THE UNUSUALLY LONG SMALL-SUBUNIT RIBOSOMAL-RNA OF PHREATAMOEBA-BALAMUTHI

The small subunit ribosomal RNA (rRNA) of the anaerobic amoeba Phreata moeba balamuthi is the longest 16S-like rRNA sequenced to date. Second ary structure analysis suggests that the additional sequence is incorp orated in canonical eukaryotic expansion regions and is not due to the presence of introns. Reverse transcriptase sequencing of total RNA ex tracts confirmed that two uncommonly long expansion regions are presen t in native P.balamuthi 16S-like rRNA. Primary sequence comparison and similar secondary structure indicate a 61 base stem and loop repeat w ithin an expansion region; a mechanism whereby the repeat may have bee n incorporated is presented. P.balamuthi provides further evidence tha t 16S-like rRNA length does not correlate with phylogenetic position.