The graph below shows a growth curve of E. coli growing in a defined medium containing equalconcentration of glucose and lactose. On the y-axis optical density provides a measure of cellnumber, higher optical density indicates greater cell number.OD (optical density)TimeBased on your knowledge regarding regulation of the lac operon, the best explanation of theseresults is that...A. The bacteria are utilizing both sugars simultaneously.B. At early time points, inhibition of the lac repressor allows for lactose metabolism.C.Cells constitutively express enzymes needed for sugar metabolism, allowing forcontinuous cell growth.D.Glucose activates CAP, allowing for cell growth at intermediate time points.E. At later time points, high cAMP allows for an increase in beta-galactosidase expression.

In the presence of both glucose and lactose, bacteria exhibit a complex growth pattern characterized by distinct phases. The initial lag phase is followed by a period of exponential growth, transitioning into stationary and death phases. Understanding the regulation of the lac operon, which controls the metabolism of lactose, sheds light on these growth dynamics. As glucose levels decline, the lac operon becomes induced, allowing bacteria to efficiently utilize lactose. This interplay between carbon sources and gene regulation governs bacterial growth and adaptation to their environment.Based on the regulation of the lac operon, the answer for these results is that B. At early time points, inhibition of the lac repressor allows for lactose metabolism.The lag phase is the initial period of slow growth, during which the bacteria are adapting to the new environment and synthesizing the enzymes necessary for growth. In this case, the bacteria are adapting to the presence of both glucose and lactose.The exponential phase is the period of rapid growth, during which the bacteria are utilizing both sugars simultaneously. This is because the lac operon is not yet fully induced, so the bacteria are able to metabolize both glucose and lactose.The stationary phase is the period of slow growth, during which the bacteria are reaching their carrying capacity. In this case, the carrying capacity is limited by the amount of available sugar.The death phase is the period of decline in cell number, during which the bacteria are dying due to nutrient depletion or other factors.The best explanation for the observed growth curve is that the bacteria are initially utilizing both glucose and lactose. However, as the glucose concentration decreases, the bacteria are able to induce the lac operon and metabolize lactose more efficiently. This leads to a period of rapid growth, followed by a period of slow growth as the lactose concentration also decreases.The bacteria are able to metabolize both glucose and lactose. However, as the glucose concentration decreases, the bacteria are able to induce the lac operon and metabolize lactose more efficiently. This leads to a period of rapid growth, followed by a period of slow growth as the lactose concentration also decreases.answer: B. At early time points, inhibition of the lac repressor allows for lactose metabolism.