1. Cell Structure Chapter 3 Nester 2nd. Ed.
MICROBIOLOGY
Cell Structure
Chapter 3
Nester 2nd. Ed.

2. Microscopic Techniques
Simple microscope - one lens
Compound microscope - two lenses
ocular and objective lenses
White light microscopy
bright field
phase contrast
interference
dark field

3. Microscopic Techniques
Ultra-violet light microscopy
fluorescence microscopy
fluorescent antibody technique - FA
Electron microscopy
transmission: regular and freeze-fracture
scanning
scanning tunneling
Handout and Figure 3.3 p. 49 all types

4. Shapes (Morphologies)of Bacteria
Figure 3.10 p. 53
cocci (coccus)
bacilli (bacillus)
spirilla (spirillus)
coccobacilli (coccobacillus)
Figure 3.11 p. 54
square
prosthecae

5. Arrangements of Bacteria
Two’s
diplobacilli
diplococci
Chains
streptobacilli
streptococci

6. Arrangements of Bacteria
Clusters (bunches)
staphylobacilli
staphylococci
Four’s
tetrads
Cube
sarcinae
Figure 3.12 p. 55 how get arrangements

7. Prokaryotic Cell Structure
Generic cell
Start with the outer structures
Then move inward
Figure 3.13c p. 55 whole cell

8. Cell Envelope Capsule, slime layer, glycocalyx Cell wall
Plasma membrane

9. Capsule, Slime Layer, Glycocalyx
thick, regular
Slime layer
loose fitting, irregular
Glycocalyx
thin short hairs called fibrils

10. Capsule, Slime Layer, Glycocalyx
Seen by negative staining
Makes colonies moist, shiny, glistening
Made of:
exopolysaccharides (outside)
peptides of D-amino acids

11. Capsule, Slime Layer, Glycocalyx
Functions
prevents phagocytosis of the bacterium
therefore the organism escapes an immune defense
attaches bacteria to surfaces
glycocalyx of Streptococcus mutans
forms plaque on teeth
sucrose is converted to glucan which is glycocalyx

12. Cell Wall Composed of sub-units found no where else in nature
Can produce symptoms of disease
Is the site of action of some of the most effective antibiotics
Determines Gram staining properties for the cell

13. Cell Wall Peptidoglycan Figure 3.19 p. 59 Gram (+)
glycan portion is composed of 2 sugars
peptido refers to the chains of amino acids
only a few of the 20 amino acids are used
can be D configuration
diaminopimelic acid
Figure 3.19 p. 59 Gram (+)
Figure 3.21 p. 60 Gram (-)

14. Cell Wall Functions confers rigidity and shape to the bacterium
holds the cell together in an hypotonic environment
water enters the bacteria
they would burst without a cell wall
less important for halophiles (salt loving bacteria)

15. Cell Wall and Penicillin
The mode of action of penicillin has selective toxicity.
It prevents formation of the amino acid cross bridges in peptidoglycan.
It works more better on Gram (+) organisms than Gram (-) organisms.
Second mode of action is suspected
Penicillin kills some bacteria without effecting the cross bridges.

16. Organisms with No Cell Wall
Mycoplasma
lack a cell wall
have a stronger plasma membrane
have sterols in their plasma membrane
provides the extra stability

17. Plasma Membrane Surrounds the cytoplasm 60% protein 40% lipid
No fatty acids
No sterols
Unit or bilayer membrane
Fluid mosaic holds true

18. Plasma Membrane Functions
contains enzymes for obtaining energy from nutrients
is a semi-permeable barrier
transports molecules
passive transport
simple diffusion
facilitated diffusion
active transport

19. Plasma Membrane Active transport
Bacteria concentrate dilute nutrients from the environment.
AT builds up high concentrations in the cell.
Bacteria are oligotrophs.
They are very efficient in active transport.
AT necessary for survival in an environment where the nutrients are in low concentration.

20. Plasma Membrane Functions
biosynthesis of DNA, cell wall parts, membrane lipids, etc.
secretion of exoenzymes
nucleases, proteases, lipases, etc.
used to recycle large molecules by degrading them
small pieces are taken up by the cell
Figure 3.29 p. 66 Gram (+)
Figure 3.30 p. 66 Gram (-)

21. Flagella Structure Figure 3.31 p. 67 parts
Gram (-) organisms have all 4 rings, the L, P, S, M rings.
Gram (+) organisms only have the S and M rings.
major component is the protein flagellin

22. Flagella Arrangement of flagella Figure 3.32 p. 67 pictures
monotrichous
lophotrichous
peritrichous
amphitrichous

23. Flagella
How they work
Flagella require energy in the form of ATP from the proton pump.
Flagella rotate one direction; the cell itself rotates in the opposite direction.
Flagella rotate at over 1000 rpm.
Figure 3.33 p. 68 rotation
Flagella push bacteria through fluids.
E. coli moves 20 body lengths per second.

24. Flagella Figure 3.34a p. 69 Bacteria in a uniform solution
swim one second
then tumble a fraction of a second
swim one second again
direction is random

25. Chemotaxis Positive - Figure 3.34b p. 69 swim toward nutrients
swim longer before tumbling
attracted by nutrients so swims longer to get there quicker
tumbles less
counter clockwise rotation

26. Chemotaxis Negative - Figure 3.34c p. 69 swims away from harm
repelled strongly initially
as it gets away it can afford to tumble
swims less and tumbles more
clockwise

27. Chemotaxis Bacteria sense nutrients or harmful substances.
The primitive nervous system causes the flagella to rotate in the correct direction.

28. Chemotaxis Organisms with multiple flagella
bundle flagella into one functional unit by rotating the flagella counterclockwise
when they reverse the rotation to clockwise the flagella unwind so tumbling occurs

29. Other Types of Taxis phototaxis aerotaxis magnetotaxis
benefits organisms that require light for photosynthesis
aerotaxis
benefits organisms that need lots of oxygen
magnetotaxis
benefits organisms that are microaerophiles

30. Cell Attachment Glycocalyx Pili (pilus) or fimbrae
Figure 3.37 p. 70; Figure 3.38 p. 70
made of the protein pilin
hollow
covered with adhesins or at the ends
various sizes
used to establish infection

31. Genetic Information Nuclear area contains the DNA Chromosomes
Figure 3.39 p. 71
Chromosomes
1-4 which are all identical
circular, super coiled, double stranded molecules
1000X longer than the length of the bacterium
histone-like proteins bind to the DNA
Figure 3.40 p. 71 folding

32. Genetic Information Plasmids double stranded, circular, DNA molecules
0.1-10% the size of the chromosome
Figure 3.41 p. 72
many copies per cell
replicate independently of the cell chromosome
not needed for the survival of the organism
carry genes for drug resistance

33. Ribosomes Protein and RNA 70S 15,000 per cell on average
anti-microbial agents effect 70S ribosomes not 80S ribosomes

34. Storage granules Nutrients stored in a form for later use
High molecular weight polymers
don’t disturb osmotic pressure of the cell
Glycogen - stores carbon and energy
Polymer of beta-hydroxybutyric acid
Volutin - chains of phosphate
metachromatic
stain red with certain blue dyes

35. Endospores “Spore” Made by some Gram (+) bacilli
Metabolically inactive
Dehydrated
Dormant for about 100 years
Resistant to chemicals, heat, drying, freezing, radiation

36. Sporogenesis The making of the endospore
It develops inside the vegetative cell.
This occurs when amounts of carbon and nitrogen are low.
A type of differentiation
Figure 3.45 p. 75 process
Figure 3.44 p. 74 spore inside cell

37. Germination The making of a new vegetative cell
Initiates when water gets into the spore coat
Re-hydration occurs
Metabolism resumes

38. Endospore Structure Core Plasma membrane - surrounds core all the DNA
protein synthesis apparatus
energy generating system based on glycolysis
dipicolinic acid - replaces water in the DNA helix
Plasma membrane - surrounds core

39. Endospore Structure Spore wall - peptidoglycan
Cortex - peptidoglycan with less cross bridges
Coat - keratin like protein
Exosporium - lipoprotein
Figure 3.46 p. 76 released spore