FIG. 2.

Phylogenetic relationships of archaeal 16S rRNA sequences as determined by maximum-likelihood analysis. Aquifex pyrophilus was used as the outgroup. The numbers at the nodes are the bootstrap values (as percentages). The bootstrap values were less than 50% for the branch points marked with small black circles and no numerical value. Sequences from Snake Pit are marked in bold type, and the remaining sequences were obtained from the RDP (32). The scale bar represents the expected number of changes per nucleotide position.