7. How do we cultivate bacteria? Flashcards
Types of bacteria and their optimum temperatures
Psychrophile - 4°c
Mesophile - 38°c
Thermophile - 60°c
Hyperthermophile - 88/106°c
Effects of pH on bacterial growth
Optimum pH dependent on extracellular activity.
Na2HPO4 and KH2PO4 - extracellular buffers.
Increasing acidity (type of bacteria)
Acidophihiles, acidothiobacillicus
Neutrality (type of bacteria)
Neutrophile, E.coli
Increasing alkalinity (type of bacteria)
Alkaliphiles, baccilicusfirmus
Effect of salinity on bacterial growth (% NaCl)
Nonhalophile - 0%
Halotolerent - 2%
Halophile - 9%
Extreme halophile - 17%
Chemostats: continuous culture/bioreactors
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.
Flow rate > Growth rate
Washout
Flow rate < Growth rate
Stationary / death phase
Bacterial growth requirements
Nutrients Optimal temperature Gas - O2 Optimal pH Moisture Ionic balance/salinity
Catabolic
Energy releasing
Anabolic
Energy consuming
Macronutrients
Carbohydrates
Proteins
Lipids
Nucleic acids
Nutrient groups
Micronutrients and macronutrients
Split depending on the amount of bacteria needed.
Measuring bacterial growth: Population density - Method
Measures light scattering by cell
Measuring bacterial growth: Population density - Positives
Simple and convenient
Non-destructive
Can be done continuously
Measuring bacterial growth: Population density - Negatives
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
Measuring bacterial growth: Population number - Method
Looking for colony-forming units.
Extrapolated to give cells in original culture.
Each colony derives from a single cell.
Measuring bacterial growth: Population number - Negatives
Only measure viable cells
Underestimates cells in chains/clusters
Laborious
Slow
Calculating generation time
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)
Dilution Rate (D) =
F (flow rate) / V (Volume)
Microfluidics
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
