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Prokaryote Reproduction
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
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Printed: April 20, 2015
AUTHORS
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
www.ck12.org
C HAPTER
Chapter 1. Prokaryote Reproduction
1
Prokaryote Reproduction
• Explain how prokaryotes reproduce.
• Define binary fission.
• Describe bacterial conjugation.
How do bacteria reproduce?
Essentially, they grow and divide. Show here is an example of Methicillin-resistant Staphylococcus aureus, or
MRSA, bacteria. Notice how one bacterium is dividing into two.
Reproduction in Prokaryotes
Unlike multicellular organisms, increases in the size of prokaryotes (cell growth) and their reproduction by cell
division are tightly linked. Prokaryotes grow to a fixed size and then reproduce through binary fission. For a
discussion of exponential growth and bacteria see http://www.youtube.com/watch?v=-3MI0ZX5WRc (10:43).
Binary Fission
Binary fission is a type of asexual reproduction. It occurs when a parent cell splits into two identical daughter
cells. This can result in very rapid population growth. For example, under ideal conditions, bacterial populations
can double every 20 minutes. Such rapid population growth is an adaptation to an unstable environment. Can you
explain why?
1
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FIGURE 1.1
Schematic diagram of cellular growth (elongation) and binary fission of
bacilli. Blue and red lines indicate old and newly-synthesized bacterial
cell wall, respectively. The DNA inside the bacterium is copied and the
daughter cells receive an exact copy of the parent DNA. Fission involves
a cytoskeletal protein FtsZ that forms a ring at the site of cell division.
Genetic Transfer
In asexual reproduction, all the offspring are exactly the same. This is the biggest drawback of this type of
reproduction. Why? Lack of genetic variation increases the risk of extinction. Without variety, there may be no
organisms that can survive a major change in the environment.
Prokaryotes have a different way to increase genetic variation. It’s called genetic transfer or bacterial conjugation.
It can occur in two ways. One way is when cells “grab” stray pieces of DNA from their environment. The other
way is when cells directly exchange DNA (usually plasmids) with other cells. For example, as shown in Figure 1.2,
the donor cell makes a structure called an F pilus, or sex pilus. The F pilus attaches one cell to another cell. The
membranes of the two cells merge and genetic material, usually a plasmid, moves into the recipient cell. Genetic
transfer makes bacteria very useful in biotechnology. It can be used to create bacterial cells that carry new genes.
Summary
• Prokaryotic cells grow to a certain size. Then they divide by binary fission. This is a type of asexual
reproduction.
• Binary fission produces genetically identical offspring.
• Genetic transfer increases genetic variation in prokaryotes.
Explore More
Use this resource to answer the questions that follow.
• Bacterial Reproduction at http://biology.about.com/od/bacteriology/a/aa080907a.htm .
1.
2.
3.
4.
5.
2
What is the outcome of binary fission.
Describe the process of binary fission.
What happens during bacterial conjugation?
What happens during bacterial transformation?
What is transduction?
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Chapter 1. Prokaryote Reproduction
FIGURE 1.2
A flowchart showing bacterial conjugation. The donor cell makes a structure
called an F pilus, or sex pilus.
The F
pilus attaches one cell to another cell.
The membranes of the two cells merge
and genetic material, usually a plasmid,
moves into the recipient cell.
Review
1. Describe binary fission.
2. Why might genetic transfer be important for the survival of prokaryote species?
3. Under ideal conditions, in 2 hours how many bacteria can result from just a single bacterium? 5 hours? 8
hours?
References
1. Zachary Wilson. Schematic diagram of cellular growth and binary fission of bacilli . CC BY-NC 3.0
2. Laura Guerin. A flowchart showing bacterial conjugation . CC BY-NC 3.0
3