FIG. 6.

Accumulation kinetics of 4-HBA in the supernatant of P. putida derivatives DOT-T1E-24 (circles) and DOT-T1E-1-10a (triangles). Early-stationary-phase cells from glucose-supplemented M9 minimal medium cultures (15 ml) were centrifuged at 5,000 × g for 10 min, washed in M9 buffer, and suspended in 30 ml of fresh medium with toluene supplied in the gas phase. 4-HBA accumulation was determined as described in the legend to Fig. 5, and cell density (solid symbols) was determined by measuring the optical density at 660 nm (OD 660 nm) (open symbols). Duplicate cultures were examined. The data are averages of two values for one typical culture, and the standard deviation was less than 5%.