Group-Specific PCR Primers to Amplify 24S a-Subunit rRNA Genes from Kinetoplastida (Protozoa) Used in Denaturing Gradient Gel Electrophoresis.

We developed and tested a set of primers for amplification of a region of the 24S a-subunit rRNA genes (24S rDNA) specific to Kinetoplastida (Protozoa). The reverse primer was supplied with a GC rich region in the 5? end in order to make the PCR product suitable for analysis by denaturing gradient gel electrophoresis (DGGE). PCR product was obtained from all the kinetoplastids tested and no PCR product was obtained from any other Eukaryotes or Prokaryotes tested. It was possible to distinguish between all pure cultures of kinetoplastids by denaturing gradient gel electrophoresis in gels ranging from 20% to 60% denaturants. PCR-DGGE analysis of DNA purified from lake sediment revealed approximately 20 bands indicating high kinetoplastid diversity. Direct cloning and sequencing of 24S rDNA sequences retrieved from the lake sediment by PCR also showed high kinetoplastid diversity. Of 43 clones, 27 different sequences were found. Alignments and phylogenetic analysis showed that a majority of the sequences were most closely related to the Bodonidae. Four sequences were closer to the Trypanosomatidae, whereas three sequences fell outside both groups. The PCR-DGGE procedure developed in this study has been shown to be useful for distinguishing between different kinetoplastid species. Thus, it may be a useful tool for evaluating the genetic diversity of this group in environmental samples, e.g., as a result of perturbation. Another possible application of this method is in fast and accurate screening for the presence and identification of pathological parasitic Kinetoplastida from environmental samples and for diagnostics of human and animal infections.