1. Archaebacteria & Bacteria
Classification
Eukaryote
Prokaryote
Old 5 Kingdom system
Monera, Protists, Plants, Fungi, Animals
New 3 Domain system
reflects a greater understanding of evolution & molecular evidence
Prokaryote: Bacteria
Prokaryote: Archaebacteria
Eukaryotes
Protists
Plants
Fungi
Animals
Archaebacteria & Bacteria

2. (a) Spherical (cocci) (b) Rod-shaped (bacilli) (c) Spiral 1 µm 2 µm
Fig. 27-2
1 µm
2 µm
5 µm
(a) Spherical
(cocci)
(b) Rod-shaped
(bacilli)
(c) Spiral

3. Structure and Function
3 basic shapes: spherical (cocci), rods (bacillus) and spiral
Cell Wall
Peptidoglycan covers cell, anchors attachments
Archaea have no peptidoglycan

4. Gram Staining Gram + : simple walls, lots of PTG
Gram - : complex walls with lipopolysaccharides less PTG
Medical significance: Gram – lipids are toxic causing fever or shock and are resistant to our defenses
Gram –: antibiotic resistance (hard for drugs to penetrate)
Antibiotics often target peptidoglycan

5. Prokaryote Cell Wall Structure
peptide side
chains
cell wall
peptidoglycan
plasma membrane
protein
Gram-positive bacteria
peptidoglycan = polysaccharides + amino acid chains
lipopolysaccharides = lipids + polysaccharides
Gram-negative bacteria
peptidoglycan
plasma
membrane
outer
outer membrane of lipopolysaccharides
cell wall

6. Fig. 27-4
200 nm
Capsule

7. Capsule vs Fimbriae Sticky and covers entire cell
Protection from dehydration and shield from immune system
Hair like appendages that stick
Ex. Neisseria gonorrhoeae sticks to mucus membranes
Shorter and more numerous than sex pilli

8. Fig. 27-5
Fimbriae
200 nm

9. Motility for most bacteria
propel themselves by flagella that are structurally and functionally different from eukaryotic flagella
PROK flagella are 1/10 the width of EUK
PROK flagella are not covered by plasma mem

10. Video: Prokaryotic Flagella (Salmonella typhimurium)
Motility
Different composition and propulsion
The motor of the flagella is the basal apparatus (rings embedded in the cell wall)
ATP proton pump generates power by turning hook attached
Hook is attached to chains of flagellin
In a heterogeneous environment, many bacteria exhibit taxis, the ability to move toward or away from certain stimuli
Video: Prokaryotic Flagella (Salmonella typhimurium)

11. 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

12. Structure cont No organelles: embedded membranes for metabolism
Ribosomes (70s instead of 80s)
Tetracycline and erythromyocin attach ribosomes
Nucleoid region for chromosome
Circular, naked chromosome
Plasmids (extra chromosomal)

13. Fig. 27-8
Chromosome
Plasmids
1 µm

14. Variations in Cell Interior
mitochondria
cyanobacterium (photosythetic) bacterium
aerobic bacterium
chloroplast
internal membranes for photosynthesis like a chloroplast (thylakoids)
internal membranes for respiration like a mitochondrion (cristae)

15. Reproduction and Adaptation
Binary fission in optimal conditions every 1-3 hours (E.coli every 20 min usually 1/24 hr)
They are small, repro binary fission and short generation time
Endopsores (ability to endure hardship)

16. 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

17. Rapid Evolution: high genetic diversity
2 strains of E.coli differ in an rRNA gene more than between a human and a platypus
Rapid reproduction
Mutation
Genetic recombination

18. Mutation
Probability of a spontaneous mutation in an E.coli gene is 1 in 10 million/division
2x1010 new E.coli per day
About 2000 bacteria will have mutations
4300 genes total in E.coli
4300 x 2000 = 9 million mutation per day in the human intestines

19. Genetic Recombination
Transformation: uptake foreign DNA
Ex. Competent cells, pneumonia
Transduction: a bacteriophage performs horizontal gene transfer
Conjugation
Plasmids

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

21. 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

22. Fig
Figure Bacterial conjugation
1 µm
Sex pilus

23. 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

24. 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

25. R Plasmids and Antibiotic Resistance
R plasmids carry genes for antibiotic resistance
Antibiotics select for bacteria with genes that are resistant to the antibiotics
Antibiotic resistant strains of bacteria are becoming more common

26. Bacterial Diversity Major nutritional modes
Role of oxygen in metabolism
Nitrogen metabolism
nitrogen fixation: converting N2 from the atmosphere into ammonia NH3
Metabolic Cooperation
colony of cyanobacterium Anabaena (filaments) genes for photosynthesis (most cells) and N fixation)few heterocytes) but one cell cannot perform both
Biofilms

27. Table 27-1
Table 27-1

28. Photosynthetic cells Heterocyte 20 µm Fig. 27-14
Figure Metabolic cooperation in a colonial prokaryote
20 µm

29. Prokaryotic phylogeny
Horizontal gene transfer (ring instead of a tree)
Archaea more closely related to eukaryotes than bacteria
polyphyletic
Eukarya
Archaea
Bacteria
Eukarya
Bacteria
Archaea

30. Domain Eukarya Eukaryotes Korarcheotes Euryarchaeotes Domain Archaea
Fig
Domain
Eukarya
Eukaryotes
Korarcheotes
Euryarchaeotes
Domain Archaea
Crenarchaeotes
UNIVERSAL
ANCESTOR
Nanoarchaeotes
Proteobacteria
Chlamydias
Figure A simplified phylogeny of prokaryotes
Spirochetes
Domain Bacteria
Cyanobacteria
Gram-positive
bacteria

31. Table 27-2
Table 27.2

32. Proteobacteria
These gram-negative bacteria include photoautotrophs, chemoautotrophs, and heterotrophs
Some are anaerobic, and others aerobic

33. Subgroup: Alpha Proteobacteria
Fig a
Subgroup: Alpha Proteobacteria
Alpha
Beta
Gamma
Proteobacteria
Delta
Epsilon
2.5 µm
Rhizobium (arrows) inside a
root cell of a legume (TEM)
Subgroup: Beta Proteobacteria
Subgroup: Gamma Proteobacteria
1 µm
0.5 µm
Nitrosomonas (colorized TEM)
Thiomargarita namibiensis
containing sulfur wastes (LM)
Figure Major groups of bacteria
For the Discovery Video Bacteria, go to Animation and Video Files.
Subgroup: Delta Proteobacteria
Subgroup: Epsilon Proteobacteria
B. bacteriophorus
10 µm
5 µm
2 µm
Fruiting bodies of
Chondromyces crocatus, a
myxobacterium (SEM)
Bdellovibrio bacteriophorus
attacking a larger bacterium
(colorized TEM)
Helicobacter pylori (colorized TEM)

34. Subgroup: Alpha Proteobacteria
Many species are closely associated with eukaryotic hosts
Scientists hypothesize that mitochondria evolved from aerobic alpha proteobacteria through endosymbiosis

35. Example: Rhizobium, which forms root nodules in legumes and fixes atmospheric N2
Arrows in the next slide are Rhizobium
Example: Agrobacterium, which produces tumors in plants and is used in genetic engineering

36. Rhizobium (arrows) inside a root cell of a legume (TEM)
Fig c
2.5 µm
Figure Major groups of bacteria—alpha proteobacteria
Rhizobium (arrows) inside a root
cell of a legume (TEM)

37. Cyanobacteria These are photoautotrophs that generate O2
Plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis
Two species of Oscillatoria,
filamentous cyanobacteria (LM)

38. Concept 27.6: Prokaryotes have both harmful and beneficial impacts on humans
Some prokaryotes are human pathogens, but others have positive interactions with humans
Prokaryotes cause about half of all human diseases
Lyme disease is an example

39. 5 µm Fig. 27-21 Figure 27.21 Lyme disease
For the Discovery Video Antibiotics, go to Animation and Video Files.

40. Pathogenic prokaryotes typically cause disease by releasing exotoxins or endotoxins
Exotoxins cause disease even if the prokaryotes that produce them are not present
Endotoxins are released only when bacteria die and their cell walls break down
Many pathogenic bacteria are potential weapons of bioterrorism