1. Chapter 18 Viruses and Bacteria

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

3. KEY CONCEPT Infections 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 cells 10, ,000 nm
viroids nm
viruses nm
prokaryotics cells ,000 nm
prion 2-10 nm

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

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

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

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

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

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

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

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

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

14. Stages of the Lytic Cycle
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.

15. A lysogenic infection does no immediate harm.
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
Many cell divisions produce a
colony of bacteria infected
with prophage.
The prophage may leave the
host’s DNA and enter the
lytic cycle.

16. Stages of the Lyogenic cycle
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.

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

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

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

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

21. Viruses cause many infectious diseases
There are many examples of viral infections.
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

22. Vaccines are made from weakened pathogens.
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 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. What do you think? Are viruses alive?
Give evidence to support this opinion:
YES NO

27. Bacteria sections 18.4 – 18.6

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

29. Bacteria -Bacteria (prokaryotes) are widespread on Earth
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.
Prokaryotes can be grouped by their need for oxygen.
obligate anaerobes are poisoned by oxygen
obligate aerobes need oxygen
facultative aerobes can live with or without oxygen

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

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

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

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

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

35. Bacteria have various strategies (plans) for survival.
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
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 CONCEPT Prokaryotes perform important functions for organisms and ecosystems.

37. Beneficial Roles of Prokaryotes Prokaryotes provide nutrients to humans and other animals.
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.

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

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

43. Bacterial Diseases and Antibiotics
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.

44. immune system may be lowered

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

46. Bacteria can evolve resistance to antibiotics.
Bacteria are gaining resistance to antibiotics.
overuse
underuse
misuse
Antibiotics must be used properly.
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.