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Site author Richard Steane
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Bacterial reproduction

Bacteria usually reproduce by a simple form of asexual reproduction called binary fission (splitting into two). This is different from the normal process of cell division in higher plants and animals which starts with mitosis. Bacteria do not have the same sort of chromosomes as these organisms so it is not necessary to have the mechanisms (mitosis) to separate them into groups. However they do contain the genetic material DNA and this must be copied before the bacterial cell divides.

bacterialdivision.gif


It is often said that bacteria can divide every 20 or 30 minutes.

Generation   Number of bacteria
1                  1
2                  2
3                  4
4                  8
5                  16
6                  32
7                  64
8                  128
9                  256
10                 512
11                 1024
12                 2048
13                 4096
14                 8192
15                 16384
16                 32768
17                 65536
18                 131072
19                 262144
20                 524288
21                 1048576
22                 2097152
23                 4194304
24                 8388608
25                 16777216
26                 33554432
27                 67108864
28                 134217728
29                 268435456
30                 536870912
31                 1073741824
32                 2147483648
33                 4294967296
34                 8589934592
35                 17179869184
36                 34359738368
37                 68719476736
38                 137438953472
39                 274877906944
40                 549755813888
41                 1099511627776
42                 2199023255552
43                 4398046511104
44                 8796093022208
45                 17592186044416
46                 35184372088832
47                 70368744177664
48                 140737488355328
49                 281474976710656
50                 562949953421312
51                 1.13 x 1015
52                 2.25 x 1015
53                 4.50 x 1015
54                 9.01 x 1015
55                 1.80 x 1016
56                 3.60 x 1016
57                 7.21 x 1016
58                 1.44 x 1017
59                 2.88 x 1017
60                 5.76 x 1017
61                 1.15 x 1018
62                 2.31 x 1018
63                 4.61 x 1018
64                 9.22 x 1018
65                 1.84 x 1019
66                 3.69 x 1019
67                 7.38 x 1019
68                 1.48 x 1020
69                 2.95 x 1020
70                 5.90 x 1020
71                 1.18 x 1021
72                 2.36 x 1021


Use the information above to work out how many bacteria there might be in 24 hours
- if they reproduced every 20 minutes
> (72 generations) - 2.36 x 1021
- if they reproduced every 30 minutes
> (48 generations) - 140737488355328 [1.4 x 1014 ]

What assumptions are these numbers based upon?
> Bacteria are provided with ideal temperature, enough "food", oxygen, and wastes do not accumulate.

Even though this reproduction results from asexual reproduction, there is still sometimes some variation in a very large population: about 1 in a million may by chance have a difference in their DNA which results in the bacterial cell holding it being different in some way.

What is this process of change called?
> mutation
In a population of 1014 bacteria, (about) how many would be affected?
> 108 (100 million)



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