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Micro Exam 1 > Jackson: Bacterial Structure and Metabolism > Flashcards

Jackson: Bacterial Structure and Metabolism Flashcards

1
Q

BACTERIAL MORPHOLOGY:

What is the Classification Scheme based on?

G+/-

Shapes

A

BACTERIAL MORPHOLOGY:
• Classification Scheme: based on cell envelope and shape
- Gram positive or Gram negative
- Rods, Cocci, Spirilla
- Pairs, tetrads, clusters, chains (not a reliable classification scheme)

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2
Q

Gram stain procedure

A

• Gram Stain: most commonly used diagnostic technique; color distinction based on bacterial cell wall constituents

  • Procedure: ~1 minute each step
    o Air dry and heat fix bacteria on slide
    o Add crystal violet, rinse
    o Add iodine (mordant), rinse
    o Add acetone/isopropyl alcohol solution (10 drops), rinse
    o Add safranin, rinse and dry
    o Examine using oil immersion (1000x) objective
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3
Q

G+/- colors

A

Color Distinction: Gram positive are purple, Gram negative are pink

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4
Q

Gram staining mechanism

A

Mechanism:

o Crystal violet penetrates peptidoglycan layer to stain cytoplasm blue
o Iodine + crystal violet complexes, and it is too large to be washed out of Gram positive bacteria (thick cell wall), but is washed out of Gram negative bacteria
o Gram negative then counterstained with safranin (pink); done in order to visualize

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5
Q

Acid-Fast Bacteria: genus?

Cell walls contain:

Gram stain?

Methods used to stain cells:

A

• Acid-Fast Bacteria (Mycobacterium):
- Need to use a special stain (diagnosis of TB)
- Cell walls contain long chain fatty acids (mycolic acid), which repels dye
o Gram stain poorly
o Hard to decolorize with acetone/alcohol
- Hot (Ziehl-Neelsen) or Cold (Kinyoun) methods are used to stain these cells

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6
Q

G+/- Cell Envelope

A

CELL ENVELOPE:
• General:

  • Gram Positive: cytoplasmic membrane + thick peptidoglycan
  • Gram Negative: cytoplasmic membrane + thin peptidoglycan + outer membrane (2 cell membranes)
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7
Q

Teichoic acid =

LPS =

A

Teichoic acid = lipoteichoic acid

LPS = endotoxin

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8
Q

Peptidoglycan aka:

Function:

A

• Cell Wall (Peptidoglycan/Murein Layer):

  • Gives bacterial cell shape and resistance to osmotic changes
  • Target for antibacterial agents
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9
Q

Composition of Peptidoglycan:

A

Disaccharide-pentapeptide subunits

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10
Q

Disaccaride types:

A
  • N-Acetylglucosamine (NAG)

* N-Acetylmuramic acic (NAM)

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11
Q

Peptide bridges between:

G+:

G-:

A

Peptide bridges between NAM cross-link subunits

  • Gram Positive: pentaglycine bridge between lysine and D-alanine
  • Gram Negative: direct link between D-alanine and diaminopimelic acid
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12
Q

B-Lactam MOA:

What form cross-links?

Penicillin structure resembles:

A

B-Lactam MOA: target peptide bridges

Penicillin binding proteins (PBPs) form cross-link

Penicillin structure resembles D-ala/D-ala intermediate (binds PBP instead, preventing crosslinking)

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13
Q

Teichoic (Mycolic) Acids (Gram Positive):

Associated with:

Also found in:

A

Techoic and lipotechioic acids provide strength to cell wall

  • Associated with inflammatory response in some Gram positive infections
  • Also found in Acid Fast Bacilli, making them resistant to phagocytic killing, drying
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14
Q

Outer Membrane only found in:

Composed of:

A

Outer Membrane (Only Gram Negative):

  • Composed of bilayer of LPS and phospholipids
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15
Q

LPS

Composition (3 parts):

What causes endotoxic shock?

A

o LPS: important virulence factor; key mediator of inflammation (shock)

Composition of LPS:
• Repeating sugar residues (O antigens) useful for bacterial typing
• Core sugars (consistent, not part of pathogenesis)
• Fatty acid moieties (lipid A) is the bioactive portion of LPS (causes endotoxic shock)

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16
Q

Where is periplasmic space found?
What is periplasmic space?
Constituents include:

A

• Periplasmic Space (Only Gram Negative):

  • Space between inner and outer membranes (contains peptidoglycan layer)
  • Constituents include enzymes that degrade antibiotics (ie. beta-lactamases)
17
Q

Cytoplasmic (Inner) Membrane:

Found where?

Composed of:

A

Gram Positive and Gram Negative

  • Composed of a lipid bilayer heavily laced with protein
18
Q

Beta-lactams interfere with the formation of (2)

A

Beta-lactams interfere with the formation of D-ala from L-ala

Beta-lactams interfere with the formation of D-ala + Lys or DAP peptide bond

19
Q

Cytoplasmic (Inner) Membrane:

Functions

A

Functions:
o Transport of solutes
o Housing enzymes involved in outer membrane and cell wall synthesis
o Assembly and secretion of extracytoplasmic and extracellular substances
o Generation of ATP
o Housing molecular sensor that monitor environmental changes

20
Q

Capsule:

Location:
Composition:
Production:
Protects cell from:

A

• Capsule:

Exterior to peptidoglycan layer (Gram positive) or outer membrane (Gram negative)

  • Composition: high molecular weight polysaccharides or amino acids
  • Production: depends on environment and growth conditions
  • Important Virulence Factor: protects cell from complement mediated killing
21
Q

Pili aka:

Definition:
Composition:
Mediates:
Antigenic and certain bacteria will:

A

• Pili (Fimbriae): hair like proteinaceous structures extending from cell membrane

  • Composition: subunits of protein called pilin, tipped with adhesins
  • Important Virulence Factor: mediate adhesion to host tissue
  • Antigenic and certain bacteria (gonococcus) will vary the antigenic composition
22
Q

Two Types of Pili

A

o Common Pili: mediate adhesion to host eukaryotic cells

o Sex Pili: join conjugating bacteria

23
Q

Flagella:

Definition:
Composition:
Function:

A

Flagella: long, helical filaments extending from cytoplasmic membrane

  • Composition: proteins called flagellins (highly antigenic; H antigens)
  • Function: cell motility
24
Q

Endospore definition:

Medically Important Endospore Formers:

A

Endospore: resting phase of bacteria when living conditions get tough

Medically Important Endospore Formers: Bacillus and Clostridium

25
Q

PROTEIN SECRETION:

Type I

Gram +/-?

Sec-dependent or independent pathway?

Mechanism:

Example:

A

• Type I: GRAM (-)

  • Sec-independent pathway

Mechanism:
o No amino-terminal signal sequence
o ABC transporters (ATP-binding cassette); therefore ATP dependent
o Bypasses periplasm, and is extruded through a hole in cytoplasmic and outer membranes

Example: E.coli hemolysin (alpha toxin)

26
Q

PROTEIN SECRETION:

Type II

Gram +/-?

Sec-dependent or independent pathway?

Mechanism:
Recognizes:
Secretes proteins into:

A

• Type II: GRAM (-) and GRAM (+)

  • Sec-dependent pathway

Mechanism:
o Recognizes proteins with signal sequence (~20 aa with conserved cleavage site)

Secretes proteins into:
• Periplasm of Gram (-)
• Extracellular environment of Gram (+)

27
Q

PROTEIN SECRETION:

Type II

Secretes proteins into:

What form pores in outer membrane?
What else is required?

Example:

A

Secretes proteins into:
• Periplasm of Gram (-)
• Extracellular environment of Gram (+)

From the periplasm, move through outer membrane to exit cell
• Secretins form pores in outer membrane
• Chaperone proteins and ATP are required

Example: several bacterial toxins

28
Q

PROTEIN SECRETION:

Type III

Gram +/-?

Sec-dependent or independent pathway?

Contact-Dependent or Independent?

Mechanism:

Requires:

Examples:

A

• Type III: GRAM (-)

  • Sec-independent pathway
  • Contact-Dependent
  • Mechanism:
    o Pore formed that injected proteins directly into eukaryotic cells
    o Requires ATPase and chaperone proteins

Examples: Yesinia pestis (plague) injects Yops to disrupt eukaryotic cell function

29
Q

Nutrient Transport

Passive Diffusion:

Active Transport:

Group Translocation:

A

Nutrient Transport

Passive Diffusion: enter by concentration gradient (water, CO2, O2, simple sugars)

Active Transport: energy dependent pumps in the cell envelope (sugars, aa, organic acids, inorganic ions)

Group Translocation: nutrient chemically modified before being brought into the cell (sugars, nucleic acids, FAs)

30
Q

EMP Pathway (Glycolysis):

A

Glucose → pyruate + NAD + CoA → Acetyl CoA

31
Q

Fermentation:

A

Incomplete glucose oxidation (anaerobic; produces acid or alcohol)

32
Q

TCA Cycle:

A

Acetyl CoA + citrate → NADH + FADH2

33
Q

ETC:

A

ETC: redox carriers in cytoplasmic membrane yield ATP

o Substrates → Dehydrogenases → Quinones → Cytochromes → Terminal oxidases

34
Q

Aerobic vs anaerobic vs Facultative

Examples

A

o Aerobic: terminal electron acceptor is oxygen (most efficient); Mycobacteria

o Anaerobic: use fermentation pathway; terminal acceptor is nitrate, nitrite, fumarate or sulfate; Clostridia

o Facultative: can use both of the above pathways; E.coli

35
Q

Lab Tests Based on Metabolic Reactions (4):

Catabolism of sugars:
H2S production detected as:
Oxidase test detects:
Catalase test checks for:

A

o Catabolism of sugars to produce acid
o H2S production detected as gas or FeS
o Oxidase test detects cytochrome oxidase c
o Catalase test checks for enzyme that breaks down toxic O2 during respiration

36
Q

Capnophilic vs Microaerophilic:

A

o Capnophilic: organism requiring CO2 at a level exceeding that of air
o Microaerophilic: organism requiring O2 at a level below that found in air

Micro Exam 1 (18 decks)

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