FIG. 3.

¹H NMR spectra of end products formed from the metabolism of [1-¹³C]galactose (20 mM) by cell suspensions of NZ9000ΔgalPMK and derivatives carrying different lac operon constructs (pLacFE, pLacABCD, pLacABCDFE) or pMG820 at an initial pH of 6.5 and under anaerobic conditions. Cell suspensions were prepared as described in Materials and Methods. Expression of the lac genes under the control of P_nisA was induced by the addition of 1 μg liter⁻¹ nisin. ¹H NMR spectra were acquired after a 10-fold dilution in ²H₂O in a Bruker AMX300 spectrometer with a 5-mm inverse detection probe head and processed with 0.1-Hz line broadening. Isotopomers of lactate, acetate, and ethanol are indicated. The end-product profile of NZ9000(pLacABCDFEG) was identical to that of NZ9000(pLacABCDFE) and was omitted for the sake of simplicity. pLacFE, PTS^Lac; pLacABCD, Tag6P pathway; pLacABCDFE, PTS^Lac and Tag6P pathway.