Figure 5. GABA export in the E. coli yhiM mutant and overexpressing strains.

(A) The E. coli strains MC4100 (white) and its knockout mutants MC4100yhiM (blue) and MC4100gadC (red) were grown in minimal medium EG, pH 5.0, supplemented with 10 mM sodium glutamate. At the indicated time intervals 1-ml aliquots were collected, the OD₆₀₀ was measured and GABA in the spent medium quantified. The values are means ± standard deviation of at least 3 independent cultures. Inset: the growth profiles (OD₆₀₀) of MC4100 (black), MC4100yhiM (blue) and MC4100gadC (red) are reported. (B) Cells from IPTG-induced cultures of the E. coli strains JM109/pREP4/pQE60 (white) and JM109/pREP4/pQEyhiM-6×His (blue) were incubated at 37 °C for 90 min in EG medium, at the indicated pH, supplemented with 1 mM sodium glutamate. The GABA exported was assayed as previously described [37]. The values are means ± standard deviation of 3 independent experiments (in duplicate) with p-value of 0.0005 (***).