1. BACTERIA (Prokaryotes)
Chapter 18:
VIRUSES
And
BACTERIA (Prokaryotes)

2. 1 nanometer (nm) = one billionth of a meter
Pathogens
Any disease causing agent is called a pathogen.
How Big Is It?
1 nanometer (nm) = one billionth of a meter
eukaryotics cells 10, ,000 nm
viroids nm
viruses nm
prokaryotics cells ,000 nm
prion 2-10 nm

3. Types of Pathogens
1. Virus - An infectious particle made only of a strand of DNA or RNA surrounded by a protein coat, NON-LIVING.
2. Bacteria - Prokaryotic unicellular microorganisms, LIVING.
Lactobacilli: rod-shaped
Enterococci: spherical
Spirochaeta: spiral

4. II. Viruses A. Traits of a Virus
1. Non-living Pathogen- there are no cell parts, no cell, no growth or response at all.
- Do not belong to any kingdom.
2. Made up of 2 Parts
a. Capsid- Protein coat which surrounds….
b. Genetic material (DNA or RNA)

5. 3. Two regions of a virus a. Head – contains the DNA or RNA b
3. Two regions of a virus a. Head – contains the DNA or RNA b. Tail – allows it to attach onto a host. 4. Ways to group or classify a virus a. Shape of the protein coat surrounding the head b. What the virus infects c. Size of the virus

6. The make-up of a viral capsid give viruses a variety of shapes.
In some, the protein coat (capsid) is surrounded by a lipid envelope.
-Protective outer coat with spiky structures of proteins and sugars may stick out.
Structure and shape are important in how a virus infects something
Each virus can only infect certain hosts.
Recognizes host by fitting surface proteins onto
receptor molecules on a host- like a lock and key

7. Viruses that infect bacteria are called Bacteriophages.
They infect the bacterial cell by piercing it and injecting DNA.
capsid
DNA
tail sheath
tail fiber
colored SEM; magnifications:
large photo 25,000; inset 38,000x

8. Viruses and Disease All viruses live as parasites.
Spread from one organism to another by air, insects, water, and food.
Viruses cause 2 types of infections.
1. Lytic Infection
Lytic – virus infects cell and causes the cell host to burst open releasing more viruses.

9. 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.

10. 2. Lysogenic Infection – does no immediate harm to the host.
- some viruses stay hidden for a long time before they are noticed.
- There are no symptoms until something triggers it to be active, and the virus just stays in the body.
Example: cold sores – Herpes simplex I
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.
The prophage may leave the host’s DNA and enter the lytic cycle.

11. 6. The human defense is the
WHITE BLOOD CELL
a. Some surround and destroy the virus
b. Others make ANTIBODIES
Chemicals made by specialized white blood cells
Help stop viruses and harmful bacterium
Foreign invaders may be destroyed directly by antibodies OR may be held captive until white blood cells can surround and destroy it

12. Vaccines are made from weakened pathogens.
A vaccine stimulates the body’s own immune response.
Vaccines are the only way to control the spread of viral disease.
-Vaccines prepare the immune system for a future attack.

13. Differences between an antiseptic and disinfectant
Antiseptic – (against microorganisms) is used to destroy microorganisms living on live or living surfaces.
Examples: Bactine, soap, listerine
Disinfectant – destroy microorganisms
living on non-living surfaces.

14. Prokaryotes Grouped based on their need for Oxygen
Prokaryotic cell- Lack nucleus and organelles.
Has DNA in the form of a circle separate from the main chromosome – Known as a Plasmid.
Members from the Domains Bacteria and Archaea comprise all of Earth’s prokaryotes.
Grouped based on their need for Oxygen
1. Obligate anaerobe – Do not need oxygen to survive. Poisoned by Oxygen
2. Obligate aerobe- Need Oxygen
3. Facultative aerobe- Can survive with or without Oxygen

15. (Structurally Different)
Bacteria and Archaea
BACTERIA
3 common shapes
Found eveywhere
Peptidoglycan in cell wall
BOTH
Prokaryotes
Unicellular
Very small
Cell wall
(Chemically Dif.)
Plasma membrane
Plasmids (DNA)
May have Flagella
(Structurally Different)
Pili
ARCHAEA
Many shapes
Extreme environments
No peptidoglycan in cell wall

16. I. Eubacteria (Prokaryotes)
A. Traits of bacteria 1. Unicellular and can be found in pairs, colonies or in chains. (Arrangement) 2. Prokaryotic cells – lack a nucleus, but have DNA 3. Microscopic, but larger than viruses could be in a line on the tip of your pencil, but they’re still larger than viruses 4. Found almost everywhere 5. Classified by shape a. cocci – round b. bacilli - rod c. spirillia - spiral

17. 3 Common shapes or types of bacteria
Lactobacilli: rod-shaped
Enterococci: spherical
Spirochaeta: spiral

18. Eubacteria (Prokaryotes)
6. A capsule protects the bacteria from drying out and helps it to stick to things. (Slime Layer) 7. Some have whip-like tails - FLAGELLA – to move. 8. Reproduce through binary fission– asexual reproduction 9. Requirements of life = Food, certain temperature, moisture, most like darkness and most need oxygen. 10. When growing conditions are not right, certain bacteria form endospores to protect themselves until conditions become favorable again.
flagellum
pili
plasmid
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.

19. Prokaryotes provide nutrients to humans and other animals.
Prokaryotes live in digestive systems of animals.
make vitamins
break down food
Used to make antibiotics – Chemicals that kill or slow bacteria growth.
- Prevents cell wall formation
Antibiotics -
Do not work on viruses!
Why don’t antibiotics affect our bodies’ own cells?

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