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Flashcards in Bacterial Nutrition/Metabolism Deck (61):
0

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

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

1

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

Leprosy
Grown in mice and nine-banded armadillo

2

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

Yes they can adjust
Very brief lag times

3

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

Doubles in 60 minutes in minimal media
Doubles in 20 minutes in rich media

4

What is an enrichment culture?

Liquid medium that favors the growth of desired organism

5

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

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

6

What is selective medium?

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

7

What is a differential medium?

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.

8

Blood agar: selective, differential, promotes, inhibits?

Not selective
Differential for hemolysis patterns
Promotes many bacteria
Inhibits none

9

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

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

10

Mannitol salt: selective, differential, promotes, inhibits?

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

11

MacConkey: selective, differential, promotes, inhibits?

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

12

Beta hemolysis is indicated by what on the plate?

Clear zone around the colonies

13

_________ _________ cannot survive in the presence of oxygen

obligate anaerobes

14

____________ ____________ cannot survive in the absence of oxygen

obligate aerobes

15

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

facultative

16

Obligate anaerobe common in abdominal abscesses?

Bacteroides fragilis

17

Obligate anaerobe that is the cause of tetanus?

Clostridium tetani

18

Why is O2 lethal?

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

19

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

-O2
Superoxide dismutase
Catalase

20

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

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

21

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

Anaerobic infections

22

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

psuedomonas aeruginosa

23

What obligate aerobe was developed for biological warfare?

Bacillus anthracis

24

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

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

25

What does phosphofructokinase do in glycolysis?

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

26

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

Iron
Sulfur-containing and electron carriers

27

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

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

28

What are siderophores?

Fe3+ specific ligands

29

Describe bacterial iron transport systems:

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

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

4

31

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

Highest affinity

32

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

The lab
The body

33

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

No, but they are helpful for diagnosis

34

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

E. coli

35

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

No
Decreased food consumption leads to decreased gastric acid secretion

36

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

Enterobacter aerogenes

37

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

Pyruvic acid
Nope but beer

38

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

proprionic acid and CO2

39

What determines bacterial shape and protects the cytoplasmic membrane?

Peptidoglycans

40

What is the most important difference between bacteria and humans?

Peptidoglycans

41

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

Peptidoglycans

42

Peptidoglycan thickness is determined by what?

Genetically determined vertical cross-linking

43

Many antibiotics interfere with what aspect of bacteria?

Peptidoglycan synthesis

44

What are the three steps of peptidoglycan synthesis?

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

45

What are the two peptidoglycan monomers?

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

46

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

NAM is made from NAG
Blocked by Fofsomycin

47

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

Requires the addition of a pentapeptide
Blocked by Cycloserine

48

Metabolic inhibitors: fosfomycin antagonizes what?

phosphoenolpyruvate

49

Metabolic inhibitors: cycloserine antagonizes what?

D-alanine

50

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

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

51

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

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

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

Vertical cross-links

53

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

1.1nm
12,000 MW

54

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

Lag
Exponential
Stationary

55

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

Smaller is faster

56

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

Larger is faster
Doubling time = 0.69(1/alpha)

57

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

Larger is faster
Doubling time = 1/mu

58

Psychrophiles: temperature range and example?

-5 to 30 degrees C
Listeria monocytogenes causes disease from inadequately pasteurized cheese

59

Mesophile temperature range

10 - 40 degrees C
Grow well at body temp

60

Thermophile temperature range, example

25 to 110 degrees C
Thermus acquaticus: source of Taq polymerase for PCR