1. SB6e. Bacteria and Viruses
Bacteria are classified into two Kingdoms –
Archaebacteria are the earliest monerans – this kingdom has three types of bacteria that are all found in extreme environments
Eubacteria can be
Heterotrophs, which must get their energy from other organisms
Photosynthetic Autotrophs, which get their energy through photosynthesis of sunlight
Chemosynthetic Autotrophs, which get their energy from the breakdown of inorganic substances

2. SB6e. Bacteria and Viruses
Structure of Bacteria
Bacteria are the smallest and simplest of living things
They are prokaryotes
They have a plasma membrane surrounded by a cell wall
They have a single DNA molecule that is found as a circular chromosome and it is NOT inside a nucleus

3. SB6e. Bacteria and Viruses
Structure of Bacteria
Bacteria are often classified by the shapes of their cells:
coccus = round,
spirillum = spiral-shaped
bacillus = rod-shaped
They can also be classified by their arrangements:
diplo- = cells are paired,
staphylo- = grape-like clusters
strepto- = long chains

4. SB6e. Bacteria and Viruses
A virus is made of DNA or RNA and a protein coat.
non-living pathogen
can infect many organisms including
Plants
Animals
Bacteria
NOT considered
to be a living organism

5. Why are viruses NOT considered to be a living organism?
SB6e. Bacteria and Viruses
Why are viruses NOT considered to be a living organism?
Living things are made up of cells and are able to live independently of other organisms
By this definition viruses are NOT alive
They share many characteristics of living things but cannot function without infecting a living cell

6. SB6e. Bacteria and Viruses
Cells
Viruses
Reproduce through cell division (sexual/asexual)
Reproduce only inside of host cell
Genetic code is DNA
Genetic code can be DNA or RNA
Use energy
Do not use energy
Respond to environment
Do not respond to environment
Change with time (evolve)
Develop and Grow
Do not develop or grow

7. SB6e. Bacteria and Viruses
Bacteriophage
Most common virus
Infect bacteria cell by attaching their “legs” to the bacterium
Injecting their genetic material into it
Virus takes control of cell and produces more viruses.
New viruses are released when the cell bursts and then they are free to infect other cells

8. SB6e. Bacteria and Viruses
Bacteriophages infect bacteria.
capsid
DNA
tail sheath
tail fiber
PROTEIN COAT

9. SB6e. Bacteria and Viruses
Viruses enter cells in various ways.
bacteriophages pierce host cells
colored SEM; magnifications:
large photo 25,000; inset 38,000x

10. SB6e. Bacteria and Viruses
What happens next?
Two different processes that occur once
genetic material of the virus is inside the
host cell
Lytic infection
Lysogenic infection

11. SB6e. Bacteria and Viruses
Lytic Infection
Injects DNA directly into the cell.
Host cell is unable to tell the difference between viral DNA and its own.
Host cell begins to make viral mRNA
Translated into viral proteins that destroy the cell DNA
Cell then makes thousands of copies of virus’s DNA
Cell bursts and releases the new viruses.

12. SB6e. Bacteria and Viruses
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.

13. SB6e. Bacteria and Viruses
Lysogenic Infection
Does not destroy host cell right away
Insert DNA into host’s DNA
Called a prophage
Exists in cell for many generations without becoming active
Once active it enters in to the lytic cycle and behaves just like lytic infection

14. SB6e. Bacteria and Viruses
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.

15. SB6e. Bacteria and Viruses
VACCINES
Vaccines have been developed for viruses such as measles, mumps and polio.
Usually a piece of the antigen (the foreign substance or part that the body reacts to) is injected into the body.
The immune system then produces antibodies against it. That way if you later come in contact with the pathogen, your body will have a defense against it.

16. SB6e. Bacteria and Viruses Natural Selection in Viruses
Because viruses are composed of genetic material, DNA & RNA, they can evolve.
Short generation times and large population sizes allow rapid evolution
When two viruses infect a cell at the same time, they may swap genetic material to make new, "mixed" viruses with unique properties.
For example, flu strains can arise this way
Heritable traits that help a virus reproduce (such as high infectivity for influenza, or drug resistance for HIV) will tend to get more and more common in the virus population over time.

17. SB6e. Bacteria and Viruses
What is a “super bug?”
Bacterial strand that is resistant to treatment from antibiotics
Evolved from:
Unnecessary use of prescription antibiotics
Overdose of antibiotics

18. SB6e. Bacteria and Viruses
What are Antibiotics?
Compound that kills or limits the growth and reproduction of bacteria
They cannot be used to treat viral infections only bacterial.
Penicillin- discovered by Alexander Fleming in 1928.
Substance secreted by a certain fungus
Lead to the creation of numerous antibiotics used to treat several different bacterial diseases
Pneumonia, tuberculosis

19. Applications of Antibiotics
SB6e. Bacteria and Viruses
Applications of Antibiotics
Used to treat human illness
Prevent infection in healthy livestock
Found in commercial feed that is given to chickens and other farm animals
Over $20 Billion is spent worldwide on antibiotics each year

20. Natural Selection in Bacteria
SB6e. Bacteria and Viruses
Natural Selection in Bacteria
Increase in antibiotic use leads to decrease in effectiveness in treating bacterial infections.
Some bacteria have the genetic ability to survive in the presence of an antibiotic.
These bacteria survive and reproduce
Passing this trait to their offspring
Result:
Population of disease causing bacteria that are resistant to antibiotics
More we use antibiotics, increase number of resistant strands

21. Limit effects of biological resistance
SB6e. Bacteria and Viruses
Limit effects of biological resistance
Limit the non-medical and unnecessary use of antibiotics
Take antibiotics as they are prescribed and for the full duration.
Stop taking prematurely resistant bacteria thrive and reproduce
Creation of new antibiotics
Use of combination drugs

22. Other Biological Resistance
SB6e. Bacteria and Viruses
Other Biological Resistance
Insects and other pests have become resistant to certain pesticides
Some widely used pesticides have become ineffective
Population of insects is not longer affected by the pesticide
Example: DDT