Bacteria and Viruses

1. Bacteria and Viruses Chapter 19

2. Bacteria & Viruses

3. 19.1 Bacteria Come in many shapes and sizes Most common microorganisms are prokaryotes Average size of 1-5 micrometers Compared to eukaryotic cells that are 10-100 micrometers in diameter

4. 2 Branches of Bacteria (Domains) Archebacteria (similar to early Earth) Confined to extreme environments Methanogens - reduce CO2 to CH4 Extreme halophiles - salt loving Thermoacidophiles Similar to early earth More closely related to eukaryotes than to modern bacteria Eubacteria(most modern) very diverse

5. Bacterial Classification

6. Prokaryotic Phylogeny

7. Prokaryotic & Eukaryotic Cells

8. Classifying Prokaryotes Eubacteria Largest prokaryote Domain Lack nuclei Cell wall of a carbohydrate- Peptidoglycan Cell membrane around cytoplasm Some have an extra cell wall on the outside to resist damage

9. Classifying Prokaryotes Archaebacteria Lack nuclei Have cell walls without peptidoglycan Are chemically different from Eubacteria Many live in extremely harsh environments

10. Bacteria Shapes

11. Identifying Prokaryotes Shapes Bacilli- Rod shaped Cocci- Spherical shaped Sprilla- spiral shaped Colorized SEM 12,000 Colorized SEM 9,000

12. Identifying Prokaryotes Cell walls Gram staining used to tell them apart Gram+ bacteria look purple Gram- bacteria look pink

13. The Bacterial Cell Wall Instead of cellulose, contain peptidoglycan A polymer of modified sugars cross-linked with amino acids The gram stain distinguishes many disease causing bacteria based on the type of cell wall Many antibiotics work by attacking the bacterial cell wall

14. Gram (+) Purple accept gram stain have simpler cell walls with large amounts of peptidoglycan Gram (-) Pink do not stain have more complex cell walls with less peptidoglycan cell walls contain lipopolysaccharides are more likely to be pathogenic (cause disease) more resistant to antibiotics The Gram Stain

15. Cell Wall & Gram Stain

16. Gram (+) & Gram (-) Gram (+)Purple&Gram (-)Pink

17. Identifying Prokaryotes Movement Flagella Lash, snake or spiral forward They do not move at all

18. About half are capable of directional movement. 3 mechanisms: flagella - different from eukaryotes spiral shaped bacteria (spirochetes) have a filament that spirals around the cell under the outer sheath some bacteria secrete slimy chemicals & glide Taxis movement toward or away from a stimulus many bacteria exhibit this form of movement Motility (movement)

19. Structures of Movement

20. Structure of Prokaryotic Flagella

21. Metabolic Diversity Heterotrophs Chemoheterotrophs: must take in organic molecules for energy and carbon Photoheterotrophs: Use sunlight for energy but need organic compounds for a carbon source

22. Metabolic Diversity Autotrophs Chemoautotrophs: perform chemosynthesis to make carbon from carbon dioxide. Does not require sunlight Photoautotrophs: use light to convert carbon dioxide and water into carbon compounds and oxygen gas.

23. Getting Energy Bacteria need a constant supply of energy Obligate aerobes- require constant supply of oxygen Obligate anaerobes- need no oxygen, for some oxygen will kill it Facultative anaerobes- survive with or with out oxygen

24. Growth and Reproduction Binary fission (to split) Conjugation Spore formation

25. Binary Fission

26. Bacterial Conjugation

27. Some bacteria form resistant cells called endospores (11,000 year old spores found) Resist extremes of temperature, pH, etc. Endospores (example: Anthrax)

28. Importance of Bacteria Only a minority cause disease Many are essential to life on earth Decomposers Break down dead matter Nitrogen Fixers Converts nitrogen into a form plants can use Humans use Bacteria Often live in symbiotic relationships with other organisms

29. 19.2 Viruses What is a virus? Particles of nucleic acid and proteins Core made up of DNA or RNA surrounded by a capsid Need to infect a living host to reproduce Head DNA Tail Tail fiber 300,000

30. Viral Structure

31. Bacteriophage

32. Are Viruses Alive? Viruses contain nucleic acids & proteins Viruses, by themselves, cannot make or use food, grow or reproduce Some scientists believe viruses were never independently living organisms Others believe viruses evolved from simple bacteria like mycoplasmas & rickettsiae Another hypothesis: viruses are genes that have escaped from the genomes of living cells Not much evidence to support any one of these

33. Viral Infection Lytic Cycle Virus attaches to host cell Injects its DNA Host makes RNA from viral DNA Cell begins to make copies of virus New viruses form Host cell bursts

34. Lytic Cycle of the T4 Phage

35. Viral Infection Lysogenic Cycle Virus attaches to host cell Injects DNA Viral DNA incorporates itself into the host DNA Viral DNA can be dormant Once it becomes active, it follows the 4 processes in the lytic cycle

36. Lytic and Lysogenic Cycle (video) http://www.youtube.com/watch?v=gU8XeqI7yts&feature=related

37. Phage Lytic and Lysogenic Cycles

38. Viral Infection Retrovirus: Genetic information is RNA Produces DNA copy and creates a prophage Example: HIV/AIDS Envelope Glycoprotein Protein coat RNA (two identical strands) Reverse transcriptase

39. 19.3 Diseases Caused by Bacteria and Viruses Pathogens- disease causing agents Bacterial Disease Viral Diseases

40. Diseases Caused By Bacteria How does bacteria produce disease? Damage the cells and tissues by breaking down the cells for food Releasing toxins (poisons into the body)

41. Preventing Diseases Vaccines Immunity Antibiotics

42. Controlling Bacteria Sterilization Disinfectants Proper food storage

43. Diseases Caused by Viruses Viruses disrupt the body’s normal equilibrium Cannot be treated with antibiotics Viruses can infect humans and plants

44. Virus-like Particles (Viroids) Viroids- single stranded RNA molecule with no capsid They cause diseases in plants Infect cell and produce more viroids by disrupting the plant metabolism

45. Virus-like Particles (Prions) Prions- contain only protein; no DNA or RNA They cause diseases in animals and humans Prions clump and cause normal protein to clump with it- creating new prions

46. Prion Action

47. Chapter 19Viruses and BacteriaMultiple Choice Practice Questions

48. 19–1 • Which characteristic distinguishes eubacteria from archaebacteria? • Eubacteria lack peptidoglycan in their cell walls. • Eubacteria contain peptidoglycan in their cell walls. • Eubacteria lack a nucleus. • Eubacteria do not possess mitochondria.

49. 19–1 • Which characteristic distinguishes eubacteria from archaebacteria? • Eubacteria lack peptidoglycan in their cell walls. • Eubacteria contain peptidoglycan in their cell walls. • Eubacteria lack a nucleus. • Eubacteria do not possess mitochondria.

50. 19–1 • Rod-shaped prokaryotes are called • bacilli. • cocci. • spirilla. • streptococci.