FIG. 4.

Growth of p-aminobenzoate auxotrophs (BN1103) transformed with various plasmids encoding genes of the abg region in liquid medium containing various concentrations of p-aminobenzoyl-glutamate. (A) Comparison of the growth of BN1103 transformed with pACYC184, pLJA, pLJB, pLJAB, pUC18, pJG128, and pLJAB/pJG128 in minimal medium containing various concentrations of p-aminobenzoyl-glutamate at 48 h after inoculation. BN1103 (pabA) cells transformed with pACYC184, pLJA, pLJB, pLJAB, pUC18, pJG128, and pLJAB/pJG128 were grown overnight in minimal medium containing the appropriate antibiotics for plasmid selection and 100 nM p-aminobenzoate, washed three times with sterile saline, and diluted 10⁵ into 5 ml of minimal medium containing antibiotic and increasing concentrations of p-aminobenzoyl-glutamate. Cultures were incubated at 37°C; the optical density (OD) (λ = 600 nm) of a 1-ml sample was measured every 24 h. The loss in volume due to evaporation was about 2.5% per day (∼8% loss after 72 h). Results are given as means ± standard errors. (B) Readings of the data from panel A at 72 h.