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Microbiology
Part 2
Bacteria and Viruses
Bacteria
There are two main types of bacteria:
 Eubacteria (“true bacteria”) are found everywhere - in
the air, on the ground, and in water…even on the page
you are writing on now.
 Archebacteria (“ancient bacteria”) are found only in
extreme environments. - for example, places that are
intensely hot (sulfur pools, ocean vents), salty (Dead
Sea), or acidic (inside digestive tract).
Bacteria
 Most bacteria are much smaller than plant and
animal cells.
 They are prokaryotic cells. This means they have
no nucleus… all the genetic material is just strewn
around loose in the cell.
 Bacteria do contain ribosomes to manufacture
protein.
Bacteria
 Some bacteria also contain the pigment
chlorophyll and are autotrophs, able to produce
their own food through photosynthesis.
 Some other autotrophic bacteria can use energy
from chemicals in their environment to produce
their food (chemosynthesis).
 Most, however, are heterotrophs, consuming a
variety of foods, breaking down dead material or
living as parasites off a host.
Bacteria
Bacteria in soil
 Almost all organisms on Earth including most
bacteria require oxygen to break down food and
release energy- they are called aerobic organisms.
 Some bacteria, however, are adapted to live
completely without oxygen and are called
anaerobic. These are usually found buried deep
in muddy swamps or bogs, in hydrothermal vents in
the ocean, or even in the human intestines!
intestinal
bacteria
Bacteria in Nature and Industry
Bacteria are involved in:
 Oxygen and food production
 Environmental recycling and cleanup
 Health maintenance and medicine production
Bacteria in Nature and Industry:
Oxygen Production
 Autotrophic bacteria use the Sun's
energy to produce their food and as a
result they release oxygen into the air.
 Scientists believe autotrophic bacteria
were responsible for adding oxygen to
the Earth's early atmosphere and
made it habitable for life as we know it.
 Today, distant ancestors of those
bacteria continue to keep oxygen
levels in the air stable.
Bacteria in Nature and Industry:
Food Production
 The activities of helpful bacteria help produce
many foods, like soy sauce, sauerkraut, pickles,
apple cider and vinegar.
 Bacteria that grow in milk help produce dairy
products such as buttermilk, yogurt, sour cream
and cheeses.
Bacteria in Nature and Industry:
Food Production
 Some bacteria, however cause food
to spoil when they break down the
food's chemicals.
 Refrigeration and heating can slow
down spoilage
 Another method to preserve food is
called pasteurization
 Named after its inventor, Louis
Pasteur, it involves heating food to a
temperature high enough to kill
harmful bacteria without changing the
flavor of the food.
Bacteria in Nature and Industry:
Environmental Recycling
 Some heterotrophic bacteria that live in soil
are decomposers - organisms that break down
large chemicals in dead organisms into smaller
chemicals.
 For example, decomposing dead leaves in the
fall and winter so the nutrients can be re-used
by the plants in the spring
Bacteria in Nature and Industry:
Environmental Recycling
 Nitrogen-fixing bacteria live in the soil and
in nodules in the roots of a type of plant
called a legume (like peanuts, soy beans
and peas).
 These helpful bacteria help plants by
converting nitrogen from the air into a form
of nitrogen plants need to survive.
 Without nitrogen-fixing
bacteria, farmers would
need to spend millions
more on fertilizer each
year.
Bacteria in Nature and Industry:
Bio-remediation (Environmental Clean-up)
Some bacteria can
digest oils.
They can convert the
poisonous chemicals in
oil into harmless
substances.
Scientists use them to
help clean-up oil spills in
oceans and gasoline
leaks in soil under gas
stations.
Bacteria and Your Health:
Natural Flora Bacteria
There are many bacteria in your body that
help keep you healthy.
◄ In your digestive system your intestines teem
with bacteria.
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◄
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Some help you digest food.
Some make vitamins like vitamin K that
your body needs.
Others compete for space and resources
with disease causing organisms, keeping
harmful bacteria from attaching to your
intestines, making you sick.
Viruses
∞ A virus is a tiny non-living particle that enters
and then reproduces inside a living cell.
∞ No organisms are safe from viruses, for every
different type of cell in every different type of
organism, there is a virus able to invade that
organism's cells.
Viruses: Characteristics
 Viruses come in many shapes.
 All viruses have two basic parts: a
protein coat that protects the virus
and an inner core made of genetic
material.
Some viruses
are surrounded
by an additional
covering called
an envelope.
Viruses: Characteristics
 Each virus contains specific surface proteins.
 They are shaped to match a particular host
cell.
 This explains why each virus has very specific
host cells that it is able to infect.
Viruses: How They Multiply
◘ Viruses are considered non-living
because they do not show all the
characteristics of life.
◘ They are not cells and do not use
their own energy to grow or
respond to their environment
◘ Although viruses can multiply, they do
so differently than organisms. Viruses
can multiply only inside a living host cell
◘ A virus acts like a parasite, as almost all
viruses destroy the cells in which they
multiply.
Viruses: How They Multiply
◘ Once inside a host cell, a virus's genetic
material takes over many of the cells functions.
◘ It instructs a cell to produce the virus's proteins
genetic material.
◘These then
assemble into new
viruses ready to
infect more host
cells.
Viruses: How They Multiply
◘ Active viruses begin
production and assembly
immediately.
◘ Makes copy after copy of
the viruses until the host cell
bursts open and new viruses
begin infecting neighboring
cells.
Viruses: How They Multiply
◘ Hidden or latent viruses do not
affect the cell right away.
◘ The virus genetic material
becomes part of the cell's genetic
material.
◘ Each time the host cell divides,
the virus genetic material is copied
along with the host material.
◘ Then under certain
circumstances, the virus's genetic
material suddenly becomes active
and all of the damaged cells begin
producing copies of the virus.
Viruses In Medicine
* Not all news about viruses is bad.
* Gene therapy takes advantage of a virus's ability
to enter a host cell.
* Scientists replace harmful virus genetic material
with good genetic material.
*They then use the
virus as a messenger
service to deliver
genetic material to cells
that need it.
Bacteria, Viruses and Your
Health
Infectious diseases are spread through:
 Contact with an infected person
 A contaminated object
 An infected animal
 An environmental source
Once contact occurs, disease-causing
agents may enter through:
 Breaks in the skin
 May be inhaled or swallowed
 May enter the moist linings of the eyes, nose,
mouth or other body openings
Treating Infectious Diseases Bacteria
 Luckily, many bacterial diseases can be treated
with antibiotics.
 An antibiotic is a chemical that will destroy
bacteria (usually by weakening the cell wall
causing the bacterial cells to burst) without
harming a person's cells.
Treating Infectious Diseases Bacteria
 Unfortunately, some bacteria are becoming
resistant to antibiotics. As resistant bacteria
survive and reproduce the number of resistant
bacteria increases.
 Today some bacterial diseases are becoming
very difficult to treat.
Treating Infectious Diseases Viruses
 Unlike bacterial diseases there are currently no
medicines that cure viral infections.
 There are many over-the-counter medicines that
can help a person feel better.
 The best treatment for a virus is usually bed rest.
Treating Infectious Diseases Viruses
Although there is no cure for a virus, a vaccine
may be able to prevent a person from getting
sick in the first place.
A vaccine stimulates the production of
chemicals that destroy specific viruses or
bacteria.
Treating Infectious Diseases Viruses
 A vaccine may be made from dead or altered
viruses or bacteria. Therefore it will not cause a
person to become sick.
 Instead the vaccine will activate a person's natural
defenses putting the body “on alert”.
 So that if the virus
or bacterium ever
invades the body it is
destroyed by
antibodies before it
can cause the disease.