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Viruses & Bacteria
Chapter 19
Pages 471 - 490
Compare/Contrast
Prokaryotes (Bacteria)
Eukaryotes
Smaller
Simpler
Has genetic material
No nucleus
Grow, reproduce, &
respond to environment
Some move by gliding
or swimming
Some have internal
membranes
Unicellular
Larger
Complex
Has genetic material
Nucleus
Grow, reproduce, &
respond to environment
All move
Have internal membranes
Unicellular & multicellular
Has organelles & cytoplasm
Bacteria
• Prokaryotes
–Smallest, most common
microorganism
–Single-celled
–Lack nucleus
–Has DNA
Bacteria
• 2 Kingdoms
• Archaebacteria
– Look similar.
– Live in harsh environments.
– Lack peptidoglycan in the cell wall.
– Have different membrane lipids.
– DNA sequences of key genes are more like
those of eukaryotes than eubacteria.
– Are thought to be ancestors of eukaryotes.
– Ex. Methangones- produce methane gas.
Bacteria
• 2 Kingdoms
• Eubacteria (pg. 472)
– live almost everywhere, larger of the two.
– Usually surrounded by a cell wall made up
of carbohydrate & peptidoglycan.
– Cell membrane inside cell wall.
– Cytoplasm.
– Ex. E coli
Bacteria
• How we Identify Prokaryotes (cont.):
– How they release energy by cellular respiration and
fermentation
• Obligate aerobes – require constant supply of oxygen. Ex.
Tuberculosis.
• Obligate anaerobes – do not require oxygen. Oxygen could
kill it. Ex. Botulism is found in canned food that’s not properly
sterilized.
• Facultative anaerobes – can survive with or without oxygen.
Can live anywhere. Ex. E coli which is found in the large
intestines or in sewage or contaminated water.
Bacteria contain:
•one circular piece of DNA
•tiny circular pieces of DNA
called plasmids
•ribosomes
Bacteria have cell walls made of:
•peptidoglycan (a sugar linked to
chains of amino acids).
•this may be covered with an outer
membrane of lipopolysaccharide
(chain of sugar with a fat attached).
Some bacteria:
• have a gelatinous layer called a
capsule surrounding the cell wall.
• form thick-walled endospores
around chromosomes when they
are exposed to harsh conditions
(drought, high temperatures) these types cause botulism
Some bacteria have:
• flagella for
locomotion.
• pili (short, thicker
outgrowths that
help cell to
attach to
surfaces)
1.Rod shaped are called bacillus
2.Sphere shaped are called
coccus
3.Spiral shaped are called
spirillum
Bacteria
• How we Identify Prokaryotes:
• Shape – bacilli, cocci, spirilla.
• By the way they move.
• By the way they obtain energy.
– Most are Heterotrophes which obtain energy by
consuming food.
» Chemoheterotroph- Ex. Botulism (food poisoning).
» Photoheterotroph- uses photosynthesis.
– Autotrophs make their own food.
» Chemoautotroph- found in deep ocean floors.
» Photoautotroph- found near surface in lakes oceans &
streams.
• The chemical nature of their cell walls.
– A method of Gram Staining is used to determine nature.
Gram (+) = violet, Gram (-) = pink.
Bacteria
• Reproduction
– Binary fission – DNA replicates & divides
producing 2 daughter cells. Asexual
reproduction.
– Conjugation – process where genetic
information is exchanged.
– Spore formation – an endospore may form
when growth conditions become unfavorable.
Bacteria reproduce:
asexually using binary fission.
Bacteria reproduce:
sexually using conjugation.
Bacteria exchange
plasmid DNA.
This is how bacteria
become antibiotic
resistant.
1.Most are heterotrophs:
a. Decomposers – feed on and recycle
organic material
b. Pathogens – parasitic, disease-causing
bacteria
• Either attack cells or secrete toxins
c. Nitrogen-fixing bacteria (Rhizobium)
• Found in nodules of soybeans,
peanuts, alfalfa, and clover
• Convert atmospheric nitrogen (N2) into
ammonia, called nitrogen fixation.
• Used in crop rotation
Nitrogen fixing bacteria
in the nodules of roots
2. Some are photosynthetic.
•These are autotrophs that use
the sun’s energy to make food.
3. Chemoautotrophs
•Obtain energy from molecules like
ammonia and methane to make food.
•Examples: Nitrobacter and Nitrosomonas
- live in soil
- have a crucial role in nitrification
(turn
ammonia into
nitrates, the
form
of nitrogen commonly
used by plants).
There are three types of bacteria based on how they obtain energy:
heterotrophs, photosynthetic, and chemoautotrophs.
This is the
anthrax
bacterium.
• work by preventing cell wall
formation, breaking up cell
membranes, or disrupting
chemical processes.
•cannot treat viral infections.
Strep throa
Streptococcus
Staphylococcus
Gonorrhea-Passed from Mother to
Baby
Syphilis
Helpful Bacteria
• Decomposers break down dead organic material
• Biotechnology - inserting helpful genes into a
plasmid
• Bioremediation - bacteria eat up oil spills
• Food production – cheese and yogurt
• Put nitrogen back into the soil
• Aid in digestion
Interdependence
Viruses and
organisms rely
on their
environment
and other
species for survival.
Viruses
Viruses are NOT cells. A virus
is an infectious agent made up
of:
•a core of nucleic acid (RNA or DNA)
•a protein coat
Alive or not?
Even scientists disagree as to
whether or not viruses are
alive. What do you think? Look
at the chart on the next page
to help you decide.
Characteristic
of life
CELL
VIRUS
Made of cells
YES
NO
Obtain & use
energy
YES
NO
Grow & develop
YES
Reproduce
YES
Respond &
adapt
Contain RNA or
DNA
Only inside a
living cell
Only inside a
living cell
YES
YES
YES
YES
Viruses
• Viruses are particles of:
– Nucleic acid
– Protein
– Lipids (only in some)
• They vary in size and structure.
• They enter living cels & use the machinery of the
infected cell to produce more viruses.
• Composed of:
– A core DNA or RNA (which has the instructions
for making copies)
– This is surrounded by a protein coat called a
capsid which binds the virus to the surface of the
host cell.
Structure
of a virus
ENVELOPE
• Envelope (part of
the protein coat)
• Capsid (part of
the protein coat)
• Nucleic acid
(either DNA or
NUCLEIC
RNA)
ACID
CAPSID
Viruses
• Bacteriophages– Viruses that infect bacteria.
– Ex. Bacteriophage T4
Bacteriophage
• A virus that
only infects
bacteria
CAPSID
HEAD
DNA
CAPSID
TAIL
FIBER
Ticking time
bombs . . .
Viruses do not reproduce,
EXCEPT inside a living cell.
They invade a living cell and
let the cell do the work for
them.
Lytic Cycle
The viral infection that
rapidly kills the host cell is
the lytic cycle.
Cycle Illustration
1
2
4
3
5
Lysogenic Cycle
The viral infection that enters
a cell, remains harmless for a
period of time (sometimes
years), and then becomes
harmful later is called the
lysogenic cycle.
Viruses
• Once inside a host cell:
pg. 481
– Lytic infection
• Virus inters cell and makes copies of itself.
• Causes cell to burst, releasing new virus particales that
can attack other cells.
• It then uses materials of host cell to make copies of its own
DNA molecule.
• Host cell is destroyed.
– Lysogenic infection
• Virus integrates its DNA into the DNA of host cell.
• The viral genetic info. replicates along with the host cell’s
DNA.
• Viral DNA that’s embedded in host’s DNA is called
prophage.
• Unlike lytic, it does not lyse the host cell right away so it
may remain a part of DNA of host for many generations.
Viruses
Retroviruses
– contain RNA as their genetic information.
– Genetic information is copied backwards.
– It may remain dormant for any length of time
before becomes active and it can cause death
of the host cell.
– Ex. AIDS, some cancers.
Retrovirus
ENVELOPE
• A virus that
contains RNA
instead of DNA
• Human
RNA
Immunodeficiency
Virus (HIV) is a
retrovirus
• HIV causes AIDS
CAPSID
Viruses
• Must infect living cells in order to
reproduce.
• Are Parasites.
• Are not considered to be living things
because they are not made up of cells &
cannot live independently.
• See Chart on pg. 483
Obj. 15 – Jenner and Pasteur
(p. 931)
• Edward Jenner, English Doctor….
– Invented vaccine
– Infected own son with cow pox (a mild
form of small pox)
– Son didn’t contract small pox
– Cow pox triggered immune system to
create an immunity against small pox
Obj. 15, cont.
• Louis Pasteur
–Pasteurization
–Disproved spontaneous generation
–Said “life came from life”
–Boiled broth to kill microorganisms
Obj. 16 – What is an
epidemiologist? (p. 457)
• A scientist who studies the causes and
controls of disease outbreaks.
• Involved in preventing disease outbreaks
and in stopping outbreaks that do occur
spreading.
• Work for CDC, FBI, etc.
Obj. 17 – Inoculation & Incubation
of culture medium
• Culture medium – either a broth or an
agar with nutrients added to it to aid in the
growth of microorganisms.
• Inoculation – referred to as a streak or
stab (putting microorganisms in a nutrient
agar or broth so they can grow)
• Incubation – usually 24 – 48 hours at a
temperature of 20º C or 37º C.
Inoculation Technique
Heat loop
Inoculation
Inoculation Broth
Inoculation Slant
Agar Deep
Agar Plate
Streak Plates
Finished Product
Pathogen – disease causing
organisms
• Virus
• Bacteria
• Fungi
• Protozoans
Bacterial Diseases
• Louis Pasteur – the first to show that bacteria
caused diseases and established the germ
theory of disease.
• Diseases:
– Tuberculosis- bacteria is inhaled into lungs which
destroys tissue and gets into the blood to travel
to other places throughout the body.
– Strep Throat- bacteria releases toxins. This bacteria
also causes scarlet fever.
– Diphtheria- infects tissues of the throat which leads to
breathing problems, heart failure, paralysis & death.
– Lyme Disease
– Tooth Decay
Obj. 18 – Koch’s Postulates (p. 930)
1. The pathogen must be found in an
animal with the disease and not in a
healthy animal.
2. The pathogen must be isolated from the
sick animal and grown in a laboratory
culture.
3. When the isolated pathogen is injected
into a healthy animal, the animal must
develop the disease.
4. The pathogen should be taken from the
second animal and grown in a laboratory
culture. The cultured pathogen should
Obj. 6 – Infectious v. Noninfectious
diseases (p. 924)
• Infectious disease - Any disease
caused by the presence of pathogens
in the body
–Easily spread from one person to
another or from one body part to
another
• Non-Infectious disease - One that
does not spread
Obj. 7 - How is disease spread?
• People – Direct contact
–Touching
–Kissing
–Sexual contact
• Object – food poisoning
• Air, Soil and Water
• Vectors – insects: malaria
Bacteria produce disease in 2
ways:
• Bacteria damage the cells & tissues of
the infected organism directly by
breaking down the cells for food.
• Bacteria release toxins (poisons) that
travel throughout the body interfering
with the normal activity of the host.
Prevention & Control
• Vaccine – a preparation of weakend or killed
pathogens. It can prompt the body to produce
immunity to the disease.
• Immunity – the body’s natural way of killing
pathogens.
• Antibodies – compounds that block the growth &
reproduction of bacteria.
– When a bacterial infection occurs, antibiotics can be
used to fight the disease.
– Animals can suffer from bacterial diseases as well.
Ex. Anthrax – sheep to farmers & wool workers which
can lead to death. (biological warfare)
Obj.11 – Active v. Passive
immunity (p. 930 – 932)
• Immunity – resistance to a particular
disease
• Active immunity - immunity that you
get because you have been exposed
to a disease
• Passive immunity – immunity that
you get because of a vaccine
Obj. 8 – T cells and B cells (p. 927 –
929)
• Both are white blood cells
• Regulated by helper T cells
• B cell response – defense that aids the removal
of extracellular pathogens
– B cells
• Stay in lymph nodes & organs
• Mature in bone marrow
• T cell response – destruction of intracellular
pathogen by cytotoxic T cells
• Both lymph, organs & circulation
• Occur in thymus gland (located in lower
neck & thorax)
• Act directly against certain pathogens
Obj. 9 – Specific v. Nonspecific (p. 924929)
• Nonspecific – always present, fights
off anything foreign to the body.
–2 lines of defense (1 outside, 1
inside)
• Specific – body has been exposed to
disease before (immunity to chicken
pox once you have already had the
disease)
Obj. 9, cont.
• 1st line of nonspecific defense
– Mucous membranes – traps it before it
can enter the body
– Skin – acts as a physical barrier
– Sweat – contains lysozyme (which
digest bacterial walls)
• 2nd line of nonspecific defense
– Inflammatory response
– Temperature response
– Proteins
– White blood cells
Obj. 9, cont.
• Temperature response
–Disease causing bacteria don’t grow
well at high temperatures
–Normal body temperature 37º C
(98.6º F)
–> 39º C (103º F) – dangerous
–>41º C (105º F) - fatal
Obj. 9, cont.
• Inflammatory
response
Obj. 9, cont.
• Protein complement system
– About 20 different proteins circulate in the
blood and became active when they
encounter certain pathogens by attaching to
the surface of proteins and damaging
plasma membrane.
• Interferons
– Protein is released by cells infected with
virus which causes nearby cells to produce
an enzyme that prevents viruses
White blood cells – patrol the bloodstreamwait to attack the pathogen
– Neutrophils – engulf bacteria, then release
chemicals that kill bacteria, can also squeeze
between cells in the walls of capillaries to
attack pathogens.
– Macrophage – ingest & kill bacteria and
clear dead cells & other debris, travel
through the body in lymphatic systems and &
between cells, concentrated in particular
organ (spleen and lungs)
– Natural killer cells – attack cells infected
with pathogens, puncture cell membrane,
water rushes into infected cell which swells &
burst (body’s defense against cancer)
Obj. 9, cont.
•
•
•
•
•
SPECIFIC RESPONSE
White Blood Cells – produced in bone
marrow and circulate in the blood and lymph
nodes
Macrophage – consume pathogens and
infected cells
Cytotoxic (killer) T cells – attack & kill
infected cells
B cells – label invaders for later destruction by
macrophages
Helper T cells – activate cytotoxic T cells & B
cells
Obj. 9, cont.
• Infected cell has an antigen
(substance that triggers an immune
response) of an invader on its surface
• White blood cells are covered with
receptor proteins that respond to
infection by binding to specific
antigens on the surfaces of the
infecting microbes
• They recognize and bind to antigens
that match their particular shape.
Viral diseases
usually cannot be cured,
but many can be prevented
by
•Good hygiene
•Immunization
VIRAL DISEASES
BACTERIAL DISEASES
Viral Diseases
• Viruses disrupt the body’s normal
equilibrium.
• Viruses attack & destroy certain body cells
causing the symptoms of the disease.
• Diseases: Chart pg. 489
–
–
–
–
–
Common cold
Influenza
AIDS
Chickenpox
Measles
• Can produce other serious diseases in both animals & plants.
• Plant viruses have a difficult time entering cells they
infect partly because plant cells have though cell walls.
Viral Diseases
• 2 Virus like particles can cause disease:
• Viroids – single-stranded RNA molecules that have
no surrounding capsoid. (cause disease in plants).
– Ex. Tobacco mosaic virus.
• Prions – particles that contain only protein which
have no DNA or RNA. (cause disease in animals &
humans).
– Ex. Foot & mouth disease in livestock.
MEASLES
SMALLPOX
HERPES
Prevention & Control
• Methods of controlling bacterial growth:
– Sterilization – heat; most can’t survive high
temperatures for long period on time.(kills
bacteria)
– Disinfectants – soaps & cleaning solutions;
sterilizes hospitals; overuse may cause bacteria
to evolve.(kills bacteria)
– Food storage – refrigeration (bacteria takes longer
to multiply at low temperatures); boiling; frying;
steaming.
– Food processing – canning (heated to high
temperature, placed into sterile jars & sealed);
chemical treatments such as salt, vinegar,sugar.
(kills bacteria)
Protection Against
• Vaccines – prevention.
• Antibiotics – viruses do not respond to
antibiotics but sometime the symptoms
can be treated.
Obj. 12 – HIV (p. 934 – 935)
• HIV is transmitted when the body fluids of
an infected individual are passed on to an
uninfected individual by direct contact or
contaminated objects.
• Breaks down immune system, so can no
longer fight off disease
– Hides in Helper T cells
• People w/HIV, then AIDS suffer from two
rare problems.
– Pneumosystis carinii – protozoan
infections of lungs
– Kaposi’s sarcoma - cancer
Obj. 13 – Allergies (p. 926)
• Occur when antigens bind to
mast cells.
• Activate mast cells which
release histamines.
–Histamines produce sneezing,
runny eyes & nose
Common Antigens that cause
allergies
• Foods
• Dust
– Milk, eggs
• Antibiotics
– Penicillin
• Cosmetics
• Pollen
• Molds
• Microbes
• Chemicals in plants – poison ivy
Obj. 14 – Autoimmune diseases
(p. 933)
• A disease in which the immune system
starts attacking body cells as if they were
pathogens.
• Affect organs and tissues in different parts
of the body.
• Graves disease, Multiple sclerosis (MS),
Rheumatoid arthritis, Systemic lupus
erythematosus (SLE), Type I diabetes
Some Autoimmune Diseases
• Rheumatoid Arthritis – exact cause is unknown,
but clear the immune system is involved.
– Involves inflammation of joint, swelling,
pain & loss of function.
• Rheumatic Fever – happens when
streptococcus bacteria causes a disease
known as strep throat.
– If left untreated, the immune system
produces antibodies that destroy
bacteria.
• Multiple sclerosis – result of destruction
by immune system of special cells that
surround nerve fibers and permit rapid
impulse transmission.
Autoimmune diseases, cont.
• Lupus – exact cause unknown, although it is
certain that both environment & genetic factors
are involved.
– Believed a genetic pre-disposition to the
disease
• Symptoms include:
– Achy joints, 100°F + fever, Arthritis,
Prolonged or extreme fatigue, Skin rashes,
Anemia, Kidney disorders
• Factors that trigger Lupus:
– Infections, Antibiotics, Ultra-violet lights,
Extreme stress, Hormones
AUTOIMMUNE DISEASES
Chapter 20 & 40 Vocabulary Quiz
1. An agent that causes a disease is a
__________.
2. The process in which two organisms
exchange genetic material is __________.
3. The four step guide for identifying specific
pathogens is called __________
__________.
4. A non living, infectious particle composed
of a nucleic acid and a protein coat is a
__________.
5. A __________ is a protein that reacts to a
specific antigen or that inactivates or
destroys toxins.
Chapter 20 & 40 Vocabulary Quiz
7. In bacterial viruses, the cycle of viral
infection, replication, and cell destruction is
called the __________ cycle.
8. A substance that can inhibit the growth of or
kill some microorganisms is called a
__________.
9. A virus that infects a bacteria is a
__________.
10. An __________ is a substance that
stimulates an immune response.
Chapter 20 & 40 Vocabulary Quiz
1. An agent that causes a disease is a
pathogen.
2. The process in which two organisms
exchange genetic material is conjugation.
3. The four step guide for identifying specific
pathogens is called Koch’s Postulate.
4. A non living, infectious particle composed
of a nucleic acid and a protein coat is a
virus.
5. An antibody is a protein that reacts to a
specific antigen or that inactivates or
destroys toxins.
6. A protective response of tissues affected by
Chapter 20 & 40 Vocabulary Quiz
7. In bacterial viruses, the cycle of viral
infection, replication, and cell destruction
is called the lytic cycle.
8. A substance that can inhibit the growth of
or kill some microorganisms is called an
antibiotic.
9. A virus that infects a bacteria is a
bacteriophage.
10. An antigen is a substance that stimulates
an immune response.