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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
Q

Are teichoic acids found on Gram positive or Gram negative bacteria?

A

only Gram positive

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26
Q

Teichoic Acid Attachment

A

polymer of ribitol linked by phosphodiester bonds to the cell wall NAM

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27
Q

Lipoteichoic Acid Attachment

A

polymer of glycerol linked by phosphodiester bonds to membrane phospholipids (so go all the way through the cell wall)

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28
Q

Can you develop antibodies to teichoic acids?

A

sure, but they’re not very protective

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29
Q

Are teichoic acids pro or anti-inflammatory?

A

proinflammatory (similar to that of Lipid A in gram-negatives)

30
Q

periplasmic space

A

concentrated gel-like matrix space (with hydrolytic enzymes, toxic enzymes, and exotoxins)

31
Q

Which has a larger periplasmic space - gram positive or negative?

A

negative

32
Q

Flagella

A

long protein structure important for locomotion/cell motility

33
Q

3 Components of the Flagellum

A
  1. Basal Body
  2. Hook
  3. Filament
34
Q

Clockwise Flagella

A

random motion (just hanging out)

35
Q

Counterclockwise Flagella

A

directional (has a purpose) in response to chemotaxis (towards nutrients, away from toxic compounds, etc)

36
Q

H antigen

A

the name of flagellin in E. coli and Salmonella

37
Q

flagellin

A

collect as polymers to make the filament of the flagella

38
Q

Salmonella Flagellar Phase Variation

A

Salmonella has two distinct flagellin genes, that can be alternatively expressed

think one population could be expressing both so harder to treat

39
Q

Pili (Fimbriae)

A

pilin subunits assembled into a filamentous structure whose main purpose is for adherence and colonization

40
Q

F pili

A

sex pili; involved in bacterial conjugation and transfer of genes from one cell to another

41
Q

Label the flagella and fimbriae.

A
42
Q

Capsule

A

simple polymeric carbohydrate structures with a slimy/mucoid appearance

43
Q

Is a capsule helpful for bacteria?

A

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
Q

Porins

A

multimeric protein channels found in the outer membrane of Gram-negative bacteria that allows the passage of small molecules through the membrane

45
Q

Is diffusion easier across the outer or inner membrane of Gram negative bacteria?

A

inner membrane

46
Q

Endospores

A

microbe can produce spores under adverse conditions (nutrient limitation, desiccation, oxygen tension) that are highly resistant to damage and are very stable

47
Q

How are endospores like bears?

A

they are metabolically dormant - not actively growing or generating energy

48
Q

Structure of Endospores

A
49
Q

What is contained in a spore core?

A

DNA
Ca++
Dipicolinic acid

50
Q

Ca++-Dipicolinic Acid Complex (2 Functions)

A

binds free water molecules to dehydrate the spores to increase heat resistance; also inserts itself between the nucleobases of DNA, increasing stability

51
Q

Two General Bacteria that form Spores

A
  1. Bacillus (aerobic)
  2. Clostridium (anaerobic)
52
Q

pyrogenicity

A

capacity to induce fever

53
Q

Main Toxic Effect of Lipid A

A

disrupts balance between pro and anti-inflammatory responses

54
Q

leukopenia

A

decrease in white blood cells

55
Q

leukocytosis

A

increase in white blood cells

56
Q

Disseminated Intravascular Coagulation (DIC)

A

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
Q

Endotoxin (Lipid A) Physiologic Effects

A

pyrogenicity
leukopenia then [due to cytokine production] leukocytosis
capillary leakage, hypotension –> septic shock –> DIC and multi-organ failure

58
Q

Cytokines induced by Endotoxin (LPS/Lipid A)?

A

TNF and IL-1 (proinflammatory)

59
Q

DIC via Endotoxin

A

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
Q

Exotoxin

A

extracellular bacterial products that have direct effects on eukaryotic cells leading to pathological events

61
Q

General Categories of Exotoxins

A
  1. Enzymatic Activity
  2. Interfere with Signal Transduction/Cellular Function
  3. Detergent/Membrane Damaging Activity
  4. Block Nerve Function
  5. A-B Toxins
62
Q

Examples of Toxins which Block nerve function

A

Tetanus and Botulinum toxins

63
Q

Membrane-Damaging Exotoxins

A

form pores in eukaryotic cell membranes (oligomeric ring)
(Strep pyogenes, Listeria monocytogenes, Staph aureus)

64
Q

phospholipase

A

degrades components of cell membrane (ex: Clostridium perfringens alpha toxin)

65
Q

A-B Toxins

A

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
Q

Host Sources of Iron (4)

A
  1. Hemoglobin
  2. Ferritin
  3. Lactoferrin
  4. Transferrin
67
Q

Do microbes need iron?

A

yes

68
Q

Why could it be hard for microbes to get iron?

A

most iron in the host is BOUND

69
Q

How do microbes get free iron?

A

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
Q

siderophores

A

iron chelators

71
Q

ferric iron reductase

A

enzyme which reduces insoluble Fe3+ to Fe2+

607 Bacteriology (24 decks)

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