Small subunit ribosomal RNA evolution in the genus Acanthamoeba.

Reverse transcription of small subunit ribosomal RNA (srRNA) was used to determine the partial nucleotide sequences of the srRNA of seven isolates of Acanthamoeba. These seven sequences and the sequence of the corresponding region in an A. castellanii previously totally sequenced were compared in order to investigate evolution of the srRNA gene in Acanthamoeba. The results of the comparisons were consistent with the hypotheses that the genus is monophyletic, that the Pussard and Pons grouping system is valid, that the Acanthamoeba expansion segments in the srRNA gene evolve at a much faster rate than the rest of the gene, and that the extent of nucleotide sequence divergence in the genus Acanthamoeba is roughly similar to that differentiating vertebrates and invertebrates.