FIG. 5.

Neighbor-joining phylogenetic tree of 16S rRNA clone sequences obtained from the Fe(III)-reducing enrichments and of the closely affiliated saturated C horizon bacterial clones (BacC-s; gray shading). The A (pink), B (red), unsaturated C (C-u) (green), and saturated C (C-s) (blue) horizons were enriched with ferrihydrite as the electron acceptor and lactate (Lac), acetate (Ac), or ethanol (Et) as the electron donor. The tree is based on 1,060 masked nucleotide positions and Geothrix fermentans is the outgroup. Bootstrap values (n = 1,000) of greater than 50% are indicated at nodes.