growth curves - noelways.com€¦ · this model depicts bacterial growth in a contained system,...
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Growth Curves
GeneralizedGrowth Curves
to Accompany Lecture
By Noel Ways
Bacterial Growth ofStaphylococcus aureus
over a 24 hour period(Generation Time: 30 minutes)
Cell wall complete,cytoplasm divided
Daughter Cells
Binary Fission(a Bacillus used in this example)
DNA divides, cell elongates
Cell wall begins to form
LogGrowth
TIME (Hours)
100101
102
103
104
105
106
107
108
109101010111012101310141015
0 6 12 18 24
0 10.5 21.0 41.5 82.0 162.5 323.0 643.5 1284.0 2564.5 5125.0 1,0245.5 2,0486.0 4,0966.5 8,1927.0 16,3847.5 32,7688.0 65,5368.5 131,0729.0 262,1449.5 524,28810.0 1,048,57610.5 2,097,15211.0 4,194,30411.5 8,388,60812.0 16,777,21612.5 33,554,43213.0 67,108,86413.5 134,217,72814.0 268,435,45614.5 536,870,91215.0 1,073,741,82415.5 2,147,483,64816.0 4,294,967,29616.5 8,589,934,59217.0 17,179,869,18417.5 34,359,738,36818.0 68,719,476,73618.5 137,438,953,47219.0 274,877,906,94419.5 549,755,813,88820.0 1,099,511,627,77620.5 2,199,023,255,55221.0 4,398,046,511,10421.5 8,796,093,022,20822.0 17,592,186,044,41622.5 35,184,372,088,83223.0 70,368,744,177,66423.5 140,737,488,355,32824.0 281,474,976,710,656
Page 2
OptimumGrowth
TemperatureMinimum
GrowthTemperature
MaximumGrowth
Temperature
NoGrowth
NoGrowth
IncreasingStress
IncreasingStress
GrowthRate
Effect of variations in physiological variables. Examples of such variables are Temperature (shown here) but alsopH, osmotic pressures, oxygen concentrations etc etc.
A General Growth Curve
Page 3
SpeciesA
SpeciesB
SpeciesC
SpeciesD
Environmental / Physiological Variable
GrowthPotential / Rate
Hypothetical Growth Curve (Closed System)
LagPhase
StationaryPhase
GrowthPhase
Death Phase
1012
1011
1010
109
108
107
106
105
104
103
102
101
100
Number ofOrganisms
Death RateExceeds
Reproductive Rate
Reproductive RateExceeds
Death Rate
Reproductive RateEquals
Death Rate
Clostridia sp. and Bacillus sp. formendospores upon enviernmental stress
RelativeNutrient
and WasteConcentrations
Nutrient Concentrations
WasteConcentrations
No LivingBacteria
Page 4
This model depicts bacterial growth in a contained system, such as a test tube. Note the effect of the bacterial growth on nutrient and waste concentrations; and then as these concen-tration change, their effect on bacterial growth.
Note that during the stationary phase, bacteria are still alive and therefore nutrients continue to decline and waste continues to increase. This will continue until there are no living bacteria.
Due to endospore forming capabilities, Closridia sp. and Bacillus sp. do not have a death phase.
LagPhase
StationaryPhase #1
StationaryPhase #2
GrowthPhase
Death Phase
1012
1011
1010
109
108
107
106
105
104
103
102
101
100
Number ofOrganisms Reproductive Rate
ExceedsDeath Rate
Death RateExceeds
Reproductive Rate
Reproductive RateEquals
Death Rate
RelativeNutrient
and WasteConcentrations
Nutrient Concentrations
WasteConcentrations
Page 5
Hypothetical Growth Curve (Open System)
Closed
Open
Open
Closed
ContinuousNutrient
Replenishment
ContinuousWaste
Removal
This model depicts an open system where there is a continuous replenishment of nutrients and a continuous removal of waste products. In such case, extinction of the bacterial does not occur, but the population stabalizes. Population size will reflect the relative nutrient supply and waste removal as well as many other environ-mental factors. This is the typical senario that occurs in nature.
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