Unit IV: Bacteria

Question 1

Structural Features of Bacteria (5)

Answer 1

Cell Wall (peptidoglycan)
Capsule (polysaccharides, increased virulence)
Glycocalyx (biofilms for adherence, protection)
Flagella (H antigens)
Pili

Question 2

Different Membrane Compositions

Answer 2

Gram Positive: thicker peptidoglycan layer without a second cell wall, teichoic and lipoteichoic acids

Gram Negative: thin peptidoglycan w/ second lipid bilayer including lipopolysaccharides

Question 3

Peptidoglycan

Answer 3

n-acetylglucosamine and n-acteylmuramic acid subunits w/ varying sidechains
Can be cross-linked or covalently linked to phospholipids

Question 4

Lipopolysaccharides

Answer 4

Lipid A, core polysaccharide, O side chian

Question 5

Teichoic Acid

Answer 5

covalently linked to peptidoglycan and extend beyond layer, involved in adherence

Question 6

4 phases of bacterial growth phase

Answer 6

Lagging Phase: adjustment phase of new enzyme production.
Exponential phase: maximal cell division for resources available, growth proportional to # of cells (constant doubling time
Stationary Phase: essential nutrients consumed, toxic metabolites produced, growth slows
Death Phase: number of viable bacteria decreases via autolysis

Question 7

5 Classifications of Bacteria

Answer 7

Aerobes: require oxygen, cannot ferment
Anaerobes: ferment and are killed in oxygen
Indifferent: ferment w/ or w/o oxygen
Facultative: respires w/ O2, ferments w/o
Microaerobic: grow best at low O2, but can grow w/o

Question 8

Heterotrphic vs autotrophic

Answer 8

Heterotrophs require any form of carbon, Autotrophs require CO2 as source of carbon

Question 9

Fermentation

Answer 9

use organic compounds as electron donors and acceptors with no net oxidation of substrates in both aerobic and anaerobic conditions

Question 10

Respiration

Answer 10

ATP generated through electron transport with O2 as final electron acceptor.

Question 11

Energy currencies

Answer 11

Higher cells generate energy currency in the form of ATP and electrochemical gradients.
Currency can also include electron holders (NADPH)

Question 12

Antimicrobial targets (4)

Answer 12

Cell wall, inner and outer plasma membranes, protein synthesis, nucelic acid synthesis

Question 13

3 Sources of Bacterial Genetic Diversity

Answer 13

Spontaneous Mutation
Recombination
Acquisition of New DNA

Question 14

Spontaneous Mutation

Answer 14

PMs, insertions, or deletions
Very rare but can give growth advantage
(ABX resistance Pseudomonas/Myco and Strep Pyogenes invasiveness)

Question 15

Recombination

Answer 15

site-specific or homologous recombination
occurs w/in an organism or between organisms
Includes phase variation through promoter changes

Question 16

Acquisition of New DNA

Answer 16

Incorporation of free DNA into chromosome or plasmid

Transposons, bacteriophage, plasmid acquisition, pathogenicity islands

Question 17

Transformation

Answer 17

Naked DNA from lysing cells taken up by bacteria in correct growth phase in correct environment
Most common between similar species

Question 18

Tranduction

Answer 18

gene transfer via bacteriophage, bacterial DNA taken up by bacteriophage and injected into new bacterium

Question 19

Conjugation

Answer 19

F plasmid contains information for conjugation (replication, sex pilus, conjugative transfer, integration), DNA replicated into recipient cell and then incorporated into plasmid or genome

Question 20

Temperate Phage

Answer 20

Cause lysogenic response in addition to lytic response. Creates prophage that suppresses viral gene expression via repressor protein until it experiences stress.

Question 21

Lysogenic Conversion

Answer 21

Prophage in lysogenic phase obtains new phenotype

Question 22

Microbial Toxins

Answer 22

macromolecular products that alter cell structure or function. Manifest as symptoms of disease or contribute to pathogenesis w/o specific signs
Include bacterial proteins and LPS of gram negatives

Question 23

Steps to determine toxin is pathogenic

Answer 23

Toxin causes same symptoms as bacteria
Antitoxin prevents symptoms
Virulence corresponds to amount of toxin
Nontoxigenic mutants are a-virulent

Question 24

Mechanisms of action for microbial toxins (5)

Answer 24

Facilitating Spread of Microbes
Damage Cellular Membrane
Stimulating Cytokine Production
Inhibiting Protein Synthesis
Modifying Intracellular Signaling

Question 25

Facilitating Spread

Answer 25

toxic enzymes break down ECM (hyaluronidase/collagenase/etc.)

Question 26

Damaging Membranes

Answer 26

called hemolysins, actually cytolysins toxins insert in membrane via recognized marker and form pore to lyse cell Lecithinases degrade membrane components

Question 27

Stimulating Cytokine Production

Answer 27

Superantigens are potent T cell activators that bind MHC II to TCR outside of antigen pocket indiscriminantly of epitope presence. Also pyrogenic exotoxins. Causes secretion of cytokines

Question 28

Inhibiting Protein Synthesis

Answer 28

``` Exotoxin A (pseudomonas/diphtheria): ribyltransferases inactivate EF2 Shiga/Ricin: RNA N-glycosidases that inactivate 60s ribosome ```

Question 29

Heat-Labile Enterotoxin

Answer 29

Vibrio Cholerae and E Coli | ADP Ribyltransferases increase cAMP by adding to the Gs protein. Active chloride secretion, diarrhea

Question 30

Pertussis Toxin

Answer 30

ADP ribyltransferase increase AC activity by inactivating Gi protein, increases cAMP

Question 31

Heat-Stable Enterotoxin

Answer 31

E Coli | Activates GC, increases cGMP

Question 32

Anthrax Edema Factor

Answer 32

Increase cAMP but requries calmodulin and calcium

Question 33

Anthrax Lethal Factor

Answer 33

Endopeptidase that cleaves Map Kinase Kinase and inactivates them.

Question 34

Clostridium Difficile Toxins A and B

Answer 34

Glucosyl transferaes alter actin cytoskeleton by transferring glucose from UDP-glucose to several Rho GTPases and inactivating them

Question 35

Inhibitors of NT release (2)

Answer 35

Botulinum toxin: flaccid peralysis via ACh | Tetanus: zinc-dependent, SNARE inactivator, stops inhibitory neurons

Question 36

2 Types of Microbial Toxins

Answer 36

Extracellular and Intracellular

Question 37

Extracellular Toxins

Answer 37

Act on PMs w/ wide variety of structure and function, specificity is only determined by target

Question 38

Intracellular Toxins

Answer 38

Must cross plasma membrane - bifunctional: activity and binding domains - use typical membrane markers as receptors (proteins or glycolipids) - Enter by endocytosis then enter cytosol (translocation domain)