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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
• 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
• 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
• 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
• 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
• 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
• Importance of Bacteria:
– Producers – that carry out photosynthesis.
– Decomposers – that break down dead matter
“natural recycler”.
– Nitrogen fixers – process in which soil bacteria
convert natural nitrogen gas into a form plants
can use.
– Human use – industry (clean up oil spills), food
production, synthesize drugs, mine minerals, &
remove waste products & poisons from water.
• Ex. E coli in intestines make vitamins that the body
cannot produce themselves which is a symbiotic
relationship (both benefit).
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.
Viruses
• Bacteriophages– Viruses that infect bacteria.
– Ex. Bacteriophage T4
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.
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
Diseases Caused by Bacteria &
Viruses
• Pathogens
– Disease- causing agents.
– Include bacteria & viruses that cause disease
(not all bacteria).
– Some live in and on the human body & help it
perform essential functions
– Chart on pg. 486
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
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)
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.
Protection Against
• Vaccines – prevention.
• Antibiotics – viruses do not respond to
antibiotics but sometime the symptoms
can be treated.
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)