A New Ciliate Species, Tetrahymena farahensis, Isolated from the Industrial Wastewater and Its Phylogenetic Relationship with Other Members of the Genus Tetrahymena

Anthropogenic activities are dumping heavy metals into the environment as waste effluents or integral part of some compounds. This has resulted in an increase in the metal concentration, beyond the permissible threshold, leading to metal toxicity for all forms of life. Metal resistant ciliates remove metal ions from contaminated water, mainly by the process of bioaccumulation. This bioaccumulation is due to low molecular weight, metal ions chelating proteins known as metallothioneins. In the present study, a new species of Tetrahymena (Tetrahymena1.7) is being reported from the local industrial wastewater. Analysis of Tetrahymena 1.7 SS rDNA showed 99% homology to seven different species of the genus Tetrahymena. SS rRNA secondary structure appeared in 40 helices with 18 variations, including 17 substitutions and one deletion. All the variations are present in 6 variable lengths, namely, V2, V3, V4, V7, V8 and V9. Cytochrome c oxidase subunit 1 (COX1) gene sequence was quite variable, with 91% homology to its closest relative T. thermophila. Since this value was higher than the intraspecific variations (≥99% homology), Tetrahyemna1.7 has been considered as a new species i.e., Tetrahymena farahensis. Phylogenetic analysis based on both SS rDNA and COX1 using maximum likelihood and neighbor joining methods showed that Tetrahymena farahensis, new species was related to T. thermophila and T. malaccensis. Thus, it appeared to be a new member of riboset A1 and coxiset A1 on the basis of SS rRNA and COX1 gene, respectively.