Analysis of 16S-23S rRNA gene internal transcribed spacer of Vibrio anguillarum and Vibrio ordalii strains isolated from fish

The 16S-23S rRNA intergenic spacer (ITS) of Vibrio anguillarum and Vibrio ordalii were PCR amplified and cloned with TA vector pCR2.1. PCR amplification obtained five products ranging from 917 to 437 bp. Three clones were obtained and analysed from all fragments with the exception of 437 bp. These products were designated ITS-1, ITS-2, ITS-3 and ITS-4. ITS-1 contained genes for tRNA(Glu(TTC)), tRNA(Lys(TTT)), tRNA(Ala(TGC)) and tRNA(Val(TAC)), while ITS-2 was almost the same as the ITS-1 sequence, but without tRNA(Val(TAC)). ITS-3 contained tRNA(Ala(TGC)) and tRNA(Ile(GAT)) and ITS-4, tRNA(Ala(GGC)) or tRNA(Glu(TTC)). The number of copies of the ribosomal operon (rrn) in V. ordalii chromosome ranged from at least six to seven and V. anguillarum had at least seven rrn. The sequences ITS-1, ITS-2 and ITS-3 showed a high similarity among the V. anguillarum and V. ordalii sequences (97.2% to 100%). Little variation was found for ITS-4, which does not seem to be sufficient to distinguish these two closely related species. Based on the findings, we confirm a close genetic relationship among V. anguillarum and V. ordalii and that they may be descended from a common ancestor in the Vibrionaceae linage.