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

2. Vocabulary Preview
Microorganism: an organism that is too small to be seen with an unaided eye
Bacteria: a certain type of microorganism
Mold: a kind of fungus
Protist: a one-celled organism that shares traits with plants or animals

3. Kinds of Microorganisms
Microorganisms: are living things
that are too small to see without
a microscope.
The environment contains
thousands of kinds of microorganisms.
Most have only one cell.

4. 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
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.

5. The blue coloring in this cheese is actually mold
The blue coloring in this cheese is actually mold. This mold, which is related to penicillin, is safe to eat
Penicillin is a substance made by a mold. It kills harmful bacteria. First used during World War II, it prevented thousands of deaths from infection.

6. Bacteria Bacteria: is a microorganism.
There are more bacteria on Earth than all other living things together.
Bacteria may be shaped like rods, spirals, or balls.

7. Mold 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.

8. Protists Protists are also microorganisms.
Marine Protists
Single-celled Protist
Protists are also microorganisms.
There are about 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 multi-celled.

9. 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 turns milk into yogurt.
They also help produce certain kinds of cheese.
Yeast is a fungus that makes bread rise.

10. Helpful Microorganisms
Many more microorganisms help people that harm them!
Without phytoplankton in the ocean, we wouldn’t have enough oxygen to breathe.
Other microorganisms make important medicines such as penicillin.
These medicines kill bacteria that causes diseases.

11. Plankton

12. Phytoplankton is made of bacteria and protists that live near the surface of the water. These organisms use photosynthesis to make their own food. They also release oxygen. Phytoplankton produces at least half of the oxygen in the air you breathe.

13. Helpful Microorganisms
Some microorganisms remove harmful bacteria from wastewater at water treatment plants.
Others help clean up oil spills.
Phytoplankton is the main food for tiny fish, which are eaten by bigger fish.
Without phytoplankton, there would be few fish that we could eat.

14. Helpful Microorganisms
Certain fungi help plants take in nutrients from the soil.
Without nutrients, the plants wouldn’t grow well, if at all.
There would be fewer plants.
This would mean less food for people and other animals.

15. Helpful Microorganisms
Microorganisms cause dead things to decay.
Without them, Earth would be covered in dead plants and animals.
We depend on microorganisms in all of these ways to survive.

16. Harmful Microorganisms
Some microorganism are harmful.
The bacteria in Salmonella and E.Coli can make you very sick.
They grow on raw chicken and other meats, raw eggs, and other raw foods.
Cooking kills them.
Harmful bacteria also grow on cooked food that is left out of the refrigerator for 2 hours or longer.
Salmonella

17. This kind of algae can suddenly “bloom,” or grow very quickly
This kind of algae can suddenly “bloom,” or grow very quickly. People call this reddish water a red tide, though it has nothing to do with tides. Some algae in a red tide contain a poison that can kill fish.
The organism that causes ringworm is a fungus, not a worm. Ringworm spreads easily and grows best on warm, moist skin.