Summary auto-generated
This study established a comprehensive Fourier-transform infrared (FT-IR) spectroscopy database for identifying coryneform bacteria and related taxa from the suborders Micrococcineae and Corynebacterineae. The database contains averaged IR spectra from 730 reference strains representing 220 species across 46 genera, with 192 species represented by type strains. The researchers validated strain identities using 16S rDNA sequence analysis, reclassifying 224 of 352 questionable strains. Internal validation achieved 98.1% correct identification at the species level among 208 test strains. External validation using 544 strains from 54 species yielded 87.3% correct species-level identification and 95.4% genus-level identification. The method's performance is comparable to existing phenotypic identification systems. FT-IR spectroscopy offers significant practical advantages: rapid identification within 25 hours from a single colony, low cost, and satisfactory differentiation capacity, making it superior to routine methods for coryneform bacteria identification despite some inherent limitations from overlapping taxonomic markers.
Key findings
- An FT-IR spectroscopy database was successfully established containing 730 reference strains covering 220 species from 46 genera of coryneform bacteria and related taxa
- Internal validation achieved 98.1% species-level identification accuracy, while simulated external validation achieved 87.3% species-level and 95.4% genus-level accuracy
- Comparative 16S rDNA sequencing led to reclassification of 224 of 352 (64%) strains with questionable identities, improving database accuracy
- FT-IR identification performs comparably to commercial phenotypic identification systems while offering advantages of speed (25 hours), low cost, and ease of handling
- Identification accuracy correlates with the number of representative strains per species in the database, suggesting that expanded strain representation improves reliability
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Abstract
An extensive Fourier-transform infrared (FT-IR) spectroscopy database for the identification of bacteria from the two suborders Micrococcineae and Corynebacterineae (Actinomycetales, Actinobacteria) as well as other morphologically similar genera was established. The database consists of averaged IR spectra from 730 reference strains, covering 220 different species out of 46 genera. A total of 192 species are represented by type strains. The identity of 352 reference strains was determined by comparative 16S rDNA sequence analysis and, if necessary, strains were reclassified accordingly. FT-IR frequency ranges, weights and reproducibility levels were optimized for this section of high-G+C Gram-positive bacteria. In an internal validation, 98.1% of 208 strains were correctly identified at the species level. A simulated external validation which was carried out using 544 strains from 54 species out of 16 genera resulted in a correct identification of 87.3% at the species level and 95.4% at the genus level. The performance of this identification system is well within the range of those having been reported in the literature for the identification of coryneform bacteria by phenotypical methods. Coryneform and related taxa display a certain degree of overlapping distribution of different taxonomical markers, leading to a limited differentiation capacity of non-genotypical identification methods in general. However, easy handling, rapid identification within 25 h starting from a single colony, a satisfactory differentiation capacity and low cost, render FT-IR technology clearly superior over other routine methods for the identification of coryneform bacteria and related taxa.