Viruses

1
Viruses
Viruses

• What are they?
• How do they work?
• Where do they come from?
• And What good are they?

2

• Viruses Making a Living by Hijacking Cells
• Not living organisms lack some attributes of
  life.
• Are infectious particles, cant replicate
  independently.
• Not cells and dont carry out metabolism
• Made of RNA or DNA usually enclosed in protein
  coat (viroids lack protein coat).

3
Protein coat (capsid) takes many shapes. DNA or
RNA is always within the capsid
4
Some viruses have an envelope to cover them!
Envelope came from hosts cell membrane when
virus budded out of host
5
Some viruses are naked!They have no envelope
Some VIRUSES have no envelope theyre naked!
HERE IS A virus THAT INFECTS BACTERIA It is
called a bacteriophage.
6
How Big are viruses?
Polio virus 20 nanometers
20nm
1 nm 0ne billionth of a meter! 3000 polio
viruses fit across the diameter of a period at
the end of a sentence in your book.
7
Viruses cant reproduce on their own

• They must invade a cell.
• Once inside a cell, they cause the cell to make
  more viruses instead of their usual proteins.
• They are intracellular obligate parasites they
  cant do anything on their own.

8

• The lytic cycle demonstrates the steps that a
  virus takes in order to take over a cell.
• The steps are
• Attachment
• Injection
• Replication
• Assembly
• lysis

1
1
5
2
4
3
9
(No Transcript)
10
Sometimes the virus doesnt kill the cell right
away and it becomes part of the cells genes.If
this happens, the virus DNA becomes a prophage
and can become activated at any time (like a time
bomb).In the meantime, the prophage is passed on
to all the offspring of that cell . Maybe for
many generations.
11

• .

12
When were viruses discovered?
Viruses have apparently always been
around. However, it wasnt until 1897 that a
Dutch scientist named Beijerinck called an
invisible agent that was smaller than bacteria a
virus (Latin for poison). He was studying
tobacco leaves that had been infected with what
we now know as tobacco mosaic virus.
13
Classification of Viruses
By Shape by Host
type by function
Animal viruses
Retroviruses attack a certain way. DNA viruses
attack another way.
Plant viruses
Bacteria viruses
14
Retroviruses
Contain RNA When infecting a cell, these viruses
have to transcribe the RNA to DNA before the
viral code can be read. This requires an enzyme,
reverse transcriptase, to Change RNA to DNA then
the viral code can be added to the cells
DNA. Once part of the cells Dna, the viral code
can cause the cell to make more viruses.
15
HIV IS A RETROVIRUS
Gp120 gp41
envelope
16
HIV LIFE CYCLE
1
2
3
4
hiv
5
gp41
6
7
17
HOW HIV GETS INTO A CELL
18
HIV infecting a T cell
hiV IN A CELL AND BUDDING OUT OF A CELL
19
(No Transcript)
20
Ways to get HIV
At birth from mother
Unprotected sex
Dirty needles
21
(No Transcript)
22
Treatment includes trying to enhance body
defenses using stem cells
23
TREATMENT INCLUDES INHIBITORS OF ENZYMES1.
Reverse transcriptase inhibitor This enzyme
allows viral RNA to code for DNA2. Protease
inhibitor This enzyme allows viral proteins to
be cut and fit into the final virus3.
Integrase inhibitor This enzyme allows the virus
DNA to join the cells DNA in the nucleus
24
Effects of treatment are evident when comparing
infections suffered by AIDS patients in 1993 with
those in 1997
25
Drug-resistant HIV
26
T-cell count as disease progresses
27
WAYS TO AVOID GETTING hiv IN THE FIRST PLACE

• ABSTINENCE.
• SAFE SEX ALTHOUGH NO METHOD IS 100 SAFE.
• DONT SHARE NEEDLES OR ANYTHING THAT CAN MIX
  BLOOD.

28

• Viruses infect many organisms, including
  bacteria, plants, and animals cause much
  agricultural loss, mild to deadly human diseases
  (cold, flu, chickenpox, herpes, rabies, AIDS,
  some types of cancer).

polio
ebola
flu
smallpox
29
Arent you glad we dont get smallpox anymore?
Smallpox has been eliminated from the world as a
result of immunizations
30

• Vertebrates defend against viruses through
• antibody-based immunity or cellular immunity.
• 1. Immune system produces specific proteins
  (antibodies) that recognize and bind viral
  particles, thereby blocking their replication.
• Immune cells called T cells recognize and destroy
  cells harboring viruses (cellular immunity).
• After first infection, body retains clones of
  antibody or T cells directed against that viral
  strain
• Rapid defense is mounted upon second infection.
• This is what happened when you recovered from
  chicken pox.

31

• This immune memory is the basis of vaccination
  vaccine consists of killed or nonfunctional
  viruses, triggers immune response in body without
  disease symptoms upon subsequent infection with
  active virus.

Dr. Edward Jenner produced the first vaccine that
was used widely. He injected cowpox pus into a
boy the boy got cowpox and recovered. Jenner
then injected the boy with smallpox pus and
waited..the boy did not get smallpox.
32
Nonviral infectious agents

• Prions
• PIECE OF PROTEIN
• CAUSE OF MAD-COW DISEASE
• CAN INFECT ANIMALS INCLUDING HUMANS

• vIROIDS
• Single strand of RNA
• Causes plant diseases

33
Human diseases caused by viruses

• Common cold
• Influenza (flu)
• Chickenpox
• Polio
• HIV
• Some pneumonia
• Some meningitis
• herpes

34

• Domain Bacteria
• Masters of Every Environment
• Bacteria exist in staggering numbers in wide
  range of habitats.
• 1. Microflora of human gut includes 600 species
  of bacteria in mouth alone quarter of feces by
  weight consists of bacteria.

YUCH!
Gut bacteria
35

• A. Bacteria exist in staggering numbers in wide
  range of habitats.
• 2. Nitrogen-fixing bacteria have symbiotic
  relationship with some plants convert molecular
  nitrogen into forms usable by plant nitrogen
  needed by animals comes ultimately from plants.
• 3. Bacteria play an important role as decomposers
  (as in city sewage plants)

36

• Bacteria varied in shapes
• 1. Cocci--spherical
• 2. Bacillirod-shaped
• Spirochetesspiral-shaped
• Bacteria enormously diverse 4,000 to 5,000
  species found living in 1 gm of forest soil.

37
Some bacteria names have prefixes that describe
their structure

• Diplo bacteria in pairs
• Ex diplococcus or diplobacillus

This diplococcus causes gonorrhea
38

• Strepto means chain of cells
• streptococcus or streptobacillus

39
Staphylo means cluster Ex
staphylococcus a major cause of infection in
hospitals
40

• Characteristics of bacteria
• 1. lack cell nucleus, as do all prokaryotes
  (eukaryotes have nucleus).
• 2. Have almost no other cell organelles, no
  cytoskeleton.
• 3. DNA present as single chromosome haploid
  organisms.

41
Bacteria cell - Prokaryotic
plasmid
42

• Reproduction is asexual, by simple splitting
  (binary fission) daughter cells genetic clone of
  parent cell.

43
Are single-celled may form colonies.(EACH DOT
ON THE PLATE IS A COLONY MADE UP OF MILLIONS OF
BACTERIA)
44

• We combat disease-causing bacteria with
  antibiotics.
• 1. Most antibiotics are from fungi, which have
  waged war of survival with bacteria.
• 2. Antibiotics must exploit differences in cell
  biology of bacteria and humans to keep from
  harming patient (e.g., penicillin destroys
  bacterial cell walls, but has no effect on animal
  cells).

45
(No Transcript)
46
Antibiotics, when placed on a paper disc, inhibit
growth of bacteria in Petri dishes. The larger
the zone of inhibition, the more effective the
antibiotic is.
Least effective most effective
47

• Mode of nutrition
• Autotrophs
• PhotoautotrophyUse light energy and carbon
  dioxide to create energy-rich carbon compounds,
  as plants do too.

48
ChemoautotrophyUse inorganic compounds (hydrogen
sulfide, ferrous iron) to fix carbon from carbon
dioxide.
49
Most Monerans are Heterotrophs
Escherichia coli
spirillum
anthrax
50

• Domain Archaea - Newly recognized as ancient
  group of prokaryotes.
• Divergent from all other life-forms majority of
  genes (from Methanococcus) unique to group, not
  previously known to science.

Stromatolites Rock formations made by some of
these bacteria
51

• Some live in extreme environments
  (extremophiles)
• High or low temperatures, high pressure, high
  salt, extreme pH.
• Thermophiles live in hot water

52
Halophiles live with high salt
Great Salt Lake
53
Endospore production preserves the cell during
hard times not a form of reproduction

• Steps in formation of an endospore

54
Endospore
Bacteria that are harmful to humans and that form
endospores Clostridium tetani causes
tetanus Clostridium botulinum causes deadly
food poisoning
55
Cell Wall Composition gram positive or gram
negative

• Gram positive Gram negative
• Stains blue stains pink

56
Respiration process of getting energy from food

• Aerobic
• Need oxygen
• Cant live without oxygen obligate aerobes
• EX TUBERCULOSIS BACTERIUM
• Prefers to live with oxygen facultative aerobes

Tb lung
57

• Anaerobic
• dont need oxYgen
• SOME CANT SURVIVE WITH OXYGEN
• THESE ARE OBLIGATE ANAEROBES
• EX TETANUS
• This baby probably got tetanus from honey dont
  give honey to a baby!

58

• SOME CAN LIVE WITH OXYGEN BUT PREFER TO LIVE
  WITHOUT IT fACULTATIVE ANAEROBES

E. coli
59
How Important are bacteria to the world?

• Decomposition most important function for
  living things. What happens to all the dead
  bodies?
• Here is a bacterium
• of decay

60
Food web
61
Nitrogen cycle
62
Cow Digestion
63
Tooth Decay
Yuch!
Dont forget to brush and floss your teeth!
64
Foods from bacteria
cheese
yogurt
sauerkraut
65
Diseases caused by bacteria
Anthrax a natural pathogen that can be used for
bioterrorism
66
Lyme disease causes illness and can lead to
arthritis
67
gonorrhea
plague
Strep throat
68
Food poisoning
Salmonella food poisoning from eggs, chicken,
mayonnaise
Botulism from improperly canned foods
69
Here is a white blood cell attacking a bacillus
70
Medical uses of bacteria

• Genetic engineering to produce medical products
  
• Insulin
• Human growth hormone

Gene for human insulin or hgh
Now all cells will have the gene and will make
the product
71
Uses of bacteria other than food production

• Bioremediation using microorganisms to rid
  environment of harmful substances
• Ex oil spill site
• Hazardous waste site
• Sewage treatment

72
Medical uses of bacteria

• Genetic engineering to produce medical products
  
• Insulin
• Human growth hormone

Gene for human insulin or hgh
Now all cells will have the gene and will make
the product
73
What conditions do bacteria need for the best
growth?

• Food source (your soup is good)
• Proper temperature - human pathogens (disease
  causers) live best at 98.6 F.
• Moisture
• Oxygen (aerobes) or not (anaerobes)
• Change any of these and the growth of bacteria
  can be slowed down or stopped.

74
We compete with bacteria for our food they eat
the same stuff we do. How do we preserve our
food?
Drying (prunes)
salting
refrigeration
pickling
freezing
75
Thats all folks!