Table 1.

Roll tube enumeration results for the nitrate-reducing, Fe(III)-reducing, and Fe cycling cultures

Culture systemElectron donor, acceptorCell density (cells ml−1)a
1 (nitrate reducing)Acetate, nitrate3.4 × 107
Acetate, Fe(III)6.0 × 105
Fe(II), nitrate2.1 × 107
Fe(II)/acetate, nitrate1.5 × 108
2 [Fe(III) reducing]Acetate, nitrateNDb
Acetate, Fe(III)1.0 × 106
Fe(II), nitrate5.2 × 102
Fe(II)/acetate, nitrate4.0 × 102
3 (Fe cycling)Acetate, nitrate5.3 × 106
Acetate, Fe(III)1.5 × 107
Fe(II), nitrate7.2 × 106
Fe(II)/acetate, nitrate6.3 × 106
  • a All cultures were incubated for 2 months prior to colony enumeration. Results are means for duplicate tubes; the ranges for duplicates were <5% of the means.

  • b ND, not determined.