Transcript Viruses – Chp. 25 - Tamaqua Area School District

VIRUSES – CHP. 25
Pathogen – any
organism that
causes disease.
Exs.) virus, bacteria,
protozoan.
Some Examples of
VIRUS Illnesses :
Polio, Chicken Pox,
Shingles, Hepatitis,
Flu, AIDS, Common
Cold.
Are Viruses Living or
Non-Living?? :
- Scientists debate this
because viruses do
not require food,
oxygen, water……yet
they can reproduce
(note – they only
reproduce inside a
living host cell).
Bacteriophage – viruses that only
attack bacteria. Ex.) T-4 virus
T-4 Virus – a famous virus in
scientific circles.
- It only attacks bacteria – it is safe
to humans.
- It is easy to grow in petri dishes
and cost is minimal.
- Because of the above factors, T-4
makes a good research specimen.
- T-4 is famous because it has been
widely studied. Most of our early
knowledge about viruses came
from studying T-4.
Virus Structure – made up of a coat and a core.
- Coat is outer protective covering made of
protein.
- Core is made up of the genetic material DNA
or RNA.
Lytic Cycle – reproductive cycle for regular viruses.
See figure 25-5 on page 492 in book.
Stages of Lytic Cycle:
1. Attachment – virus latches onto cell.
2. Entry – virus injects its DNA into cell.
3. Replication – virus DNA takes over the cell’s
machinery and directs it to make virus parts.
4. Assembly – virus parts get put together.
5. Release – newly made viruses break out of cell
and can now go and attack more cells. (note –
the cell dies in the process).
Lysogenic Cycle – reproductive cycle for LATENT
viruses.
 Latent Viruses – infect
you now, but do not
make you sick for a
period of time. Exs.)
HIV, Herpes, Shingles.
3 Major Ways That Germs are Transmitted
1. Airborne
Transmission – enter
the body with the air
breathed in. Exs.)
smallpox, chicken
pox, polio, measles,
flu, common cold.
Prevention –
vaccines, avoid sick
people, cover your
mouth when
sneezing and
coughing.
2. Food and Water Transmission
– most effect stomach and
intestines. Gets into
food/water from intestinal
wastes. Exs.) hepatitis A,
salmonella, botulism, E. coli.
Prevention – good hygiene,
wash hands, check canned
food for damage, keep
foods refrigerated/frozen,
cook meats/eggs well done,
have drinking water tested.
3. Contact Transmission – shaking hands, kissing,
touching, sex, sharing cups, towels, etc.
- Watch wounds of all kinds
Prevention – practice safe sex, good hygiene, disinfect
wounds.
Chapter 25 - Bacteria
Classification Kingdoms of Bacteria
1. Archaebacteria – rare – only
found in a few places on
earth. Exs.) in the boiling
water of hot springs, in very
salty waters where no other
bacteria thrive, at the ocean
vents where water is
superheated.
 Eubacteria – “true” bacteria – common,
everyday bacteria. They are found just about
everywhere, including in and on our bodies.
Prokaryotic Cells (Prokaryotes) = Bacteria
- Thought to be the oldest cells on earth.
- Do not have a true nucleus that houses the DNA.
Bacterial DNA just floats unprotected inside the cell.
- Very simple structure.
They do not have any
parts that are seen in
more complex cells.
- ***BACTERIA ARE
THE ONLY CELLS ON
EARTH THAT ARE
PROKARYOTIC.***
Bacterial Shapes – Used for
Identification
 1. Coccus (Cocci)
 2. Bacillus (Bacilli)
 3. Spirillum (Spirilla)
1. Coccus (Cocci) – round, sphere shaped.
-
-
Diplococcus – 2 joined in a pair.
Staphylococcus – clumps/clusters of
cells…many cause “staph” infection.
Streptococcus – strips/chains of cells….
cause “strep” throat.
Tetrad – 4 cells arranged in a square.
2. Bacillus (Bacilli) – elongated rod shapes
- Diplobacillus – 2 joined.
- Streptobacillus – strips/chains.
3. Spirillum (Spirilla) – bent rods like a
boomerang, or corkscrew shaped. Spirilla
only occur in the single form, they do not join
together in any way.
See top of page 470 in book.
Nutrition in Bacteria
Autotrophs – “Cyanobacteria” – SOME bacteria are
photosynthetic and can make there own food.
Heterotrophs – MOST bacteria rely on other
organisms to make food for them. 2 types:
- Saprophytes – get food from dead
organisms….many of these bacteria compete
with us for our food and spoil it.
- Parasites – get food from living cells. These are
the pathogens that infect us and make us sick.
Respiration in Bacteria
Obligate Aerobes – require oxygen and cannot
live without it…….most bacteria.
Obligate Anaerobes – do not grow in the
presence of oxygen. They use other gases
such as methane or they conduct
fermentation.
Facultative Bacteria – live with or without
oxygen. They grow faster with oxygen.
Factors That Affect the Growth of
Bacteria
1. Temperature :
- 79 – 100 degrees Fahrenheit – optimum growth
range for many bacteria.
- Refrigeration/cooking inhibits bacteria.
- Body uses fever as defense mechanism to kill off
temperature sensitive bacteria.
2. Moisture:
- Bacteria are 90% water and dryness makes them
inactive
- We dry many foods to preserve them such as pasta,
dried fruit and beans, cereal, rice, potatoes.
Factors That Affect the Growth
of Bacteria
3. Radiation – sunlight and ultraviolet light kills
bacteria by mutating their DNA.
- We put ultraviolet lights in operating rooms to
kill germs.
4. Chemicals – many kill bacteria. Exs.) chlorine,
vinegar (acetic acid) to pickle foods, sugar, salt,
artificial preservatives.
Bacteria
Reproduction
and Survival
Binary Fission = simple
cell division….the
bacterium splits in 2.
- This is how bacteria
REPRODUCE when
growth conditions are
good.
Bacteria Reproduction and Survival
Spore Formation – Bacterium makes a tough
protein wrapper to protect only its DNA when
conditions are not good. This is called a
SPORE.
- This is how bacteria
SURVIVE when
conditions are not
suited for growth.
Spores can survive
quite harsh
conditions.