FIG. 3.

Hydrogen-dependent growth of wild-type and hydrogenase-deficient strains in the presence of AQDS and fumarate. Acetate-fumarate-grown cultures were washed in isotonic basal wash medium (22) prior to inoculation to eliminate carryover of acetate and fumarate. Cultures were supplied with a small amount of acetate as a carbon source (0.1 mM for AQDS curves [A and B] and 1 mM for fumarate curves [C and D]). For each panel, wild-type and mutant cultures were inoculated and incubated in parallel. Data are the mean ± standard deviation of triplicate cultures. When two transfers are shown, the time of the second transfer (5%) is indicated by a vertical arrow. Cell densities at time zero were ∼6 × 10⁶/ml for AQDS growth curves (A and B) and ∼2.5 × 10⁶/ml for fumarate growth curves (C and D). For AQDS growth curves, final cell densities at the end of first and second transfers were 4.87 × 10⁷ ± 0.5 × 10⁷ and 3.6 × 10⁷ ± 1.06 × 10⁷/ml, respectively, for the wild-type strain and 3.81 × 10⁷ ± 0.41 × 10⁷ and 2.88 × 10⁷ ± 0.25 × 10⁷/ml, respectively, for the Hya-deficient strain. O.D., optical density.