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Microbiology-1 > Bacterial Nutrition & Metabolism > Flashcards

Bacterial Nutrition & Metabolism Flashcards

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Biology 101 flashcards
1
Q

Bacteria grow in living animals?

A

Treponema Pallidum

  • causes syphilis
  • needs to be grown in rabbit testes
  • loses infectivity if grown in primary cell culture

Mycobacterium Leprae

  • causes leprosy
  • grown in mice & nine-banded armadillo
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2
Q

Techniques to isolate specific organisms?

A

Enrichment cultures, selective medium, differential medium

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3
Q

Enrichment Medium

A
  • Liquid medium favors growth
  • minimal conditions
  • ex. Azotobacter- nonvolatile nitrates to fix nitrogen
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4
Q

Selective medium

A
  • agar plates, selects one and/or inhibits others

- takes advantage of specific metabolic requirements or specific set of conditions that inhibit growth.

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5
Q

Differential Medium

A
  • agar plate, colonies of desired orgsm have distinct appearance.
  • NOT necessarily selective
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6
Q

Blood Agar (selective, differential, promotes, inhibits)

A

S: no
D: Hemolysis patterns
P: Many bacteria
I: -

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7
Q

Eosin Methylene Blue (EMB) (selective, differential, promotes, inhibits)

A

S: dyes inhibit growth
D: lactose fermentation, purple or metallic green
P: enteric gram - rods
I: gram +

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8
Q

Mannitol Salt (selective, differential, promotes, inhibits)

A

S: high Mannitol (5%) inhibits growth
D: Mannitol fermentation, yellow around colonies
P: Gram + (staph)
I: gram -

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9
Q

MacConkey (MAC) (selective, differential, promotes, inhibits)

A

S: Bile salts and crystal violet inhibit growth
D: Lactose fermentation, Dark pink colonies due to pH indicator
P: Gram-
I: Gram +

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10
Q

Which medium promotes gram -?

A
  • EMB: enteric gram-

- MAC

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11
Q

which medium promotes gram +?

A

Mannitol salt

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12
Q

Blood Agar hemolysis patterns?

A

A. beta (complete)
-clear zone around colony
-ex. S. pyrogenes
B. alpha (partial)
-indistinct zone of partial RBC lysis around colony, greenish to brownish discoloratoin
-S. pneumonia, viridans group of streptococci.
C. gamma (no hemolysis)

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13
Q

Eosin Methylene Blue bacterial growth?

A

A. Ecoli- ferments lactose
B. P aeruginosa- no fermentation
C. e. aeruginosa- weak fermentation
D. S aureus- inhibited by eosin and Methylene blue (gram +)

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14
Q

Mannitol Fermentation bacterial growth?

A

yellow, Staphylococcus aureus

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15
Q

MacConkey growth?

A

lactose fermentation (pink)

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16
Q

Obligate Anaerobes

A

cannot survive in the presence of O2

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17
Q

Obligate Aerobes

A

cannot survive in the absence of 02

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18
Q

Facultative anaerobes or aerobes

A

can survive in the presence or absence of oxygen

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19
Q

Examples of Obligate anaerobes

A

ex. Bacteriodes fragilis: common in abdominal abcesses

ex. clostridium tetani: causative agent of tetanus

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20
Q

Why is 02 lethal?

A
  1. auto-oxidation of flavines generate superoxide radical -O2
    - highly toxic!
  2. Lack enzymes that dispose of -02
    • superoxide dismutase
    • catalase
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21
Q

Examples of Obligate Aerobes

A

Ex. Pseudomonas aeruginosa: cause nosocomial infections

ex. bacillus anthracis: biological warfare, bioterrorism potential

22
Q

Why is 02 required?

A
  • cannot generate enough energy from glycolysis, Krebs cycle is essential!
  • lack PFK (F6P–>F16BP)
  • Make triose P using Pentose shunt
  • creates an ATP deficit that can only be offset by oxidative phosphorylation.
23
Q

Why is iron critical for bacteria?

A
  1. cofactor for enzyme
    • sulfur containing enzymes
    • electron carriers
24
Q

In what state does Iron exist in the envirn?

A

ferric state Fe3+ as insoluble hydroxides, carbonates and phosphates

25
Q

How is iron found in cells?

A

Bound to cellular proteins

26
Q

How does Iron get into the cell?

A
  1. Bacteria make Siderophores which scavenge Fe3+.
  2. Membrane R bind the siderophores
  3. Transport proteins takes up the complex and moves it into the cell. Fe3+–>Fe2+ (useful form).
27
Q

Importance of Iron update systems?

A
  1. Iron updates systems are redundant- 4 distinct systems in E. Coli
  2. Loss of high affinity may lead to loss of ability to cause disease
28
Q

Comparative Metabolism

A
  • similar pathways in bacteria and mammals.

- diff good for diagnosis NOT useful for therapy

29
Q

Which bacteria can ferment lactose?

A

E. Coli, normal component of the gut
S. dysenteriae indicates disease
E. Coli resistant to acid

30
Q

Which bacteria cannot ferment lactose?

A

Shigella- inhibited by even low concentrations of acid.

Inadequate food consumption–>decreased gastric acid secretion–>infection w/ Shigella

31
Q

What product does Enterobacter aerogenes produce and what type of bacteria is it?

A

-acetonin
-gram - rod
Normally present in field water
If ecoli present the contaminate sewage

32
Q

How does yeast produce ethanol?

A

pyruvic acid–>ethanol (not med. useful)

33
Q

How does bacteria make ethanol?

A

pyruvate–>acetyl coa–>acetaldehyde–>ethanol

34
Q

How do bacteria use pyruvic acid?

A

make proprionic acid + CO2
(no medical relevance)
(CO2 generates holes in swiss cheese)

35
Q

what is an important diff btw humans and bacteria?

A

peptidoglycan

  • give bacterial cells wall rigidity
  • determines bact shape & protecs cytop. membrane
36
Q

What is the structure of peptidoglycan?

A

NAG-NAM-NAG-NAM-ETC

37
Q

What type of bacteria can vertical cross link peptidoglycan?

A

Gram + NOT gram -

thus have thicker walls, retain gram stain crystal violet, walls are porous

38
Q

what determines the thickness of the cells wall?

A
  • peptidoglycan vertical cross-links

- antibiotics affect crosslinking thus are lethal.

39
Q

What are the steps in pepitdoglycan synthesis?

A
  1. peptidoglycan monomer
  2. extension of glycan chain
  3. cross-linking of glycan strands.
40
Q

What does the drug Fofsomycin prevent?

A
  • prevents formation of peptidoglycan monomer
  • NAM cannot make NAG
  • Antagonizes Phosphoenolpyruvate
41
Q

What the Cycloserine prevent?

A

-It blocks the formation of DALA -DALA-DALA during the production of NAM

42
Q

What does Bacitracin target?

A

Blocks the linking of NAG and NAM pentapeptide

43
Q

What do the antibiotics: B-lactams (penicillins, cephalosporins) and vanocomycin block?

A

Binds to transpeptidase, thus cannot catalyze cross-linking

44
Q

What are the phases of growth in culture?

A
  1. Lag (enzyme productin)
  2. Exponential or Logarithmic (doubling time)
  3. Stationary (growing=dying)
45
Q

What is the doubling time?

A

(mean generation time)

  • the amount of time it take to double (Td)
  • smaller is faster
46
Q

What is the instantaneous growth rate (alpha)?

A

td=0.69 (1/alpha)

-larger is faster

47
Q

what is the exponential growth rate (u)?

A

td=1/u

-larger is faster

48
Q

What is the optimal temperature of psychrophiles?

A
  • 5 to 30C

ex. listeria monocytogenes, which has causes disease from inadequately pasteurized cheese.

49
Q

what is the optimal temperature for mesophiles?

A

10 to 40C

pathogens grow well at body temperature

50
Q

what is the optimal temp for Thermophiles?

A

25 to 100C

ex. Thermus acquaticus, source of Tap polymerase

Microbiology-1 (8 decks)

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