C16S — A Hidden Markov Model based algorithm for taxonomic classification of 16S rRNA gene sequences

Recent advances in high throughput sequencing technologies and concurrent refinements in 16S rDNA isolation techniques have facilitated the rapid extraction and sequencing of 16S rDNA content of microbial communities. The taxonomic affiliation of these 16S rDNA fragments is subsequently obtained using either BLAST-based or word frequency based approaches. However, the classification accuracy of such methods is observed to be limited in typical metagenomic scenarios, wherein a majority of organisms are hitherto unknown. In this study, we present a 16S rDNA classification algorithm, called C16S, that uses genus-specific Hidden Markov Models for taxonomic classification of 16S rDNA sequences. Results obtained using C16S have been compared with the widely used RDP classifier. The performance of C16S algorithm was observed to be consistently higher than the RDP classifier. In some scenarios, this increase in accuracy is as high as 34%. A web-server for the C16S algorithm is available at http://metagenomics.atc.tcs.com/C16S/.

► First HMM based algorithm for ‘taxonomic classification’ of 16S rRNA gene sequences.
► Results obtained using simulated data sets indicate high classification efficiency.
► C16S accurately classifies 16S rDNA fragments originating from known/unknown microbes.
► C16S algorithm is suitable for obtaining accurate estimates of microbial diversity.