TABLE 2.

Methionine quantifications.

	WTmet Biosensor		HPLC assay
Sample	Cell density	L-met (mM)	L-met (mM)
Controls
Medium	ND	ND	ND
SK11	ND	ND	ND
L-met 0.06 mM	0.300 ± 0.020	0.043 ± 0.005	0.068 ± 0.001
WT PrtP +	ND	ND	ND
Supernatants
WW4	0.297 ± 0.006	0.041 ± 0.005	0.052 ± 0.001
IPLA838	ND	ND	0.003 ± 0.001
NCDO176	0.173 ± 0.022	0.014 ± 0.001	0.014 ± 0.002
codY PrtP +	0.110 ± 0.001	0.008 ± 0.001	0.004 ± 0.002
rel PrtP +	0.140 ± 0.036	0.011 ± 0.001	0.009 ± 0.001

Values indicate concentration (μM). After the strains were grown in CDMcasein-met medium, the concentrations of methionine in the culture supernatants were measured using a HPLC assay coupled with fluorescence detection and with the WTmet biosensor. Strains with positive (WW4, IPLA838, NCDO176) and negative (SK11) methionine secretion capacity are shown. In addition, two elution samples of the NCDO176 (E1 and E2) were also quantified. Positive (standard methionine solution containing L-met 0.06 mM) and negative (CDMcasein-met) controls are shown. Quantification below the detection limit of the HPLC assay (<0.001 mM) and WTmet biosensor (<0.004 mM) are indicated as ND. Quantifications were performed in duplicates, and average values are shown. Error is shown as SD.