1. Chapter 7
Bacteria and Viruses

2. Lesson 2 Bacteria in Nature
Chapter 7
Lesson 2
Bacteria in Nature

3. Beneficial Bacteria
Most bacteria are beneficial and only a fraction cause diseases.
Many organisms, including humans, depend on bacteria to survive.
Bacteria living inside the intestines of humans and other animals help with digestion and other body processes.
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4. Bacteria can help some organisms, including humans and cows, digest food.
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5. Beneficial Bacteria (cont.)
Bacteria aid in the processes of decomposition and nitrogen fixation.
Decomposition is the breaking down of dead organisms and organic waste.
Nitrogen fixation is the conversion of nitrogen into a form that plants can use.
Organisms use nitrogen to make proteins.
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6. The roots of some plants, including beans and peas, have nodules that contain nitrogen- fixing bacteria.
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7. Beneficial Bacteria (cont.)
The use of organisms, such as bacteria, to clean up environmental pollution is called bioremediation.
These organisms often break down harmful substances into less harmful material that can be used as landfill or fertilizers.
Bacteria are used to make foods such as yogurt, cheese, buttermilk, vinegar, and soy sauce.
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8. Good For the Environment
Nitrogen-Fixing Plants need nitrogen to grow
Nitrogen-Fixing bacteria take nitrogen from the air and change it into a form plants can use
Recycling
Bacteria decompose dead organic matter
Cleaning Up
Bioremediation- use of bacteria to change pollutants into harmless chemicals
Good For the Environment

9. Good for People
Antibiotics
Insulin
Foods
Good for People

10. Pathogenic bacteria- cause diseases
Harmful Bacteria
Pathogenic bacteria- cause diseases
Harmful Bacteria

11. Harmful Bacteria
Of the 5,000 known species of bacteria, relatively few are considered pathogens-agents that cause disease.
pathogen
from Greek pathos, means “to suffer”; and gen, means “to produce”
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12. Harmful Bacteria (cont.)
Some pathogens normally live in your body, but cause illness only when your immune system is weakened.
Other bacterial pathogens can enter your body through a cut, the air you breathe, or the food you eat.
Once inside your body, they can reproduce and cause disease.
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13. Harmful Bacteria (cont.)
Bacteria can harm your body and cause disease in one of two ways.
Some bacteria make you sick by damaging tissue.
Other bacteria cause illness by releasing toxins.
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14. Harmful Bacteria (cont.)
Antibiotics are chemicals that stop the growth and reproduction of bacteria.
Many types of bacteria have become resistant to antibiotics over time.
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15. Harmful Bacteria (cont.)
resistance
Science Use the capacity of an organism to defend itself against a disease
Common Use the act of opposing something
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16. Harmful Bacteria (cont.)
Random mutations occur to a bacterium’s DNA that enable it to survive or “resist” a specific antibiotic.
Over time, resistant bacteria will reproduce to become more common.
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17. Lesson 2

18. Harmful Bacteria (cont.)
Over time bacteria on food reproduce and begin breaking down the food, causing it to spoil.
Pasteurization is a process of heating food to a temperature that kills most harmful bacteria.
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