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Cell Biology Chapter Nine: The Microscopic World • 9.1 Protozoans • 9.2 Bacteria • 9.3 Viruses Investigation 9B Investigating Pond Water • Which microscopic organisms are found in 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.”