MIMG 101 FINAL QUESTIONS AND
ANSWERS
What are the advantages in prokaryotic cell motility? -
correct answer ✅Passive:
- air/ocean currents
- aerosolized (cough or sneeze, spread of covid)
*Active*:
- microbes use cellular structures to actively move in their
environment (find food, avoid danger, ex pathogen vs host)
Capillary Assay and William Pfeffer 1883 Experiment (How to set
up, include what conditions, expectations) -
correct answer ✅1. Create batch culture of evenly suspended
bacteria
2. Insert thin tube with small diameter into batch culture
3. Allow tube to sit in culture for a period of time, count the
number to bacteria (count total cells)
Include:
- Control (medium)
- Repellent
,MIMG 101 FINAL QUESTIONS AND
ANSWERS
Expectations:
- Attractant: if bacteria can move, anticipate more movement into
capillary than for control
- Repellant: opposite
Why is it important for the total cell number to be the same in each
condition? -
correct answer ✅- Looking for movement, having a higher number
of cells may cause us to think there's more movement
- Maybe bacteria in tube just replicates more
- Need to differentiate between bacteria that grows faster in tube
or if actually moving
Photo, Thermo, Aero, Osmo, Magnetotaxis -
correct answer ✅Taxis = directed migration in response to a
gradient of stimulus
- Photo = light
- Thermo = heat
- Aero = oxygen
- Osmo = osmotic strength
,MIMG 101 FINAL QUESTIONS AND
ANSWERS
- Magneto = magnetic field
4 Key Elements of Taxis -
correct answer ✅1. Sense external signal (Receptors, channels on
surface to sense external signal)
2. Transduce external signal into internal signal
3. Alter behavior (motility)
4. Scalable (can adapt to a range of stimulus concentrations)
E. Coli Swimming Behavior (2) -
correct answer ✅Random walk:
- no stimulus present
- run ~1s
- tumble 0.1s, once every second
Biased random walk:
- runs are longer when moving toward attractant
- presence of attractant = tumble less frequently
- effect on tumbling frequency is the same in all regions of the
gradient (outside -> inside, perimeter -> center)
, MIMG 101 FINAL QUESTIONS AND
ANSWERS
- E. Coli can remember, sense temporal gradient
Sense Temporal Gradient -
correct answer ✅- E. Coli can sense change in conc. of attractant
[A], not just presence/absence
- Still random, but biased towards attractant
- Never stop, move toward is longer run
- Scalable factor
- Temporal sensing (important)
- E. Coli can remember concentration changes of molecule at any
time
- Takes sample of environment, know if inc or dec, if inc then it will
continue running
- Sense time, not in space
Flagellar Arrangements, How do you visualize bacterial flagella? -
correct answer ✅- monotrichous = single at one end
- amphitrichous = single at each end
- lophotrichous = many at one end
- *peritrichous* (focus) = many all around
ANSWERS
What are the advantages in prokaryotic cell motility? -
correct answer ✅Passive:
- air/ocean currents
- aerosolized (cough or sneeze, spread of covid)
*Active*:
- microbes use cellular structures to actively move in their
environment (find food, avoid danger, ex pathogen vs host)
Capillary Assay and William Pfeffer 1883 Experiment (How to set
up, include what conditions, expectations) -
correct answer ✅1. Create batch culture of evenly suspended
bacteria
2. Insert thin tube with small diameter into batch culture
3. Allow tube to sit in culture for a period of time, count the
number to bacteria (count total cells)
Include:
- Control (medium)
- Repellent
,MIMG 101 FINAL QUESTIONS AND
ANSWERS
Expectations:
- Attractant: if bacteria can move, anticipate more movement into
capillary than for control
- Repellant: opposite
Why is it important for the total cell number to be the same in each
condition? -
correct answer ✅- Looking for movement, having a higher number
of cells may cause us to think there's more movement
- Maybe bacteria in tube just replicates more
- Need to differentiate between bacteria that grows faster in tube
or if actually moving
Photo, Thermo, Aero, Osmo, Magnetotaxis -
correct answer ✅Taxis = directed migration in response to a
gradient of stimulus
- Photo = light
- Thermo = heat
- Aero = oxygen
- Osmo = osmotic strength
,MIMG 101 FINAL QUESTIONS AND
ANSWERS
- Magneto = magnetic field
4 Key Elements of Taxis -
correct answer ✅1. Sense external signal (Receptors, channels on
surface to sense external signal)
2. Transduce external signal into internal signal
3. Alter behavior (motility)
4. Scalable (can adapt to a range of stimulus concentrations)
E. Coli Swimming Behavior (2) -
correct answer ✅Random walk:
- no stimulus present
- run ~1s
- tumble 0.1s, once every second
Biased random walk:
- runs are longer when moving toward attractant
- presence of attractant = tumble less frequently
- effect on tumbling frequency is the same in all regions of the
gradient (outside -> inside, perimeter -> center)
, MIMG 101 FINAL QUESTIONS AND
ANSWERS
- E. Coli can remember, sense temporal gradient
Sense Temporal Gradient -
correct answer ✅- E. Coli can sense change in conc. of attractant
[A], not just presence/absence
- Still random, but biased towards attractant
- Never stop, move toward is longer run
- Scalable factor
- Temporal sensing (important)
- E. Coli can remember concentration changes of molecule at any
time
- Takes sample of environment, know if inc or dec, if inc then it will
continue running
- Sense time, not in space
Flagellar Arrangements, How do you visualize bacterial flagella? -
correct answer ✅- monotrichous = single at one end
- amphitrichous = single at each end
- lophotrichous = many at one end
- *peritrichous* (focus) = many all around
