Identifying and
Classifying Bacteria
Ch. 23
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
 Archaebacteria
vs Eubacteria
Archaebacteria
 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
Eubacteria:
 Surrounded
by a cell wall
made of peptidoglycan.
 Example: rhizobiumnitrogen–fixing bacteria
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
review
 What
role do chemosynthetic
bacteria have in the
ecosystem?

http://www.youtube.com/watch?v=4lmwb
BzClAc&NR=1
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
Genetic recombination
Sharing or exchanging of
genetic material
3 types:
1. Conjugation
2. Transformation
3. Transduction
1. Conjugation
A
temporary bridge forms
between two cells.
 A plasmid, a separate section
of DNA, is transferred from
one cell to the other.
 Often the plasmid contains
useful genes, like antibiotic
resistance.
2. Transformation
 Bacteria
takes in DNA from the
environment.
 Dead bacteria may break
apart and release DNA.
 Other bacteria can pick up this
DNA and become genetically
different.
3. Transduction
 Viruses
can pick up small
amounts of DNA from a host
bacteria.
 When it infects another
bacteria, the new DNA is
transferred into that cell.
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.
 But most used in treatment
still come from bacteria.
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.
Which diseases are preventable
by better sanitation practice?
 Cholera
 Salmonella
 Tetanus
 Staph
What are other ways that antibiotic
resistance is passed?
 Genetic
recombination