA operons, documented in P. salmonis strains LF-89 and EM-90 (4). However, the P. salmonis-specific ITS primers described by Marshall et al (14) are reported to amplify only one ITS region, allowing strain-to-strain comparisons (4). Of the isolates studied by Mauel et al (17)-four Chilean isolates, one Canadian isolate, and one Norwegian isolate-ITS data analysis indicates phylogenetic diversity between isolates from different geographic regions.…”

Bacillus anthracis Diverges from Related Clades of the Bacillus cereus Group in 16S-23S Ribosomal DNA Intergenic Transcribed Spacers Containing tRNA Genes

“…The 16S-23S rDNA intergenic transcribed spacers (ITS) are the most variable regions of the ribosomal operon, and, apart from interoperonic nucleotide substitutions, insertions, and deletions, such ITS can be differentiated, given the presence of the different numbers and types of tRNA genes (9,10,31,49). Since the ITS have fewer functional constraints than the adjacent ribosomal genes, which undergo concerted evolution (17)(18)(19), their sequences can contain traces of ribosomal operon rearrangements and species-specific or even strain-specific traits that are useful for strain typing.…”