1. What are microorganisms?
Chapter 5 Lesson 2
What are microorganisms?

2. Microorganism
An organism that is too small to be seen with the unaided eye.

3. Bacteria
A certain type of organism.

4. Mold
A kind of fungus.

5. Protist
A single-celled or multi-celled organism that shares traits with plants and animals.

6. Kinds of Microorganisms
Thousand of kinds of microorganisms.
Most single-celled.
More bacteria on Earth than all living things together.
Bacteria may be shaped like rods, spirals, or balls.

7. Kinds of Microorganisms
You probably have some of this kind of bacteria, called staph, on your skin right now. Staph bacteria can cause annoying pimples or boils. They can also cause serious infections of the blood, bones, and lungs.

8. Kinds of Microorganisms
Strep bacteria can be a serious health threat. They cause illness in newborn babies. They can also harm pregnant women, children, older adults, and adults who have certain other illnesses.

9. Kinds of Microorganisms
Yeasts and molds are fungi that are microorganisms.
Fungi look a little like plants, but they can’t make their own food.
Fungi are decomposers. They break down decaying plants and animals in the environment.

10. Kinds of Microorganisms
The blue coloring in this cheese is actually mold. This mold, which is related to penicillin, is safe to eat.

11. Kinds of Microorganisms
Penicillin is made by a mold. It kills harmful bacteria.

12. Kinds of Microorganisms
Protists are also microorganisms.
80,000 kinds of protists.
Some, like algae, make their own food.
Others, such as protozoans, hunt for food like animals do.
Protists can be single-celled or multicellular.

13. Kinds of Microorganisms
Golden Alga
Amoeba catching its prey.

14. Kinds of Microorganisms
Microorganisms are everywhere! Certain bacteria in our digestive systems help break down the foods we eat. Without them, we could not use the nutrients in the food.
Without other microorganisms, we would have fewer foods to eat. Bacteria turn milk into yogurt. They also help produce certain kinds of cheese. Yeast is a fungus that makes bread rise.

15. Helpful and Harmful Microorganisms
Ways microorganism are helpful.
Phytoplankton in the ocean helps produce the oxygen we breathe.    
Phytoplankton is made of bacteria and protists that live near the surface of the water. They use photosynthesis to make their own food. They also release oxygen providing at least half of the oxygen in the air you breathe.

16. Helpful and Harmful Microorganisms
Ways microorganism are helpful.
Used to make medicines like penicillin that kill bacteria that cause disease.
Remove harmful bacteria from wastewater at water treatment plants and help clean up oil spills.
Certain fungi help plants take in nutrients from the soil helping them grow.

17. Helpful and Harmful Microorganisms
Ways microorganism are helpful.
Cause dead things to decay. Without them, Earth would be covered with dead plants and animals.

18. Helpful and Harmful Microorganisms
Ways microorganism are harmful.
The bacteria Salmonella and E. coli can make you very sick. They grow on raw chicken and other meats, raw eggs, and other raw foods.
Harmful fungi can kill crops. They can also rot wood, spoil food, and cause several kinds of skin diseases, including athlete’s foot.

19. Helpful and Harmful Microorganisms
Ways microorganism are harmful.
Some kinds algae can suddenly grow very quickly. This causes the water to turn red and kills fish.

20. Helpful and Harmful Microorganisms
Ways microorganism are harmful.
The organism that causes ringworm is a fungus, not a worm. Ringworm spreads easily and grows best on warm, moist skin.