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Microbiology & Parasitology > Microbiology - Bacteria > Flashcards

Microbiology - Bacteria Flashcards

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1
Q

Enumerate the 4 steps in Gram-staining

A
  1. Crystal violet dye application
  2. Iodine fixation
  3. Wash w/ 95% alcohol
  4. Safranin dye application
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2
Q

Basic molecular structure of peptidoglycan

A

repeating units of a disaccaride with 4 amino acid chains

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3
Q

What is transpeptidase?

A

Enzyme that links peptidoglycan sub-units, thus forming the bacterial cell wall

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4
Q

Major component of the bacterial cell wall

A

Peptidoglycan

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5
Q

Describe the action of penicillin and lysozyme against the bacterial cell wall

A

Penicillin binds to transpeptidase (also called penicillin-binding protein) and disrupts formation of the peptidoglycan cell wall

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6
Q

2 major layers of Gram-positive bacterial envelope

A
  1. inner cytoplasmic membrane

2. peptidoglycan cell wall

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7
Q

4 major layers of Gram-negative bacterial envelope

A
  1. inner cytoplasmic membrane
  2. periplasmic space
  3. peptidoglycan cell wall
  4. outer membrane w/ lipopolysaccharide
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8
Q

Contents of the periplasmic space?

A

Bacterial enzymes

Beta lactamases

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9
Q

Differentiate the structure of the inner membrane and the outer membrane in Gram-negative bacteria

A

Inner membrane: phospholipid bilayer w/ proteins

Outer membrane
outer leaflet: Lipopolysaccharide
inner leaflet: phospholipid layer w/ proteins

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10
Q

What is teichoic acid?

A 
Polysaccharide
Unique component of Gram-positive peptidoglycan layer
Antigenic determinant (for serologic identification)
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11
Q

What is murein lipoprotein?

A

Helical lipoprotein

Anchors outer membrane to the peptidoglycan layer

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12
Q

3 components of bacterial Lipopolysaccharide

A
  1. Outer Oligosaccharide chains
  2. Core polysaccharide chain
  3. Lipid A (endotoxin)
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13
Q

What are porins?

A

proteins allowing passage of nutrients through the outer membrane in Gram-negative bacteria

Not present in Gram-positive bacteria

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14
Q

Explain how gram-negative bacteria are more resistant to penicillin and lysozyme despite having a thinner peptidoglycan layer

A

Penicillin and Lysozyme are unable to penetrate the gram-negative outer membrane

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15
Q

Major genera of pathologic Gram-positive bacteria

A
  1. Streptococcus
  2. Staphylococcus
  3. Enterococcus
  4. Bacillus
  5. Clostridium
  6. Corynebacterium
  7. Listeria
  8. Mycobacterium
  9. Actinomyces
  10. Nocardia
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16
Q

Gram-positive cocci

A

Streptococcus
Staphylococcus
Enterococcus

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17
Q

Gram-positive rods

A

Bacillus
Clostridium
Corynebacterium
Listeria

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18
Q

Spore-forming gram-positive bacteria

A

Bacillus

Clostridium

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19
Q

Non spore-forming gram-positive bacteria

A

Corynebacterium

Listeria

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20
Q

Gram-negative cocci

A

Neisseria

Moraxella

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21
Q

Gram-negative spirochetes

A

Treponema
Borrelia
Leptospira

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22
Q

What are periplasmic flagella?

A

Flagella located under the outer membrane of spirochetes, which allow them to spin around and thrust forward

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23
Q

Unique characteristic of Mycoplasma bacterial envelope

A

No peptidoglycan layer or cell wall, so they are neither gram-positive or gram-negative

24
Q

Gram-negative enterics

A 
(CHEESY Salmon Sushi and Pork Back is Vibrant Protein) 
Camplyobacter
Helicobacter
Enterobacter
Escherichia
Serratia
Yersinia
Salmonella
Shigella
Pseudomonas 
Bacteroides 
Vibrio
Proteus
25
Q

Fungus-like bacteria

A

(NO ACTING . . . like Fungi)
Actinomyces
Nocardia

26
Q

Acid-fast bacteria

A

Mycobacterium

Nocardia

27
Q

Enzymes for oxygen utilization

A

Catalase
Peroxidase
Superoxide dismutase

28
Q

Function of catalase

A

Breaks down hydrogen peroxide to water and oxygen

29
Q

Function of peroxidase

A

Breaks down hydrogen peroxide to water and oxygen

30
Q

Function of superoxide dismutase

A

Breaks down superoxide radicals into hydrogen peroxide and oxygen

31
Q

Describe:

  1. obligate aerobes
  2. facultative anaerobes
  3. microaerophilic bacteria
  4. obligate anaerobes
A
  1. Use oxygen via Glycolysis, TCA cycle, and ETC similar to animals
  2. Similar to obligate aerobes but have the ability to use fermentation in anaerobic states
  3. Use oxygen but without ETC. No catalase or peroxidase, only superoxide dismutase.
  4. Do not use oxygen
32
Q

Differentiate:

phototrophs vs chemotrophs

A

phototrophs - use light as an energy source

chemotrophs - use chemical compounds as an energy source

33
Q

Differentiate:

autotrophs vs heterotrophs

A

autotrophs - use inorganic substances for energy

heterotrophs - use organic substances for energy

34
Q

What is the Embden-Meyerhof pathway?

A

Energy pathway involving breakdown of glucose to pyruvate (Glycolysis)

35
Q

Obligate intracellular bacteria

A

Chlamydia

Rickettsia

36
Q

Tick-borne infections

A

Rickettsia
Ehrlichia
Franciscella
Borrelia

37
Q

Explain Genetic Transformation

A

Transformation - fragments of DNA from bacteria are transferred to recipient bacteria via adsorption and penetration

38
Q

Explain Genetic Transduction

A

Transduction - involvement of bacteriophages in the transfer of DNA material from one bacteria to another

39
Q

Differentiate Generalized and Specialized Transduction

A

Generalized transduction - transfer of pure bacterial DNA via bacteriophage

Specialized transduction - transfer of prophage with bacterial DNA via bacteriophage.
This is the process involved in Lysogenic Conversion.

40
Q

Differentiate Virulent and Temperate Bacteriophages

A

Virulent - Bacteriophage takes control of bacterial DNA replication system to produce new bacteriophages, causing bacterial lysis

Temperate - Bacteriophage DNA incorporates itself into host bacterial DNA and becomes a prophage.

41
Q

What is a prophage?

A

A component of bacteriophage DNA that incorporates itself into the bacterial DNA, where it awaits activation.

“Ticking time bomb”

42
Q

What are Lysogenic Bacteria?

A

Lysogenic Bacteria are those that have prophages incorporated into their DNA

43
Q

Explain the process of Bacterial Conjugation

A

Use of Sex Pili to transfer genetic material in the form of F plasmids from one bacteria to another

44
Q

What is an HFR cell?

A

Bacteria that has F plasmid incorporated into its chromosomal DNA.

45
Q

What is an F plasmid?

A

F plasmids are extrachromosomal rings of DNA that are responsible for the initiation of conjugation.

46
Q

What are transposons?

A

Mobile genetic code that can insert themselves into bacteria even without having DNA homology

47
Q

Methods for differentiating Staphylococcus from Streptococcus

A
  1. Gram stain
    Staph: grape-like
    Strep: strip-like
  2. Catalase
    Staph: (+)
    Strep: (-)
48
Q

Classification of Streptococci based on hemolytic properties

A

alpha hemolytic: only partial hemolysis

beta hemolytic: full hemolytic activity

gamma hemolytic: non-hemolytic

49
Q

What is the Lancefield classification of Streptococci?

A

Lancefield classification is based on the antigenic properties of the C carbohydrate, which is found on the bacterial cell wall of Streptococci

There are multiple groups based on Lancefield classification, from A through S.

50
Q

Main pathogenic species of Group A Beta-Hemolytic Streptococci

A

Streptococcus pyogenes

51
Q

What are the classic diseases caused by Group A Beta-Hemolytic Strep?

A

Local invasion diseases:

  1. Pharyngitis
  2. Skin Infections - Erysipelas, Pyoderma, Cellulitis, Impetigo
  3. Necrotizing Fascitis
  4. Scarlet Fever
  5. Streptococcal Toxic Shock Syndrome

Delayed antibody-mediated diseases:

  1. Rheumatic Fever & Heart Disease
  2. Acute Post-Strep Glomerulonephritis
52
Q

What is C carbohydrate?

A

Antigen found on cell wall of Streptococci. Variations of antigenicity of C carbohydrate are the basis of Lancefield classifications

53
Q

What is M protein?

A

Major virulence factor of Streptococci, responsible for inhibition of complement system and protects the bacteria from phagocytosis

54
Q

What is Streptolysin?

What are its 2 types?

A

Major virulence factor of Streptococci, responsible for its hemolytic properties (destroys RBCs and WBCs)

2 types:
Streptolysin O - oxygen labile
Streptolysin S - oxygen stable

55
Q

What is pyrogenic exotoxin?

A

Virulence factor found only in some strains of Streptococci. Responsible for development of Scarlet Fever.

It has superantigenic properties and can also lead to development of Streptococcal Toxic Shock Syndrome

Microbiology & Parasitology (1 decks)

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