Module 7 - Microbial Growth

Question 1

What are the 4 requirements for microbial growth + one example of each if applicable

Answer 1

1. Carbon source
2. Energy source: electrong trading from redox rxn
3. Inorganic nutrients: nitrogen, phosphorus
4. Favourable environmental conditions: pH, temp

Question 2

Explain the two types of reproductive strategies in eukaryotes

Answer 2

Mitosis: asexual reproduction/cell division
Meiosis: producing gametes, sexual

Question 3

How do archaea and bacteria reproduce

Answer 3

Binary fission: asexual reproduction to produce two identical daughter cells

Question 4

Sketch the microbial growth curve + labels

Answer 4

Lag phase, log phase, stationary phase, death phase, long term stationary phase

Question 5

Explain the lag phase

Answer 5

Cells synthesizing new components

Question 6

Explain the exponential growth phase / log phase

Answer 6

Rate of growth and division is constant and maximal

Question 7

Explain the stationary phase

Answer 7

Number of viable cells remains constant, cells stop reproducing or death is balancing out new reproduction

Question 8

Explain the death phase

Answer 8

Number of viable cells declines, apoptosis (cell suicide) occurs

Question 9

Why does growth rate plateau even with many nutrients

Answer 9

Not enough surface area / space to uptake all nutrients

Question 10

What are the 3 equations related to growth rate

Answer 10

mew = (mew m [S])/k s + [S]
td = ln(2)/mew
xt = x0 • e^t•mew

Question 11

What is the volume of a cocci bacteria

Answer 11

4/3pi r^3

Question 12

Explain the steps of bacterial growth in a batch reactor + how is it different than the normal growth curve

Answer 12

1. Lag
2. Log
3. Stationary
4. Death

Question 13

What is the equation for cell
growth in the presence of a limiting substrate. Which variable is the substrate + what is this model called

Answer 13

m = (m max • [S])/(K s + [S])
substrate = [S]
monod model

Question 14

What are 3 types of cell growth measurement

Answer 14

1. Direct cell count (all cells)
2. Viable cell count
3. Measurement of cell mass

Question 15

What are the two types of direct cell count?

Answer 15

1. Chamber counting
2. Electric counter

Question 16

What are the two types of viable cell counts

Answer 16

1. Plating methods
2. Membrane filtration

Question 17

What is Beer-Lambert’s Law + what does it measure?

Answer 17

A = epsilon • b • c

A = absorbance
epsilon = molar absorbivity
b = path length
c = concentration

Question 18

What is a continuous culture

Answer 18

Cells are grown in an environment that have nutrients and waste removal provided. Cells kept in log phase.

Question 19

What is a chemostat

Answer 19

Culture medium provides minimal nutrients. It flows in and out at a rate D.

Question 20

What is a turbidostat reactor

Answer 20

Uses photo detector to measure density

Question 21

Name 6 environmental factors affecting cell growth

Answer 21

1. pH
2. temperature
3. oxygen
4. pressure
5. solutes
6. radiation

Question 22

What are biofilms

Answer 22

complex communities on microbes that grow on surfaces. once attached the attachment becomes stronger with the formation of EPS

Question 23

What is quorum sensing

Answer 23

The process in which bacteria monitor population density with small proteins. These proteins can express target genes to regulate functions