Bacteria and Viruses

Bacteria and Viruses

Middle School

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Learning Objectives

• Define and describe the characteristics of bacteria and viruses.

• Explain the different ways that bacteria and viruses reproduce.

• Describe the roles of helpful and harmful types of bacteria.

• Understand why antibiotics treat bacteria but do not work on viruses.

Key Vocabulary

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Bacteria

Bacteria are microscopic, single-celled organisms without a nucleus. They can be found almost everywhere on our planet.

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Virus

A virus is a tiny, nonliving particle that contains genetic material and needs a host to reproduce.

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Pathogenic

Pathogenic microorganisms are germs, like some bacteria or viruses, that have the ability to cause diseases.

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Host Cell

A host cell is a living cell that a virus invades and uses to make more copies of itself.

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Antibiotic

An antibiotic is a type of medicine used to kill bacteria or prevent them from growing and multiplying.

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Binary Fission

Binary fission is how bacteria reproduce, where one cell splits into two identical new cells.

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What are Bacteria?

• Bacteria are microscopic, single-celled organisms that lack a cell nucleus.

• They are the most abundant living things on Earth that need to reproduce.

• Bacteria exist in three main shapes: rod-shaped, round-shaped, and spiral-shaped.

• A thick cell wall provides protection, and a flagellum helps with movement.

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Multiple Choice

A newly discovered organism is unicellular, has a cell wall, and lacks a nucleus. Which of the following structures would it use for movement?

• Host Cell

• Capsid

• Nucleus

• Flagellum

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Helpful and Harmful Bacteria

Helpful Bacteria

• ​Most bacteria are helpful decomposers that recycle nutrients in the soil.

• ​​Many types of bacteria are used to produce foods like cheese and yogurt.

• ​Millions of bacteria live in our intestines and help us digest our food.

Harmful Bacteria

• ​Some pathogenic bacteria can cause diseases in people, like strep throat or tetanus.

• ​​Harmful bacteria can also spoil the food we eat and pollute our water.

• ​We can control harmful bacteria with antibiotics, antiseptics, and by heating food.

Multiple Choice

Which of the following is a beneficial role of bacteria?

• Helping to produce yogurt

• Causing strep throat

• Spoiling food

• Polluting water supplies

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What are Viruses?

• A virus is a tiny, nonliving particle, and is not a cell.

• It has genetic material surrounded by a protein coat called a capsid.

• Viruses must infect a living host cell to be able to reproduce.

• They cause human diseases like the common cold, influenza, and AIDS.

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Multiple Choice

Why is a virus considered nonliving?

• It contains genetic material.

• It can cause human diseases.

• It has a capsid.

• It cannot reproduce without a host cell.

Reproduction of Bacteria and Viruses

• Bacteria can reproduce by dividing into two identical cells.

• Some bacteria exchange genetic material to create a new organism.

• A virus invades a host cell to make more viruses.

Multiple Choice

What is the primary difference in how bacteria and viruses reproduce?

• Both bacteria and viruses need a host cell to reproduce.

• Viruses must use a host cell, while bacteria can reproduce on their own.

• Bacteria use a host cell, while viruses divide on their own.

• Both bacteria and viruses reproduce through binary fission.

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Common Misconceptions

Misconception	Correction
All bacteria are harmful and make you sick.	Most bacteria are harmless or even helpful to us.
Viruses are living cells.	Viruses are not cells and are considered nonliving.
Antibiotics can be used to treat viral infections.	Antibiotics only work against bacteria, not viruses.
Bacteria and viruses reproduce in the same way.	Bacteria reproduce on their own; viruses need a host cell.

Multiple Choice

Why is it incorrect to take an antibiotic for the flu?

• Antibiotics are only for preventing diseases, not treating them.

• The antibiotic will make the flu symptoms worse.

• The flu is caused by a virus, and antibiotics only work on bacteria.

• The flu is caused by bacteria, but antibiotics don't work on that type.

Multiple Choice

How does the process of binary fission in bacteria differ from viral replication?

• Binary fission destroys the parent cell, while viral replication keeps the host cell alive.

• Binary fission is a form of independent asexual reproduction, while viral replication requires a host cell.

• Binary fission involves two parents, while viral replication involves only one.

• Binary fission creates genetic diversity, while viral replication does not.

Multiple Choice

A doctor is treating a patient with an infection. The pathogen reproduces by taking over the patient's cells and forcing them to make new copies until they burst. What type of pathogen is it, and what treatment would be ineffective?

• It is a bacterium; pasteurization would be ineffective.

• It is a bacterium; antiseptics would be ineffective.

• It is a virus; a vaccine would be ineffective.

• It is a virus; antibiotics would be ineffective.

Multiple Choice

Which of the following structural components is found in bacteria but is absent in viruses?

• Protein coat (capsid)

• Nucleic acid (DNA or RNA)

• Cell wall

• Lipid envelope

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Summary

• Bacteria are living, single-celled organisms; viruses are nonliving particles.

• Bacteria reproduce on their own, while viruses need a host cell.

• Bacteria come in three shapes and can be helpful or harmful.

• Antibiotics kill bacteria but do not work against viruses.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4