Cells Growth Flashcards
*Autocatalytic
* Characterize by specific growth rate.
- growth
*Cell Growth
*can be measured directly or indirectly
* direct measurement
*Cell Concentration
* Mass or cell number basis
Cell number counting
hemocytometer, plate counts and particle counts
Hemocytometer
Advantage: Accurate, typically low noise in measurement.
Disadvantage: time-consuming, carcinogenic, mutagenic stains
Plate counts
Advantages: counts viable cells, fairly accurate
Disadvantage: noisy, takes days
CFU
colony forming units
Particle Counters
- measure particle size contribution\
Advantage: very quick, obtain a size distribution in addition to a count
Disadvantages: solution must be particle-free for accurate count, finicky hardware, expensive, complicated
Mass concentration
- most common units to report biomass
*obtained by centrifuging sample, drying, and weighing
Advantages: Mass concentration is typical variable in models, simple, low-tech method
Disadvantage: the presence of solids makes it inaccurate, and difficult to measure low biomass conc.
Indirect concentration measurements
- Turbidometer or spectrophotometer
- substrate uptake or product evolution
- Luciferin/ ATP fluorescence.
- Protein or DNa/RNA conc. measurements
the measure of the amount of light that passes through a turbid sample
Optical Density
reported with the wavelength of the light used in the measurement
Optical Density
often measured in OD and converted to mass per volume with a standard curve
Biomass
Batch Cultures
- fixed amount of substrate present at beginning
- is seeded with an innoculum
5 phases of growth
Lag, Exponential, deceleration, stationary, death
Lag Phase
