From Bioinformatic Modeling to Clinical Observation: Potential Implications of Ribosomal RNA Folding in Blastocystis sp. Isolates from Symptomatic and Asymptomatic Carriers.

Here, 18S-rDNA sequences of Blastocystis sp., previously documented from symptomatic (cases) and asymptomatic (controls) carriers, were analyzed to determine their population structure, predict their secondary structure, and examine their interactions with ribosomal proteins (Bud23, RPS5, and RPS18). Phylogenetic and population differentiation analyses were performed using STRUCTURE software V2.3.4. Moreover, an analysis of the rRNA secondary structure and folding of each sequence was performed, and their probability of interaction with ribosomal proteins was determined. Phylogenetic and haplotype analyses sorted the sequences into genetic subtypes ST1, ST2, and ST3, while the population structure showed each cluster as a differentiated subpopulation, suggesting incipient speciation or cryptic species differentiation. Furthermore, the analysis of the secondary structure of rRNA exhibited specific arrangements for each subtype. In addition, the probability of interaction between 18S-rRNA sequences of Blastocystis from cases and controls with RPS5 and RPS18 was significant, matching the biological plausibility of the previously documented finding that control isolates had a lower generation time than isolates obtained from cases. These findings reinforce the hypothesis that ribosomal subtypes ST1-ST3 of Blastocystis represent evolutionarily distinct lineages with the potential to be recognized as future species. Furthermore, they underscore the functional relevance of 18S-rRNA sequences from clinical isolates of Blastocystis.