Chapter 18 Viruses and Bacteria

1. Chapter 18 Viruses and Bacteria

2. Give evidence to support this opinion: YES NO What do you think? Are viruses alive?

3. KEY CONCEPTInfections can be caused in several ways.

4. Viruses, bacteria, viroids, and prions can all cause infection. • Any disease-causing agent is called a pathogen. 1 nanometer (nm) = one billionth of a meter 100 nm eukaryotics cells10,000-100,000 nm viroids5-150 nm viruses50-200 nm prokaryotics cells200-10,000 nm prion2-10 nm

5. A virus is made of DNA or RNA and a protein coat. • non-living pathogen • can infect many organisms • A viroid is made only of single-stranded RNA. • causes disease in plants • passed through seeds or pollen

6. causes misfolding of other proteins • results in diseases of the brain • A prion is made only of proteins.

7. 18.2Viruses exist in a variety of shapes and sizes.

8. Viruses have a simple structure. genetic material capsid, a protein shell maybe a lipid envelope, a protective outer coat capsid surfaceproteins nucleic acid nucleic acid capsid Surface proteins lipidenvelope capsid nucleic acid surfaceproteins lipid envelope Viruses differ in shape and in ways of entering host cells. enveloped(influenza) helical(rabies) polyhedral(foot-and-mouth disease)

9. Bacteriophages infect bacteria. capsid DNA tail sheath tail fiber

10. Viruses enter cells in various ways. colored SEM; magnifications: large photo 25,000; inset 38,000x • bacteriophages pierce host cells

11. viruses of eukaryotes enter by endocytosis • Viruses enter cells in various ways.

12. viruses of eukaryotes also fuse with membrane • Viruses enter cells in various ways.

13. A lytic infection causes the host cell to burst. host bacterium The bacterophage attachesand injects it DNA into a host bacterium. The host bacterium breaks apart, or lyses. Bacteriophages are ableto infect new host cells. The viral DNA forms a circle. The viral DNA directs the hostcell to produce new viral parts.The parts assemble into newbacteriophages. The virus may enter the lysogenic cycle, in which the host cell is not destroyed. Viruses cause two types of infections.

14. Event 1 – The bacteriophage attaches and injects its DNA into a cell. Event 2 – The viral DNA forms a circle Event 3 – The viral DNA directs the host cell to produce new viral parts that assemble into new bacteriophages. Event 4 – The host bacterium breaks apart and bacteriophages are able to infect new host cells. Final Outcome- The virus destroys the host cells. Stages of the Lytic Cycle

15. A lysogenic infection does no immediate harm. The prophage may leave the host’s DNA and enter the lytic cycle. The viral DNA is called a prophage when it combines with the host cell’s DNA. Although the prophage is not active, it replicates along with the host cell’s DNA. Many cell divisions produce a colony of bacteria infected with prophage.

16. Event 1 – The bacteriophage attaches and injects its DNA into a cell. Event 2 – The viral DNA forms a prophage by combining with the host cell’s DNA Event 3- The prophage replicates along with the host cell’s DNA Event 4 – Many cell divisions produce a colony of cells infected with the virus Final Outcome – The prophage may leave the host’s DNA and enter the lytic cycle or may continue to incubate in the host’s cells. Stages of the Lyogenic cycle

17. 18.3 Some viral diseases can be prevented with vaccines.

18. There are many examples of viral infections. common cold Viruses cause many infectious diseases

19. influenza Viruses cause many infectious diseases • There are many examples of viral infections. • common cold

20. influenza Viruses cause many infectious diseases • There are many examples of viral infections. • common cold • SARS

21. HIV (Human Immunodeficiency Virus) A retrovirus, it copies it genetic material “backwards”. Destroys host’s white blood cells HIV mutates very quickly, makes it a challenge to treat HIV-infected white blood cell Viruses cause many infectious diseases • There are many examples of viral infections.

22. Vaccines contain weakened virus or parts of a virus that it is suppose to protect against. Doesn’t cause illness in organism. A vaccine stimulates the body’s own immune response. Vaccines prepare the immune system for a future attack. Vaccines are made from weakened pathogens. • Vaccines are the only way to control the spread of viral disease.

23. How to avoid getting and spreading the flu virus Wash your hands often Get plenty Of rest Drink lots of water Get a flu shot Avoid sick people Eat healthy foods Like fruits and vegetables

24. How do viruses and cells compare? Reproduction: Viruses- only reproduce with a host cell Cell- independent cell division Genetic Code: Virus- DNA or RNA Cell- DNA Growth and Development: Virus- no Cell- yes, cells increase in size and number

25. Obtain and Use Energy: Virus- no Cell- yes Respond to the environment:Virus- no Cell- yes Change over time: Virus- yes Cell- yes

26. Give evidence to support this opinion: YES NO What do you think? Are viruses alive?

27. Bacteriasections 18.4 – 18.6

28. 18.4Bacteria and archaea are both single-celled prokaryotes.

29. Prokaryotes can be grouped by their need for oxygen. obligate anaerobesare poisoned byoxygen Bacteria-Bacteria (prokaryotes) are widespread on Earth.-They are an important part of communities in which we live.-Make up the Domains of Archaea and Bacteria-Grouped based on their need for oxygen. • obligate aerobes need oxygen • facultative aerobes can live with or without oxygen

30. Archaebacteria prokaryote cell wall – no peptiodoglycan unicellular autotrophic or heterotrophic Eubacteria prokaryote cell wall – has peptiodoglycan unicellular autotrophic or heterotrophic General Characteristics of Bacteria

31. Bacteria commonly come in three forms. rod-shaped, called bacilli Lactobacilli: rod-shaped Spirochaeta: spiral Enterococci: spherical Bacteria and archaea are structurally similar but have different molecular characteristics. • spiral, called spirilla or spirochetes • spherical, called cocci • Archaea have many shapes.

32. Bacteria and archaea have similar structures. pili plasmamembrance flagellum chromosome cell wall plasmid This diagram shows the typical structure of a prokaryote. Archaea and bacteria look very similar, although they have important molecular differences. • plasmid • flagellum • pili

33. Bacteria and archaea have molecular differences. GRAM NEGATIVE GRAM POSITIVE • The amount of peptidoglycan within the cell wall can differ between bacteria • Archaea have different lipids entirely

34. Gram staining identifies bacteria. Gram-negative bacteria have a thin layer of peptidoglycan and stain red. Gram-positive bacteria have a thicker peptidoglycan layer and stain purple. • stains polymer peptidoglycan • gram-positive stains purple, more peptidoglycan • gram-negative stains pink, less peptidoglycan

35. Conjugation In conjugation, genetic material transfers between prokaryotes. DNA passes through a structure called a conjugation bridge which connects the cells. conjugation bridge TEM; magnification 6000x Bacteria have various strategies (plans) for survival. • Formation of Endospores • When conditions are very bad for growth and survival, some bacteria may survive by forming endospores. • Endospores can last for hundreds of years.

36. KEY CONCEPTProkaryotes perform important functions for organisms and ecosystems.

37. Bacteria are important parts of animal digestive system. -Bacteria benefit from a stable home and source of food. -Host animal benefits because the bacteria help break down foods and produce vitamins and other nutrients. Beneficial Roles of ProkaryotesProkaryotes provide nutrients to humans and other animals.

38. Bacteria are important to human nutrition because they are used to make many common foods. • Bacteria help ferment many foods. • yogurt, cheese • pickles, sauerkraut • soy sauce, vinegar

39. Prokaryotes have many functions in ecosystems. photosynthesize recycle carbon, nitrogen,hydrogen, sulfur fix nitrogen Prokaryotes play important roles in ecosystems.

40. Bioremediation uses prokaryotes to break down pollutants. • oil spills • biodegradable materials

41. 18.6 Understanding bacteria is necessary to prevent and treat disease.

42. Bacteria cause disease by invading tissues or making toxins. A toxin is a poison released by an organism. Some bacteria cause disease.

43. Some Bacteria can cause disease in plants and animals. Bacteria can cause illness in 2 basic ways. Bacteria can attack the cells in one of the body’s tissues. Ex. Tuberculosis (TB) – caused by bacteria that invade the lungs and use the tissues for nutrients. Bacteria can make poisons called toxins that can be carried in the blood to other parts of the body. ex. Food poisoning – toxins released by a type of bacteria. Bacterial Diseases and Antibiotics

44. immune system may be lowered

45. Antibiotics may stop bacterial cell wall formation. Antibiotics are used to fight bacterial disease. • Antibiotics do not work on viruses. • Prevention is best method to fight bacterial disease.

46. A bacterium carries genes for antibiotic resistance on a plasmid. A copy of the plasmid is transferred through conjugation. Resistance is quickly spread through many bacteria. Bacteria can evolve resistance to antibiotics. • Bacteria are gaining resistance to antibiotics. • overuse • underuse • misuse • Antibiotics must be used properly.