Analysis of 16S-23S intergenic spacer regions and rrn operon copy number of Aeromonas culicicola MTCC 3249T

The 16S-23S intergenic spacer and 23S rRNA gene sequence were determined for A. culicicola MTCC 3249(T) Ten different ISR, indicative of ten rrn operons, were found in the strain that were grouped in three major types. Of the three types, ISR I was non-coding while ISR II and III coded for tRNA(Glu(UUC))). The tRNA(Glu(UUC)) sequence was identical to that of E. coli. Both ISR I and II were represented by three clones whereas four clones represented ISR III. The number of nucleotide differences between all these ISR ranged from 4 to 157. There were ten rrn operons present in A. culicicola MTCC 3249(T) as confirmed by Southern hybridization analysis. The 23S rRNA gene sequence analysis of A. culicicloa showed 89.6% homology to that from E. coli with differences of 292 bases, whereas it was 98.6% similar to A. hydrophila 23S rRNA gene with 38 nucleotide differences. The sequences of the helix 21 region were identical in both A. culicicola MTCC 3249(T) and A. hydrophila and showed two nucleotides different at 389 and 390th positions as compared to E. coli. The upstream and downstream regions of 23S rRNA gene in the strain showed high sequence similarity with A. hydrophila and E. coli indicating their importance in processing of rRNA molecules.