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Chapter 19

Chapter 19. Bacteria and Viruses. I. Prokaryotes. Prokaryotes: single-celled organisms that lack a nucleus 1. Eubacteria – walls contain peptidoglycan (a carbohydrate) 2. Archaebacteria – lack peptidoglycan, DNA similar to eukarotes. Identifying Prokaryotes 1. Shapes

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Chapter 19

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  1. Chapter 19 Bacteria and Viruses

  2. I. Prokaryotes • Prokaryotes: single-celled organisms that lack a nucleus 1. Eubacteria – walls contain peptidoglycan (a carbohydrate) 2. Archaebacteria – lack peptidoglycan, DNA similar to eukarotes

  3. Identifying Prokaryotes 1. Shapes a. Bacilli (rod shaped) b. Cocci (spherical) c. Spirilla (spiral)

  4. 2. Cell Walls a. Gram-positive (w/peptidoglycan) – purple b. Gram-negative (w/o peptidoglycan – red

  5. 3. Arrangement • Staphyl: Clumps or clusters b. Strepto: long chains

  6. 4. Movement • Propelled by tail-like structure called flagella b. Glide along a slime secretion c. Move along like snakes d. Some don’t move

  7. Obtaining Energy 1. Autotrophs a. Photoautotrophs: obtain energy from photosynthesis b. Chemoautotrophs: obtain energy from inorganic molecules

  8. 2. Heterotrophs a. Can cause food poisoning b. Photoheterotrophs: photosynthetic, but also need organic compounds for nutrition

  9. Releasing Energy 1. Obligate aerobes: require oxygen 2. Obligate anaerobes: cannot live in presence of oxygen 3. Facultative anaerobes: do not need oxygen, but can live in the presence of it

  10. Growth and Reproduction 1. Binary fission: cell divides, asexual 2. Conjugation: transfer of genetic information from one cell to another, sexual 3. In unfavorable conditions, many bacteria can form endospores – can remain dormant for months or years

  11. II. Bacteria in Nature • Decomposers 1. Help recycle nutrients – break down dead organisms 2. Used in sewage treatment

  12. Nitrogen Fixers 1. Nitrogen fixation: converting nitrogen into a form plants can use 2. Rhizobium grow on roots of soybeans and other legumes – converts nitrogen to ammonia for the plant

  13. Bacteria and Disease 1. Pathogen: disease-causing agents 2. 2 ways bacteria cause disease a. Break down tissues for food b. Release toxins 3. Many can be prevented with vaccines, can be treated with antibiotics

  14. Human Uses of Bacteria 1. Food – cheese, yogurt, buttermilk, sour cream, pickles, sauerkraut 2. Industry – cleaning up oil spills, mining minerals, synthesizing drugs

  15. 3. Bacteria live in our digestive tract to help in digestion (called normal flora)

  16. Controlling Bacteria 1. Sterilization: destroy bacteria by subjecting them to great heat or chemicals a. Boiling, frying, steaming can all kill bacteria b. Disinfectant chemical solutions can be used in homes and hospitals 2. Refrigeration – bacteria grow slowly at low temperatures

  17. III. Viruses • Viruses: particles of nucleic acid and protein 1. Nucleic acid = DNA or RNA that contains instructions for making new copies of the virus 2. Capsid: outer protein coat

  18. Viral Infection 1. Infect cells and replicate inside host cell 2. Bacteriophage: viruses that infect bacteria

  19. 3. 2 types of viral infections a. Lytic infection: virus enters cell, make copies of itself and causes the cell to burst b. Lysogenic infection: virus embeds its DNA into DNA of host and is replicated with host cell’s DNA

  20. Viruses and Disease 1. Many viruses can be prevented through the use of vaccines (polio, measles, influenza) 2. Oncogenic viruses cause cancer 3. Retroviruses contain RNA 4. Prions contain no DNA or RNA, only protein

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