FIG. 5.

(A) Growth, urease expression, and culture pH versus time. The pH values (•) and the OD₆₀₀ (○) of batch cultures of wild-type S. salivarius in BHI are shown. The urease specific activities of cultures were determined every 30 min beginning at 4 h and 30 min postinoculation. The specific activities are expressed as nanomoles of urea hydrolyzed per minute per milligram of protein. The time at which ⁶³Ni²⁺ was added to the cultures in the nickel accumulation time course study is indicated by a vertical arrow. (B) Nickel accumulation in late-exponential phase S. salivarius. Values are the means and standard deviations of four independent samples.