Hampl V., Čepička I., Tachezy J. & Flegr J. (2002) Phylogenetic position and relationship of flagellates of the genus Monocercomonas from different host species. Abstrakt, J.Eukaryotic Microbiology, 49, 8A.

ISSN 1066-5234,

IF 1,739

ABSTRACT. The genus Monocercomonas Grassi, 1879 (order Trichomonadida) comprises more than 20 species mostly parasitic in reptiles but also in other vertebrates and in insects. Important morphological feature of this genus is the absence of costa and undulating membrane, characteristic structures of a typical trichomonad cell. Family Monocercomonadidae Kirby, 1944, established for trichomonads with similarly reduced cell morphology, comprises besides parasitic also free-living genera (Pseudotrichomonas, Ditrichomonas, Monotrichomonas). This family was regarded to be the most primitive group of trichomonads from the evolutionary point of view. However, results of sequencing of 16S rRNA of some species suggested that they probably represent higher branches in the trichomonad tree. Moreover, they indicate that the free-living genera are unrelated to the genus Monocercomonas. Here we sequenced the gene for 16S rRNA of two isolates of Monocercomonas ruminantium from cattle and eight isolates of Monocercomonas sp. from different reptile species. Strains from reptiles formed one clade with the bootstrap value 100 in the phylogenetic tree of trichomonads. On the other hand sequences of the two isolates of Monocercomonas ruminantium were placed with 100% bootstrap support among the free-living genera of trichomonads, i.e. into a branch of species unrelated to other representatives of the genus Monocercomonas. The sequences of these isolates differed only in one nucleotide and were closely related (97.1 %) to the sequence of Pseudotrichomonas keilini. Our results strongly suggest that taxonomic classification of Monocercomonas ruminantium should be revised. Furthermore, close relationship of this parasitic species with free-living trichomonads pose interesting questions regarding the evolution of parasitism in this group.