1. Chapter 19: Bacteria and Viruses

2. Viruses Means “poison” in Latin Nonliving
Composed of nucleic acids enclosed in a protein coat
Smaller than bacteria (can vary in structure and size)
Can only replicate
Make copies of itself
Need a host/living cell to reproduce
No cell respiration, growth, response to stimuli
Not considered a living cell

3. 1935: W. Stanley
1st to identify a virus
Tobacco Mosaic Virus

4. Structure of a Virus Inner core of nucleic acid (DNA or RNA)
Outer protein coat called a capsid
Gives virus its shape
Some viruses have a membrane (envelope) over the capsid
Can have spikes, hooks, etc.

5. Bacteriophage Special group of viruses Infect bacteria
Inject their nucleic acid into bacteria like a syringe

6. Viruses are classifies by the type of host they infect
Plant viruses
Animal viruses
Bacterial viruses

7. Viruses are often species-specific
Some are cell-type specific
Ex: cold viruses affect respiratory cells
Ex: Polio virus  affects nerve cells

8. 2 Types of Reproduction
Lytic cycle (short): takes about 30 minutes to produce 200 new viruses
Virus enters cell  reproduces  exits cell
Kills host cell: causes host cell to break open
Steps: ex: cold virus
attachment
entry
replication
assembly
lysis and release

9. Lysogenic Cycle (long)
Virus has an inactive (dormant) period
Steps: ex: herpes, HIV, and chickenpox
attachment and entry
provirus formation (prophage)
viral DNA integrated into host’s chromosomes
normal cell activity
activation of the lytic cycle

10. Retrovirus RNA virus with the enzyme reverse transcriptase
Makes viral DNA from host cell RNA
Ex: HIV

11. Fighting Viruses Natural defenses
Skin, mucus membranes, white blood cells, antibody production, interferon
Vaccines
Preparation of weakened or killed virus/viral proteins
Some produce life-long specific antibodies
Antibiotics do not kill viruses

12. How Viruses are Spread Air (measles, cold) Food and water (hepatitis)
Animal/insect bites (rabies, encephalitis)
Insects (flies can “carry” viruses)
Sexual contact (HIV, Herpes)
1st line of defense  skin and membranes

13. Chapter 19 Review #1 A typical virus has a core composed of ___.
a. capsid proteins c. membrane envelopes
b. surface proteins d. DNA or RNA
2. The outer layer of a virus is composed of ____.
a. RNA b. viral genes c. DNA d. proteins
3. A(an) _____ is a preparation of weakened or killed pathogens that can prompt the body to produce immunity to a disease.

14. Bacteria Prokaryotic: Unicellular organisms Have no nucleus
No membrane-bound organelles

15. Divided into 2 Kingdoms Archaebacteria
Live in extreme habitats (usually no oxygen present)
Cell walls lack peptidoglycan (starch)
3 types:
Methanogens
Produce methane gas
Live in marshes, lake sediments, and cow digestive tracts
Found at sewage disposal plants to help break down sewage

16. Extreme Halophiles
Lives only in places where there is a high salt concentration
Found in Utah’s Great Salt Lakes and the Dead Sea

17. Thermoacidophiles Lives in hot, acidic waters of sulfur springs
Found in volcanic vents

18. Eubacteria Live almost everywhere Cell walls made of peptidoglycan
Divided up based on how they get their food
Autotrophs
Make their own food
2 types:
Photosynthetic
Need sunlight
Ex: cyanobacteria (blue-green algae)
Chemosynthetic
Use sulfur and nitrogen to make food

19. Eubacteria Heterotrophs Use others/consumes to get food 2 ways:
Parasitism, mutualism, commensalism
Gets food from other living things
Saprophytes
Feed on dead organisms/wastes
Decomposers

20. Structure of Bacteria Very small in size All have: Some have: DNA Pili
Cell membrane Capsule
Cell wall Flagella
Ribosomes
Genes are in a big circular chromosome (not paired chromosomes)

21. Cell wall keeps bacteria from bursting
Most bacteria live in a hypotonic environment
1928: Alexander Fleming
Accidentally discovered Penicillin
1st antibiotic
Destroys bacteria by interfering with its ability to make a cell wall

22. Identifying Bacteria Gram Staining
Based on differences in a bacterium’s cell wall
Gram positive: will stain a blue/purple color
Gram negative: will stain a pink color

23. Shapes of Bacteria Bacteria have 3 shapes: Cocci: sphere-shaped
Bacilli: rod-shaped
Spirilla: spiral-shaped

24. Bacteria can grow in patterns
Diplo-: arranged in pairs
Staphylo-: cells arranged like grapes
Strepto-: arrangement of chains of cells

25. Asexual Reproduction Binary Fission
Exponential growth: 12481632…etc
Very fast (every 20 minutes)
Cells produced are genetically identical

26. Sexual Reproduction Called conjugation
DNA is exchanged through structures called pili that connect cells together

27. Metabolism Breaking down food to release energy
3 groups of bacteria based on way they metabolize:
Obligate aerobes: require oxygen
Ex: Mycobacterium tuberculosis

28. Facultative anaerobes: can live with or without oxygen
Ex: E. coli

29. Obligate anaerobes: die in the presence of oxygen
Ex: Clostridium, Treponema

30. Importance of Bacteria
Help fertilize fields
Recycles nutrients: breakdown dead materials/waste (called saprophytes)
Produce foods and medicines/antibiotics
Nitrogen fixation: makes a usable form of nitrogen

31. Harmful Bacteria: called pathogens
Can cause disease in plants and animals
Interferes with normal body function
Affects homeostasis
Can release a toxin that attacks the host (like a poison)

32. Survival Adaptations Produce endospores
Contain bacterial DNA and cytoplasm
Covered with a tough, outer case that resists temperature extremes, drying out, and harsh chemicals
Dormant: resting state (can be as long as 1,000 years)
Does not reproduce during this time
Can germinate when environmental conditions improve
Must be exposed to high heat under pressure to be killed
Called sterilization

33. Chapter 19 Review #2 A ______ is a disease-causing agent.
2. List 4 ways to identify prokaryotes.
3. One way to control bacterial growth is by subjecting them to great heat, a process called _____.
4. Bacteria can also cause disease by releasing ______ that harm the body.