1. Microbiology: A Systems Approach
PowerPoint to accompany
Microbiology: A Systems Approach
Cowan/Talaro
Chapter 4
Procaryotic Profiles: The Bacteria and Archaea
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2. Chapter 4 Topics Cell Shapes, Arrangement, and Sizes
External Structures
Cell Envelope
Internal Structures
Classification

3. Relative size of a bacterial cell compared to other cells including viruses.
Fig The dimension of bacteria

4. Cell shapes
Coccus
Rod or bacillus
Curved or spiral
Cell arrangements

5. Scanning electron micrographs of different bacterial shapes and arrangements.
Fig SEM photograph of basic shapes.

6. Cellular shapes and arrangements are specific characteristics that can be used to identify bacteria.
Fig Bacterial shapes and arrangements

7. Some bacteria (ex. Corynebacterium) have varied shapes called pleomorphism.
Fig Pleomorphism in Corynebacterium

8. External Structures
Flagella
Pili and fimbriae
Glycocalyx

9. Flagella Composed of protein subunits Motility (chemotaxis)
Varied arrangement (ex. Monotrichous, lophotrichous, amphitrichous)

10. Different arrangements of flagella exist for different species.
Fig. 4.3 Electron micrograph depicting types of flagella arrangements.

11. Three main parts of the flagella include the basal body, hook, and filament.
Fig. 4.2 Details of the basal body in gram negative cell

12. The rotation of the flagella enables bacteria to be motile.
Fig. 4.4 The operation of flagella and the mode of locomotion in bacteria with polar and peritrichous flagella.

13. Chemotaxis is the movement of bacteria in response to chemical signals.
Fig. 4.5 Chemotaxis in bacteria

14. Spirochete bacteria have their flagella embedded in the membrane.
Fig. 4.6 The orientation of periplasmic flagella on the
spirochete cell.

15. Pili and fimbriae
Attachment
Mating (Conjugation)

16. Fimbriae are smaller than flagella, and are important for attachment.
Fig. 4.7 Form and function of bacteria fimbriae

17. Pili enable conjugation to occur, which is the transfer of DNA from one bacterial cell to another.
Fig. 4.8 Three bacteria in the process of conjugating

18. Glycocalyx Capsule Slime layer Protects bacteria from immune cells
Enable attachment and aggregation of bacterial cells

19. The capsule is tightly bound to the cell, and is associated with pathogenic bacteria.
Fig Encapsulated bacteria

20. The slime layer is loosely bound to the cell.
Fig. 4.9 Bacterial cells sectioned to show the types
of glycocalyces.

21. The slime layer is associated with the formation of biofilms, which are typically found on teeth.
Fig Biofilm

22. Cell envelope Cell wall Cytoplasmic membrane Non cell wall
Gram-positive
Gram-negative
Cytoplasmic membrane
Non cell wall

23. Cell wall Gram positive cell wall Gram-negative cell wall
Thick peptidoglycan (PG) layer
Teichoic acid and lipoteichoic acid
Acidic polysaccharides
Lipids – mycolic acids - Mycobacteria
Gram-negative cell wall
Thin PG layer
Outer membrane
Lipid polysaccharide
Porins

24. PG is a complex sugar and peptide structure important for cell wall stability and shape.
Fig Structure of peptidoglycan in the cell wall

25. Structures associated with gram-positive and gram-negative cell walls.
Fig A comparison of the detailed structure of
gram-positive and gram-negative cell walls.

27. Mutations can cause some bacteria to lose the ability to synthesize the cell wall, and are called L forms.
Fig The conversion of walled bacterial cells to L forms

28. No cell wall
No PG layer
Cell membrane contain sterols for stability

29. Mycoplasma bacteria have no cell wall, which contributes to varied shapes.
Fig Scanning electron micrograph of Mycoplasma pneumoniae

30. Cytoplasmic membrane Fluid-Mosaic Model Phospholipids
Embedded proteins
Energy generation
Selective barrier; semipermeable
Transport

31. Internal Structures Cytoplasm Genetic structures Storage bodies Actin
Endospore

32. Cytoplasm Area inside the membrane About 80% water
Gelatinous solution containing water, nutrients, proteins, and genetic material.
Site for cell metabolism

33. Genetic structures Single, circular chromosome Nucleoid region
Deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)
Plasmids
Ribosomes

34. Most bacteria contain a single circular double strand of DNA called a chromosome.
Fig Chromosome structure

35. A ribosome is a combination of RNA and protein, and is involved in protein synthesis.
Fig A model of a procaryotic ribosome.

36. Inclusion bodies enable a cell to store nutrients, and to survive nutrient depleted environments.
Fig An example of a storage inclusion
in a bacterial cell.

37. Actin is a protein fiber (cytoskeleton) present in some bacteria, and is involved in maintaining cell shape.
Fig Bacterial cytoskeleton

38. During nutrient depleted conditions, some bacteria (vegetative cell) form into an endospore in order to survive.
Fig Microscopic picture of an endospore formation

39. Some pathogenic bacteria that produce toxins during the vegetative stage are capable of forming spores.
Table 4.1 General stages in endospore formation

40. Classification Phenotypic methods Molecular methods Taxonomic scheme
Unique groups

41. Phenotypic methods Cell morphology -staining
Biochemical test – enzyme test

42. Molecular methods
DNA sequence
16S RNA
Protein sequence

43. The methods of classification have allowed bacteria to be grouped into different divisions and classes.
Table 4.3 Major taxonomic groups of bacteria

44. An example of how medically important families and genera of bacterial are characterized.
Table 4.4 Medically important families and genera of bacteria.

45. Unique groups of bacteria
Intracellular parasites
Photosynthetic bacteria
Green and purple sulfur bacteria
Gliding and fruiting bacteria
Archaea bacteria

46. Intracellular bacteria must live in host cells in order to undergo metabolism and reproduction.
Fig Transmission electron micrograph of rickettsia.

47. Cyanobacteria are important photosynthetic bacteria associated with oxygen production.
Fig Structure and examples of cyanobacteria

48. Green and purple sulfur bacteria are photosynthetic, do not give off oxygen, and are found in sulfur springs, freshwater, and swamps.
Fig Behavior of purple sulfur bacteria

49. An example of a fruiting body bacteria in which reproductive spores are produced.
Fig Myxobacterium

50. Archaea bacteria Associated with extreme environments
Contain unique cell walls
Contain unique internal structures

51. Archaea bacteria that survive are found in hot springs (thermophiles) and high salt content areas (halophiles).
Fig Halophile around the world