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Microbiology > Bacterial Nutrition/Metabolism > Flashcards

Bacterial Nutrition/Metabolism Flashcards

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Biology 101 flashcards
0
Q

Mycobacterium leprae: what does it cause, where does it have to grow to be studied?

A

Leprosy

Grown in mice and nine-banded armadillo

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1
Q

Treponema pallidum: what does it cause, where does it have to be grown to study?

A

Syphilis

Needs to be grown in rabbit testes (loses infectivity if grown in primary cell culture)

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2
Q

Can bacteria rapidly adjust from rich to poor nutrients? Is lag time experienced after transitions?

A

Yes they can adjust

Very brief lag times

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3
Q

E. coli example for nutrient transition/doubling time change?

A

Doubles in 60 minutes in minimal media

Doubles in 20 minutes in rich media

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4
Q

What is an enrichment culture?

A

Liquid medium that favors the growth of desired organism

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5
Q

For an enrichment culture, the conditions are usually minimal for the organism. Example?

A

Azotobacter - leave out nonvolatile nitrates so that it has to fix nitrogen

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6
Q

What is selective medium?

A 
Solid medium (agar) that specifically selects one type of organism and inhibits the growth of others
Takes advantage of specific metabolic requirements/set of conditions
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7
Q

What is a differential medium?

A 
Solid medium (agar) plates on which the organism of interest has a distinctive appearance.
It is not necessarily selective, which means that other organisms can grow.
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8
Q

Blood agar: selective, differential, promotes, inhibits?

A

Not selective
Differential for hemolysis patterns
Promotes many bacteria
Inhibits none

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9
Q

Eosin methylene blue: selective, differential, promotes, inhibits?

A

Selective - dyes inhibit growth
Differential - lactose fermentation, purple or metallic green
Promotes - enteric gram negative rods
Inhibits - gram +

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10
Q

Mannitol salt: selective, differential, promotes, inhibits?

A

Selective - high mannitol (5%) inhibits growth
Differential - mannitol fermentation, yellow around colonies
Promotes - gram positive staph
Inhibits - gram negative

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11
Q

MacConkey: selective, differential, promotes, inhibits?

A

Selective - bile salts and crystal violet inhibit growth
Differential - lactose fermentation, dark pink colonies due to pH indicator
Promotes - gram negative
Inhibits - gram positive

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12
Q

Beta hemolysis is indicated by what on the plate?

A

Clear zone around the colonies

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13
Q

_________ _________ cannot survive in the presence of oxygen

A

obligate anaerobes

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14
Q

____________ ____________ cannot survive in the absence of oxygen

A

obligate aerobes

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15
Q

Anaerobes/aerobes can survive in the presence/absence of oxygen if they are what?

A

facultative

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16
Q

Obligate anaerobe common in abdominal abscesses?

A

Bacteroides fragilis

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17
Q

Obligate anaerobe that is the cause of tetanus?

A

Clostridium tetani

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18
Q

Why is O2 lethal?

A

Auto-oxidation of flavines generates the toxic superoxide radical
-O2
FADH2 + O2 –> FAD + -O2 + H+

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19
Q

Anaerobes lack critical enzymes to get rid of what? What are these two enzymes?

A

-O2
Superoxide dismutase
Catalase

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20
Q

What are the reactions catalyzed by superoxide dismutase and catalase? Which type of bacteria lack these enzymes?

A

2 -O2 + 2H+ –> H2O2 + O2
2 H2O2 –> 2 H2O + O2
Anaerobes lack these enzymes

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21
Q

High oxygen tension (hyperbaric chamber) can be used to combat what type of infections?

A

Anaerobic infections

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22
Q

What obligate aerobe is the cause of (some?) nosocomial infections?

A

psuedomonas aeruginosa

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23
Q

What obligate aerobe was developed for biological warfare?

A

Bacillus anthracis

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24
Q

Why do aerobes require oxygen? How do they make triose phosphates?

A

They lack *phosphofructokinase so they can’t generate enough energy from glycolysis
Require Kreb’s cycle
Pentose shunt

25
Q

What does phosphofructokinase do in glycolysis?

A

Converts F6P to F1,6BP which is then converted to glyceraldehyde 3P

26
Q

________ is essential as a cofactor for many enzymes. What specific type of enzymes (2)?

A

Iron

Sulfur-containing and electron carriers

27
Q

Most iron in the environment exists in what state? Most iron in cells?

A

Ferric Fe3+ state as insoluble hydroxides, carbonates, and phosphates.
Iron in the cells is bound to cellular proteins.

28
Q

What are siderophores?

A

Fe3+ specific ligands

29
Q

Describe bacterial iron transport systems:

A

Membrane receptors bind siderophores (unique receptor for each siderophore)
Transporter proteins then take up the complex and move into the cell (unique transporter for each complex)
Fe3+ is then reduced to Fe2+, which is usable

30
Q

Iron uptake systems are redundant. How many distinct systems are there in E. coli?

A

4

31
Q

Loss of only the ___________ ___________ iron uptake system may lead to loss of the ability to cause disease

A

Highest affinity

32
Q

Low affinity iron uptake systems are suitable for growth in _______ but not in ________

A

The lab

The body

33
Q

Can metabolic differences in animals and bacteria be exploited for therapy?

A

No, but they are helpful for diagnosis

34
Q

E. coli and shigella dysenteriae, which ferments lactose and is a normal component of the body?

A

E. coli

35
Q

Shigella dysenteriae, is it resistant to acid? How could decreased food consumption lead to infection?

A

No

Decreased food consumption leads to decreased gastric acid secretion

36
Q

Enterobacter aerogenes vs E. coli: which produces acetoin and which is usually present in field water?

A

Enterobacter aerogenes

37
Q

Yeast converts ___________ ______ to ethanol. Is this medically useful?

A

Pyruvic acid

Nope but beer

38
Q

Some bacteria use pyruvic acid to make what? (relevant for cheese)

A

proprionic acid and CO2

39
Q

What determines bacterial shape and protects the cytoplasmic membrane?

A

Peptidoglycans

40
Q

What is the most important difference between bacteria and humans?

A

Peptidoglycans

41
Q

What gives bacterial cell walls its rigidity and strength? (only true bacteria have it)

A

Peptidoglycans

42
Q

Peptidoglycan thickness is determined by what?

A

Genetically determined vertical cross-linking

43
Q

Many antibiotics interfere with what aspect of bacteria?

A

Peptidoglycan synthesis

44
Q

What are the three steps of peptidoglycan synthesis?

A

Peptidoglycan monomer
Extension of the glycan chain
Cross-linking of the glycan strands

45
Q

What are the two peptidoglycan monomers?

A

NAG: N-acetyl-glucosamine
NAM: N-acetyl-muramic acid

46
Q

Peptidoglycan monomer: First NAM is made from what? What is this step blocked by?

A

NAM is made from NAG

Blocked by Fofsomycin

47
Q

Peptidoglycan monomer: Second, NAM requires the addition of what? What is this step blocked by?

A

Requires the addition of a pentapeptide

Blocked by Cycloserine

48
Q

Metabolic inhibitors: fosfomycin antagonizes what?

A

phosphoenolpyruvate

49
Q

Metabolic inhibitors: cycloserine antagonizes what?

A

D-alanine

50
Q

Extension of the chain: what happens and what inhibits this step?

A

NAG and NAM-pentapeptide are linked together in an alternating chain
Blocked by Bacitracin

51
Q

Cross-linking step: what happens and what is this step blocked by?

A

Pentapeptide on one NAM is cross-linked to the pentapeptide on another NAM
Blocked by many antibiotics including beta-lactams (penicillins, cephalosporins) and vancomycin

52
Q

Gram + bacteria have thicker cell walls because of more what?

A

Vertical cross-links

53
Q

Gram + cell walls are porous. What are the size of the pores and what size molecule can fit through?

A

1.1nm

12,000 MW

54
Q

Growth of a culture diluted into fresh medium can be divided into 3 phases of growth:

A

Lag
Exponential
Stationary

55
Q

Doubling time (mean generation time): smaller is faster or slower?

A

Smaller is faster

56
Q

Instantaneous growth rate (alpha): larger is faster or slower? How does it relate to doubling time?

A

Larger is faster

Doubling time = 0.69(1/alpha)

57
Q

Exponential growth rate (mu): larger is faster or slower? How does it relate to doubling time?

A

Larger is faster

Doubling time = 1/mu

58
Q

Psychrophiles: temperature range and example?

A

-5 to 30 degrees C

Listeria monocytogenes causes disease from inadequately pasteurized cheese

59
Q

Mesophile temperature range

A

10 - 40 degrees C

Grow well at body temp

60
Q

Thermophile temperature range, example

A

25 to 110 degrees C

Thermus acquaticus: source of Taq polymerase for PCR

Microbiology (10 decks)

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