The behaviour of NAD+ and NADH in Acinetobacter calcoaceticus during n-alkane assimilation

The behaviour of the nicotinamide adenine dinucleotides NAD+ and NADH in Acinetobacter calcoaceticus during n-alkane assimilation was studied, acetate and succinate being used as reference carbon sources. The intracellular concentration of the two nucleotides was found to increase during the exponential growth phase, reaching its maximum in the phase of decreasing growth rates. In the exponential phase, the NAD+/NADH quotients were less than 1 and showed only unimportant variations. In the phase of decreasing growth rates, the concentration of NADH showed a distinct decrease, reaching its minimum in the stationary phase. Parallel to this, the concentration of NAD+ showed a continuous increase until the stationary phase was reached. This resulted in an increase, during the phase of decreasing growth rates, of the NAD+/NADH quotients to values greater than 1, similarly as recorded in the stationary phase. There were no fundamental differences in this behaviour between the individual carbon sources.