Question

In some circumstances, when two different carbon sources are available, growth will occur first using one carbon source, then after a short lag period, growth will resume using the second carbon growth source.

a. This process is called _____ growth.

Answer 1

Diauxic growth is when a cell uses one carbon source and then switches to another after the first is depleted. In the given E. coli growth curve example, glucose is used first, leading to rapid growth, followed by a lag phase and then slower growth on xylose once glucose is exhausted.

Step-by-step explanation:

The process described in the student's question, where a cell uses one carbon source for growth and then switches to another after the first is depleted, is known as diauxic growth. Tackling Monod's research, we can clarify what is occurring at different points (A-D) in the growth curve. At point A, the E. coli is primarily using glucose as its carbon source for growth, causing a rapid increase in population. The xylose-use operon is not being expressed at this point because the presence of glucose typically represses the expression of enzymes for the metabolism of other sugars.

After glucose is exhausted, demonstrated by a leveling off of the growth curve at point B, the cells enter a short lag phase as they begin to express the necessary enzymes for the uptake and metabolism of xylose. At point C, we observe the resumption of growth as the bacteria start to use xylose. As these enzymes are less efficient or the substrates are utilized less favorably, the second phase of growth is slower compared to the first phase. Finally, at point D, the growth rate declines again as the bacterial population exhausts the xylose.

Answer 2

Answer: Diauxic growth

Step-by-step explanation:

The diauxic growth or diphasic growth is a bacterial growth which is characterized by the growth in two phases depending upon the source of carbon used.

The preferred carbon source is consumed first, this leads to enhance the growth in the bacteria, followed by the lag phase. During the process of lag phase the bacteria start to metabolize the second carbon source and the growth resumes.

For example, a colony of E.coli bacteria was cultured in a medium containing the glucose, and lactose sugars. At the initial level the bacteria was capable of using the glucose sugar and growth became rapid this is followed by a lag phase. In the lag phase the bacteria started to utilize the lactose sugar and again the growth resumes.