RFLP analysis of PCR-amplified small subunit ribosomal DNA of three fish microsporidian species

The phylogenetic relationships of the microsporidian species Microgemma cau lleryi, Pleistophora finisterrensis and Tetramicra brevifilum were investig ated on the basis of restriction fragment length polymorphism (RFLP) analys is of PCR-amplified small-subunit rDNA (SSUrDNA). Using PCR primers specifi c for microsporidian SSUrDNA, a single product was obtained from each speci es, and heteroduplex analysis indicated a high degree of sequence homology among the 3 products. In RFLP analysis of the PCR-amplified SSUrDNA, the en zymes AluI and DdeI gave restriction patterns that differed among all 3 spe cies. Phylogenetic analysis using restriction patterns as differential char acters indicated that Microgemma caulleryi and Tetramicra brevifilum are mo re closely related to each other than to Pleistophora finisterrensis.