Study on Analysis of Several Molecular Identification Methods for Ciliates of Colpodea (Protista, Ciliophora)

Abstract

The application of molecular techniques to accurately identify protozoan species can correct previous misidentifications based on traditional morphological identification. Colpodea ciliates have many toxicological and cytological applications, but their subtle morphological differences and small body size hinder species delineation. Herein, we used Cox I and β-tubulin genes, alongside fluorescence in situ hybridization (FISH), to evaluate each method in delineating Colpodea species. For this analysis, Colpoda harbinensis n. sp., C. reniformis, two populations of C. inflata, Colpoda compare grandis, and five populations of Paracolpoda steinii, from the soil in northeastern China, were used. We determined that (1) the Cox I gene was more suitable than the β-tubulin gene as a molecular marker for defining intra- and interspecific level relationships of Colpoda. (2) FISH probes designed for Colpoda sp., C. inflata, Colpoda compare grandis, and Paracolpoda steinii, provided rapid interspecific differentiation of Colpodea species. (3) Colpoda harbinensis n. sp. was established and mainly characterized by its size in vivo (approximately 80 × 60 μ m ), a reniform body in outline, one macronucleus, its spherical shape, a sometimes nonexistent micronucleus, 11–15 somatic kineties, and five or six postoral kineties. In conclusion, combining oligonucleotide probes, DNA barcoding, and morphology for the first time, we have greatly improved the delineation of Colpodea and confirmed that Cox I gene was a promising DNA barcoding marker for species of Colpodea, and FISH could provide useful morphological information as complementing traditional techniques such as silver carbonate.

Internal Transcribed Spacers as Phylogenetic Markers Enable Species-level Metataxonomic Analysis of Ciliated Protozoa

“…However, ciliates have relatively simple morphological features, and these features often provide limited taxonomic resolution at the species level. Moreover, some ciliates cannot be cultured in the laboratory [9], and it requires experience and expertise to distinguish some of the minute diagnostic features [10]. To circumvent these limitations, researchers have used sequencing and analyzing of the small subunit ribosomal RNA (18S rRNA) gene for identification, classification, and community profiling of ciliates [11][12][13].…”