Bacterial Structures & Morphology Flashcards

1
Q

Explain the major structures of a bacterial cell and their functions

A

Cell wall: protection
Nucleoid: section that has the chromosome
no membrane-bound organelles: (can use plasma membrane instead of mitochondria to make ATP/energy)
Ribosomes: 70S (80S in eukaryotes)

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2
Q

Describe the Gram stain procedure

A

1) crystal violet (gram positive)
2) gram iodine –> fixing step
3) decolorizer (alcohol or acetone)
4) safranin red (gram negative)

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3
Q

Discuss the cell wall structure and chemical components of Gram-positive and Gram-negative bacteria

A

Gram positive: lysine used for cross-linking to penultimate D-alanine of adjacent peptide; use amino acid bridge; peptidoglycan layer is 3-D
Gram negative: DAP used for cross-linking to penultimate D-alanine of adjacent peptide; peptidoglycan layer is 1 molecule thick

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4
Q

Differentiate Gram-positive and Gram-negative cell walls and their chemical components

A

Gram positive: lipoteichoic acids transverse cell wall and anchor in membrane; inner membrane is lipid bilayer with integral proteins
Gram negatve: outer membrane bottom leaflet is made up of phospholipid and top layer is made up entirely of lipopolysaccharides – O antigens (outside) and lipid A (anchor); inner membrane is lipid bilayer with integral proteins

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5
Q

Identify bacterial capsule, flagellar arrangement, and endospore position under the light microscope

A

(practice)

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6
Q

Describe bacterial shapes

A
  • coccus: round
  • Bacillus: rod-shaped
  • Coccobacillus: round oval
  • fusiform bacillus: long oval
  • vibrio: curved
  • spirillium: wavy, spiral-like
  • spirochete: spiral with flagella
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7
Q

Endospore function

A
  • found in Bacillus and Clostridium
  • bacterial genome wrapped in thick coat
  • dormant form like fungal spores, but not reproductive
  • survive harsh environments for years
  • induced by harsh conditions
  • resist dessication, UV, heat, chemical disinfectants
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8
Q

How do you identify the species from an endospore?

A
  • round or oval

- terminal, subterminal, or central

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9
Q

Somatic pilli function

A

adhesion to cells

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10
Q

Sex pilli function

A

hollow tube for sharing genes (conjugation)

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11
Q

Flagella function

A
  • run and tumble
    • rotate counterclockwise for movement
    • clockwise to tumble
    • runs on proton gradient at proton motor
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12
Q

Contrast Spirillum and Spirochete

A

Spirillum: use flagella for movement, spiral shaped
Spirochete: use internal flagella for movement, wavy (looks like an asterik head on)

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13
Q

What enzyme catalyzes cross-linking?

A

transpeptidase/penicillin-binding protein

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14
Q

How is cross-linking inhibited?

A
  • B-lactams
    • bind penicillin-binding protein
    • resemble transition state of reaction
    • leads to compromising cell wall structure
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15
Q

What do autolysins do?

A

remodel cell wall – there is constant turnover

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16
Q

What’s the importance of O antigens?

A

identify species and strains

17
Q

Importance of periplasmic space

A

contain peptidoglycan and enzymes to destroy antibiotics

18
Q

How does the outer membrane of gram-negative bacteria help protect against disinfectants or antibiotics?

A

porin proteins channel chemicals into the cell

19
Q

Describe bacterial arrangements

A

strepto: chain
staphylo: clusters
diplo: 2
tetrads: 4
sarcinae: 8 (cube-shaped)

20
Q

Steps of cell wall biosynthesis

A

1) UDP NAM and NAG are synthesized
2) amino acids added to UDP NAM to form NAM-pentapeptide
3) NAM-pentapeptide transferred to bactoprenol phosphate to generate Lipid I (joined by pyrophosphate bond)
4) UDP transfers NAG to Lipid I to make Lipid II
5) flippase flips Lipid II across the membrane
6) increase Lipid II length by attaching to end of growing peptidoglycan chain
7) bactoprenol-p leaves to other side of membrane to start cycle again (vancomycin can inhibit here)
8) transpeptidation forms peptide cross links between peptidoglycans