J. Bacteriol., 04 1996, 2272-2278, Vol 178, No. 8
Copyright © 1996, American Society for Microbiology

Salmonella typhimurium LT2 possesses three distinct 23S rRNA intervening sequences

NR Mattatall and KE Sanderson
Salmonella Genetic Stock Centre, Uniersity of Calgary, Alberta, Canada. nmattata@acs.ucalgary.ca

The rrl genes for 23S rRNA of Salmonella typhimurium LT2 are known to carry intervening sequences (IVSs) at two sites, helix-25 and helix-45, which are excised by RNase III during rRNA maturation, resulting in rRNA which is fragmented but nevertheless functional. We isolated DNA fragments containing the seven rrl genes from BlnI, I-CeuI, and SpeI genomic digests following pulsed-field gel electrophoresis and used these DNA fragments as templates for PCRs utilizing primers upstream and downstream of helix-25 and helix-45. Variance in amplicon length and cycle sequencing indicated that rrlG and rrlH have IVSs in helix-25 of approximately 110 bp which are only 56% identical. rrnA, rrnB, rrnC, rrnD, rrnE, and rrnH have IVSs of approximately 90 bp in helix-45, and all have the same nucleotide sequence. Twenty-one independent wild-type strains of S. typhimurium from Salmonella Reference Collection A were analyzed for IVSs by using PCRs with genomic DNAs and by denaturing agarose electrophoresis of RNAs. Many strains resemble LT2, but some have no IVSs in helix-25 and others have IVSs in helix-45 in all seven rrl genes. However, the IVSs in individual wild-type lines are relatively stable, for several LT2 isolates separated over many years by many single-colony isolations are indistinguishable from one another, with the exception of line LB5010, which differs by one helix- 25 IVS. We postulate that IVSs have entered strain LT2 by three independent lateral-transfer events and that the IVS in helix-45 was dispersed to and maintained in the same sequence in six of the seven rrl genes by the mechanism of gene conversion.

This article has been cited by other articles:

• Santoyo, G., Martinez-Salazar, J. M., Rodriguez, C., Romero, D. (2005). Gene Conversion Tracts Associated with Crossovers in Rhizobium etli. J. Bacteriol. 187: 4116-4126 [Abstract] [Full Text]  
• Zaporojets, D., French, S., Squires, C. L. (2003). Products Transcribed from Rearranged rrn Genes of Escherichia coli Can Assemble To Form Functional Ribosomes. J. Bacteriol. 185: 6921-6927 [Abstract] [Full Text]  
• Pronk, L. M., Sanderson, K. E. (2001). Intervening Sequences in rrl Genes and Fragmentation of 23S rRNA in Genera of the Family Enterobacteriaceae. J. Bacteriol. 183: 5782-5787 [Abstract] [Full Text]  
• Zahn, K., Inui, M., Yukawa, H. (2000). Divergent mechanisms of 5' 23S rRNA IVS processing in the {alpha}-proteobacteria. Nucleic Acids Res 28: 4623-4633 [Abstract] [Full Text]  
• Evguenieva-Hackenberg, E., Klug, G. (2000). RNase III Processing of Intervening Sequences Found in Helix 9 of 23S rRNA in the Alpha Subclass of Proteobacteria. J. Bacteriol. 182: 4719-4729 [Abstract] [Full Text]  
• Pabbaraju, K., Miller, W. L., Sanderson, K. E. (2000). Distribution of Intervening Sequences in the Genes for 23S rRNA and rRNA Fragmentation among Strains of the Salmonella Reference Collection B (SARB) and SARC Sets. J. Bacteriol. 182: 1923-1929 [Abstract] [Full Text]  
• Miller, W. L., Pabbaraju, K., Sanderson, K. E. (2000). Fragmentation of 23S rRNA in Strains of Proteus and Providencia Results from Intervening Sequences in the rrn (rRNA) Genes. J. Bacteriol. 182: 1109-1117 [Abstract] [Full Text]