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Microbiology Exam 1 > Microbial Metabolism > Flashcards

Microbial Metabolism Flashcards

1
Q

The ____ differences between bacteria (prokaryotes) and eukaryotes can be utilized for the development of antibacterial therapies

A

metabolic

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2
Q

True or False. Bacteria exist in a diploid state.

A

FALSE. they exist in a haploid state

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3
Q

What is the reproduction process of bacteria called?

A

binary fission

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4
Q

The discrete area where the double-stranded DNA circle is located is called ____

A

nucleoid

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5
Q

In binary fission, a single cell divides into ___ daughter cells

A

two (binary)

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6
Q

What are the 4 phases to a typical bacterial growth curve?

A

1) lag phase
2) exponential phase
3) stationary phase
4) decline phase

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7
Q

Name this phase:
nutrients are deplete and toxic waste products/ metabolites are accumulating in media. viable cell count remains constant

A

stationary phase

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8
Q

Name this phase:

bacteria multiply rapidly by binary fission and populations doubles at a constant rate

A

exponential phase

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9
Q

Name this phase:

cells accumulate metabolites necessary for maximal cell growth, but little to no actual cell division

A

lag phase

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10
Q

Name this phase:

decrease in number of live bacteria

A

decline phase

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11
Q

Name this phase:

bacteria are less susceptible to killing by antimicrobials

A

stationary phase

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12
Q

Name this phase:

spore-forming bacteria (Gram (+)) initiate sporulation process

A

stationary phase

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13
Q

Which phase has little to no cell division?

A

lag, stationary and decline phases

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14
Q

In which phase are bacteria most susceptible to antimicrobials?

A

lag and exponential phase

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15
Q

In which phase are more bacteria killed than are generated?

A

decline phase

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16
Q

In which phase are bacteria doubling at a constant rate?

A

exponential phase

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17
Q

What are the requirements for growth (3)?

A

1) energy source
2) source of carbon and nitrogen
3) water and various ions

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18
Q

Growth in culture is determined by what factors?

A

1) pH optimum
2) aerobic vs. anaerobic
3) nutrients/ composition of media
4) temperature

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19
Q

How is cell density determined?

A

colony counts on agar plates or by turbidity (spectrophotometry)

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20
Q

These bacteria exclusively utilize respiration to meet its energy need

A

aerobic

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21
Q

These bacteria utilizes fermentation to meet its energy needs

A

anaerobe

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22
Q

These bacteria can respire or ferment

A

facultative anaerobes

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23
Q

These bacteria grow best at low oxygen levels but can grow without oxygen as well

A

microaerophilic

24
Q

What are two ROS that are highly toxic to cells?

A

1) hydrogen peroxide (H2O2)

2) superoxide anion (O2-)

25
Q

What are the two major mechanisms bacteria use to counteract ROS?

A

1) catalase

2) SOD (superoxide dismutase)

26
Q

What’s the mechanism of catalase?

A

catalyzes the breakdown of H2O2 to H20 and O2

27
Q

What’s the mechanism of SOD?

A

help detoxify O2-

28
Q

True or False. Both prokaryotes and eukaryotes have SOD

A

True

29
Q

Bacteria that lack catalase and SOD are ____ to oxygen and are likely _____

A

1) sensitive

2) anaerobic

30
Q

Do microaerophilic bacteria contain catalase and SOD?

A

yes, in small amounts

31
Q

Do facultative anaerobes contain catalase and SOD?

A

yes

32
Q

What type of energy production is this?

molecular oxygen is the terminal electron acceptor

A

aerobic respiration

33
Q

What type of energy production is this?

compounds other than oxygen such as nitrate or sulfate are used as terminal electron acceptors

A

anaerobic respiration

34
Q

What type of energy production is this?
anaerobic process where organic metabolic intermediate derived from a fermentable substrate is used as final electron acceptor

A

fermentation

35
Q

Which type of energy production is the most efficient?

A

aerobic respiration

36
Q

Which type of energy production is the least efficient?

A

fermentation

37
Q

True or False. End products of fermentation can be measured and sometimes diagnostic for certain bacteria

A

True

38
Q

What are some targets that are unique to bacteria that we can use for selective toxicity?

A

1) nucleic acid synthesis
2) DNA replication
3) transcription/ translation

39
Q

How can we selectively inhibit microbial nucleic acid biosynthesis?

A

folate. bacteria have to synthesize it while humans must ingest it as part of our diet. Recall that folate is essential to the synthesis of purines and thymidine. antibiotics can thus target folate synthesis

40
Q

How can we selectively inhibit microbial DNA replication?

A

target bacterial DNA gyrase

41
Q

What is bacterial DNA gyrase do?

A

responsible for unwinding and winding of DNA during replication

42
Q

What drug targets bacterial DNA gyrase?

A

quinolones

43
Q

In bacteria, transcription and translation occur simultaneously (co-transcriptional translation), how is this possible?

A

no nuclear membrane to separate the processes

44
Q

What bacterial ribosome is an important target of antimicrobial action?

A

70S

45
Q

What is the general structure of peptidoglycan?

A

polysaccharide polymer cross-linked by peptide

46
Q

Peptidoglycan is a linear chain of alternating sugars, what are these sugars?

A

1) N-acetyglucosamine (NAG)

2) N-acetlymuramic acid (NAM)

47
Q

What are the steps to peptidoglycan biosynthesis?

A

1) activation of sugars by adding UDP
2) a pentapeptide is added to UDP-NAM
3) UDP-NAM-pentapeptide is attached to bactoprenol through pyrophosphate link with release of UMP
4) NAG is added to NAM-pentapeptide-bactoprenol complex
5) bactoprenol carries the complex across the membrane
6) disaccharide (NAM and NAG) is added to end of the growing peptidoglycan chain by transglycosylases
7) bacteroprenol is recycle and converted back to pyrophosphate bactoprenol

48
Q

Where in the cell does peptidoglycan biosynthesis start and where does it end?

A

starts on the inner surface of membrane (cytoplasm)

ends on the outer surface of membrane

49
Q

What is the role of bactoprenol?

A

lipid carrier that transports NAM-NAG precursor across the membrane

50
Q

How does vacomycin work as antibiotic?

A

prevents elongation of peptidoglycan chain

51
Q

How does bacitracin work as antibiotic?

A

prevents recycling of bactoprenol

52
Q

True or False. Antibiotics are used to block peptidoglycan synthesis at the same steps

A

False. different steps are used as targets for antibiotics

53
Q

Once the growing chain of peptidoglycan is on the outer leaflet of cell membrane, what’s the next process in its biosynthesis?

A

transpeptidation - cross-linking of the pentapeptide side chains, making the mesh-like structure

54
Q

The pentapeptide added to UDP-NAM must be in a specific order, what is it?

A 
aa #1:  variable
aa#2: variable
aa#3: diamino amino acid
aa#4: D-ala
aa#5: D-ala
55
Q

Where does transpeptidation occur on the growing peptidoglycan chain?

A

between the free amine of the diamino amino acid in the third position and D-ala in the fourth position of the other peptide chain

56
Q

Transpeptidases are also called _____

A

penicillin binding proteins (PBP)

57
Q

True or False. During peptidoglycan formation amino acids are added without the help of transfer RNA and ribosomes.

A

TRUE

Microbiology Exam 1 (10 decks)

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