Files in this Data Supplement:

• Supplemental file 1 - Photo of groundwater seep site (Fig. S1); pH, Fe(II), and Fe(III) content of groundwater seep over time (Fig. S2); X-ray diffraction spectrum for native and microbially reduced seep materials (Fig. S3); growth and metabolism of dissimilatory Fe(III)-reducing bacterial isolates (Fig. S4); diagram of microbial Fe redox cycling model (Fig. S5); composition of 16S rRNA gene clone libraries from Fe(III)-reducing enrichment cultures (Table S1); lists of primary dependent variables (Table S2), process and rate equations (Table S3), mass conservation equations (Table S4), and parameter values (Table S5) in the microbial Fe redox cycling model.
  PDF file, 109K.