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

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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.