Use of 16S Ribosomal RNA Sequences to Infer Relationships among Archaebacteria.

We have increased the amount of 16S ribosomal RNA rRNA sequence data that can be gathered by dideoxynucleotide-terminated sequencing from rRNA-specific primers with reverse transcriptase. We have compiled phylogenetically useful, partial or complete sequences of the 16S rRNA from about 220 organisms and organelles. An aligned collection of published 16S rRNA sequences is available in printed form or in several electronically accessible forms. The 16S rRNA data were used to infer the relationships among the archaebacteria, and of the archaebacteria to the eubacteria and eukaryotes. Our programs for phylogentic tree inference are available for use in the VAXVMX operating system environment. We examined sources of systematic error in the inference of molecular phylogenies and concluded that lineage-to-lineage variations in the rate of accumulating mutations in the rRNA gene can lead to significant errors, which can be decreased by using models of sequence evolution that acknowledge that all sites in the molecule are not equally mutable. Keywords Microbial ecology Hydrothermal vents Hot springs Metazoa.