Identification of a new copper resistant protist isolate Tetrahymena RT-I subsp. nov

Ciliates are among the most divergent eukaryotic organisms and yet remained uncharacterized at the molecular level. historically,classification of phylum protozoa was done on the basis of classical morphological criteria,which proved to be labile and less effectual. in this situation,molecular methods targeting ribosomal dna,particularly small subunit ribosomal dna (ss rdna),might endow with solid basis for classification as already proved for bacteria and archaea. a new isolated ciliate,tetrahymena rt-1,was found to be copper resistant and the current study presents its physical characteristics,phylogenctic analysis and comparison with other closely related species of the genus. the alignment of the sequences was done using clustal w and homologues were selected from result of blastp search of genbank. t. tropicalis and t. mobilis were found to have 98.6% sequence similarity with tetrahymena rt-1. by sequence alignment,basepair differences with these and other closely related species were observed specially in two regions,viz.,484-756 and 1325-1672 bp. in addition to t-→a,a-→t and g-→t transversions common to other species of the genus tetrahymena,certain specific trans versions viz.,a-→c,c→a and g→c were also observed in tetrahymena rt-1. phylogenetic analysis revealed its grouping with other members of the borealis rather than australis group while ss rdna sequence homology and comparison seems insufficient for definite identification. on the basis of sequence homology,the isolate tetrahymena rt-1 is suggested to be a new subspecies of tetrahymena tropicalis and named as tetrahymena tropicalis lahorensis subsp. nov. copyright 2011 zoological society of pakistan.