RESUMO
Linguistic similarities and dissimilarities between 5 S rRNA sequences allowed taxonomical separation of species and classes. Comparisons with the molecule from mammals distinguished fungi and plants from protists and animals. Similarities to mammalians progressively increased from protists to invertebrates and to somatic-type molecules of the vertebrates lineage. In this, deviations were detected in avian, oocyte type, and pseudogene sequences. Among bacteria, actinobacteria were most similar to the mammalians, which could be related to the high frequency of associations among members of these groups. Some archaebacterial species most similar to the mammalians belonged to the Thermoproteales and Halobacteria groups. Comparisons with the soybean mitochondrial molecule revealed high internal homogeneity among plant mitochondria. The eubacterial groups most similar to it were Thermus and Rhodobacteria gamma-1 and alpha-2. Other procedures have already indicated similarities of Rhodobacteria alpha to mitochondria but the linguistic similarities were on the average higher with the first two groups.