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Under the Microscope

Microorganisms are living things that can only be seen through a microscope. Imagine that you have just discovered a new microorganism. The first thing that you want to do is to tell the scientific community all about your new discovery.

Section 19-1

Interest Grabber

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1. Describe your microorganism in detail.

2. Describe its habitat.

3. Classify your microorganism by giving it a genus and species based on its characteristics.

Section 19-1

Interest Grabber continued

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19–1 BacteriaA. Classifying Prokaryotes

1. Eubacteria2. Archaebacteria

B. Identifying Prokaryotes1. Shapes2. Cell Walls3. Movement

C. Metabolic Diversity1. Heterotrophs2. Autotrophs3. Releasing Energy

Section 19-1

Section Outline

D. Growth and Reproduction1. Binary Fission2. Conjugation3. Spore Formation

E. Importance of Bacteria1. Decomposers2. Nitrogen Fixers3. Human Uses of Bacteria

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Section 19-1

Concept Map

are classified into the kingdoms of

live in harsh environments such as

include a variety of lifestyles such as

Bacteria

Eubacteria Archaebacteria

Infecting large organisms

Thick mudLiving in soilAnimal

digestive tracts

Salty lakes Hot springs

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Peptidoglycan

Cell wall

Cell membrane

Ribosome

Flagellum DNA Pili

Section 19-1

The Structure of a Eubacterium

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What Viruses Mean to You

If you have ever had a cold, you are probably familiar with the word virus. It is a word that makes most people frown.

Section 19-2

Interest Grabber

1. What do you think of when you hear the word virus? Make a list of all the words you can think of that relate to viruses.

2. What are two things that you would like to find out about viruses?

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19–2 Viruses

A. What Is a Virus?

B. Viral Infection

1. Lytic Infection

2. Lysogenic Infection

C. Retroviruses

D. Viruses and Living Cells

Section 19-2

Section Outline

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T4 BacteriophageTobacco Mosaic

Virus Influenza Virus

Head

Tail sheath

DNA

Tail fiber

RNACapsid

Surfaceproteins Membrane

envelope

RNA

Capsidproteins

Section 19-2

Figure 19-9 Virus Structures

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Figure 19-10 Lytic and Lysogenic Infections

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Section 19-2

Figure 19-11 Viruses and Cells

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Bacteria vs. Humans

Bacteria are all around you—in the air you breathe, under your feet, on your skin, and even in your body! They may be tiny, but they can still have an impact on your life.

Use what you already know about bacteria to answer these questions.

Section 19-3

Interest Grabber

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1. In what ways are bacteria similar to humans?

2. In what ways are bacteria different from humans?

3. How can bacteria be harmful?

Section 19-3

Interest Grabber continued

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Section 19-3

Section Outline

19–3 Diseases Caused by Bacteria and Viruses

A. Bacterial Disease in Humans

1. Using Cells for Food

2. Releasing Toxins

3. Preventing Bacterial Disease

B. Bacterial Disease in Animals

C. Controlling Bacteria

1. Sterilization by Heat

2. Disinfectants

3. Food Storage and Processing

D. Viral Disease in Humans

E. Viral Disease in Animals

F. Viral Disease in Plants

G. Viroids and Prions

1. Viroids

2. Prions

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Tooth decay

Lyme disease

Tetanus

Tuberculosis

Salmonella food poisoning

Pneumonia

Cholera

Streptococcus mutans

Borrelia burgdorferi

Clostridium tetani

Mycobacterium tuberculosis

Salmonella enteritidis

Streptococcus pneumoniae

Vibrio cholerae

Regular dental hygiene

Protection from tick bites

Current tetanus vaccination

Vaccination

Proper food-handling practices

Maintaining good health

Clean water supplies

Disease Pathogen Prevention

Section 19-3

Common Diseases Caused by Bacteria

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Oncogenic viruses

Retrovirus

Adenoviruses

Herpesviruses

Poxviruses

DNA

RNA

DNA

DNA

DNA

Cancer

Cancer, AIDS

Respiratory infections

Chickenpox

Smallpox

Type of Virus Nucleic Acid Disease

Section 19-3

Common Diseases Caused by Viruses

Click the image to play the video segment.

Video

Lytic and Lysogenic Cycles

The latest discoveries in microorganisms and viruses

Links from the authors on smallpox vaccinations

Career links on epidemiologists

Interactive test

Articles on bacteria and viruses

For links on bacteria, go to www.SciLinks.org and enter the Web Code as follows: cbn-6191.

For links on the lytic cycle, go to www.SciLinks.org and enter Web Code as follows: cbn-6192.

Go Online

Interest Grabber Answers

1. Describe your microorganism in detail.

Students should describe the appearance of their imaginary organism. A possible answer might include its color and shape.

2. Describe its habitat.

Students should describe whether it lives in water, soil, or another organism; if it is a plant or animal; and how it gets its energy.

3. Classify your microorganism by giving it a genus and species based on its characteristics.

Students should specify a name for their organism.

Interest Grabber Answers

1. What do you think of when you hear the word virus? Make a list of all the words you can think of that relate to viruses.

Possible answers: disease, sickness, AIDS virus, infection, microscopic, vaccines, flu, cold

2. What are two things that you would like to find out about viruses?

Possible answers: How are viruses related to bacteria? How do viruses cause disease? How do viruses reproduce? How do viruses spread from person to person?

Interest Grabber Answers

1. In what ways are bacteria similar to humans?

Like humans, bacteria are alive, and some can move. Both obtain energy, exchange gases, grow, and reproduce.

2. In what ways are bacteria different from humans?

Unlike humans, bacteria are extremely small; some can live in harsher environments and without oxygen; some bacteria use sunlight to produce their own food.

3. How can bacteria be harmful?

Bacteria cause diseases, release poisonous chemicals, and compete with humans for food.

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