Phylogenetic diversity of parabasalian symbionts from termites, including the phylogenetic position of Pseudotrypanosoma and Trichonympha

The phylogenetic diversity of parabasalian flagellates from termite hindgut s has been examined by small subunit ribosomal RNA (rRNA) amplification and sequencing. Two species of particular interest, the giant trichomonad Pseu dotrypanosoma giganteum and the hypermastigote Trichonympha magna, were iso lated from the gut of Porotermes adamsoni by micropipetting, and the rRNA g enes from these small populations amplified and sequenced. rRNA genes repre senting Hypermastigida and the Trichomonadida families Devescovinidae and T richomonadidae, were also recovered by amplification from whole hindguts of three termites, P. adamsoni, Cryptotermes brevis, and Cryptotermes dudleyi . The parabasalian rRNA genes from C. brevis were found to comprise a uniqu e and extremely heterogeneous lineage with no clear affinities to any known parabasalian rRNAs. In addition, one of the sequences isolated from P. ada msoni was found to be similar to another uncharacterised rRNA gene from Ret iculitermes flavipes. The phylogeny of all known parabasalian small subunit rRNAs was examined with these new sequences. We find many taxonomic groups to be supported by rRNA, but not all. We have found the root of parabasali a to be very difficult to discern accurately, but have nevertheless identif ied several possible positions.