Analysis of restriction fragment length polymorphisms in the ribosomal DNAof a selection of anaerobic chytrids

Anaerobic chytrid strains (representing four genera and seven species based on morphological characters), obtained from a variety of hosts, were analy sed for variability within the 5' terminal segment of the ribosomal large s ubunit (LSU) gene, first internal transcribed spacer (ITS1), and the interg enic spacers (IGS) of the ribosomal repeat unit. In the analyses of the rib osomal LSU gene, strains of Neocallimastix, Orpinomyces, and Anaeromyces cl ustered into distinct groups, but Piromyces strains did not. Although the s ize of polymerase chain reaction products for the ITS1 region varied among strains, restriction fragment length polymorphism analysis was not useful i n distinguishing between the strains. In the analyses of restriction fragme nt profiles of the IGS, strains of Orpinomyces and Anaeromyces clustered in to distinct groupings that corresponded with morphological characters. In c ontrast, Neocallimastix strains clustered into two distinct groups. Conside rable variability was observed in the IGS for strains of Piromyces. Analysi s of this region split strains of Piromyces rhinzinflata obtained from a si ngle bison into at least two distinct genetic groupings. Furthermore, the P iromyces strains obtained from bovine, wapiti, and moose clustered accordin g to host. Overall, our molecular data suggest that morphological character s as observed under the light microscope are insufficient for the designati on of phylogenetic species of Neocallimastix and Piromyces, and that integr ation of molecular and morphological data will be required to establish a n atural classification system for the anaerobic members of the Chytridiomyco ta.