SEQUENCE VARIATION IN THE RIBOSOMAL INTERNAL TRANSCRIBED SPACERS, INCLUDING THE 5.8S RDNA, OF NAEGLERIA SPP

The ribosomal internal transcribed spacer (ITS), including the 5.8S rD NA, from the majority of the 11 described species of the amoeboflagell ate Naegleria and from Willaertia magna have a size between 300 and 45 0 bp, In N. jadini and N. minor these products are approximately 750 b p long. The products from strains of the pathogenic N. fowleri vary be tween 323 and 423 bp, These length variations in N. fowleri are due to insertions of short repeats in the ITS1, causing the elongation of on e stem-loop in the putative secondary structure. In all other species the sizes were identical from strains of the same species. In N. jadin i and N. minor there are long inserts in the ITS2. Naegleria italica, N. clarki and N. galeacystis have shorter inserts in the ITS2, These i nserts cause the elongation of one stem-loop in the putative secondary structure proposed for the ITS2. Because of the small differences in sequence between N. fowleri and N. lovaniensis the ITS does not provid e target sequences for specifically identifying the pathogenic N. fowl eri, However, differences in ITS1 do allow to distinguish different N. fowleri isolates. The ITS and 5.8S rDNA sequences will be of addition al help in describing new Naegleria spp., which becomes more based on molecular data because morphological differences are scarce in these o rganisms.