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Bacteria
Bacteria – 2 Domains
(Archaebacteria and Eubacteria)
• There are more bacteria on Earth than stars in the
sky!
• The closest estimate is that there are 5 million
trillion trillion bacteria on Earth – that’s a 5 with
30 zeroes after it.
• Bacteria produce the air we breathe, clean the
water we drink, and create fertile soil.
• Less than one percent of bacteria cause diseases.
Bacteria are prokaryotic
plasmid
Most bacteria die when
conditions get bad:
• These conditions could be a change in
temperature, loss of food, exposure to specific
toxic chemicals, change in pH (acid levels), etc.
• Some bacteria can preserve themselves during bad
times, then they can re-grow and resume their
lives. They do this by producing an endospore.
• Endospores can preserve the cell’s DNA until
conditions get better again. They are resistant to
all the bad conditions.
Endospore production – preserves the cell during
hard times– not a form of reproduction
Endospore
Bacteria that are harmful to
humans and form endospores:
Clostridium tetani – causes
tetanus (lock jaw)
Clostridium botulinum –
causes food deadly poisoning
Bacterial Reproduction
Binary fission is an asexual
reproductive process. All offspring
should be genetically identical to the
parent cell and to each other.
Using binary fission, some bacteria can
divide as often as every 20 minutes!
Binary Fission
DOUBLING
Etc.
Methods of DNA Exchange
Even though bacteria reproduce asexually,
they show methods of exchanging DNA
pieces that increases their variability.
There are 3 main methods:
a) Conjugation
b) Transduction
c) Transformation
Methods of Exchanging DNA
Conjugation – two bacteria join by a
cytoplasmic bridge and exchange small
circles of DNA called plasmids. The cells
may in this way exchange useful
information.
Conjugation
Conjugation animation
Methods of Exchanging DNA
Transduction - the process by which DNA is
transferred from one bacterial cell to
another by infection with a virus. Viruses
that infect bacteria are called
bacteriophages.
Bacteriophage
Transduction
Bacterial transduction animation
Methods of Exchanging DNA
Transformation- a living bacterial cell takes
in the DNA from a dead bacterial cell. The
DNA is then incorporated into the genome
of the living cell.
Transformation
Bacterial transformation animation
DOMAIN Archaebacteria
Are EXTREMOPHILES (love extreme environments)
Are usually found in harsh environments – hot, salty,
acidic.
Ancient – probably resemble the first bacteria and
therefore the first life forms on the planet
Exobiologists (biologists who are looking for life on
other planets or moons) guess that they should be
looking for these types of cells. WHY?
Archaebacteria :
Methanogens
(generate methane)
• produce methane – live in digestive tract of
mammals, in swamps and sewage)
Archaebacteria:
Thermophiles
• can live in extremely hot water – found in hot
springs
Halophiles
• Live in very salty water, such as the Great
Salt Lake in Utah and the Dead Sea
Eubacteria – true bacteria
• Many types – modern bacteria
• Classification is by:
–
–
–
–
Cell shape
Cell wall composition
Nutrition
Respiration
Cell Shape
Coccus - round
Bacillus - rod
Spirillum
Names can tell a lot about the
bacterial growth
• Some bacteria grow alone, but others stick
together
• Diplo…means two
– Diplococcus
– Diplobacillus
• Strepto… means chain
- as in streptococcus
- and streptobacillus
•Staphylo… means cluster
•As in staphlyococcus
or
Cell Wall Composition –
Gram positive or Gram negative
Gram Positive
Gram negative
Stains blue because cell wall retains
Stains pink because cell
wall does not
retain violet stain ( Absorbs saffrin
violet stain
Bacterial colonies consist of millions of
bacterial cells growing together.
Sample Colony Characteristics
Size: 2mm diameter
Shape: Circular
Elevation: Convex
Surface: Smooth
Density: Opaque
Colonies growing into each
other
Nutrition – Autotrophic or
Heterotrophic
Autotrophs –make their own food
– use sun’s energy or chemical energy
– E.g cyanobacteria (blue-green algae, nitrogenfixing bacteria)
Most Bacteria are
Heterotrophs
Escherichia coli
Spirillum
Found in intestines
Anthrax
Deadly respiratory
bacteria
Can cause
certain STD’s
Types of Heterotrophic Bacteria
Saprophytic - Those bacteria who live and
get nutrients by digesting dead
plants/animals. These bacteria are
decomposing bacteria.
Saprophytic
colony on tree
trunk
Types of Heterotrophic Bacteria
Parasitic – obtain food by living attached to
or inside living organisms. These are
harmful to the host organism, as they feed
directly on the tissues of the organism.
These may cause disease (in which case, they
are called pathogens).
Types of Heterotropic Bacteria
Parasitic bacteria
Staphylococcus aureus
– causes pimples, boils,
pneumonia, sepsis
Streptococcus mutans – causes
tooth decay
Types of Heterotrophic Bacteria
Mutualistic or Symbiotic bacteria – these
bacteria feed off of other living organisms
but have no harmful effect on the host
organism.
Types of Heterotrophic Bacteria
Mutualistic or Symbiotic Bacteria
E. Coli – intestinal bacteria
Nitrogen fixing bacteria –
plant roots
Respiration – process of getting
energy from food
Aerobic bacteria
These bacteria need oxygen to metabolize (break down)
food. If a bacterium cannot live without oxygen, it is
known as an obligate aerobe.
» EX – TUBERCULOSIS (Tb) BACTERIUM
Tb lung
If a bacterium prefers to live with oxygen it is known as a
facultative aerobe.
Anaerobic bacteria These bacteria do not need
oxygen. In some cases, these bacteria cannot survive
in the presence of oxygen, in which case they are
called obligate anaerobes.
EX – TETANUS
This baby probably got tetanus from honey –
don’t give honey to a baby!
Some bacteria can live in the presence of
oxygen, but do not require it for survival.
These are known as facultative anaerobes.
E. coli
How important are bacteria
to the world?
• Decomposition – most important
function for living things. What
happens to all the dead bodies?
• Bacteria are important
Decomposers.
Food web
Nitrogen cycle
Bacteria recycling and incorporating nitrogen
(N), for protein manufacturing.
Cow Digestion
Bacteria in the stomach
- Help breakdown
plant products for
herbivores.
Foods from bacteria
cheese
yogurt
sauerkraut
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
Antibiotics, if used cautiously, can cure
bacterial infections
Antibiotics are tested using Petri dishes and
paper soaked in the antibiotic – anywhere the
antibiotic inhibits growth, a zone of inhibition
will be seen
Not effective
Most effective
Antibiotic Resistance
Antibiotics are chemicals that are selectively
toxic (they are toxic to certain cells, and not
others). They kill or inhibit the growth or
reproduction of bacterial cells.
Some prevent bacterial cells from producing
parts they need, other actually break the
bacterial cell wall.
Antibiotic Resistance
Some bacteria have evolved defenses against
antibiotics. They may inactivate the antibiotic or a
mutation may have changed the bacterial
compound that would normally be affected by the
drug.
Because bacteria are able to exchange DNA
(conjugation, transduction, transformation), it is
easy for the resistance to be passed on to other
bacteria.
Antibiotic resistance animation
Bacteria
http://www.bozemanscience.com/bacteria
• Read section 2.2 pages 59- 66 and answer
questions #1, 2, 3, 5, and 7