1. Chapter 27
Bacteria and Archaea

2. Overview: Masters of Adaptation
Prokaryotes thrive almost everywhere, including places too acidic, salty, cold, or hot for most other organisms
Most prokaryotes are microscopic, but what they lack in size they make up for in numbers
There are more in a handful of fertile soil than the number of people who have ever lived

3. They have an astonishing genetic diversity
Prokaryotes are divided into two domains: bacteria and archaea
Video: Tubeworms

4. Fig. 27-1
Figure 27.1 Why is this lakebed red?

5. Concept 27.1: Structural and functional adaptations contribute to prokaryotic success
Most prokaryotes are unicellular, although some species form colonies
Most prokaryotic cells are 0.5–5 µm, much smaller than the 10–100 µm of many eukaryotic cells
Prokaryotic cells have a variety of shapes
The three most common shapes are spheres (cocci), rods (bacilli), and spirals

6. (a) Spherical (cocci) (b) Rod-shaped (bacilli) (c) Spiral 1 µm 2 µm
Fig. 27-2
Figure 27.2 The most common shapes of prokaryotes
1 µm
2 µm
5 µm
(a) Spherical
(cocci)
(b) Rod-shaped
(bacilli)
(c) Spiral

7. Cell-Surface Structures
An important feature of nearly all prokaryotic cells is their cell wall, which maintains cell shape, provides physical protection, and prevents the cell from bursting in a hypotonic environment
Eukaryote cell walls are made of cellulose or chitin
Bacterial cell walls contain peptidoglycan, a network of sugar polymers cross-linked by polypeptides

8. Archaea contain polysaccharides and proteins but lack peptidoglycan
Using the Gram stain, scientists classify many bacterial species into Gram-positive and Gram-negative groups based on cell wall composition
Gram-negative bacteria have less peptidoglycan and an outer membrane that can be toxic, and they are more likely to be antibiotic resistant

9. Many antibiotics target peptidoglycan and damage bacterial cell walls

10. Fig. 27-3 layer Figure 27.3 Gram staining Carbohydrate portion
of lipopolysaccharide
Outer
membrane
Peptidoglycan
layer
Cell
wall
Cell
wall
Peptidoglycan
layer
Plasma membrane
Plasma membrane
Protein
Protein
Gram-
positive
bacteria
Gram-
negative
bacteria
Figure 27.3 Gram staining
20 µm
(a) Gram-positive: peptidoglycan traps
crystal violet.
(b) Gram-negative: crystal violet is easily rinsed away,
revealing red dye.

11. (a) Gram-positive: peptidoglycan traps crystal violet.
Fig. 27-3a
Peptidoglycan
layer
Cell
wall
Plasma membrane
Protein
Figure 27.3 Gram staining
(a) Gram-positive: peptidoglycan traps
crystal violet.

12. of lipopolysaccharide
Fig. 27-3b
Carbohydrate portion
of lipopolysaccharide
Outer
membrane
Cell
wall
Peptidoglycan
layer
Plasma membrane
Protein
Figure 27.3 Gram staining
(b) Gram-negative: crystal violet is easily rinsed
away, revealing red dye.

13. Gram- Gram- positive negative bacteria bacteria 20 µm Fig. 27-3c
Figure 27.3 Gram staining
Gram-
positive
bacteria
Gram-
negative
bacteria
20 µm

14. A polysaccharide or protein layer called a capsule covers many prokaryotes

15. Fig. 27-4
200 nm
Figure 27.4 Capsule
Capsule

16. Some prokaryotes have fimbriae (also called attachment pili), which allow them to stick to their substrate or other individuals in a colony
Sex pili are longer than fimbriae and allow prokaryotes to exchange DNA

17. Fig. 27-5
Figure 27.5 Fimbriae
Fimbriae
200 nm

18. Video: Prokaryotic Flagella (Salmonella typhimurium)
Motility
Most motile bacteria propel themselves by flagella that are structurally and functionally different from eukaryotic flagella
In a heterogeneous environment, many bacteria exhibit taxis, the ability to move toward or away from certain stimuli
Video: Prokaryotic Flagella (Salmonella typhimurium)

19. Flagellum Filament Cell wall Hook Basal apparatus Plasma membrane
Fig. 27-6
Flagellum
Filament
50 nm
Cell wall
Hook
Basal apparatus
Figure 27.6 Prokaryotic flagellum
Plasma
membrane

20. Filament Cell wall Hook Basal apparatus Plasma membrane Fig. 27-6a
Figure 27.6 Prokaryotic flagellum
Plasma
membrane

21. Prokaryotic flagellum (TEM)
Fig. 27-6b
50 nm
Figure 27.6 Prokaryotic flagellum
Prokaryotic flagellum (TEM)

22. Internal and Genomic Organization
Prokaryotic cells usually lack complex compartmentalization
Some prokaryotes do have specialized membranes that perform metabolic functions

23. (a) Aerobic prokaryote (b) Photosynthetic prokaryote
Fig. 27-7
0.2 µm
1 µm
Respiratory
membrane
Figure 27.7 Specialized membranes of prokaryotes
Thylakoid
membranes
(a) Aerobic prokaryote
(b) Photosynthetic prokaryote

24. (a) Aerobic prokaryote
Fig. 27-7a
0.2 µm
Respiratory
membrane
Figure 27.7 Specialized membranes of prokaryotes
(a) Aerobic prokaryote

25. (b) Photosynthetic prokaryote
Fig. 27-7b
1 µm
Figure 27.7 Specialized membranes of prokaryotes
Thylakoid
membranes
(b) Photosynthetic prokaryote

26. The prokaryotic genome has less DNA than the eukaryotic genome
Most of the genome consists of a circular chromosome
Some species of bacteria also have smaller rings of DNA called plasmids

27. Chromosome Plasmids 1 µm Fig. 27-8
Figure 27.8 A prokaryotic chromosome and plasmids
1 µm

28. The typical prokaryotic genome is a ring of DNA that is not surrounded by a membrane and that is located in a nucleoid region

29. Reproduction and Adaptation
Prokaryotes reproduce quickly by binary fission and can divide every 1–3 hours
Many prokaryotes form metabolically inactive endospores, which can remain viable in harsh conditions for centuries

30. Fig. 27-9
Endospore
Figure 27.9 An endospore
0.3 µm

31. Prokaryotes can evolve rapidly because of their short generation times

32. 0.1 mL (population sample) Fitness relative to ancestor
Fig
EXPERIMENT
Daily serial transfer
0.1 mL
(population sample)
Old tube
(discarded
after
transfer)
New tube
(9.9 mL
growth
medium)
RESULTS
1.8
1.6
Figure Can prokaryotes evolve rapidly in response to environmental change?
Fitness relative
to ancestor
1.4
1.2
1.0
5,000
10,000
15,000
20,000
Generation

33. 0.1 mL (population sample)
Fig a
EXPERIMENT
Daily serial transfer
0.1 mL
(population sample)
Old tube
(discarded
after
transfer)
New tube
(9.9 mL
growth
medium)
Figure Can prokaryotes evolve rapidly in response to environmental change?

34. Fitness relative to ancestor
Fig b
RESULTS
1.8
1.6
Fitness relative
to ancestor
1.4
1.2
Figure Can prokaryotes evolve rapidly in response to environmental change?
1.0
5,000
10,000
15,000
20,000
Generation

35. Prokaryotes have considerable genetic variation
Concept 27.2: Rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotes
Prokaryotes have considerable genetic variation
Three factors contribute to this genetic diversity:
Rapid reproduction
Mutation
Genetic recombination

36. Rapid Reproduction and Mutation
Prokaryotes reproduce by binary fission, and offspring cells are generally identical
Mutation rates during binary fission are low, but because of rapid reproduction, mutations can accumulate rapidly in a population
High diversity from mutations allows for rapid evolution

37. Genetic Recombination
Additional diversity arises from genetic recombination
Prokaryotic DNA from different individuals can be brought together by transformation, transduction, and conjugation

38. Transformation and Transduction
A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment in a process called transformation
Transduction is the movement of genes between bacteria by bacteriophages (viruses that infect bacteria)

39. Fig
Phage DNA A+ B+ A+ B+
Donor
cell
Figure Transduction

40. Fig
Phage DNA A+ B+ A+ B+
Donor
cell A+
Figure Transduction

41. Fig
Phage DNA A+ B+ A+ B+
Donor
cell A+
Recombination
Figure Transduction A+ A– B–
Recipient
cell

42. Fig
Phage DNA A+ B+ A+ B+
Donor
cell A+
Recombination
Figure Transduction A+ A– B–
Recipient
cell A+ B–
Recombinant cell

43. Conjugation and Plasmids
Conjugation is the process where genetic material is transferred between bacterial cells
Sex pili allow cells to connect and pull together for DNA transfer
A piece of DNA called the F factor is required for the production of sex pili
The F factor can exist as a separate plasmid or as DNA within the bacterial chromosome

44. Fig
Figure Bacterial conjugation
1 µm
Sex pilus

45. The F Factor as a Plasmid
Cells containing the F plasmid function as DNA donors during conjugation
Cells without the F factor function as DNA recipients during conjugation
The F factor is transferable during conjugation

46. Fig
F plasmid
Bacterial chromosome
F+ cell
F+ cell
Mating
bridge
F– cell
F+ cell
Bacterial
chromosome
(a) Conjugation and transfer of an F plasmid
Recombinant
F– bacterium
Hfr cell A+ A+ A+
F factor
Figure Conjugation and recombination in E. coli A+ A– A+ A– A– A+ A–
F– cell
(b) Conjugation and transfer of part of an Hfr bacterial chromosome

47. Fig
F plasmid
Bacterial chromosome
F+ cell
Mating
bridge
F– cell
Bacterial
chromosome
(a) Conjugation and transfer of an F plasmid
Figure 27.13a Conjugation and recombination in E. coli

48. Fig
F plasmid
Bacterial chromosome
F+ cell
Mating
bridge
F– cell
Bacterial
chromosome
(a) Conjugation and transfer of an F plasmid
Figure 27.13a Conjugation and recombination in E. coli

49. Fig
F plasmid
Bacterial chromosome
F+ cell
F+ cell
Mating
bridge
F– cell
F+ cell
Bacterial
chromosome
(a) Conjugation and transfer of an F plasmid
Figure 27.13a Conjugation and recombination in E. coli

50. The F Factor in the Chromosome
A cell with the F factor built into its chromosomes functions as a donor during conjugation
The recipient becomes a recombinant bacterium, with DNA from two different cells
It is assumed that horizontal gene transfer is also important in archaea

51. Fig
Hfr cell A+ A+ A+
F factor A– A–
F– cell
(b) Conjugation and transfer of part of an Hfr bacterial chromosome
Figure 27.13b Conjugation and recombination in E. coli

52. Fig
Hfr cell A+ A+ A+ A+
F factor A– A– A+ A–
F– cell
(b) Conjugation and transfer of part of an Hfr bacterial chromosome
Figure 27.13b Conjugation and recombination in E. coli

53. Fig
Recombinant
F– bacterium
Hfr cell A+ A+ A+ A+
F factor A– A+ A– A– A+ A–
F– cell
(b) Conjugation and transfer of part of an Hfr bacterial chromosome
Figure 27.13b Conjugation and recombination in E. coli

54. Fimbriae Cell wall Circular chromosome Capsule Sex pilus Internal
Fig. 27-UN3
Fimbriae
Cell wall
Circular chromosome
Capsule
Sex pilus
Internal
organization
Flagella

55. You should now be able to:
Distinguish between the cell walls of gram-positive and gram-negative bacteria
State the function of the following features: capsule, fimbriae, sex pilus, nucleoid, plasmid, and endospore
Explain how R plasmids confer antibiotic resistance on bacteria

56. Distinguish among the following sets of terms: photoautotrophs, chemoautotrophs, photoheterotrophs, and chemoheterotrophs; obligate aerobe, facultative anaerobe, and obligate anaerobe; mutualism, commensalism, and parasitism; exotoxins and endotoxins