Microbial Growth Flashcards
Chapter 1
What does microbial growth refer to?
Microbial growth refers to an increase in the number of cells, not the size of the cells.
What factors influence microbial growth?
Nutrient availability, transport of nutrients into the cells, aeration, oxygen supply, temperature, and pH.
What is the microbial growth curve?
It represents the number of live cells in a bacterial population over time and consists of four stages: Lag Phase
Exponential (Log) Phase
Stationary Phase
Death (Decline) Phase
What occurs during the lag phase of microbial growth?
Microorganisms adapt to a new environment with available nutrients and pH. There is no increase in cell number, though cellular weight may increase slightly.
What determines the length of the lag phase?
The new set of physiological conditions and the phase at which the microorganisms were existing when inoculated.
What characterizes the exponential (log) phase?
Rapid cell division occurs, cell mass increases, and metabolic activity is high.
What happens during the stationary phase?
Growth slows or stops due to substrate depletion and the accumulation of metabolic end products.
The number of dividing cells equals the number of dying cells, resulting in no overall growth.
What biotechnological importance does the stationary phase have?
Cells may produce secondary metabolites such as antibiotics during this phase.
What marks the death (decline) phase in microbial growth?
Cells die exponentially due to the cessation of metabolic activity and depletion of energy reserves.
What is generation time?
The time required to double the initial bacterial population during the exponential growth phase.
What is the formula for calculating generation time?
g = t
3.32(logN2 - logN1)
