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Prokaryotes:
Bacteria vs. Archaea
Bacteria vs. Archaea
Classification of Bacteria and Archaea
1) Classification based on shape
 3 shapes:
-Cocci = spherical
-Bacilli = rod-shaped
-Spirilli = spirals
 Aggregation:
-tendency to stick together in smalls
groups
2) Classification based on the cell wall
• Peptidoglycan
-Chain-link combination of alternating
amino acids and sugars
-Gives rigidity to the cell wall (protects cell and
gives it it’s shape)
• Link to Penicillin
- Penicillin affects the final formation of
peptidoglycan. It binds to the molecule
and stops the cell wall construction (destroys
the bacteria, that is why it is
used as an antibiotic!!)
• The importance of the Gram Stain

Bacteria only
**Pink stain
• Gram negative (–)
– Majority of bacteria
– Thin protein layer on
their cell wall
**Purple stain
• Gram Positive (+)
– Thick protein layer on their cell wall
– Absorbs the stain

Information used in determining which
antibiotics to use.
+
Thick protein layer on Cell wall
3) Classification based on nutrition
• some bacteria use photosynthesis (autotrophs)
ex. Cyanobacteria (blue-green algae)
• archaea produce methane (methanogenesis)
(autotrophs)
ex. Live in digestive tract of cows to help
digest cellulose and in turn produce methane.
• Both heterotrophs
ex. decomposers
» photosynthesis
Cyanobacteria
4) Classification based on habitat
• both live in aerobic and anaerobic conditions
• Bacteria are mostly mesophiles
-grow best in environments with moderate
temperatures, not extreme
• archaea can be extremophiles
-live in extreme habitats
-deep sea vents, hot springs
-volcanic crater & mine drainage lakes
-salt lakes
Reproduction of Archaea and Bacteria
• Binary fission:
-Result: cells with the same genetic material
-Process:
• Makes copies of its single chromosome
• Cell elongates
• Builds a partition (septum)
– P. 301
• Conjugation (p. 302)
-in less optimal conditions
-ability to exchange DNA
which results in cells with
new genetic material
• Endospores (bacteria only)
Endospore can withstand extreme conditions
and heat.
• Creation of a hard walled structure that
protect the genetic material
-Resistant
to high temperatures, freezing,
a
drying, toxic chemicals and radiation
• Results in bacteria being able to remain
dormant for very long periods of time
Bacteria vs. Archaea Summary
Shape
Bacteria
Coccispherical
Cell wall
With
Peptidoglycan
Nutrition
Autotrophs
(photosynthesis)
Habitat
Mostly
mesophiles
Reproduction
Binary
fission
Survival
Tactics
Conjugation
Endospores
Bacilli – rod
Heterotrophs
(predation)
Spirilli- spiral
shape
Archaea
Coccispherical
Bacilli – rod
Spirilli spiral shape
Without
peptidoglycan
Autotrophs
(methanogenesis)
Heterotrophs
(predation)
Some
extremophiles
Binary
fission
Conjugation
Archaea and biotechnology
•
Archaea are currently used for:
a) Sewage treatment
b) Archaeaocin (new antibiotics)
c) Enzyme production
– Due to the extreme conditions they
inhabit
– Low lactose milk
– Cloning DNA
Bacteria in Biotechnology
• Bacteria are currently used for
a) Food Production
i)Cheese, yogurt
b) Production of antibiotics
c) Natural pesticides