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FHDM: Unit 1 - Childhood Dehydration > Bacterial Cell Wall & Metabolism - Dr. Turner > Flashcards

Bacterial Cell Wall & Metabolism - Dr. Turner Flashcards

1
Q

Why are 3 reasons to study the cell wall of bacteria?

A
  1. Components of the cell wall are targets for antimicrobial therapy
  2. Variations in the cell wall contribute to antigenicity
  3. Bacterial cell wall components (LPS) can cause fever, shock and death
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2
Q

What are 3 functions of the bacteria cell wall?

A
  1. Rigid
  2. Gives bacterial cells shape
  3. Protects bacteria from osmotic lysis
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3
Q

What is the the structure of peptidoglycan

A

Composed of two alternating amino sugars

  1. N-acetylglucosamine (NAG)
  2. N-acetylmuramic acid (NAM)
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4
Q

What enzyme cleaves of peptidoglycan?

A

Lysozyme cleaves between N-acetylglucosamine and the N-acetylmuramic acid

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5
Q

What are the 3 steps for cell wall synthesis

A
  1. Assembly of NAM-NAG precursor in the cytoplasm

2. Transport across the inner membrane by bactoprenol (BP)

  1. Polymerization and conversion of BPP to BP
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6
Q

What covalently links alternating NAG and NAM molecules by peptide side chains?

A

Transpeptidases- covalently link alternating NAG and NAM molecules by peptide side chains

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7
Q

Whats another word for transpeptidases?

A

The transpeptidases are called penicillin-binding proteins (PBPs)

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8
Q

Name 3 antibiotics that target bacterial cell wall . How does each one function?

A

β-Lactam antibiotics (penicillin) binds to inhibit the enzymes that catalyze the transpeptidase reaction that links chains of NAG-NAM Polymers together.

Vancomycin binds NAG-NAM-peptide precursor at the D-ala- D-ala and blocks its incorporation into the peptidoglycan chain (transglycosylation) and cross-linking (transpeptidation).

Bacitracin inhibits the recycling of BPP the lipoprotein that translocates NAM-NAG precursors across the inner membrane.

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9
Q

Is the cell wall thicker in gram negative or gram positive

A

its thicker in gram postive

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10
Q

Is techoic acid found in gram postive or gram negative

A

gram positive

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11
Q

are gram positive or gram negative sensative to penicillin

A

gram positve are sensitive, gram negative are not

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12
Q

are gram negative or gram postive susceptible to penicillin

A

gram postive are more susceptible

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13
Q

is lps found on gram negative or gram positive

A

gram negative

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14
Q

Whats another term for LPS

A

Endotoxin

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15
Q

variations in the cell wall contribute to _____

A

antigenicity

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16
Q

What are the 3 regions of endotoxin

A
  1. Lipid A (endotoxin)
  2. Core polysaccharide
  3. O antigen
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17
Q

What is the function of endotoxin

A

Responsible for toxicity of endotoxin and promotes inflammation and fever (pyrogenic)

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18
Q

What part of LPS is responsible for toxicity of endotoxin and promotes inflammation and fever (pyrogenic)

A

Lipid A

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19
Q

When is lipid A released

A

During infection Gram negative bacteria release Lipid A when the cell dies

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20
Q

What part of LPS is essential for structure and viability

A

Core Polysaccharide

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21
Q

What is the function of somatic O antigens?

A

Repeating carbohydrate units, Attached to the core and extends away from the cell

Occur in a variety of combinations

Distinguishes serotypes (strains) of a species

Accounts for antigenic diversity among serotypes

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22
Q

What contributes to the antigenic diversity ?

A

Somatic O Antigen

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23
Q

T/F LPS is produced by gram negative bacteria only

A

True

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24
Q

What is the function of LPS

A

Causes acute-phase inflammatory responses

It induces macrophages to produce acute phase cytokines like IL-1, TNFα, IL-6

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25
Q

What cytokines are activated in LPS

A

acute phase cytokines like IL-1, TNFα, IL-6

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26
Q

Describe the effects of low level and high level LPS

A

Low levels: initiate protective responses including fever

High levels: lead to Activation of complement pathway (C3a, C5a)

Vasodilation and capillary leakage

Hypotension and shock and even death

Disseminated intravascular coagulation DIC

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27
Q

Do Peptidoglycan, teichoic acid, lipoteichoic acid lead to endotoxin-like pyrogenic responses?

A

Yes, Peptidoglycan, teichoic acid, lipoteichoic acid can also lead to endotoxin-like pyrogenic responses (just not as severe).

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28
Q

What is the LPS receptor

A

LPS receptor= CD14/TLR4/MD2

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29
Q

What doe LPS promote?

A

LPS promotes the secretion of proinflammatory cytokines including tumor necrosis factor-α and interleukin-1.

30
Q

What is LOS ? Where is it found? How is it different than LPS?

A

Similar to LPS

Present in Neisseria gonorrhoeae, N. meninigitidis

Lacks the O antigen portion of LPS

Readily shed from the bacteria

Role in evasion of host immune response

31
Q

What is the function of flagella? What are the 3 parts? What antigen is found on it?

A

Organelles for locomotion

Composed of flagellin – helically coiled protein subunits

Ropelike propellers

Composed of 3 parts (basal body, hook, filament)

H antigens

32
Q

Flagella undergo _____ variation

A

Undergo phase variation

33
Q

How do flagella propel cells?

A

Propel cells by rotation motion

34
Q

What kind of bacteria is this

A

Peritrichous Bacterium

35
Q

Look!

A
  1. Peritricous Bacteria
36
Q

What kind of bacteria is this

A

Lophotricous

37
Q

What kind of bacteria is this

A

Monotricous Bacteria

38
Q

Discuss what bacteria are attracted to and repelled from

A

Bacteria swim in counterclockwise direction toward chemoattractants.

They swim away from repellants.

39
Q

How fast do e coli grow

A

double every 18-20 minutes

40
Q

does mycobacterium grow slow or fast

A

slow, double every 18 hrs

41
Q

what are the 4 stages of growth for bacteria

A

lag, exponential, stationary, decline

42
Q

what is bacterial growth dependent on

A

availability of nutrients and environmental conditions.

43
Q

Describe each of the 4 stages of bacterial growth

A
  1. Lag- There is no cell division
  2. Exponential- The bacteria will grow and divide
  3. Stationary- Decreased growth rate (depletion of nutrients or buildup of toxic by-products)
  4. Death
44
Q

List 3 gram + bacteria with spores.

What is the function of spores?

A
  1. Bacillus anthracis
  2. Clostridium tetani or botulinum
  3. Clostridium difficile

Spore protects the bacterium DNA from

Heat, Radiation and Chemical agents

45
Q

What is found in the core of the spore?

A

Core contains dipicolinic acid

46
Q

Can you kill spores?

A

Must autoclave to kill spores (surgical equipment) by steaming at 121°C for 15 minutes

47
Q

What are the 4 respiratory classifications of bacteria

A
  1. Obligate Aerobes - Bordetella pertussis (whooping cough) , Mycobacterium tuberculosis (TB)
  2. Microaerophiles- Borrelia burgdorferi, Helicobacter pylori
  3. Obligate anaerobe- Prevotella, Clostridium, Bacteroides
  4. Facultative anaerobes- The family Enterobacteriaceae (E. coli, Enterococcus), Staph and Strep
48
Q

What is the term for this: An organism which requires oxygen for growth and oxygen-based metabolism (Cellular respiration). They use oxygen as the terminal electron acceptor during aerobic respiration.

A

Aerobe

49
Q

What is the term for this: require oxygen but at levels lower than atmospheric

A

Microaerophiles

50
Q

What is the name of this : An organism that does not require oxygen for growth

A

Anaerobe

51
Q

What is the term for this: anaerobes can survive in the presence of oxygen but do not use oxygen as a terminal electron acceptor

A

Aerotolerant

52
Q

What is the term for this: Organisms which are capable of producing energy through aerobic respiration and then switching back to fermentation depending on the amounts of oxygen and fermentable material in the environment.

A

Facultative anaerobe

53
Q

What is this called: Organism that lives in anaerobic environment. Exposure to atmospheric levels of oxygen is lethal because they lack superoxide dismutase and catalase enzymes that convert lethal forms of oxygen.

A

Obligate anaerobe

54
Q

What are the 3 kinds of enrichment media

A

Blood agar

Brain or Heart infusion

Chocolate agar

55
Q

What are 3 selective media

A

Antibiotic containing agar

MacConkey

Mannitol salts agar

56
Q

Whats the difference between selective and differential media

A

Selective media- designed for the recovery of specific organisms that may be present in a mixture of other organisms (stool sample). The media are supplemented with inhibitors that allow you to grow a subset of bacterial species

Differential Media- Differentiates closely related organisms or groups of organisms based on the organism’s biochemical characteristics. Allows for the identification of species based off physical appearance

57
Q

What is blood agar used for

A

Useful for detecting hemolytic ability of Gram-positive cocci typically Streptococci, but also some Staphylococci.

58
Q

Some blood agar has some white colonies, what has caused this?

A

Several Gram-positive cocci produce exotoxins called hemolysins which destroy red blood cells in the media, generating a clear zone around the colonies.

59
Q

What’s the difference between alpha, beta and gamma hemolysis?

A

Alpha hemolysis (α-hemolysis)-partial lysis of red blood cells- leaving a greenish discoloration

Beta hemolysis (β-hemolysis)- complete lysis of red cells resulting in the formation of a clear zone around the colonies.

Gamma hemolysis (γ-hemolysis)- no lysis

60
Q

Give an example of alpha, beta and gamma hemolysis of blood agar

A

Streptococcus viridians= Alpha hemolytic

Streptococcus pyogenes= Beta hemolytic

Staphylococcus epidermidis= Gamma hemolytic

61
Q

Mannitol is selective for what bacteria

A

Selective medium used for the isolation of Staphylococci

62
Q

something was grown on mannitol causing a yellow color. What was it ?

A

S. aureus can ferment mannitol, producing yellow-colored colonies on the agar

63
Q

McConkey is both ______ and ________

A

Both selective and differential.

64
Q

What 2 things inhibit growth of Gram-positive bacteria on mcconkey agar

A

Bile salts and crystal violet inhibit growth of Gram-positive bacteria

65
Q

something is grown on mcconkey agar causing bright pink color what does this tell us

A

Lactose fermenters will be bright pink when grown on MacConkey’s while non-fermentors are no

66
Q

What kind of bacteria are inhibited on Eosine Methylene Blue Media?

A

Eosine blue and methylene blue inhibit Gram-positive bacteria.

67
Q

Something is plated on Eosine Methyline Blue , you see a bright green color , what has occured

A

Fermentation of lactose produces acidic products which turn the methylene blue purple or a metallic , green sheen with high lactose fermentation.

Basically it means that its lactose positive

68
Q

What is chocolate agar?

A

is a non-selective, enriched growth medium. It is a variant of the blood agar plate. It contains red blood cells, which have been lysed by heating very slowly to 56 °C.

69
Q

What is thayer martin agar? What is it selective for?

A

Thayer Martin Agar has 5% “chocolate” sheep blood and antibiotics.

Used for culturing and isolating Neisseria bacteria, including Neisseria gonorrhoeae and Neisseria meningitidis, as the medium inhibits the growth of most other microorganisms.

70
Q

the production of white bubbles indicates what enxyme

A

catalyze

71
Q

What is the oxidase test

A

Cytochrome c oxidase is detected by using a chromogenic reducing agent called tetramethyl-p-phenylenediamine giving purple color

FHDM: Unit 1 - Childhood Dehydration (4 decks)

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