Diauxic growth
Diauxic growth, diauxie or diphasic growth is any cell growth characterized by cellular growth in two phases. Diauxic growth, meaning double growth, is caused by the presence of two sugars on a culture growth media, one of which is easier for the target bacterium to metabolize. The preferred sugar is consumed first, which leads to rapid growth, followed by a lag phase. During the lag phase the cellular machinery used to metabolize the second sugar is activated and subsequently the second sugar is metabolized. This can also occur when the bacterium in a closed batch culture consumes most of its nutrients and is entering the stationary phase when new nutrients are suddenly added to the growth media. The bacterium enters a lag phase where it tries to ingest the food. Once the food starts being utilized, it enters a new log phase showing a second peak on the growth curve. Growth phases Jacques Monod discovered diauxic growth in 1941 during his experiments with Escherichia coli and Bacillus subtilis. While growing these bacteria on various combination of sugars during his doctoral thesis research, Monod observed that often two distinct growth phases are clearly visible in batch culture, as seen in Figure