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Medical Microbiology > Lecture 3: Bacterial Metabolism and Growth > Flashcards

Lecture 3: Bacterial Metabolism and Growth Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

What are four features that make bacterial metabolism unlike human?

A

1) Faster
2) More diverse energy sources
3) Simplicity in macromolecules
4) Has LPS, toxins, peptidoglycan

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2
Q

___: acquire carbon from organic sources; ___ fix CO2 as a primary means of acquiring carbon
A. Heterotrophs; Autotrops
B. Autotrops; Heterotrophs

A

A. Heterotrophs; Autotrops

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3
Q

Most pathogenic bacteria are ____

A

heterotrophs

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4
Q

What are the two types of autotrophs?

A

1) Photoautotrophs: harvest light energy
2) Chemoautotrophs: cellular energy comes from oxidation/reduction of inorganic ions

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5
Q

True or False: Fastidious heterotrophs have MORE complex growth requirements and tend to be SLOWER growing while non-fastidious heterotrophs tend to have LESS complex

A

True

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6
Q

___ is an an example of a non-fastidious bacteria while ___ is an example of a fastidious bacteria

A

Mycoplasma (fastidious)
E. Coli (non-fastidious)

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7
Q

Low levels of Fe++ can induce _____ ____ to produce toxin

A

Corynebacterium diptheriae

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8
Q

True or False: Low or high levels of ions can serve as signals for pathogen

A

True

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9
Q

True or False: Most pathogens are thermophils

A

False - most pathogens are mesophiles (growth between 20-55 C)

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10
Q

___ display growth > 55 degrees C
while ___ display growth at < 20 degrees C

A

Thermophile; Cryophile/Psychrophile

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11
Q

Bacteria must be able to protect themselves from deleterious effects of oxygen (O2) or otherwise will only grow ____

A

anaerobically

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12
Q

True or False: Vibrio cholerae and V. parahaemolyticus are halophiles

A

True (meaning they have a special ionic requirement)

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13
Q

True or False: Refrigeration is NOT an acceptable method of maintaining or obtaining sterile conditions

A

True

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14
Q

Why are aerobes and facultative anaerobes able to grow in the presence of O2?

A

Because they make enzymes that detoxify superoxide radicals (O2-) and H2O2

Note: both superoxide radicals and H2O2 are made in the presence of O2 during cellular metabolism

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15
Q

Which enzyme detoxifies O2?
Which enzyme detoxifies H2O2?

A

Superoxide Dismutase: detoxifies O2-
Catalase: detoxifies H2O2

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16
Q

Which two enzymes are present in aerobes and facultative anaerobes, but NOT in obligate anaerobes?

A

Catalase and Superoxide Dismutase

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17
Q

Which of the following is an obligate aerobe (meaning: requires O2 and metabolizes via respiration)?
A. Mycobacterium tuberculosis
B. Campylobacter jejuni
C. Facultative anaerobes

A

A. Mycobacterium tuberculosis

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18
Q

True or False: Facultative anaerobes (most pathogens) grow well with or without oxygen

A

True

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19
Q

Campylobacter jejuni is an example of:
A. Obligate Aerobes
B. Microaerophiles
C. Facultative Anerobe

A

B. Microaerophiles

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20
Q

Aerotolerant anaerobes cannot use ____, but will tolerate it while Obligate anaerobes are inhibited or killed by any ____

A

oxygen

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21
Q

Lactobacillus is an ____ while Clostridium and Bacteroides are _____
A. Aerotolerant; Obligate Anaerobes
B. Obligate Anaerobes; Aerotolerant

A

A. Aerotolerant; Obligate Anaerobes

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22
Q

Special requirements are needed to collect specimens and culture ___ from specimens
A. Aerotolerant anaerobes
B. Facultative anaerobes
C. Anaerobes

A

C. Anaerobes

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23
Q

True or False: Lactobacillus produce lactic acid, making it an acidophile, while Bacillus is an alkaliphile

A

True

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24
Q

True or False: Most human pathogens are neutrophiles

A

True

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25
Q

Respiration and Fermentation generate __ and ___

A

ATP and NAD+

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26
Q

What is the function of respiration?

A

Provide energy via: Proton Motive Force for ATP synthesis (production) during the conversion (recycling) of NADH2 to NAD

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27
Q

Why is respiration a unique enzymatic process?

A

Because most of the process must occur in a membrane vesicle or sack !!

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28
Q

What is the terminal electron acceptor in aerobic respiration (oxidative phosphorylation)?
A. SO4
B. NO3
C. Sulfur
D. Fumarate
E. O2

A

E. O2

29
Q

Which type of compounds serve as terminal electron acceptors in anaerobic respiration?
A. O2
B. Organic compounds
C. Inorganic compounds (Nitrate, Sulfate)

A

C. Inorganic compounds

30
Q

What occurs when NO3 is present in drinking water? Why is this of particular medical significance in pregnant females?

A

Elevated NO3 in drinking water can lead the normal flora (bacteria) in the GI tract to be converted to NITRATE (NO3) → NO2 (nitrite) → oxidizes ferrous iron (fe 2+) to ferric iron (fe 3+ in Hb)

The presence of NO2 can cause MetHb (methemoglobinemia) - which is an ABNORMAL form of O2 that cannot bind oxygen

31
Q

True or False: Humans and pathogens (aerobic and facultative anaerobes) use aerobic respiration, while obligate anaerobes/facultative anaerobes use anaerobic respiration

A

True

32
Q

Which type of respiration is characterized by formation of water and use of oxygen as terminal electron acceptors?
A. Aerobic Respiration
B. Anaerobic Respirationy

A

A. Aerobic Respiration

33
Q

Which type of respiration is characterized by lack of water formation and use of inorganic compounds as terminal electron acceptors?

A

Anaerobic Respiration

34
Q

___: a simpler process than respiration, which results in the incomplete oxidation of a carbon substrate. It is less efficient process than respiration.

A

Fermentation

35
Q

Fermentation consists of catabolic pathways where ___ compounds serve as electron donors and acceptors
A. Inorganic compounds
B. Organic Compounds
C. NO3

A

B. Organic compounds

36
Q

In fermentation, substrates are partially oxidized, generating end products that share what three features?

A

1) 1, 2, 3, or 4 carbon compounds
2) Accept electrons from from NADH2
3) Excreted from cell

37
Q

Fermentation of pyruvate => ___ and ___

A

ethanol + CO2

38
Q

Which of the following uses: an EC gradient, makes the MOST ATP, and uses oxygen and inorganic compounds as electron acceptors?
A. Respiration
B. Fermentation

A

A. Respiration

39
Q

Which of the following uses: substrate-level phosphorylation to produce ATP, generates LESS ATP (partial oxidation), and organic compounds serve as electron donors and acceptors?
A. Respiration
B. Fermentation

A

B. Fermentation

40
Q

Which of the following bacteria make lactic acid, which demineralize the tooth, leading to dental carries?

A

Streptococcus mutans

41
Q

Acidification of vagina and skin can occur via bacteria such as ____ (which produce lactic acid) and ____ (which produce propionic acid)

A

Lactobacillus (lactic acid)
Cutibacterium acnes (proprionic acid)

42
Q

True or False: Abscesses are basic and aerobic, in part, due to fermentative metabolism of bacteria in the abscess

A

False - abscesses are ACIDIC and ANAEROBIC

43
Q

True or False: Many abx are not effective at low pH and low pH kills surrounding viable human cells (phagocytes)

A

True

44
Q

What are three common end products in the fermentation process for species of Clostridium?

A

1) H2
2) CO2
3) Many four carbon compounds

45
Q

Clostridium uses ___ are an electron or hydrogen carrier

A

Ferredoxin (iron-sulfur)

46
Q

What enzyme is required for ferredoxin to be recycled from the reduced to the oxidized form?

A

Hydrogen Lyase

47
Q

Which organism is known to cause gas gangrene (aka: myconecrosis)? Mechanism?

A

Clostridium perfringens

  • Result of production of H2 gas, which is INSOLUBLE in tissues
  • Tracks along fascial planes, separating muscle tissues
  • In muscle tissues, collapses blood vessels, impedes perfusion, and helps to create anaerobic conditions
48
Q

True or False: Urease hydrolyzes urea producing ammonia (NH4+) and CO2

A

True

49
Q

Proteus spp. are responsible for what condition in humans?

A

UTI’s

50
Q

___ is produced as a result of the release of urease by Proteus, which leads pH to increase from 6 to 7

A

Ammonia

51
Q

How does Proteus play a role in kidney stones?

A

Proteus releases urase, which leads to ammonia production, which makes urine more basic

The more basic the urine lead Calcium and NH4+ ions in the urine to form salts, which can precipitate and lead to calculi (kidney stones)

52
Q

Which bacteria can cause stomach ulcers? How?

A

H. pylori
-Urease is made, which generates NH4+ (ammonium)
- Ammonium raises the microenvironment pH of stomach mucus lining, therby encouraging the growth of H. pylori

53
Q

True or False: The bacterial peptidoglycan cell wall is critical to cell integrity against osmotic pressure and acts as a selective target of antimicrobials (since eukaryotes LACK a cell wall!)

A

True

54
Q

In the first step of peptidoglycan synthesis, there is the synthesis of ___ and ___, while covalent bonded to UDP.

Where in the cell does this occur?

A

GlcNAC (NAG) and MurNAC (NAM)

  • Cytosol
55
Q

In step 2 of peptidoglycan synthesis, there is an addition of ____ to the __ portion of the UDP-NAM complex to form a side chain

A

pentapeptide; NAM

56
Q

In the third step of peptidoglycan synthesis, there is transfer of NAG and NAM-pentapeptide from UDP to ____ (carrier lipid of cell membrane) and release of UMP

Following this, there is addition of crossbridge to ___ side chain

A

bactoprenol
pentapeptide

57
Q

What occurs in the 4th step of peptidoglycan synthesis?
A. Final cross-linking
B. Synthesis of NAG and NAM
C. Addition of crossbridge to pentapeptide
D. Transfer of subunit (pentapeptide-NAM-NAG) through the cell membrane to growing end of peptidoglycan chain

A

D. Transfer of subunit (pentapeptide-NAM-NAG) through the cell membrane to growing end of peptidoglycan chain

58
Q

The final step in peptidoglycan synthesis is final crosslinking (transpeptidation) - which is accomplished by actions of which enzyme?

A

Transpeptidases (also known as: penicillin binding proteins or PBP)

59
Q

In the last stage of peptidoglycan synthesis, PEP side chains are crossed with the release of the terminal alanine. This process is blocked by which of the following?
A. Vancomycin
B. Cycloserine
C. Bacitracin
D. Penicillin

A

D. Penicillin

60
Q

Synthesis of linking pentapeptide (PEP) is blocked by which of the following?
A. Vancomycin
B. Cycloserine
C. Bacitracin
D. Penicillin

A

B. Cycloserine

61
Q

Recycling of BPP is blocked by:
A. Vancomycin
B. Cycloserine
C. Bacitracin
D. Penicillin

A

C. Bacitracin

62
Q

What does this display?

A

Illustrates the growth of a population of pure culture of bacteria in liquid medium (in vitro)

63
Q

___ phase: phase in which there is no change in cell number
A. Stationary Phase
B. Lag Phase
C. Exponential Phase

A

B. Lag Phase

64
Q

_____: the phase in the bacterial growth cycle that follows the log phase and where NO net increase in cell number occurs
A. Stationary Phase
B. Lag Phase
C. Exponential Phase
D. Death Phase

A

A. Stationary Phase

65
Q

____: the phase in the cycle that follows the stationary phase and where cell death occurs at a logarithmic rate
A. Stationary Phase
B. Lag Phase
C. Exponential Phase
D. Death Phase

A

D. Death Phase

66
Q

True or False: The generation time is defined as the time required for a parent to divide into two daughter cells (also known as: doubling time)

A

True

67
Q

Bacteria with a short mean generation time (GT) generally produce what type of infections? What type of Ag dose is required?

A

Fulminant (rapidly progressing) infections
- Requires high Ag dose

68
Q

Bacteria with a long mean generation time generally produce what type of infections? What type of Ag dose is required?

A

Chronic infections
- Requires low Ag dose

69
Q

Why are inhibitors of protein/peptidoglycan synthesis (e.g antibiotics) more effective against FAST growing organisms?

A

Their activity works best in log phase

Medical Microbiology (31 decks)

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