Download Bacteria

Identifying and
Classifying Bacteria
What is a prokaryote?
 Cells
that lack a true nucleus.
 Cells that lack membranebound organelles.
 Most surrounded by a cell wall.
 Many secrete a protective
slime capsule.
How big is a prokaryotic cell?
 1-
5 micrometers
 (1 millionth of a meter)
Classification
 Archae
vs Bacteria
Archae
 Surrounded
by a cell wall
lacking peptidoglycan.
 Live in extreme conditions
Examples of Archae
 Methanogens:
convert H2
and CO2 into methane gas for
energy
 Halophiles: love salt
 Thermoacidophiles: love
heat and acid
Bacteria:
 Surrounded
by a cell wall
made of peptidoglycan.
 Example: E. coli
Identifying Prokaryotes
1. Shape:
• Coccus – spherical
• Bacillus – rod-shaped
• Spirillum – spiral
• Vibrio – comma shape
Coccus
Bacillus
Vibrio
Spirillum
Cocci and Bacilli may
group together
Prefixes for arrangements:
Diplo – two
Ex.
Diplococcus
Strepto – chain
Streptococcus
Streptobacillus
Staphylo - clustered
Staphylococcus
2. Motility: ability to move
 Flagella: whip-like structure
used to propel bacteria
 Slime: glide along slime
secretion
 Spiral motion: cork-screw
motion (spirillum)
3. Metabolism: Oxygen or NOT
 Obligate
Aerobes: Need
oxygen
 Obligate Anaerobes: cannot
live in oxygen
 Facultative anaerobes: can live
with or without oxygen
3.Metabolism: Obtaining Energy
Autotroph vs. Heterotroph
• Photoautotroph- uses light
energy for photosynthesis
• Chemoautotroph- uses
energy from inorganic
chemicals for chemosynthesis
•
•
Photoheterotrophs- uses
photosynthesis and eats
organic compounds
Heterotroph – consumes
organic compounds
Bacterial Reproduction
Asexual: Binary fission
1.
2.
3.
Circular DNA replicates
Cell membrane and cell wall
divide
Identical daughter cells
separate
How fast does this happen?
http://www.youtube.com
/watch?v=gEwzDydciWc
&feature=related
approximately
20 minutes
every
Disease
 Pathology
is the study of
disease.
 Pathogens: organisms that
cause disease.
Gram-staining Test
 Gram-positive:
bacteria
contain lots of peptidoglycan in
cell walls. Stains purple.
 Gram- negative: bacteria
contain little peptidoglycan in
cell walls. Stains red.
Exotoxins
 Poisonous
proteins that are
released by some grampositive bacteria.
For example

Clostridium tetani secretes an
exotoxin that causes tetanus.
 Tetanus
muscles.

causes stiffness in
Clostridium botulinum produces a
very powerful exotoxin that
causes the fatal disease, botulism.
 1 g of botulism toxin can kill 1
million people.
Endotoxins
 Lipids
and carbohydrates in
the cell membranes of some
Gram-negative bacteria, that
are poisonous.
 They are released when the
bacteria die.
For example:
species of Salmonella,
are endotoxin producing
bacteria.
 Salmonella typhi, causes
typhoid fever.
 Most
Antibiotics
 Antibiotics
interfere with the
bacteria’s cellular activities.
For example:
 Penicillin:
blocks the building
of the cell wall.
“Accidently” discovered by
Alexander Fleming in 1920s
 Tetracyline: blocks protein
synthesis.
Where do antibiotics come from?
 Antibiotics
are naturally made
by some fungi and bacteria.
 Some are made synthetically in
labs.
Antibiotic-Resistance
 Bacteria can quickly adapt to
their environment because of
their rapid rate of reproduction.
1.
2.
3.
Antibiotic-Resistance
If one bacterium mutates and
becomes resistant,
then in the presence of
antibiotics, bacteria not
resistant die
Those with the resistance
take over the population.