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MICROBIOLOGY: CMOD-Week 1 > (01) Bacterial Struct And Class > Flashcards

(01) Bacterial Struct And Class Flashcards

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1
Q

What are the two major shapes of bacteria?

A
  • Bacilli (rods)

- Spheres (cocci)

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2
Q

Define each of the following arrangements.

  • Strepto-
  • Diplo-
  • Staphylo-
A 
Strepto = Chains
Diplo = Pairs
Staphylo = Grape-like Clusters
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3
Q

What are the most common infectious agents?

A

Staphylococci

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4
Q

What are group of bacteria is:

  • comma shaped
  • spiral shaped
A 
comma = vibrio
Spiral = Spirilli
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5
Q

Cell walls:

  • Bacteria
  • Animals
  • Plants
  • Fungi
A

Bacteria - Peptidoglycan
Animals - NONE
Plants - Cellulose
Fungi - Chitin

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6
Q

Bacterial Peptidoglycan Cell wall:

  • Role in Pharm.
  • Structural Role
  • Classification
A

Pharm:
- Difference in Prokaryotes and Eukaryotes makes it an important target

Structural Role:
- Provides Rigidity

Classification:

  • Gram +
  • Gram -
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7
Q

What is the difference between a Gram + and Gram - cell wall?

A

Gram +
- Thick and heavily cross-linked

Gram -
- Thin and lightly cross-linked

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8
Q

What are the roles of Pili?

A

Disease:
- Attach the Bacteria to the Host Cell surface

Sex:
- Sex Pilus allows for transmission of genetic material during conjugation

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9
Q

Capsules:

  • Job
  • Presence
  • Common in which disease?
  • ink
A

Job:
- Protect Encapsulated Bacteria From Phagocytosis

Presence:
- NOT present in all bacteria

Disease:
- Meningitis is often caused by capsulized bacteria

Ink:
- Often excludes ink such as India ink

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10
Q

Spores

  • formed by which type?
  • Formed when?
  • Purpose?
A

Bacteria:
Gram + rods

When:
- Times of Stress, nutrient limitation

Purpose :
- Dehydrated and dormant, allowing potential pathogens to survive for a VERY long time

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11
Q

Gram + Cell Wall:

  • Thickness
  • Cross-linking
  • Major Components
  • Roles of Components
A

Thickness:
> 40 Layers

Cross-linking:
- Lots

Major Components:

  • Peptidoglycan
  • Teichoic Acid (endotoxic effects?)
  • Lipoteichoic Acid (endotoxic effects?)
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12
Q

What are Teichoic Acid and Lipoteichoic Acid?

A

Polymers of Glycerol Phosphate and Ribitol Phosphate

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13
Q

What is the major barrier to the environment in both Gram Positive and Gram Negative Bacteria?

A

Cytoplasmic Membrane

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14
Q

Gram - Cell Wall:

  • Thickness
  • Number of Lipid Membranes
  • Peptidoglycan location
A

Thickness:
- 2 layers of Peptidoglycan Thick

Number of Lipid Membranes:
- 2

PG Location:
- BETWEEN two lipid membranes (in periplasm)

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15
Q

Outer Membrane:

  • Charge
  • Purpose of Charge
  • Unique Proteins
  • Porins
A

Outer Membrane Serves as an additional Permeability Barrier

Charge:
- Outer Membrane = NEGATIVE

Purpose of Charge:

  • Evade Phagocytosis
  • Hinder Antibiotic Uptake
  • Avoid the action of Complement

Unique Protein:
- Lipopolysaccharide (LPS)

Porins:
- Allow Substrates to enter the periplasm

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16
Q

T or F: the Periplasm contains many degradative proteins.

A

True, these help to degrade antibiotics

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17
Q

What are the components of LPS?

- purpose of each

A
  1. Lipid A (endotoxin)
    - toxic phospholipid
  2. Core Polysaccharide
  3. O Antigen
    - Major Surface antigen of Gram - bacteria
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18
Q

Lipid A and Septic Shock

A

Recognized by innate immune system and elicits CYTOKINE STORM causing septic shock

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19
Q

Gram (-) Type I Protein Secretion System.

  • Transporter Type
  • From Where, To Where?
  • Other imp. features
  • Type of Bacteria with it?
A

Transporter:
- ABC (ATP Binding Cassette)

From and To:
- Pumps from CYTOPLASM directly to EXTRACELLULAR SPACE

Important:
- Allows drugs to be pumped out leading to DRUG RESISTANCE

ALL GRAM (-) Bacteria

20
Q

Gram (-) Type II Protein Secretion System.

  • Purpose
  • From Where, To Where?
  • Type of Bacteria with it?
A

Purpose:
- General Secretory Pathway

From and To:
- From CYTOPLAM to PERIPLASM then to extracellular space

ALL GRAM (-) Bacteria

21
Q

Gram (-) Type III Protein Secretion System.

  • Purpose
  • From Where, To Where?
  • Type of Bacteria with it?
A

Purpose:
- Pathogenesis, DIRECT INJECTION of toxins

From and To:
Hydrophobic protein spans from CYTOPLASM of bacteria into CYTOPLASM of animal (crosses 3 membranes total)

ONLY PATHOGENIC GRAM (-) BACTERIA HAVE THIS

22
Q

4 steps of Gram Staining

A
  1. Crystal Violet (color)
  2. Gram Iodine (fixes color)
  3. Decolorizer (EtOH or Acetone)
    - color lost in gram (-) cells
  4. Safarin Red
    - colors gram (-) cells, gram (+) cells remain purple
23
Q

What is formed by removal of cell walls from bacteria?

- what happens to these?

A
  • Protoplast = bacteria w/o cell wall
  • Bacterial Cell Lyses happens

**This is why cell walls are an important target

24
Q

Peptidoglycan

  • Disaccharides and arrangement
  • Linking Enzyme
A
  • Repeating NAM (N-acetylmuramic acid) and NAG (N-acetylglucosamine)
  • Transglycoslyase = linking enzyme
25
Q

Pentapeptides

  • linkage to sugar
  • linkage to other pentapeptides
  • enzyme?
A

Pentapeptides linked to the NAM (N-acetylmuramic acid) of the peptidoglycan

Pentapeptides link to other pentapetides to form interstrand crosslinks

Enzyme for Crosslinking:
- Transpeptidases and Carboxypeptidases (aka penicillin binding proteins)

26
Q

What is the difference in crosslinking between Gram (-) and Gram (+) bacteria?

A

In gram (+) bacteria a PENTAGLYCINE interpeptide lins the polypeptides

27
Q

What is found at the terminal end of NAM-pentapeptides?

  • purpose
  • removed by?
A

Terminal D-alanine

Purpose:
- Critical to Cross-linking Process

Removed by:
Carboxypeptidases

***Target for antimicrobials

28
Q

What do Cycloserine and Vancomycin affect?

- how do they differ?

A
  • The D-alanine at the terminal end of the pentapeptides

Cycloserine - inhibits their incorporation into the pentapeptide

Vancomycin - masks their availability for crosslinking

29
Q

Cell Wall Assembly (4 steps)

A
  1. NAM and NAG are made into a disaccharide IN CYTOPLASM
  2. NAM-NAG is linked to Lipid Carrier via Diphosphate bond IN CYTOPLASM
  3. NAM-NAG added to growing Peptidoglycan chain after being carried across membrane by Lipid carrier
  4. Lipid carrier dephosphorlyated and returns to inner leaflet
30
Q

How do the following affect cell wall assembly?

  1. Lysozyme
  2. Bacitracin
A

Lysozyme:
- Cleaves NAM-NAG bond

Bacitracin:
- Prevents dephosphorylation of disphosphate from lipid carrier so it cannot be recycled

31
Q

Where can lysozyme be found?

A
  • Tears
  • Saliva
  • Lysosomes of Phagocytotic cells
32
Q

ß-lactam

  • resembles
  • Bound by
  • Job
A

Resembles:
D-alanine D-alanine terminal pair

Bound By:
Traspeptidases (penicillin-binding proteins)

33
Q

What are examples of ß-lactams?

A
  • PENICILLIN
  • Cephalosporins
  • Carbapenems
  • monobactams
34
Q

What is the difference between the action of ß-lactams and drugs like vancomycin?

A

Vancomycin bind D-alanine D-alanine while ITS STILL ATTACHED TO ITS LIPID CARRIER

35
Q

What enzymes allow for resistance to be conferred against ß-lactams?

A
  1. ß-lactamases

2. Mutated Transpeptidases that no longer bind ß-lactams

36
Q

How does Vancomycin resistance occur?

A

D-alanine D-lactone is synthesized

  • D-alanine D-lactone is not recognized by vacomycin but can still by linked by transpeptidases
37
Q
  • *What is required for ß-lactams to work?

- why?

A

CELL GROWTH

  • Growing Cells have AUTOLYSINS that cleave sugars for new subunit insertion
  • ß-lactams inhibit new cross-links from forming and the cell LYSES
38
Q

What are three notable examples that cannot be stained by gram stain?

  • Why doesn’t gram stain work?
  • what diseases are caused by these?
A
  1. Mycoplasma
    - Lack a Cell wall
    - cause an atypical pneumonia in humans
  2. Chlamydia
    - Lack Peptidoglycan
    - Pneumonia, Blindness, Genital infections
  3. Mycobacterium
    - Waxy Coat containing Mycolic Acid
    - TB and Leprosy
39
Q

How are Mycobacterium cells stained?

A
  1. Carbol Fuchsin penetrates the waxy coat to enter the cells
  2. Cells are washed using acid-alcohol (acid-alcohol destains Gram organisms)

**These cells are call ACID-FAST

40
Q

What are:

  • aerobes
  • anaerobes
  • facultative anaerobes

**which account for the majority of pathogens?

A

Aerobes:
- need O2 to live

Anaerobes:
- Killed in the Presence of O2

Facultative Anaerobes:
- LIVE IN BOTH ENVIROMENTS

***MOST PATHOGENS ARE FACULTATIVE ANAEROBES

41
Q

What type of bacteria grows in the absence of oxygen but grow optimally at low O2 concentration?

A

Microaerophilic bacteria

42
Q

What 8 factors are used to classify bacteria?

A
  1. Morphology
  2. Arrangement
  3. Staining Properties
  4. Growth Properties
  5. Fermentation Properties
  6. Other Enzymatic and Virulence properties
  7. Antigenicity
  8. Genotype
43
Q

What is Serotyping?

A
  • Looking at the antigens on a given bacteria
44
Q

What bacteria type is associated with the Lancefield Antigen?

A

Streptococcus

45
Q

What method would you use to distinguish between the strains of a genus?
- why would you want to do this?

A

Serotyping

  • helps determine the SOURCE and SEVERITY of the infections
46
Q

Escherichia Coli O157:H7

  • disease?
  • what does each part mean?
A

Causes Diarrheal outbreaks

Escherichia = genus
Coli = species
O157 = O-antigen on LIPOPOLYSACCHARIDE of the strain
H7 = H antigen found on the Flagella of the strain
47
Q

What is the most common method used to Genotype a bacteria?

- when would this be used?

A

RFLP (restriction fragment length polymorphism)
- digest the genome to get specific fragment of different lengths

  • Use this during outbreaks

MICROBIOLOGY: CMOD-Week 1 (10 decks)

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