Conservation of the mosaic structure of the four internal transcribed spacers and localisation of the rrn operons on the Streptococcus pneumoniae genome

Abstract

The detection of heterogeneity of the 16S^23S ribosomal intergenic transcribed spacer (ITS) region has become rather common over the past years for identification and typing purposes of bacteria. The ITS not only varies in sequence and length, but also in number of alleles per genome and in their position on the chromosome together with the ribosomal clusters. The ITS characterisation has allowed discrimination of several species within a genus and variation in ITS sequences between the multiple rrn operons present within a genome may be as high or greater than between strains of the same species or subspecies. It is important to understand the variability of ITS sequences in a given genome to gain insights into bacterial physiology and taxonomy. The present study describes the possibility to type Streptococcus pneumoniae by PCR-ribotyping of the spacer region, the determination of the molecular structure of the ITS, and the determination of the number and localisation of rrn operons in this microorganism. Our results show that the genome of S. pneumoniae contains four ribosomal operons, showing the same genomic organisation among strains, each containing a single ITS allele of 270 bp. The ITS sequence presents a mosaic organisation of blocks highly conserved intra-and inter-species within the genus Streptococcus, giving no possibility for variations to arise.

Development of Two PCR-Based Techniques for Detecting Helical and Coccoid Forms of Helicobacter pylori

“…This has been possible due to the high interand intraspecific variability (8,17,33,34,40). The advantage of this region is that the flanking 16S and 23S rRNA genes at the 5Ј and 3Ј ends of the ISR contain highly conserved sequences (i.e., the 16S and 23S rRNA genes).…”

16S-23S Intergenic Spacer (ITS) Region Sequence Analysis: Applicability and Usefulness in Identifying Genera and Species Resembling Non- Hemolytic Streptococci

“…It is known that bacterial genomes can contain several rrn operons, e.g. Enterococcus has three copies of this operon [27] and Streptococcus pneumoniae has four operons [28]. The ITS sequence tends to present a mosaic organization of blocks, highly conserved at intra-and interspecies level, within the genus Streptococcus [28].…”

“…Enterococcus has three copies of this operon [27] and Streptococcus pneumoniae has four operons [28]. The ITS sequence tends to present a mosaic organization of blocks, highly conserved at intra-and interspecies level, within the genus Streptococcus [28]. But in other genera, both length and copy number can vary from strain to strain [26].…”

Genotyping Techniques for Determining the Diversity of Microorganisms

“…In silico analysis of ISR length variability in 27 genomically sequenced bacterial species revealed that while in some species ISR length is variable within and between isolates, in others ISR lengths are limited to one or two sizes, usually dependent on the number of tRNAs present (Christensen et al, 1999). For example, while the multiple copies of the S. enterica serovar Typhimurium, serovar Infantis, and serovar Derby ITS fragments are polymorphic, they are conserved in other Salmonella species, as well in Listeria, Streptococcus, and certain species of Staphylococcus (Giannino et al, 2003;Gurtler & Stanisich, 1996;Lagatolla et al, 1996;Marsou et al, 1999). As consequence depending of the construction of rRNA operon amplification of its noncoding fragments can be a very useful technique for identifying bacteria to the species level (if the sequence is conserved) or for their differentiation if the target fragment of gene characterize with high polymorphism.…”