PHYLOGENETIC IDENTIFICATION OF THE SYMBIOTIC HYPERMASTIGOTE TRICHONYMPHA-AGILIS IN THE HINDGUT OF THE TERMITE RETICULITERMES-SPERATUS BASEDON SMALL-SUBUNIT RIBOSOMAL-RNA SEQUENCE

The phylogeny of a symbiotic hypermastigote Trichonympha agilis (class Parabasalia; order Hypermastigida) in the hindgut of the lower termit e Reticulitermes speratus was examined by a strategy that does not rel y on cultivation. From mixed-population DNA obtained from the termite gut, small subunit (16S-like) ribosomal RNA sequences were directly am plified by the polymerase chain reaction method using primers specific for eukaryotes. Comparative sequence analysis of the clones revealed two kinds of sequences, one from the termite itself and the other from a symbiotic protist. A fluorescent-labeled oligonucleotide probe for the latter sequence was designed and used in whole-cell hybridization experiments to provide direct visual evidence that the sequence origin ated from a large hypermastigote in the termite hindgut, Trichonympha agilis. According to the phylogenetic trees constructed, the hypermast igote represented one of the deepest branches of eukaryotes. The hyper mastigote along with members of the order Trichomonadida formed a mono phyletic lineage, indicating that this hypermastigote and trichomonads shared a recent common ancestry.