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607 Bacteriology > Bacterial Structure > Flashcards

Bacterial Structure Flashcards

1
Q

Steps of Gram Staining

A
  1. Heat fixation
  2. Crystal violet
  3. Iodine treatment
  4. Decolorization
  5. Counterstain (safranin)
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2
Q

Color of Gram Positive Stains

A

purple/blue

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3
Q

Color of Gram Negative Stains

A

pink/red

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4
Q

peptidoglycan

A

cell wall which prevents bacteria from exploding

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5
Q

Why is peptidoglycan (cell wall) a good drug target?

A

the synthesis (needs enzymes) and the structure are unique to bacteria/prokaryotes

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6
Q

Gram Positive Structure

A

thick peptidoglycan with teichoic and lipoteichoic acids and a very small periplasmic space above the cell membrane

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7
Q

Gram Negative Structure

A

phospholipid outer membrane coated with LPS and porins, a thin peptidoglycan and a large periplasmic space encompassing the cell wall above the inner cell membrane

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8
Q

Peptidoglycan (cell wall) Structure

A

carbohydrate backbone made up of strands of repeated disaccharides of NAM-NAG linked together by peptide bridges

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9
Q

NAM

A

N-acetylmuramic acid (not Vietnam)

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10
Q

NAG

A

N-acetylglucosamine

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11
Q

interpeptide bridge

A

pentaglycine chain connects NAMs between strands in the cell wall

links L-lysine and D-alanine

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12
Q

Gram Positive NAM Interpeptide Bridges

A
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13
Q

Gram Negative NAM Interpeptide Bridges

A
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14
Q

Muramyl Dipeptide (MDP)

A

component of NAM that has proinflammatory activity [similar to LPS]

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15
Q

DD-transpeptidase

A

enzyme which catalyzes the transpeptidation of the crosslinks the peptide sidechains on peptidoglycan strands

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16
Q

Penicillin Similarities to NAM

A

the beta lactam ring of penicillin is structurally similar to D-alanine-alanine

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17
Q

Penicillin MOI

A

irreversibly binds to the enzyme DD-transpeptidase preventing it from binding to D-alanine-alanine so then the cell wall can’t even form (no cross-linking occurs)

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18
Q

lysozyme

A

aka N-acetylmuramide glycanhydrolase

enzyme which cleaves the link between NAM and NAG therefore breaking down the cell wall

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19
Q

LPS (Lipopolysaccharide)

A

major component of Gram-negative outer membrane

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20
Q

Three Components of LPS

A
  1. O-antigen (O-polysaccharides)
  2. Core region
  3. Lipid A (endotoxin)
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21
Q

O-antigen

A

carbohydrate which confers smoothness, reduces surface hydrophobicity, is highly antigenic, and often used for serotyping

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22
Q

“rough” strains or mutants

A

has the O-antigen component of LPS removed and is therefore more susceptible to clearance by macrophages and neutrophils via phagocytosis

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23
Q

Lipid A

A

aka endotoxin, the toxic component of LPS

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24
Q

Why is LPS considered an endotoxin if it’s on the surface of the cell?

A

a man with a fancy name classified exotoxins as those which are RELEASED by the bacteria into the surrounding environment and endotoxins are those kept as part of the bacterial cell and would only be released upon its destruction

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25
Are teichoic acids found on Gram positive or Gram negative bacteria?
only Gram positive
26
Teichoic Acid Attachment
polymer of ribitol linked by phosphodiester bonds to the cell wall NAM
27
Lipoteichoic Acid Attachment
polymer of glycerol linked by phosphodiester bonds to membrane phospholipids (so go all the way through the cell wall)
28
Can you develop antibodies to teichoic acids?
sure, but they're not very protective
29
Are teichoic acids pro or anti-inflammatory?
proinflammatory (similar to that of Lipid A in gram-negatives)
30
periplasmic space
concentrated gel-like matrix space (with hydrolytic enzymes, toxic enzymes, and exotoxins)
31
Which has a larger periplasmic space - gram positive or negative?
negative
32
Flagella
long protein structure important for locomotion/cell motility
33
3 Components of the Flagellum
1. Basal Body 2. Hook 3. Filament
34
Clockwise Flagella
random motion (just hanging out)
35
Counterclockwise Flagella
directional (has a purpose) in response to chemotaxis (towards nutrients, away from toxic compounds, etc)
36
H antigen
the name of flagellin in E. coli and Salmonella
37
flagellin
collect as polymers to make the filament of the flagella
38
Salmonella Flagellar Phase Variation
Salmonella has two distinct flagellin genes, that can be alternatively expressed think one population could be expressing both so harder to treat
39
Pili (Fimbriae)
pilin subunits assembled into a filamentous structure whose main purpose is for adherence and colonization
40
F pili
sex pili; involved in bacterial conjugation and transfer of genes from one cell to another
41
Label the flagella and fimbriae.
42
Capsule
simple polymeric carbohydrate structures with a slimy/mucoid appearance
43
Is a capsule helpful for bacteria?
YES, they cover/hide more highly antigenic cellular components and protect the bacterium from the immune response/phagocytosis also protects from harsh environments; capable of host mimicry
44
Porins
multimeric protein channels found in the outer membrane of Gram-negative bacteria that allows the passage of small molecules through the membrane
45
Is diffusion easier across the outer or inner membrane of Gram negative bacteria?
inner membrane
46
Endospores
microbe can produce spores under adverse conditions (nutrient limitation, desiccation, oxygen tension) that are highly resistant to damage and are very stable
47
How are endospores like bears?
they are metabolically dormant - not actively growing or generating energy
48
Structure of Endospores
49
What is contained in a spore core?
DNA Ca++ Dipicolinic acid
50
Ca++-Dipicolinic Acid Complex (2 Functions)
binds free water molecules to dehydrate the spores to increase heat resistance; also inserts itself between the nucleobases of DNA, increasing stability
51
Two General Bacteria that form Spores
1. Bacillus (aerobic) 2. Clostridium (anaerobic)
52
pyrogenicity
capacity to induce fever
53
Main Toxic Effect of Lipid A
disrupts balance between pro and anti-inflammatory responses
54
leukopenia
decrease in white blood cells
55
leukocytosis
increase in white blood cells
56
Disseminated Intravascular Coagulation (DIC)
widespread activation of the clotting cascade that results in the formation of blood clots in the small blood vessels throughout the body aka "death is coming"
57
Endotoxin (Lipid A) Physiologic Effects
pyrogenicity leukopenia then [due to cytokine production] leukocytosis capillary leakage, hypotension --> septic shock --> DIC and multi-organ failure
58
Cytokines induced by Endotoxin (LPS/Lipid A)?
TNF and IL-1 (proinflammatory)
59
DIC via Endotoxin
IL-1 and TNF produced in response to LPS --> monocytes and neutrophils adhere to endothelial cells, which release cytokines that activate platelets and increase procoagulant production --> microthrombosis and DIC
60
Exotoxin
extracellular bacterial products that have direct effects on eukaryotic cells leading to pathological events
61
General Categories of Exotoxins
1. Enzymatic Activity 2. Interfere with Signal Transduction/Cellular Function 3. Detergent/Membrane Damaging Activity 3. Block Nerve Function 4. A-B Toxins
62
Examples of Toxins which Block nerve function
Tetanus and Botulinum toxins
63
Membrane-Damaging Exotoxins
form pores in eukaryotic cell membranes (oligomeric ring) (Strep pyogenes, Listeria monocytogenes, Staph aureus)
64
phospholipase
degrades components of cell membrane (ex: Clostridium perfringens alpha toxin)
65
A-B Toxins
multicomponent exotoxin with at least one Active and one Binding subunit binding attaches to target cell surface, toxin is taken up into vacuole in the host cell cytoplasm; pH then drops and A component is released, causing damage to cell (receptor mediated endocytosis)
66
Host Sources of Iron (4)
1. Hemoglobin 2. Ferritin 3. Lactoferrin 4. Transferrin
67
Do microbes need iron?
yes
68
Why could it be hard for microbes to get iron?
most iron in the host is BOUND
69
How do microbes get free iron?
bacteria releases proteases to release the iron from their bound molecules, and will then release siderophores to pick up the iron this is actually happening simultaneously
70
siderophores
iron chelators
71
ferric iron reductase
enzyme which reduces insoluble Fe3+ to Fe2+

607 Bacteriology (24 decks)

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