Microbial Growth and Culture DARLINA DAUD
Feb 23, 2016
Microbial Growth and Culture
DARLINA DAUD
Growth and Cell Division
Microbial Growth Defined:
1. Mother or parent cell doubles in size2. Divides into two daughter cells
Microbial growth is defined as the increase in the number of cells, which occurs by cell division
Cell DivisionBinary fission (equal cell division):
A cell duplicates its components and divides into two cells
Septum: A partition that grows between two daughter cells and they separate at this location
Budding (unequal cell division): A small, new cell develops from surface of exisiting cell and subsequently separates from parent cell
Binary Fission
Thin section of the bacterium Staphylococcus, undergoing binary fission
Environmental Factors Influencing Growth
1. Temperature2. O2 3. pH4. Osmotic Pressure5. Others: radiation,
atmospheric pressure
•Psychrophiles: cold-loving•Mesophiles: moderate temperature-loving•Thermophiles: heat-loving•Each has a minimum, optimum, and maximum growth temperature
Temperature
OxygenObligate aerobesFacultative anaerobes Obligate anaerobesAerotolerant Microaerophiles
pHAcidophiles
Neutrophiles
Alkalophiles
Osmotic Pressure
Phases of Growth Consider a population of
organisms introduced into a fresh, nutrient medium
Such organisms display four major phases of growth
1. The lag phase2. The logarithmic phase3. The stationary phase4. The death phase
The Lag PhaseOrganisms do not increase significantly
in number
They are metabolically active
Grow in size, synthesize enzymes, and incorporate molecules from medium
Produce large quantities of energy in the form of ATP
The Log PhaseOrganisms have adapted to a growth
medium
Growth occurs at an exponential (log) rate
The organisms divide at their most rapid rate
a regular, genetically determined interval (generation time)
Stationary Phase:1. Cell division decreases to a point that
new cells are produced at same rate as old cell die.
2. The number of live cells stays constant.
Decline (Death) Phase: 1. Condition in the medium become less
and less supportive of cell division2. Cell lose their ability to divide and thus
die3. Number of live cells decreases at a
logarithmic rate
Growth in Batch CultureGrowth is generally used to refer to the
acquisition(perolehan) of biomass leading to cell division, or reproduction
A “batch culture” is a closed system in broth medium in which no additional nutrient is added after inoculation of the broth
Growth in Continuous CultureA “continuous culture” is an open system
in which fresh media is continuously added to the culture at a constant rate, and old broth is removed at the same rate.
This method is accomplished in a device called a chemostat.
Typically, the concentration of cells will reach an equilibrium level that remains constant as long as the nutrient feed is maintained.
Standard Growth Curve