Ben-Gurion University of the Negev
Faculty of Engineering Sciences
Department of Biotechnology Engineering
369-1-3041
General Microbiology for Biotechnology
Dr. Ariel Kushmaro, Ph.D., Lecturer
Bacterial growth curve experiment
1.
growth curve experiment
Go to: http://www-micro.msb.le.ac.uk/LabWork/bact/bact1.htm
2.
Growth curve exercise
How many viable bacteria were there in your sample?
Time (minutes)
Dilution Factor
Plate Counts
(CFU)
Average Plate
Count (CFU)
0
15
30
45
60
90
120
150
210
270
330
390
420
450
10^4
10^4
10^4
10^4
10^5
10^5
10^5
10^6
10^6
10^6
10^6
10^5
10^5
10^5
199,205,214
196,215,201
198,207,213
272,254,263
42,38,46
80,84,79
173,168,184
42,33,36
49,55,52
55,49,58
59,55,48
263,253,255
180,176,184
57,66,63
206
204
206
263
42
81
175
37
52
54
54
257
180
62
Number of living
cells in the
culture
2060000
2040000
2060000
2630000
4200000
8100000
17500000
37000000
52000000
54000000
54000000
25700000
18000000
6200000
a.
Now, graph the results of the experiment, put time (in minutes) on the x-axis and
numbers of living bacteria on the y-axis (log).
b.
Calculate a growth rate and generation time using this formula:
k= [log (xt) - log (x0)] / 0.301 * t
k= the number of population doublings in one hour (called the growth rate constant)
x0= the number of cells/milliliter at the beginning of the log phase
xt= the number of cells/ml at some later time
t= the number of hours between the beginning and the later time
1/k= the Generation Time (the amount of time it takes for a population to double in number)
Answers
Log CFU
Growth curve experiment
10
8
10
7
10
6
0
15
30
45
60
90 120 150 210 270 330 390 420 450
Time (minutes)
Growth rate:
k= [log (xt) - log (x0)] / 0.301 * t
k= 7.568-6.08/0.301*1=2.19
1/k=27min.