Cell Biology

Chapter Nine: The MicroscopicWorld

• 9.1 Protozoans

• 9.2 Bacteria

• 9.3 Viruses

Investigation 9B

• Which microscopic organisms are found in pond water?

Investigating Pond Water

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.

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.

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.

9.2 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. .

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.

9.2 Bacteria and the beginning of life

• Scientists believe that bacteria were the first organisms on Earth.

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

9.2 The importance of bacteria

• Bacteria are an important part of the nutrient cycles that all life depends upon.

9.2 The importance of bacteria

• Bacteria are “nature’s recyclers.”