Assume a starting culture is 120 cells/mL and a generation time of 30 min per ge
ID: 50756 • Letter: A
Question
Assume a starting culture is 120 cells/mL and a generation time of 30 min per generation. Describe the growth of the culture at the indicated time points. How many generations have passed at the indicated time points? The bacteria reach 10^10 cells per mL. How long will it take them to reach STATIONARY PHASE in terms of time (hr) and generations.
TIME in HOURS => CULTURE DENSITY (CELLS/mL) => GENERATIONS
0 => 1.20 * 10^2 => Generation 0
1 => ? => Generation ?
2 => ? => Generation ?
3 => ? => Generation ?
? => Stationary phase 10^10 cells/mL => Generation ?
Explanation / Answer
The generation time of bacteria is the time required for doubling their number.
Formula to calculate number of bacteria after "n" generations = Initial bacterial number *2n
Thus, the number of bacteria after 2 generations (1 hr) = 120*4 = 480 cells/ml
the number of bacteria after 4 generations (2 hr) = 120*16 = 1920 cells/ml
the number of bacteria after 6 generations (3 hr) = 120*64 = 7680 cells/ml
The number of generations reuired to produce N number of cells = 3.3 (logN - log N0)
Where, logN = final number of cells, log N = initial number of cells
= 3.3 (log 1010 - log 120) = 3.3 (10 - 2.07) = 26 (approximately).
The number of generations required to reach a count of 1010 cells/ml = 26 (or 13 hrs)
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