16S rRNA gene sequence analyses of the metagenome derived from waters of river Mahananda at Siliguri: An approach to understand bacterial diversity

Abstract

Bacterial community of the sub-Himalayan river Mahananda at Siliguri, India was characterized by amplification and sequencing of 16S rRNA genes. Analysis of almost complete 115 sequences revealed a total of 43 operational taxonomic units (OTUs). Statistical analysis revealed that coverage of the clone library was 81.73%. All sequences had >85% similarity to 16S rRNA gene sequences retrieved from the DNA databases. The sequences largely constituted of the class <i style="mso-bidi-font-style:normal">Proteobacteria </i>(10.43% Alpha subdivision, 50.43% Beta subdivision, 9.56% Gamma subdivision & 14.7% Epsilon subdivision), phylum <i style="mso-bidi-font-style:normal">Bacteroidetes</i> (8.69%) and <i style="mso-bidi-font-style:normal">Firmicutes</i> (5.21%), besides single representative belonging to the candidate division OP 11 (0.86%). 31.3% of the total clones showed high similarity to uncultured bacteria, suggesting the usefulness of this technique in uncovering microbial diversity in river water. Abundance of Comamonads (61.76%) among <i style="mso-bidi-font-style:normal">Betaproteobacteria</i> indicated transition to eutrophic state, confirming borderline healthy state of Mahananda River at Siliguri. The most dominant genus of this clone library was <i style="mso-bidi-font-style:normal">Arcobacter</i>, whose presence in environmental waters being associated with fecal pollution has been confirmed.