FIG. 1.

H₂ consumption by strain 2CP-C with 2-CP as the electron acceptor and H₂ as the electron donor. (A) Two freshly inoculated cultures containing 0.2 mM acetate were fed 2-CP. After the H₂ concentration was less than 0.01 ppmv, the cultures were fed 100 ppmv of H₂. 2-CP was respiked when it was depleted, except for the 14-day period indicated by the arrows. (B) Triplicate cultures were initially fed 2 mM acetate and 2-CP. After 4 mM 2-CP had been added, all of the acetate was consumed and the H₂ threshold concentrations were less than 0.01 ppmv. The cultures were then fed 2-CP and 2,500 ppmv of H₂, and H₂ consumption was monitored again. Note the logarithmic scale of the y axis. The detection limit for H₂ was 0.01 ppmv, and the open circles indicate data that could not be quantified due to the limitations of the detection method. The data were averaged, and the variability between cultures was less than 20%. No H₂ consumption was observed in cultures that did not receive 2-CP.