Biotechnology uses living organisms to make products people need, and bacteria are the workhorses. They multiply astonishingly quickly and can build complex molecules such as proteins. Extended: there are few ethical concerns about using them, and their plasmids make it easy to give them new genes.
Bacteria are useful in biotechnology and genetic modification because of their rapid reproduction rate and their ability to make complex molecules, such as proteins. Extended: there are few ethical concerns over their manipulation and growth, and they contain plasmids, small circular pieces of DNA that can be cut open and used to carry new genes into them.
Fig. 1: a bacterial cell with its circular chromosome and plasmids; dividing about every 20 minutes, one cell becomes 8 in an hour
Section 01
One cell becomes millions.
Press Start dividing. The single bacterium splits in two, and each new cell splits again. Watch the TIME and BACTERIA counters: under good conditions a bacterium can divide about every 20 minutes, so the number doubles three times every hour.
Time
Number of divisions
Number of bacteria
0 min
0
1
1 hour
3
8
2 hours
6
64
5 hours
15
32 768
10 hours
30
about 1.1 billion
Rapid reproduction: a huge population, and so a large amount of product, can be grown in hours or days, far faster than growing plants or animals.
Complex molecules: bacteria use the instructions in their DNA to build large, complicated molecules such as proteins (enzymes, and human insulin once they carry the human gene).
Easy to grow: they need only simple nutrients, a suitable temperature and pH, and can be grown in large fermenters.
Examiner trap
Doubling is not adding. After 1 hour there are 8 bacteria, not 3 or 4: each 20 minutes the number is multiplied by 2 (1, 2, 4, 8, ...).
Stage 1 · Learn
Check what the sim just showed you
Four quick checks. Each correct answer earns XP and records this skill on your profile.
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In the sim, the bacteria divide every 20 minutes. How many bacteria are there after 1 hour, starting from one?
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Which labelled structures in the large bacterium are small rings of DNA?
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Why does a fast reproduction rate make bacteria useful in biotechnology?
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Which of these is an example of a complex molecule made by bacteria?
Section 02
Few ethical worries, and plasmids.
Extended. Look again at the large bacterium in the sim with its labels on. As well as the large circular chromosome it has small rings of DNA called plasmids. These, together with the lack of ethical objections, make bacteria the first choice for genetic modification.
Few ethical concerns: bacteria are single-celled organisms without a nervous system, so very few people object to growing them in huge numbers, changing their genes and killing them when the product is collected. Changing the genes of animals raises far more objections.
Plasmids: small circular pieces of DNA separate from the main chromosome. A plasmid can be cut open, have a new gene inserted and be put back into a bacterium, so it carries the gene in.
Copied every division: the plasmid is copied each time the bacterium divides, so every new cell inherits the inserted gene.
Same genetic code: bacteria read DNA in the same way as human cells, so a human gene inside a bacterium can be used to make the human protein.
Examiner trap
A plasmid is not the bacterial chromosome and it is not a nucleus. Bacteria have no nucleus: the chromosome lies free in the cytoplasm, and plasmids are extra small rings of DNA.
Stage 2 · Exam
Exam-style questions
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State the two Core reasons why bacteria are useful in biotechnology and genetic modification.
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Extended: why are there few ethical concerns over the manipulation and growth of bacteria?
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Extended: why are plasmids useful in genetic modification?
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A bacterium divides every 30 minutes. How many bacteria come from one cell after 3 hours?
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Why bacteria are used, mastered.
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