Microbial Metabolism

Question 1

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

Answer 1

metabolic

Question 2

True or False. Bacteria exist in a diploid state.

Answer 2

FALSE. they exist in a haploid state

Question 3

What is the reproduction process of bacteria called?

Answer 3

binary fission

Question 4

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

Answer 4

nucleoid

Question 5

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

Answer 5

two (binary)

Question 6

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

Answer 6

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

Question 7

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

Answer 7

stationary phase

Question 8

Name this phase:

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

Answer 8

exponential phase

Question 9

Name this phase:

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

Answer 9

lag phase

Question 10

Name this phase:

decrease in number of live bacteria

Answer 10

decline phase

Question 11

Name this phase:

bacteria are less susceptible to killing by antimicrobials

Answer 11

stationary phase

Question 12

Name this phase:

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

Answer 12

stationary phase

Question 13

Which phase has little to no cell division?

Answer 13

lag, stationary and decline phases

Question 14

In which phase are bacteria most susceptible to antimicrobials?

Answer 14

lag and exponential phase

Question 15

In which phase are more bacteria killed than are generated?

Answer 15

decline phase

Question 16

In which phase are bacteria doubling at a constant rate?

Answer 16

exponential phase

Question 17

What are the requirements for growth (3)?

Answer 17

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

Question 18

Growth in culture is determined by what factors?

Answer 18

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

Question 19

How is cell density determined?

Answer 19

colony counts on agar plates or by turbidity (spectrophotometry)

Question 20

These bacteria exclusively utilize respiration to meet its energy need

Answer 20

aerobic

Question 21

These bacteria utilizes fermentation to meet its energy needs

Answer 21

anaerobe

Question 22

These bacteria can respire or ferment

Answer 22

facultative anaerobes

Question 23

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

Answer 23

microaerophilic

Question 24

What are two ROS that are highly toxic to cells?

Answer 24

1) hydrogen peroxide (H2O2)

2) superoxide anion (O2-)

Question 25

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

Answer 25

1) catalase | 2) SOD (superoxide dismutase)

Question 26

What's the mechanism of catalase?

Answer 26

catalyzes the breakdown of H2O2 to H20 and O2

Question 27

What's the mechanism of SOD?

Answer 27

help detoxify O2-

Question 28

True or False. Both prokaryotes and eukaryotes have SOD

Answer 28

True

Question 29

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

Answer 29

1) sensitive | 2) anaerobic

Question 30

Do microaerophilic bacteria contain catalase and SOD?

Answer 30

yes, in small amounts

Question 31

Do facultative anaerobes contain catalase and SOD?

Answer 31

yes

Question 32

What type of energy production is this? | molecular oxygen is the terminal electron acceptor

Answer 32

aerobic respiration

Question 33

What type of energy production is this? | compounds other than oxygen such as nitrate or sulfate are used as terminal electron acceptors

Answer 33

anaerobic respiration

Question 34

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

Answer 34

fermentation

Question 35

Which type of energy production is the most efficient?

Answer 35

aerobic respiration

Question 36

Which type of energy production is the least efficient?

Answer 36

fermentation

Question 37

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

Answer 37

True

Question 38

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

Answer 38

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

Question 39

How can we selectively inhibit microbial nucleic acid biosynthesis?

Answer 39

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

Question 40

How can we selectively inhibit microbial DNA replication?

Answer 40

target bacterial DNA gyrase

Question 41

What is bacterial DNA gyrase do?

Answer 41

responsible for unwinding and winding of DNA during replication

Question 42

What drug targets bacterial DNA gyrase?

Answer 42

quinolones

Question 43

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

Answer 43

no nuclear membrane to separate the processes

Question 44

What bacterial ribosome is an important target of antimicrobial action?

Answer 44

70S

Question 45

What is the general structure of peptidoglycan?

Answer 45

polysaccharide polymer cross-linked by peptide

Question 46

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

Answer 46

1) N-acetyglucosamine (NAG) | 2) N-acetlymuramic acid (NAM)

Question 47

What are the steps to peptidoglycan biosynthesis?

Answer 47

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

Question 48

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

Answer 48

starts on the inner surface of membrane (cytoplasm) | ends on the outer surface of membrane

Question 49

What is the role of bactoprenol?

Answer 49

lipid carrier that transports NAM-NAG precursor across the membrane

Question 50

How does vacomycin work as antibiotic?

Answer 50

prevents elongation of peptidoglycan chain

Question 51

How does bacitracin work as antibiotic?

Answer 51

prevents recycling of bactoprenol

Question 52

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

Answer 52

False. different steps are used as targets for antibiotics

Question 53

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

Answer 53

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

Question 54

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

Answer 54

``` aa #1: variable aa#2: variable aa#3: diamino amino acid aa#4: D-ala aa#5: D-ala ```

Question 55

Where does transpeptidation occur on the growing peptidoglycan chain?

Answer 55

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

Question 56

Transpeptidases are also called _____

Answer 56

penicillin binding proteins (PBP)

Question 57

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

Answer 57

TRUE