Environmental Effects on Microbial Growth

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Environmental Effects on Microbial Growth

• Utilizing E. coli as the Experimental Microbe

Presented by Jackie Martinez, Jacqui Mullings,
Robert Johnson, and Jerry James
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Outline
1. Introduction
2. Metabolic Engineering
3. Environmental Effects
4. Computer Model
5. Conclusion
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Introduction

• Objective - To create a mathematical computer
  model
• Escherichia coli
• Lives in intestines of animals
• Both helpful harmful strains
• Shape/Size - cylindrical
• Aerobic/anaerobic
• Motility
• Reproduction

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Reproduction
Log Phase
Lag Phase
Life Cycle
Stationary Phase
Death Phase
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Rationale

• One of the most studied and researched microbes
• Used as a host species in the study of viral
  genetics
• Used as an indicator species for fecal matter
• Pathogenic strain of E. coli 0157 causes an
  estimated
• 200,000 of food poisoning and 250 deaths in the
• United States each year
• Important to the Biotech industry

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Metabolic Engineering

• Metabolic engineering is the practice of
  optimizing
• genetic and regulatory processes within cells
  to
• increase the cells' production of a certain
  substance
• Used to create difficult-to-synthesize chemicals
• Medicine
• Industry
• Forced mutation and artificial selection
• Detect and reinforce natural genetic traits
• Eliminate unfavorable tendencies
• Improve general cell health

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Approach
Computer Model
pH Level
Nutrients
Temperature
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Computer Model
A number of cells after time t P the initial
number of cells r growth rate t time in
hours
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Temperature

• Thrives at 37 Celsius
• Heat shock - production of heat shock proteins
  to
• prevent inactivation
• Cold shock - production of cold shock proteins
  to
• prevent inactivation

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Temperature
Tmin minimum temperature at which growth
occurs Tmax maximum temperature at which
growth occurs Topt optimal temperature for
growth µ specific growth rate µopt optimal
growth rate
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Temperature
Tmin 2.62C Tmax 49.23C Topt
37.71C µopt 2.635 h-1
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Temperature
Figure 1.1 - Growth rate of E. coli due to
temperature. Growth rate is in h-1 (per
hour), and temperature is in C (degrees Celsius).
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pH Level

• E. coli belongs to the neutrophilic class
• E. coli responses to pH variation
• E. coli produces enzymes to neutralize acidity
  and
• alkalinity

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pH Level
pHmin minimum pH level at which growth
occurs pHmax maximum pH level at which growth
occurs pHopt optimal pH level for growth µopt
optimal growth rate
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pH Level
pHmin 4.2 pHmax 9.8 pHopt 7.0 µopt
2.635 h-1
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pH Level
Figure 1.2 - Growth rate of E. coli due to pH
level. Growth rate is in h-1 (per hour), and pH
level is on the pH scale from zero to 14, seven
being neutral.
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Nutrients

• E. coli is an enteric bacterium
• Glucose is the preferred substrate
• iron is the preferred mineral
• Deprivation of nutrients

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Nutrients
µ specific growth rate µmax maximum growth
rate Ks Monod saturation constant s set of
parameters
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Nutrients
µmax 0.92 h-1 Ks 76 µg/L
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Nutrients
Figure 1.3 - Growth rate of E. coli due to
substrate concentration. Growth rate is in h-1
(per hour), and substrate concentration is in
µg/L (micrograms per liter).
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Growth Example
Temperature 31C produces a growth rate of r
2.273 h-1
Figure 1.4 - Number of E. coli cells over a
two-hour time period
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Conclusion

• Modeling environmental variables
• Inhibitory or supportive environments
• Models may be adjusted for other organisms
• Industry
• Current research future models

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Questions?