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1 Microbiology Oral/Med > Bacterial Structure 2&3. 3 > Flashcards

Bacterial Structure 2&3. 3 Flashcards

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1
Q

Cell wall of bacteria

A

a structure exterior to the cell membrane that provides rigidity and stability to the bacterial cell

  • Cell walls consist of Peptidoglycan
  • G- or G+
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2
Q

Gram (+) composed of?

A

peptidoglycan and teichoic acid (purple)

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3
Q

Gram (-) composed of?

A

peptidoglycan and an outer membrane (red)

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4
Q

Peptidoglycan consists of?

A

strands of alternating repeats of N-acetyl glucose-like sugars
•N-acetylglucosamine (NAG)
•N-acetylmuramic acid (NAM)

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5
Q

N-acetylmuramic acid (NAM) is cross linked between?

A

strands by short peptides

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6
Q

Our body prodcuces what enzyme that destroys peptidoglycan? This leads to?

A

Lysozyme

*leads to lysis of bacteria cell

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7
Q

NAG and NAM are linked by?

A

a beta 1-4 glycosidic covalent bond -this is the lysozyme sensitive region

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8
Q

What four AA make the tetrapeptide bound to NAM in peptidoglycan?

A
  • L-alanine
  • D-alanine
  • D-glutamic acid
  • either lysine or diaminopimelic acid
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9
Q

Tetrapeptide cross-links are formed by? Provide the cell wall with what physical traits?

A

Tetrapeptides interaction on separate strands of peptidoglycan; provide the cell wall of prokaryotes with extreme strength and rigidity

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10
Q

define peptidoglycan interbridge

A

Tetrapeptide cross-links between layers of peptidoglycan

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11
Q

In G+, peptidoglycan interbridge is often?

A

a pentaglycine

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12
Q

In G-, peptidoglycan interbridge is often?

A

a direct link between one tetrapeptide that often contains a diaminopimelic acid (DAP) and the other tetrapeptide

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13
Q

Penicillin preevnts?

A

prevents crosslinkage of cell wall peptidoglycan (weakening the cell wall) aka transpeptidation

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14
Q

A hydrophobic alcohol called _______ facilitates transport of new glycan units across cytoplasmic membrane for formation of peptidoglycan

A

bactoprenol

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15
Q

bactoprenol and vancomycin inhibit?

A

the bactoprenal dependent process of transporting glycan units across cytoplasm

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16
Q

How thick is G+ Peptidoglycan layer? composed of?

A
  • about 200-800 Angstroms (1 Angstrom = 10-8 centimeter) thick
  • composed of many layers of peptidoglycan
17
Q

Teichoic acids are associated with

A

peptidoglycan of Gram (+) bacteria

18
Q

Teichoic acids function in? Bind?

A

adherence; binds Mg++ ions for the cell

19
Q

describe the 3 types of Teichoic acid

A 
1) one type -contains
glycerols (3-carbon sugar alcohol)
repeated again and again and linked
by phosphates with D-ala or Dglucose
2) second type -contains ribitols (a 5-
carbon sugar alcohol) repeated
again and again linked by
phosphates with D-ala or D-glucose
3) third type - lipoteichoic – contains
glycerols or ribitols with a terminal
fatty acid that is integrated into the
cytoplasmic membrane
20
Q

Mycobacteria is? contain? Peptidoglycan is bound with?

A

an acid fast bacteria

  • contain mycolic acid layer that is exterior to peptidoglycan (mycobacteria outer membrane)
  • Peptidoglycan is bound with Arabinogalactan
21
Q

In addition to peptidoglycan, the outer membrane of G- contain?

A
  • lipopolysaccharide (LPS),
  • proteins
  • Lipoproteins
  • Phospholipids
  • type I, II, III, IV, and V secretion devices
22
Q

Periplasm

A

space between membranes, contains other proteins, mainly for transport

23
Q

Porin proteins are integrated with?

*Provides channel for?

A

both leaflets of the outer
membranes of G-
*provide a channel to shuttle small nutrients from the outside to the inside

24
Q

G- bacteria have an outer membrane that can be? Therefore it is referred to as?

A

physiologically toxic to the host during an infection

*referred to as endotoxin

25
Q

Shwartzman reaction follows the release of large amounts of?

A

endotoxin into the bloodstream

26
Q

Neisseria bacteria shed large amounts of a related molecule to endotoxin called lipooligosaccharide (LOS). This results in?

A

resulting in fever and severe

symptoms

27
Q

penicillin is much less effective against Gram (-) or Gram (+) peptidoglycan? Why?

A

Gram (-) peptidoglycan

*Peptidoglycan of Gram (-) bacteria is thicker! But no more than 1 to 2 layers

28
Q

Exterior portion of Lipopolysaccharides of G- are composed of

A

“O” specific polysaccharide

29
Q

“O” specific polysaccharide are often called?

Has a what motif?

A
  • often called repeat polysaccharide (up to 40x)

* has various six carbon sugar motifs that are repeated again and again

30
Q

Middle portions of Lipopolysaccharides of G- are composed of ?

A 
core polysaccharide-that contains
•ketodeoxyoctonate (KDO),
•heptoses,
•glucose,
•galactose,
•NAG (N-acetylglucosamine)
31
Q

•Inner portions of Lipopolysaccharides of G- are composed of?

A

*•Lipid A
•diphospho-(NAG)2
•fatty acids are attached
•Lipooligosaccharide (LOS) of Neisseria species lacks the O-antigen portion of LPS, has a core polysaccharide plus lipid A, and is readily shed from the Neisseria bacteria

32
Q

example of endotoxin

A

G- bacteria’souter membrane- can be physiologically toxic to the host during an infection

33
Q

Protoplasts are?

A

are wallless bacteria that can survive in isotonic solutions but not hypotonic solutions
•In hypotonic solutions protoplasts lyse

34
Q

How is it possible for a protoplast to survive without a cell wall?
How do the mycoplasma species do it?

A

1) produce unusually tough membranes
2) live in osmotically protected habitats, such as the animal body =Mycoplasma species**
3) evolve to survive in an animal body without cell walls due to selective pressure of penicillin (L-forms). They are penicillin resistant

35
Q

Gram stain reaction gives us what information?

A

If the bacteria is G+ (purple) or G- (red)

36
Q

What is responsible for differences in the Gram stain reaction?

A

The structural differences between the cell walls of gram-positive and gram-negative Bacteria

37
Q

Alcohol can readily penetrate the lipid rich outer membrane of? Alcohol then extracts?

A

G- bacteria

*alcohol extracts the insoluble crystal violet-iodine complex from the cell

1 Microbiology Oral/Med (26 decks)

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