1. Ch. 27 Bacteria and Archaea
Objective:
Understand the general structure and motility of bacteria and how genetic recombination increases diversity.

2. 27.1 Structural and Functional Adaptations Contribute to Prokaryotic Success
Very adaptable (extreme salt, pH, and temp).
Most are unicellular (0.5-5 um) but still perform all of life’s functions.
(a) Spherical
(b) Rod-shaped
(c) Spiral
1 m
3 m

3. Cell Surface Structures
All bacteria have a cell wall.
Archaeal bacteria do NOT have a layer of peptidoglycan in their cell walls.
Eubacteria have differing amount of peptidoglycan
Gram positive: stains violet due to thick layer peptidoglycan.
Gram negative: stains red due to extra membrane past peptidoglycan.
(a) Gram-positive bacteria: peptidoglycan traps crystal violet.
Gram-positive
bacteria
Peptido-
glycan
layer
Cell
wall
Plasma
membrane
10 m
Gram-negative
Outer
Plasma membrane
Carbohydrate portion
of lipopolysaccharide
(b) Gram-negative bacteria: crystal violet is easily rinsed
away, revealing red dye.

4. Motility
About half of known bacteria can move (taxis) toward/away from a stimulus
Most commonly via flagella either surrounding the body or found at 1 end. Works like a helicopter with a motor, hook, and filament.
Flagellum
Hook
Motor
Filament
Rod
Peptidoglycan
layer
Plasma
membrane
Cell wall
20 nm

5. Internal Organization and DNA
No membrane bound organelles but plasma membrane folds on itself to make metabolic membranes.
(a) Aerobic prokaryote
(b) Photosynthetic prokaryote
Respiratory
membrane
Thylakoid
membranes
0.2 m
1 m

6. Internal Organization and DNA
Smaller, circular DNA found in nucleoid (not nucleus) with very small plasmids (self replicating DNA)
Chromosome
Plasmids
1 m

7. Reproduction and Adaptation
Reproduce every couple of hours (under optimal conditions) by binary fission.
Division stops due to space limits, metabolic toxins, eaten, etc.
Short generation time leads to quick evolution.

8. Reproduction and Adaptation
Endospores develop in harsh conditions.
Duplicated DNA in a tough, multilayered structure.
Water is removed and metabolism stops.
Coat
Endospore
0.3 m

9. 3 mechanisms for prokaryotic genome combinations
27.2 Rapid Reproduction, Mutation, and Genetic Recombination Promote Genetic Diversity in Prokaryotes
3 mechanisms for prokaryotic genome combinations
Transformation
Transduction
Conjugation

10. Transformation Changes genotype and phenotype by uptake of foreign DNA
Ex: harmless strains of the bacteria that can cause pneumonia become pathogenic if they come in contact with a pathogenic cell.

11. Transduction
Recombinant cell
Recipient
cell
Recombination A A B
Donor cell B
Phage
A “mutant” phage with bacterial DNA infects a bacteria cell.

12. Conjugation
Sex pilus
1 m
A donor bacteria makes a copy of its DNA, attaches to another bacteria via a (sex) pilus, the DNA travels to recipient forming a recombined cell.
F plasmid
Bacterial chromosome
F cell
(donor)
F cell
(recipient)
Mating
bridge
Bacterial
chromosome
(a) Conjugation and transfer of an F plasmid
Hfr cell
(b) Conjugation and transfer of part of an Hfr bacterial chromosome
F factor A A
Recombinant
F bacterium