EXPERIMENTAL PROPOSAL
CREATING AND TESTING A MATHEMATIC MODEL TO PREDICT GROWTH CURVES OF
E. COLI AFTER EXPOSURE TO ELEVATED TEMPERATURES
Team 3March 31, 2014
Problem statement The purpose of this study is to
create and validate a mathematical model of a growth curve of bacterial behavior after thermal shock at various temperatures
Facts about E. Coli Escherichia coli (E. coli) is a type of
bacteria commonly found in the intestinal tracts of large mammals
The growth and decay rate are also affected by: Temperature Initial concentration of bacteria Presence of antibacterial substances pH levels Oxidation reduction potential
Facts about E. Coli In our experiment, we demonstrate how
the growth curve is affected by thermal shock
E. Coli grows well between 21oC to 50oC with an optimum at about 37oC .
E. coli can divide every 20 minutes At temperatures of 0°C (32°F) E. coli
are unable to divide, keeping the population stable
E. coli is killed above 70°C (160°F)
Growth Curve of E. coli
Lag phase: the population remains temporarily unchanged
Log phase: the cells divide at a constant rate depending on temperature conditions
Stationary phase: the population growth is limited by temperature Death phase: the number of cells decreases
The E.coli Growth Curve
Hypothesis
The growth curves of colonies shocked at temperatures (45-650C) demonstrate longer lag times but accelerated exponential growth when compared to a control grown at 37°C
Mathematic model to predict growth curve
WE WILL APPLY THIS EQUATION TO CREATE THE GROWTH CURVE MODEL[17]
(1- NMIN /N)C
Where: (Nmin) = minimum
population of E.coli (Nmax) = maximum
population of E.coli r = Temperature-
dependent constant C= Adjustment factor N= number colonies at
time t
Experimental Design
Materials and EquipmentSpectrophotometer and cuvettesInoculation Loop 1000μL and 100μL micropipettesBeakers and hot plates Incubator (37oC) Reagents:
Distilled water and deionized water Culture of E.Coli Nutrient broth as a food source
Experimental Setup
Thermal Shock: Initially raise bacterial environment
temperature to 450C, 550C, 600C, and 700C Growth continued at 370C after thermal shock Control group grown at 370C
Measure growth Create a concentration ladder Measure cloudiness in a test tube as the
number of cells increase (turbidity) using a spectrophotometer
Data Analysis
Mintab and MATLAB software Plot mathematical growth curve and
experimental growth curves Regression analysis
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QUESTIONS ?