FIG. 4.

Unrooted phylogenetic tree showing affiliations based on partial bacterial 16S rRNA sequences and selected sequences from members of different bacterial clusters, including the γ and β subclasses of the Proteobacteria, the Cytophaga-Flavobacterium-Bacteriodes group (CF), the newly described Holophaga-Geothrix-Acidobacterium phylum (HGA), and the green nonsulfur bacteria (GNSB). The tree was simplified for clarity by omitting all sequences between clusters. The numbers in parentheses indicate the references in which the clustered sequences were described. The scale bar indicates 10% estimated sequence divergence.