TABLE 3.

A prb mutant is affected in the uptake of proline betaine at low osmolarity^a

Strain	Growth with PB	PB uptake activityb (nmol/min/mg of protein) ± SD
		Exponential phase	Stationary phase
Rm1021	No	0.56 ± 0.10	0.70 ± 0.10
	Yes	0.53 ± 0.05	1.82 ± 0.12
S7	No	0.51 ± 0.05	0.69 ± 0.03
	Yes	0.39 ± 0.05	0.78 ± 0.03

^aCells were grown in MCAA medium with or without 100 μM PB and harvested at mid-log phase (A₆₀₀ of 0.4) or early stationary phase (A₆₀₀ of 1.5).

^bUptake measurements of PB were done at a final substrate concentration of 40 μM. Values are means from duplicates of three independent cultures ± standard deviations.