Bacteria and Viruses Chapter 19

Bacteria and Viruses
Chapter 19
Bacteria
• Bacterial cells do not have
nuclei so they are Prokaryotic.
• Bacteria used to be collectively
grouped into the Kingdom
Monera but now it is separated
into 2 Kingdoms: Eubacteria and
Archaebacteria.
Eubacteria
• Common bacteria, wide variety
of organisms that live almost
everywhere
• Some can cause disease
• Eubacteria have a cell wall that
contains a carbohydrate called
peptidoglycan.
Archaebacteria
• Ancient bacteria that live in very
harsh environments.
• Have cell walls that lack
peptidoglycan.
• In fact their DNA is more like that
of a eukaryote than a
eubacteria’s. This is why many
people believe that archaebacteria
are the early ancestors of
eukaryotes.
Structure
• Bacteria do not have a
nucleus.
• Bacteria tend to be smaller
than eukaryotic cells.
• Bacteria are single-celled
organisms but sometimes they
stick together and live in
colonies.
Structure
• Bacteria have a single circular
strand of DNA.
• Bacteria reproduce by binary
fission, which is basically when
the cell pinches in half.
• Some bacteria have flagella that
help to propel them.
Shape
• Bacilli –rod shaped
• Cocci—spherical shaped
• Spirilla—spiral shaped
Cocci Bacteria
• Cocci bacteria can group together to
form:
– Chains—streptococci
– Clusters—staphylococcus
Obtaining Energy
• Bacteria can be either autotrophs or
heterotrophs.
Obtaining Energy
• Bacteria can be either autotrophs or
heterotrophs.
–Autotrophs—make their own energy
• photoautotroph –perform
photosynthesis like plants (cyanobacteria)
• Chemoautotroph-obtain energy from
inorganic materials like sulfur and
ammonia
–Heterotrophs—must obtain energy from
another source
Releasing Energy
• Bacteria can release energy through
cellular respiration (requires Oxygen) or
fermentation (does not require Oxygen)
–Obligate Aerobes—require Oxygen
–Obligate Anaerobes—require Oxygenfree conditions
–Facultative Anaerobes—do not require
Oxygen but can survive in its presence
Reproduction
• Bacteria can reproduce at an
incredible rate. Some will divide in
as little as 20 minutes. If there were
unlimited resources, bacteria could
reproduce to equal 4000 times the
mass of the Earth in 48 hours.
• Binary fission (assexual)
Endospore
• Some bacteria like anthrax form
spores that allow them to remain
dormant for months, years, even
centuries.
• This allows them to survive
through extreme heat or
total lack of nutrients.
Bacteria in Nature
• Bacteria can be useful. Many
help to capture energy from the
sun others breakdown dead or
decaying material so that the
nutrients and materials can be
recycled into a form that other
organisms can use.
Human Uses
• Food processing
• Digest oil spills
• Synthesize drugs and
chemicals
Bacteria and Disease
• Bacteria cause disease in 2
ways:
–Destroy the hosts tissues (Tb)
–Release toxins that poison the
host (C. botulism)
• See chart p. 486/489
Antibiotics
• Antibiotics are used to block
the growth and reproduction of
bacteria.
• Why are some bacteria drug
resistant?
Controlling Bacteria
• Sterilization—is the process of
destroying the bacteria on a
nonliving surface by extreme heat or
chemicals.
• What is the difference between an
antiseptic and a disinfectant?
STOP
Viruses
• Viruses are particles of nucleic acid
(either DNA or RNA) surrounded by
a protein coat (called a capsid).
• Viruses vary in size and structure.
• Viruses can only replicate by
entering a host cell and using
that cell’s materials to copy itself.
Viral Infection
• When a virus enters a cell it will
begin one of 2 cycles: p 481
– Lytic Cycle—virus enters a cell,
copies itself, and bursts the cell
– Lysogenic Cycle—virus enters a
cell, embeds its DNA into the cell’s
DNA so that it is replicated along
with the host cell, eventually this
virus will wake up and begin
destroying the cells.
HIV
• Human Immunodeficiency Virus—The virus
that causes AIDS
• HIV attaches to and enters macrophages ( a
type of white blood cell). It then uses an enzyme
called reverse transcriptase to change its RNA
into DNA. This process causes many mistakes
(mutations). This is why HIV mutates or
changes so easily. This new DNA is embedded
in the host cell’s DNA. When the virus replicates
it does not burst the cell, instead the new viruses
are released by budding. A person with HIV
usually shows no symptoms of the disease for at
least 8-10 years.
HIV
• Eventually the HIV virus begins to
invade T cells. When the virus
replicates in the T cells it burst and
destroys them. It is the low number
of T cells that leave the body unable
to protect itself against infection thus
the onset of AIDS.
http://learn.genetics.utah.edu/content/begin/cells/scale/
Emerging Viruses
• 1.
• 2.
• 3.
West Nile
Avian Flu
Hanta Virus
Prions
• Prions are disease-causing proteins
with no nucleic acid.
• These proteins are folded into
shapes that prevent them from
working.
• Contact with a prion will cause a
protein in your body to become
folded incorrectly and not function.
• Mad Cow disease or CreutzfeldtJakob Disease is caused by prions.
• Prions cannot be destroyed by
cooking
Bacteria…
All of these photos are of different types of bacteria. Many bacteria have cilia
and/or flagellum for locomotion. These are single celled organisms
Capable of
multiplying by
themselves
Single Cell Organism
Can be
harmful or
beneficial
to humans
Rigid Cell
Wall
This type of
infection is treated
with antibiotics
Staph
Infection
Strep
Throat
Pneumonia
Meningitis
Viruses…
Viruses are not considered living organisms because they do
not have the ability to reproduce on their own.
They must have a host cell to reproduce.
Viruses are very simple and contain either DNA or RNA.
Flu
Chicken
Pox
Common
Cold
HIV
Non-living
Must have
a host to
reproduce
Has a
protein
coat
Viruses differ from bacteria in that
all viruses —
A
B
C
D
cause insect-borne diseases
can be destroyed by antibiotics
have rigid cell walls
must be reproduced in living cells
D
Which of the following is found in
both cells and viruses?
A
B
C
D
Silica
Genetic material
Digestive cavity
Flagella
B
Some antibiotics cause patients to exhibit
digestive side effects. These side effects are
most often the result of —
A
B
C
D
bacteria being killed in the digestive tract
the antibiotics being converted into stomach acids
too much water being drawn into the digestive tract
the stomach wall being torn
A
Which of the following explains
why antibiotics can treat flu-like
symptoms caused by bacteria but
are ineffective against flu?
A
B
C
D
Flu is a response to an antigen.
Antibiotics require time to work.
Antibiotics strengthen antibodies.
Flu is caused by a virus.
D
Lactose is a naturally occurring sugar found in
milk. Some dairy products, such as yogurt,
may contain live bacteria. These products are
useful to people who lack the ability to digest
lactose. What does this information
demonstrate?
A
B
C
D
Bacteria raise the acidity of processed foods.
Some bacteria interfere with digestion.
Bacteria can prevent insulin production.
Some bacteria are beneficial to human health.
D