2. Cell Biology

3. Chapter Nine: The Microscopic World
9.1 Protozoans
9.2 Bacteria
9.3 Viruses

4. Investigating Pond Water
Investigation 9B
Investigating Pond Water
Which microscopic organisms are found in pond water?

5. 9.2 Bacteria
Bacteria are organisms that consist of a single, prokaryotic cell.
Bacterial cells have a cell membrane that is surrounded by a tough cell wall.
Bacteria can live in soil, water or air.

6. 9.2 Size and shape of bacteria
Bacteria are not easy to measure using meters, centimeters, or even millimeters.
Micrometers (μm) are used to measure them.
Bacteria are much smaller than most other cells.

7. 9.2 Size and shape of bacteria
Bacteria are identified based on the shape of their cells.
Rod-shaped bacteria are called bacilli.
Ball-shaped bacteria are called cocci.
Spirilla are spiral-shaped bacteria.
Bacilli in your intestine help with digestion.

9. 9.2 Movement and feeding Bacteria get around in many ways.
Some bacteria move using flagella.
Others have a slimy layer to grip surfaces.
Some are carried by the movement of air or liquids. .

10. 9.2 Movement and feeding
Photosynthetic bacteria can make their own food from sunlight and carbon dioxide, just like plants.
Bacteria that break down dead organisms get their food by absorbing it.
These blue green bacteria use sunlight to make food.

11. 9.2 Bacteria and the beginning of life
Scientists believe that bacteria were the first organisms on Earth.

13. 9.2 The importance of bacteria
Bacteria are useful in many areas of industry.
Yogurt and cheese are made with certain types of bacteria.
Bacteria break down waste products in sewage.
Bacteria can help clean up oil spills.
Bacteria also cause diseases:
strep throat
respiratory infections
infected wounds

14. 9.2 The importance of bacteria
Bacteria are an important part of the nutrient cycles that all life depends upon.

15. 9.2 The importance of bacteria
Bacteria are “nature’s recyclers.”