5. Measuring Microbial Growth, How Microbes Obtain Energy

Question 1

4 ways of measuring microbial growth? Describe

Answer 1

1. Counting (microscope)
   - Stain
   - Use Petroff-Hausser slide
2. Cell mass (biomass)
   - Wet/dry weight
3. Spectrophotometry
4. Cell constituent concentration
   - Protein/DNA/ATP/NADH

Question 2

Spectrophotometry: wavelength organisms will absorb light at?

Answer 2

550-600 nm

Question 3

Problem with some of the methods of measuring microbial growth?

Answer 3

Cannot distinguish between live/dead organisms (except for cell constituent conc for ATP/NADH)

Question 4

Solution to live/dead organisms in solution counting? Minor problem with the solution?

Answer 4

Plate suspension to get colony forming units (CFU)

If cells are clumped = colony came from >1 cell ==> CFU may underestimate

Question 5

2 important molecules generated from conversion of glucose to pyruvate (aka glycolysis)?

Answer 5

NADH, ATP

Question 6

Byproduct of pyruvate to acetyl-CoA conversion?

Answer 6

CO2

Question 7

4 molecules generated from citric acid cycle in cytosol of prokaryotes?

Answer 7

NADH, FADH2, ATP, CO2

Question 8

5 environmental factors that affect microbial growth?

Answer 8

1. Solutes and water activity (aw)
2. pH
3. Temperature
4. Oxygen
5. Pressure

Question 9

Microbes that grow optimally at high pressures are known as?

Answer 9

Barophilic

Question 10

Definition of water activity?

Answer 10

Quantitative measure of water AVAILABILITY in the habitat

Water complexed with molecules = unavailable

Question 11

Formula for water activity?

Answer 11

aw = vapour pressure of a sample/vapour pressure of pure water

Question 12

Water pressure is ________________ to osmotic pressure

Answer 12

inversely proportional

Question 13

4 types of ‘-philes’ of various temperatures => rank them from lowest temp for optimal growth to highest

Answer 13

Psychorophiles, mesophiles, thermophiles, hyperthermophiles

Question 14

3 types of ‘-philes’ of varying pH’s. Rank from most acidic to most basic

Answer 14

Acidophiles, neutrophiles, alkalophiles

Question 15

Optimal growth temperature is always skewed towards ________________

Answer 15

max temperature

Question 16

Microbes that live in high pressure habitats have evolved to strengthen ____________ to withstand high pressure

Answer 16

cell molecules

Question 17

Will NAD(P)H reduce O2 or will H2O reduce NADP+?

Why?

Answer 17

NAD(P)H will reduce O2

e- always move from more negative to more positive reduction potential