Phylogeny and nucleotide sequence of a 23S rRNA gene fromNeisseria gonorrhoeaeandNeisseria meningitidis

Abstract

The genus Neisseria includes two important human pathogens, Neisseria gonorrhoeae and Neisseria meningitidis, causing gonorrhea and meningitidis, respectively. The very close relationship between these two species has been shown by a variety of approaches, including DNA-DNA hybridization, interspecies transformation and DNA restriction endonuclease pattern (1, 2, 3). Based on 16S rRNA sequence comparisons Neisseria gonorrhoeae was grouped to the (-proteobacteria (4). By Southern hybridization we identified four distinct rRNA loci in the genome of Neisseria gonorrhoeae and Neisseria meningitidis, respectively (data not shown). This confirms the results previously found for Neisseria gonorrhoeae (5). The polymerase chain reaction (PCR) was used to amplify one 23S rRNA gene from the chromosome of Neisseria gonorrhoeae and Neisseria meningitidis and their nucleotide sequence was determined. The DNA sequence of the 23S rRNA genes from the two Neisseria species is 2890 bp in length. The G+C content of the 23S rRNA gene is 52.1 mol% and 51.6 mol% for Neisseria gonorrhoeae and Neisseria meningitidis, respectively, which is in accordance with the overall base composition of the genomic DNA (50-53 mol%). The high sequence similarity (>98%) (Table 1) confirms the close relationship of these organisms. The sequence differences are mainly restricted to the known variable regions of the 23S rRNA gene (6). In Table 1 sequence similarities with two other proteobacteria, Pseudomonas cepacia (6) representative for the f-subgroup and E. coli belonging to the 'y-subgroup, are shown. A phylogenetic tree based on the Kn." values (7) is outlined in Figure 1. The analysis of the secondary structure reveals that both Neisseria 23S rRNAs harbour a typical helix 16 found in all proteobacteria rRNAs (6). In spite of the great homology between the two investigated neisserial rRNAs the differences may be useful for the design of species-specific probes for rapid identification of these pathogens.

Comparison of Phenotypic and Genotypic Techniques for Identification of Unusual Aerobic Pathogenic Gram-Negative Bacilli

“…Another potential limitation of the 16S rDNA sequencing application in general is the inability to assign a species for recently diverged species (10,12,44). Since our study was limited to gram-negative bacilli and to a relatively small number of analyses, we did not encounter this problem.…”