7. How do we cultivate bacteria?

Question 1

Types of bacteria and their optimum temperatures

Answer 1

Psychrophile - 4°c
Mesophile - 38°c
Thermophile - 60°c
Hyperthermophile - 88/106°c

Question 2

Effects of pH on bacterial growth

Answer 2

Optimum pH dependent on extracellular activity.

Na2HPO4 and KH2PO4 - extracellular buffers.

Question 3

Increasing acidity (type of bacteria)

Answer 3

Acidophihiles, acidothiobacillicus

Question 4

Neutrality (type of bacteria)

Answer 4

Neutrophile, E.coli

Question 5

Increasing alkalinity (type of bacteria)

Answer 5

Alkaliphiles, baccilicusfirmus

Question 6

Effect of salinity on bacterial growth (% NaCl)

Answer 6

Nonhalophile - 0%
Halotolerent - 2%
Halophile - 9%
Extreme halophile - 17%

Question 7

Chemostats: continuous culture/bioreactors

Answer 7

Systems open
Fresh media added while spent media removed.
Steady-state.
Constant active state.
Imporotant in bioprocessing
Once at equilibrium - Volume, population density, growth rate and metabolic state constant.

Question 8

Flow rate > Growth rate

Answer 8

Washout

Question 9

Flow rate < Growth rate

Answer 9

Stationary / death phase

Question 10

Bacterial growth requirements

Answer 10

Nutrients
Optimal temperature
Gas - O2
Optimal pH
Moisture
Ionic balance/salinity

Question 11

Catabolic

Answer 11

Energy releasing

Question 12

Anabolic

Answer 12

Energy consuming

Question 13

Macronutrients

Answer 13

Carbohydrates
Proteins
Lipids
Nucleic acids

Question 14

Nutrient groups

Answer 14

Micronutrients and macronutrients

Split depending on the amount of bacteria needed.

Question 15

Measuring bacterial growth: Population density - Method

Answer 15

Measures light scattering by cell

Question 16

Measuring bacterial growth: Population density - Positives

Answer 16

Simple and convenient
Non-destructive
Can be done continuously

Question 17

Measuring bacterial growth: Population density - Negatives

Answer 17

Low sensitivity
May not be accurate enough (may absorb light, don’t know what we are looking at)
More efficient to look at population number

Question 18

Measuring bacterial growth: Population number - Method

Answer 18

Looking for colony-forming units.
Extrapolated to give cells in original culture.
Each colony derives from a single cell.

Question 19

Measuring bacterial growth: Population number - Negatives

Answer 19

Only measure viable cells
Underestimates cells in chains/clusters
Laborious
Slow

Question 20

Calculating generation time

Answer 20

b = B x 2^n
(b = final cell number, B = Initial cell number, n = number of divisions)

g = t / n 
(g = generation time, t = duration of exponential growth, n = number of divisions)

Question 21

Dilution Rate (D) =

Answer 21

F (flow rate) / V (Volume)

Question 22

Microfluidics

Answer 22

An emerging technology aiding the understanding of bacterial physicolgy.
Microscope timelapses are okay but need a way to maintain order, growth and follow individual cells as the colonies become too congested.
Need to build an agar pad with tracks to hold cells in some form of order.
Fresh media goes in
Waste media goes out
MICROFLUIDICS = NANOCHEMOSTATS