Team:Imperial College London/Drylab/Autoinduction/Model2

Rationale

This model is important for several reasons (stated earlier). Since the secondary sources we are using are in the lactose family, we will inevitably switch on the lac operon, which could be involved in the changes we see in bacterial metabolism.
Reviewing what we have previously seen:

• In a glucose-lactose rich medium, consumption of glucose is energetically more favourable because extra energy is required to make lactose enzymes (permease and b-galactosidase)
• This model includes:
  • lac operon transcription and translation processes
  • glucose and lactose transport
  • Inducer exclusion
  • Catabolite repression
  • The assumption of constant growth rate in diauxic growth models no longer applies: It is only valid in the exponential phase. Normally growth rate is time dependent.

Model assumptions

• Volume of glucose and lactose in the pool is infinite, so densities are kept constant.
• They also assume in a second experiment that glucose and lactose constant but they can vary densities of glucose and lactose with time.

Model Predictions

• Lactose growth:

When lactose is the only carbon source, the graph has a sigmoid shape: For different extracellular lactose concentrations, it saturates around 4mM so adding 40mM outside will not make a difference.

• Growth in a mixture of glucose and lactose:
  • Now there will be two growth phases, where one nutrient will be consumed first and then the other.
  • In switching from consumption of the primary source to consumption of the secondary source, a lag period will be observed, which is found in experiment to last around 36 minutes.

  about the model.

Simulations