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Bacteria 19-1
What are Bacteria?
Bacteria are:
• prokarytoic, meaning they do not store their DNA
in a nucleus
• unicellular
• classified into two domains/kingdoms based on
their cell walls and habitat
Bacteria are classified into two
domains/kingdoms
a. Domain Archaea, Kingdom Archaebacteria
1. Cell wall: Does not contain the carbohydrate
peptidoglycan, but it is still present
2. Habitat: Extreme environments (high salt, high
heat, no oxygen, etc.)
Deep sea vent
Bacteria are classified into two
domains/kingdoms
b. Domain Bacteria, Kingdom Eubacteria
1. Cell wall: Contains the carbohydrate peptidoglycan
2. Habitat: All over the earth, in soil, on and inside
organisms (including you)
Two different kinds of
eubacteria magnified 1000X
Streptococcus and E. coli
Please make sure you label the
following:
Parts of Bacteria
1. Plasma (cell) membrane- selectively
permeable for exchange of nutrients
and waste
2. Cytoplasm- jelly like fluid inside cell
3. Cell Wall- made of peptidoglycan in
Eubacteria
4. DNA- free in cytoplasm but
clustered in a “nucleoid region”
Parts of Bacteria
5. Pili- small protein extensions used
to anchor themselves OR sex pili
aide in exchanging DNA
6. Flagella- whip-like tail for movement
7. Ribosomes- translate genetic
material into proteins
Classification: Scientists use several
characteristics to classify Eubacteria.
– Shape
– Cell wall
– Metabolism
Classification: Shape
There are three basic shapes of
bacteria:
1. Coccus (cocci, pl.) -round shape,
2. Baccillus (bacilli, pl.)- rod shaped
3. Spirillum (spirilli, pl.)- corkscrew
shaped
More prefixes…
• Staphylo- clump of grapes
• Strepto- in a line
• Diplo- two
• What would this be?
Classification: Cell wall
• Cell Wall: Eubacteria are also identified
by thickness of their cell wall. Scientists
use a method called Gram staining to
determine cell wall thickness.
– Gram + : bacteria stains purple, meaning they
have a thick cell wall of peptidoglycan
– Gram - : bacteria stains light pink, meaning
they have a thin wall of peptidoglycan
Gram + or - ?
Gram + or - ?
How would we classify these bacteria?
•
•
•
Left?
– streptobacillus, Gram +
Center?
– staphylococcus, Gram +
Right?
– bacillus, Gram -
Classification: Metabolismnourishment
•
•
Bacteria can also be classified by how
they obtain energy and use it.
They can be heterotrophs (must obtain
their food/energy from another source) or
autotrophs (can make their own food by
capturing energy). There are two kinds
of autotrophs:
Classification: Metabolismnourishment
1. Chemoautotrophs- make their own food starting
with energy from inorganic molecules like ammonia,
hydrogen sulfide, sulfur, or nitrates
2. Photoautotrophs- make their own food using light
energy
3. Chemoheterotrophs- consume food for energy and
carbon
4. Photoheterotrophs- are photosynthetic, but must
consume their carbon compounds
Classification: Metabolismrespiration- using their food
1. Obligate aerobes- requires O2 supply, like
Tuberculosis mycobacterium
2. Obligate anaerobes- cannot grow in
presence of O2, like Clostridium botulinum
3. Facultative anaerobes- do not require O2 but
are not harmed by its presence, can live
anywhere like Escherichia coli.
Reproduction
1.Bacteria reproduce asexually, through a
process called binary fission, in which one
cell splits into two.
a. Binary fission includes three steps
i.
ii.
iii.
DNA replication
cell growth
Cytokinesis (division of cytoplasm)
Binary fission 
1. _____________
2. _____________
3. Cytokinesis_____
Reproduction
b. All offspring are identical to the original
bacterial cell.
c. Binary fission is quick and can take as little as
20 minutes.
d. Genetic variation in bacteria is due to:
1. Mutations
2. Small parts of DNA can be exchanged through sex
pili, which are like little tunnels through which the
DNA can pass from one cell to another- this is
called conjugation.
Reproduction
• Spore formation happens when the
environment is UNFAVORABLE for
reproduction
– They can stay dormant for months or even years
– Ex: Anthrax
Importance of Bacteria
1. Producers: Some are producers in food
webs, capturing energy by photosynthesis.
2. Decomposers: When all organisms die,
their organic matter must be returned to the
soil for other organisms. Decomposers are
involved in the cycles of matter (the carbon,
nitrogen, and phosphorus cycles).
Importance of Bacteria
3. Nitrogen fixers: Some bacteria live on the
roots of trees and convert nitrogen into a
form that plants can use called ammonia.
This is a mutualistic symbiotic relationship
between the plant and the bacteria.
4. Food production: Bacterial fermentation is
used to make yogurt, sour cream, vinegar,
buttermilk, and more.
Importance of Bacteria:
Human Uses
5. Human Health: E. coli
bacteria living in our
intestines use undigested
food to produce vitamins K
and B12 for us that we
cannot make on our own.
In return, we provide them
with a warm environment.
This is a mutualistic
symbiotic relationship.
Viruses 19-2
Viral Structure
Viruses have a simple structure:
1.genetic material (DNA or RNA)
2.a protein coat called a capsid that
surrounds the genetic material
3.Sometimes they have an envelope outside
of the capsid (made of lipids and proteins).
• Viruses are very small. If an average virus
were the size of an average person, a
bacterial cell would be the size of a
dinosaur over ten stories tall.
• http://learn.genetics.utah.edu/content/begi
n/cells/scale/
Name tells
you this
virus infects
bacteria
Name tells
you this
virus causes
influenza
Are Viruses Living Things?
*
*
Living things. . .
1. Are made of cells
2. Can reproduce
3. Based on a universal genetic code
4. Grow and develop
5. Obtain and use materials and energy
6. Respond to the environment
7. Maintain homeostasis
8. As a group, change over time
Make sure you star your paper!
Viral Characteristics
Viruses only have the characteristics with
stars. They are NOT considered to be
living because:
1.
2.
They use a host cell for energy
They use a host cell for replication
Viral Characteristics
Viruses are considered parasites because
they rely on a host and can destroy the
host cells.
Viruses are pathogens; a pathogen is
something that can cause a disease or
illness (could be a virus, bacterium,
fungus, etc.).
Virus Names
Viruses are named for either:
1.the disease they cause (example:
influenza virus causes influenza) or
2.the area they infect (example: rhinovirus
infects the nose)
Viral Infection of cells
1.Viruses cannot replicate on their own, they
must hijack cells to make more virus. A
viral infection of only one cell produces
thousands of viruses.
Viral Infection of cells
2. Viral infection is specific for only one cell type.
a. Cells have receptors on the surface of their cell
membranes that recognize products to take into a cell.
b. Viruses mimic things to be let in, and trick the cell into
taking them in.
Cell surface receptors
Viral Infection of cells
2.Viral infection is specific for
only one cell type.
a. Viruses have antigens
(markers) on their surface.
c. Only when the viral antigen
binds to the cell receptor
(fitting together like puzzle
pieces) can a virus infect a
cell.
Viral
antigens
Which type of cell will be infected by
the virus shown below?
How do viruses infect cells?
• Once inside the host cell, one of two
different processes can occur:
– Lytic cycle
– Lysogenic cycle
A. Lytic Cycle: Viral DNA enters a cell,
reprograms the cell to makes copies of the
virus, and causes the cell to burst
releasing new viruses.
B. Lysogenic cycle: A virus integrates its
DNA into the DNA of the host cell, and the
viral genetic information replicates along
with the host cell DNA. Lysogenic
infections may become lytic if the viral
DNA leaves the host DNA.
To lytic cycle
From lysogenic cycle
• Video Clip
Activity: Cell, Virus, or Both?
Contains nucleic acid as genetic material
Activity: Cell, Virus, or Both?
Can grow and develop
Activity: Cell, Virus, or Both?
Can only be replicated in a host
Activity: Cell, Virus, or Both?
Can reproduce on its own
Activity: Cell, Virus, or Both?
Obtain and use materials and energy
Activity: Cell, Virus, or Both?
Respond to the environment
Activity: Cell, Virus, or Both?
Maintain homeostasis
Activity: Cell, Virus, or Both?
Can contain DNA
Activity: Cell, Virus, or Both?
Which is smallest?
Activity: Cell, Virus, or Both?
Activity: Cell, Virus, or Both?
DNA Viruses vs. RNA Viruses
1.DNA viruses do not mutate frequently
because they utilize the host cell's DNA
polymerase to make more copies of the
viral DNA. Remember, DNA polymerase
can proofread and correct errors
(mutations) during DNA replication. That
is why you only need a vaccine for a DNA
virus once. Examples: smallpox, HPV
(warts, cancers).
DNA Viruses vs. RNA Viruses
2. RNA viruses have a high mutation rate
because when the cell copies RNA for
new viruses, the enzyme used cannot
proofread and fix mutations. Examples:
Influenza, common cold virus (rhinovirus).
DNA Viruses vs. RNA Viruses
a. Some RNA viruses use their RNA to make
DNA which gets integrated into the host cell;
called retroviruses.
b. When retroviruses make a copy of the RNA
as DNA, the DNA can integrate into host cell
DNA causing a lysogenic infection.
c. Example: Human Immunodeficiency Virus
(HIV), Ebola virus
Symptoms of Viral Infections
Lytic Infections: If you have a lytic
infection, you will have symptoms of the
infection because your cells are being
destroyed and your immune system is
fighting the infection.
Symptoms of Viral Infections
Lysogenic Infections: You can have a viral
infection and not know it if the infection is
lysogenic. In this cause you will not show
any symptoms of the infections. It is
dormant.