Summary auto-generated
This study analyzed 16S–23S rDNA internally transcribed spacer (ITS) sequences from 33 Nocardioides strains, two Aeromicrobium species, and Terrabacter tumescens to clarify their evolutionary relationships. The researchers used PCR amplification and direct sequencing to determine these ITS sequences, which ranged from 328 to 539 base pairs in Nocardioides strains. The analysis revealed that some strains contained two different types of ITS sequences from different rRNA gene clusters. Within N. albus, nucleotide similarity ranged from 84.1% to 100%, while N. simplex strains showed 97.7–100% similarity. The study found that N. luteus, 'N. flavus', and 'N. fulvus' strains were nearly identical or differed by only one base pair in their ITS sequences, suggesting they should be classified as the same species. The 16S–23S ITS sequences proved useful for discriminating between closely related strains and species within Nocardioides, but were less appropriate for determining relationships between distantly related organisms at the genus level. These findings support using ITS sequences as an additional taxonomic marker alongside traditional DNA–DNA reassociation studies.
Key findings
- 16S–23S ITS sequences ranged from 328–539 bp in Nocardioides strains and showed high variability suitable for discriminating between closely related species and strains
- N. luteus, 'N. flavus', and 'N. fulvus' strains were nearly identical (differing by ≤1 bp) in their ITS sequences, suggesting they should be reclassified as the same species
- Some Nocardioides strains contained two distinct types of 16S–23S ITS sequences from different rRNA gene clusters on their genomes
- 16S–23S ITS sequences are useful taxonomic markers for inferring relationships among closely related organisms but inappropriate for determining phylogenetic relationships between distantly related organisms at the genus level
- The mean intraspecific nucleotide similarity in N. albus ranged from 84.1–100% and in N. simplex from 97.7–100%, demonstrating the discriminatory power of ITS analysis
This summary was generated automatically from the article PDF and is not part of the original publication. Refer to the PDF for the authoritative text.
Abstract
The 16S–23S internally transcribed spacer (ITS) sequences were analysed to clarify inter- and intraspecific relationships among strains of the genus Nocardioides and the relationship between two Aeromicrobium species. The 16S–23S ITS regions from 33 Nocardioides strains, two Aeromicrobium species and Terrabacter tumescens were sequenced directly after polymerase chain reaction (PCR) amplification and λ exonuclease treatment. The genomes of some Nocardioides strains included two types of 16S–23S ITS sequences. The sizes of the 16S–23S ITS sequences of Nocardioides strains ranged from 328 to 539 bp. The 16S–23S ITS sequences of Aeromicrobium erythreum NSP37T, Aeromicrobium fastidiosum NSP38Tand T. tumescens NSP39Twere 349, 355 and 386 bp long, respectively. Nucleotide similarity among 16S–23S ITS sequences of Nocardioides albus strains and of Nocardioides simplex strains was 84·1-100% and 97·7-100%, respectively. The 16S–23S ITS sequence of Nocardioides luteus was identical to that of Nocardioides fulvus NSP32Tand was only 1 bp different from that of Nocardioides fulvus strains. However, the 16S–23S ITS sequences of N. fulvus NSP32Tshowed only a low degree of similarity to N. fulvus NSP32T(54·8%). The degree of 16S–23S ITS similarity between N. luteus NSP20Tand N. albus strains ranged from 85 to 93%. The mean nucleotide similarity values between the type strains of validly described Nocardioides species were highly divergent at 68·1±16·8%. The two Aeromicrobium species showed a level of 16S–23S ITS similarity of 71·2%. In this study, 16S–23S ITS sequences of the members of the genera Nocardioides and Aeromicrobium were useful for inferring the relationships between closely related strains and species. However, they were not found to be appropriate for elucidating the phylogenetic relationships between distantly related organisms at the genus level.