Unit IV: Bacteria Flashcards

1
Q

Structural Features of Bacteria (5)

A

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

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2
Q

Different Membrane Compositions

A

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

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

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3
Q

Peptidoglycan

A

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

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4
Q

Lipopolysaccharides

A

Lipid A, core polysaccharide, O side chian

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5
Q

Teichoic Acid

A

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

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6
Q

4 phases of bacterial growth phase

A

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

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7
Q

5 Classifications of Bacteria

A

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

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8
Q

Heterotrphic vs autotrophic

A

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

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9
Q

Fermentation

A

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

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10
Q

Respiration

A

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

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11
Q

Energy currencies

A

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

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12
Q

Antimicrobial targets (4)

A

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

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13
Q

3 Sources of Bacterial Genetic Diversity

A

Spontaneous Mutation
Recombination
Acquisition of New DNA

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14
Q

Spontaneous Mutation

A

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

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15
Q

Recombination

A

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

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16
Q

Acquisition of New DNA

A

Incorporation of free DNA into chromosome or plasmid

Transposons, bacteriophage, plasmid acquisition, pathogenicity islands

17
Q

Transformation

A

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

18
Q

Tranduction

A

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

19
Q

Conjugation

A

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

20
Q

Temperate Phage

A

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

21
Q

Lysogenic Conversion

A

Prophage in lysogenic phase obtains new phenotype

22
Q

Microbial Toxins

A

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

23
Q

Steps to determine toxin is pathogenic

A

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

24
Q

Mechanisms of action for microbial toxins (5)

A
Facilitating Spread of Microbes
Damage Cellular Membrane
Stimulating Cytokine Production
Inhibiting Protein Synthesis
Modifying Intracellular Signaling
25
Facilitating Spread
toxic enzymes break down ECM (hyaluronidase/collagenase/etc.)
26
Damaging Membranes
called hemolysins, actually cytolysins toxins insert in membrane via recognized marker and form pore to lyse cell Lecithinases degrade membrane components
27
Stimulating Cytokine Production
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
28
Inhibiting Protein Synthesis
``` Exotoxin A (pseudomonas/diphtheria): ribyltransferases inactivate EF2 Shiga/Ricin: RNA N-glycosidases that inactivate 60s ribosome ```
29
Heat-Labile Enterotoxin
Vibrio Cholerae and E Coli | ADP Ribyltransferases increase cAMP by adding to the Gs protein. Active chloride secretion, diarrhea
30
Pertussis Toxin
ADP ribyltransferase increase AC activity by inactivating Gi protein, increases cAMP
31
Heat-Stable Enterotoxin
E Coli | Activates GC, increases cGMP
32
Anthrax Edema Factor
Increase cAMP but requries calmodulin and calcium
33
Anthrax Lethal Factor
Endopeptidase that cleaves Map Kinase Kinase and inactivates them.
34
Clostridium Difficile Toxins A and B
Glucosyl transferaes alter actin cytoskeleton by transferring glucose from UDP-glucose to several Rho GTPases and inactivating them
35
Inhibitors of NT release (2)
Botulinum toxin: flaccid peralysis via ACh | Tetanus: zinc-dependent, SNARE inactivator, stops inhibitory neurons
36
2 Types of Microbial Toxins
Extracellular and Intracellular
37
Extracellular Toxins
Act on PMs w/ wide variety of structure and function, specificity is only determined by target
38
Intracellular Toxins
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)