PHYLOGENETIC ANALYSIS OF FRESHWATER DIATOMS FROM SILICA RICH SITES OF ASSAM, INDIA

Abstract

Diatoms constitute an important group of eukaryotic phytoplankton possessing genetic ability to mineralize amorphous silica into complex structures. Phylogenetic analysis was performed using dnadist module of PHYLIP package, and neighbor-joining method was employed to generate the phylogenetic relationship among the sequences. In order to investigate the phylogenetic relationships among the diatoms at higher taxonomic levels, nucleotide sequence of the nuclear-encoded SSU rRNA coding regions from 21 different diatoms were compared to homologous coding regions from other heterokonts. To provide more accuracy and information to the identification and phylogenetic placement of the analyzed sequences, the highly similar closest matches were used in phylogenetic analysis. In the present investigation, the phylogenetic analysis revealed that the 21 different diatoms of the four study sites could be clustered into six major clades on the basis of their 18S rDNA sequence homology. This finding could further be used for phylogenetic placement of more diatom flora and for proper selection of diatoms to be exploited in nanotechnology.