(VAB) Bacteria Reproduction Lesson

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Wash or Sanitize?

Does hand sanitizer work as well as washing your hands?

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Is it scientifically correct? Check out the following lessons to find out.

How Does Bacteria Reproduce?

Two types of reproduction are seen in bacteria: binary fission and conjugation.

Binary Fission Conjugation

In binary fission, a bacterium doubles its size by elongating. It also replicates its DNA before dividing in half, producing 2 identical cells. This is asexual reproduction.

Conjugation is a process where two bacteria can transfer genetic material from one cell to another. They do this by using pili (singular: pilus) that link one bacterium to the other. The genetic material (called an F plasmid) is copied and then transferred; the F plasmid is a ring of circular DNA that frequently contains antibiotic resistance genes. Therefore, conjugation will double the number of resistant bacteria in a population.

Steps to Binary Fission:

Steps to

Conjugation:

Steps to Binary Fission: Step 1- Replication of DNA The bacterium uncoils and replicates its chromosome, essentially doubling its content. Step 2- Growth of a Cell After copying the chromosome, the bacterium starts to grow larger in preparation for binary fissions. It is followed by an increase in cytoplasmic content. Another prominent trait of this stage is that the two strands migrate to opposite poles of the cell. Step 3-Segregation of DNA The cell elongates with a septum forming at the middle. The two chromosomes are also separated in this phase. Step 4- Splitting of Cells A new cell wall is formed at this phase, and the cell splits at the centre, dividing the parent cell into two new daughter cells. Each of the daughter cells contains a copy of the nuclear materials as necessary organelles. Steps to Conjugation: Conjugation is a process where two bacteria can transfer genetic material from one cell to another. They do this by using pili (singular: pilus) that link one bacterium to the other. The genetic material (called an F plasmid) is copied and then transferred; the F plasmid is a ring of circular DNA that frequently contains antibiotic resistance genes. Therefore, conjugation will double the number of resistant bacteria in a population.

Do Bacteria Ever Go Dormant?

YES!

When the environment gets tough and food gets scarce, some bacteria can form an endospore. The bacteria divides within its cell wall and one of the two cells engulfs the other, becoming dormant. Dormancy is a state of inactivity in some organisms where growth and metabolism temporarily stop. The endospore that is formed is highly resistant to destruction.

Image showing an endospore and a culture of endsospores and non-dormat cells

Endospores can be revived after decades of dormancy; they will start to grow quickly when conditions are favorable.

Pasteurization is a process of heating and cooling food products repeatedly so that the endospores which break out of dormancy into regular bacterial form during cooling will be killed if heated again.

Let's Think!

How is binary fission similar to eukaryotic mitosis? How is it different? Flip through the cards below to find out. 

 

Challenge and Before You Go

Practice Time! Use the knowledge you learned from the lesson to complete the practice activities below.

 

  Before You Go - You Need To Know

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The following key points are from the explore section of the lesson. You must know the following information before moving to the next lesson. This is just a summary of the key points.

  • What are the two ways bacteria can reproduce?
    • Binary fission (cell dividing in half to produce two cells) and Conjugation (transfer of genetic information from one cell to another)
  • What is an endospore?
    • A tough, protective covering that bacteria form when conditions become harsh. The bacteria go into a state of dormancy. When conditions become better, the endospore disappears.
  • What is dormancy?
    • A state of inactivity in some organisms where growth and metabolism stop.

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