Structure of 16S and 23S ribosomal RNA genes in Campylobacter species : phylogenetic analysis of the genus Campylobacter and presence of internal transcribed spacers

16S and 23S ribosomal RNA (rRNA) genes from campylobacteria were studied by polymerase chain reaction and DNA sequence analysis using universally conserved oligonucleotide primers. In the 16S rRNA gene sequences of all C. sputorum strains tested, an insertion oi about 250 bp was found that was not present in the 16S rRNA genes of other Campylobacter species. This insertion was not present on the rRNA level in C. sputorum, and the 16S rRNA was found to be fragmented in this organism. From the length of the fragments, it could be concluded that the insertion is an internal transcribed spacer, which is probably excised during rRNA maturation. Similar internal transcribed spacers were also found in the 23S rRNA genes from several Campylobacter strains. On the basis of partial 23S rRNA gene sequences about 875 bp in length and comprising some of the most variable helices, phylogenetic analysis was performed on 17 Campylobacter strains. The results of this analysis were compared to a phylogenetic tree based on complete 16S rRNA sequences