FIG. 7.

Phylogenetic tree reflecting the relationship of sulfate-reducing bacteria within the saturated C horizon (C-s) based on an ∼500-bp region of dsrAB gene fragment. The tree was constructed by neighbor joining based on Jukes-Cantor-corrected DNA distances. Bootstrap values (n = 1,000) of greater than 50% are indicated at nodes. Tree topologies and clade designations were stable and consistently recovered by analysis of the DSR α subunit, β subunit, or partial α and β subunit genes. Thermodesulfovibrio islandicus of the Nitrospira phylum is the outgroup.