1. Staphylococcus bacteria in nose

2. Structure
Unicellular
Prokaryotic
Lack membrane organelles
Some species form colonies
0.5–10 µm, much smaller than the 10–100 µm of many eukaryotic cells

3. Most Common Shapes Most common shapes: spheres (cocci) rods (bacilli)
and spirals

4. Bacterial Cell Wall maintains cell shape provides physical protection,
prevents the cell from bursting in a hypotonic environment
Bacterial cell walls contain peptidoglycan, a network of sugar polymers cross-linked by polypeptides (proteins)

5. Peptidoglycan
sugar
sugar
polypeptide

6. Gram Stain Classification
Using the Gram stain, scientists classify bacterial into Gram + or Gram - groups based on cell wall composition
Gram - bacteria: less peptidoglycan outer membrane that can be toxic  more likely to be antibiotic resistant
Many antibiotics target 1) peptidoglycan and damage bacterial cell walls or 2)bacterial ribosomes, inhibiting protein synthesis

7. Gram Stain Classification

8. (a) Gram-positive: peptidoglycan traps crystal violet.
layer
Cell
wall
Plasma membrane
Protein
Figure 27.3 Gram staining
(a) Gram-positive: peptidoglycan traps
crystal violet.

9. of lipopolysaccharide
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.

10. Gram- Gram- positive negative bacteria bacteria 20 µm
Figure 27.3 Gram staining
Gram-
positive
bacteria
Gram-
negative
bacteria
20 µm

11. Structure
A polysaccharide or protein layer called a capsule covers many bacteria

12. Bacterial Motility
Most motile bacteria use flagella to propel themselves
Many exhibit taxis, the ability to move toward or away from certain stimuli

13. Fimbriae (also called attachment pili)
allows them to stick to their substrate or other individuals in a colony

14. Internal Organization
lack complex compartmentalization (ex. no nucleus, ER, mitochondrion, etc.)
Often perform metabolic functions using highly folded extensions of plasma membrane
(a) Aerobic prokaryote
(b) Photosynthetic prokaryote

15. Genome
Most of the genome consists of a circular chromosome located in a nucleoid region
Some have smaller rings of DNA called plasmids
Plasmids w/ short codes of DNA that may be beneficial to bacteria (Ex. some code for antibiotic resistance)

16. Genome
Sex pili are longer than fimbriae and allow prokaryotes to exchange DNA during conjugation

17. Plasmid F factor
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

18. Plasmid F factor F plasmid Bacterial chromosome F+ cell Mating bridge
(a) Conjugation and transfer of an F plasmid
Figure 27.13a Conjugation and recombination in E. coli

19. Plasmid F factor F plasmid Bacterial chromosome F+ cell Mating bridge
(a) Conjugation and transfer of an F plasmid
Figure 27.13a Conjugation and recombination in E. coli

20. Plasmid F factor and R factors
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
R plasmids carry genes for antibiotic resistance
Antibiotics select for bacteria with genes that are resistant to the antibiotics

21. Reproduction and Adaptation
Quick reproduction by binary fission
every 1–3 hours
Beneficial mutations can accumulate rapidly in a population, allowing for rapid evolution
ex. Antibiotic resistant strains are becoming more common
Many form inactive endospores
to remain viable in harsh conditions

22. Endospore
Figure 27.9 An endospore
0.3 µm

23. Genetic Recombination
DNA from different individuals can be brought together by conjugation, transformation, transduction

24. Transformation
A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment in a process called transformation

25. Transduction
Transduction is the movement of genes between bacteria by vectors like bacteriophages (viruses that infect bacteria)

26. Phage DNA A+ B+ A+ B+
Donor
cell
Figure Transduction

27. Phage DNA A+ B+ A+ B+
Donor
cell A+
Figure Transduction

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

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

30. Pathogenic Prokaryotes
Prokaryotes cause about half of all human diseases
Lyme disease is an example

31. 5 µm
Figure Lyme disease
For the Discovery Video Antibiotics, go to Animation and Video Files.

32. Fig a
Figure Lyme disease
Deer tick

33. Fig c
Figure Lyme disease
Lyme disease rash

34. Pathogenic Prokaryotes
Bacteria 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