Carbon dioxide production (mmol liter medium−1) by G. oxydans strains during growth with glucose (275 mM; 50 g liter−1). Cultivation was carried out in duplicate in bioreactors (Dasgip, Jülich, Germany) under pH and aeration control. a and a′, G. oxydans N44-1 pBBR1MCS4; b and b′, G. oxydans N44-1 mgdH::kan pBBR1MCS4; c and c′, G. oxydans N44-1 ΔmgdH sgdH::kan pBBR1MCS4 cultivated with either 15% dissolved oxygen (c) or 30% dissolved oxygen (c′).