When E. coli is grown in medium containing both glucose and lactose,
A) the cells growth fastest after lactose is used up.
B) the cells use lactose first, then glucose.
C) the cells grow fastest initially when glucose is available.
D) the cells use the glucose and then stop growing.
E) the cells grow at the same rate until all sugars are depleted.

Question

When E. coli is grown in medium containing both glucose and lactose, 
A) the cells growth fastest after lactose is used up.
B) the cells use lactose first, then glucose.
C) the cells grow fastest initially when glucose is available.
D) the cells use the glucose and then stop growing.
E) the cells grow at the same rate until all sugars are depleted.

Quizplus · Accepted Answer

E. coli first uses glucose as it is the preferred energy source and grows fastest initially until glucose is exhausted. After glucose is used up, the cells switch to lactose utilization but with a slower growth rate. Thus, the cells grow fastest initially when glucose is available.

When E Coli Is Grown in Medium Containing Both Glucose and and Lactose