Summary auto-generated
This study evaluated temperature-gradient gel electrophoresis (TGGE) as a taxonomic tool for classifying coryneform bacteria. Researchers analyzed 115 reference strains from eight genera (Aeromicrobium, Agromyces, Arthrobacter, Aureobacterium, Cellulomonas, Curtobacterium, Nocardioides, and Terrabacter) by amplifying a variable region of the 16S rRNA gene and separating the products based on DNA melting behavior. TGGE produced distinct band patterns that generally distinguished between genera or groups of species, though resolution varied by genus. The technique identified nine misclassified strains and revealed 16S rRNA gene heterogeneity within three Curtobacterium strains. Findings were confirmed using fatty acid methyl ester (FAME) analysis. The authors conclude TGGE is useful for rapid screening of pure cultures and detecting contamination or misclassification without extensive sequencing, making it a practical addition to polyphasic bacterial taxonomy approaches.
Key findings
- TGGE successfully differentiated coryneform bacterial strains at varying taxonomic levels—from genus-specific to species-specific—depending on the group examined.
- The technique identified nine strains with incorrect taxonomic classifications, confirmed by fatty acid analysis, including misidentified Arthrobacter, Cellulomonas, Nocardioides, and Terrabacter strains.
- Evidence of 16S rRNA gene heterogeneity was found in three Curtobacterium strains, suggesting multiple different 16S rRNA gene copies within single genomes.
- TGGE offers a rapid, cost-effective screening method for detecting culture contamination and verifying strain authenticity in pure cultures before sequencing.
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Abstract
Strains belonging to the Gram-positive coryneform soil bacteria were screened genotypically by temperature-gradient gel electrophoresis (TGGE). This method allows the sequence-specific separation of amplified fragments of 16S rRNA genes. A total of 115 reference strains representing the majority of the species of the genera Aeromicrobium, Agromyces, Arthrobacter, Aureobacterium, Cellulomonas, Curtobacterium, Nocardioides and Terrabacter were characterized. Depending on the genus investigated, the resolution limit of the technique appeared to be at the species or genus level or intermediate between the two. Aberrant TGGE profiles of strains within particular taxa revealed genomic heterogeneity and generic misclassification of nine strains studied. Beyond that, indications of 16S rRNA gene heterogeneity were found within the genomes of three Curtobacterium strains. The misclassifications revealed by TGGE were confirmed using whole-cell fatty acid methyl ester analysis and subsequent comparison with a database. TGGE has been demonstrated to be a useful tool in bacterial taxonomy.