Single-cell PCR on protargol-impregnated euplotid ciliates: a combined approach of morphological and molecular taxonomy

Ciliates are considered one of the most diverse protozoa and play significant roles in ecology. For successful taxonomic study of these microscopic eukaryotes, a staining procedure is necessary, due mainly to intrinsic difficulties in recognizing characteristics from living cells. Although molecular taxonomy has been used to resolve the ambiguities associated with traditional morphology-based taxonomy, extraction of genomic DNA from stained ciliate cells is not available yet. In the present study, we describe a method to extract genomic DNA from a single protargol-impregnated euplotid cell. By using $HgCl_2$ as a fixative and modulating the exposure time of bleach solution in the protargol impregnation, high-quality genomic DNA can successfully be extracted from a stained single cell with minimal loss of morphological integrity. This technique will contribute to the effectiveness of combined approaches of molecular and morphological taxonomy from single ciliate cells.