MicroBio 13: Microbial Growth Flashcards
an increase in cell number. not in cell size since these micro organisms grow and divide by binary fission.
Bacterial Growth
Enumerate the Physical Factors affecting growth
- pH
- temperature
- radiation
- Osmotic pressure
- Salinity
Chemical factors affecting growth
- O2
- Carbon
- Nitrogen
- Phosphorus
Group of microbes based on temperature requirement
- Psychrophiles or Cryophiles
- Mesophiles
- Thermophiles
- Hyperthermophiles
Classification of bacteria based on pH
pH Levels:
0 - 2 extreme acidophiles
3 - 5 acidophiles
6 - 8 neutrophiles
9 - 11 alkalophiles
12 - 14 extreme alkalophiles
Growth of bacterial population where
- Rate of growth is constant
- M.o. are growing and dividing at a maximal rate possible given the genetic potential, the nature of the medium or conditions of growth.
Log Phase or Exponential Phase
Growth of bacterial population where
- there is no increase in cell no.
- Cells are synthesizing new components such as DNA replication, protein synthesis
Lag Phase
Growth of bacterial population where
- Population growth ceases and the growth curve becomes horizontal
- Total number remains constant due to a balance between cell division and cell death due to nutrient limitation, O2 avaibility for aerobic microbes and accumulation of waste products limit the growth
Stationary Phase
Growth of bacterial population where
- Detrimental environment changes like nutrient deprivation and the build up of toxic wastes lead to the decline in the number of viable cells characteristic of the death phase.
Death Phase
In Death Phase, most of the microbial population dies in _______ manner
logarithmic manner
Measurement of Microbial Growth examples
- Direct count method
- Viable count method
- Turbidometric measurement
Measurement of Microbial Growth equals to what?
= measurement of cell. no
This needs to be used together with dilution plate method initially to create a standard curve, which can be repeatedly used later.
Turbidometric measurement
this counts both dead and live bacteria
Ex: Hemacytometer
Direct count method
This counts live cells only
Ex: Dilution plating methods
Viable count method
