standard growth curves

• • A closed culture is a culture where nutrients are not replaced.
  • Toxic by-products of metabolic processes or death build up until the conditions are such that microorganisms can no longer survive
• • The typical population growth curve seen in a closed culture.
  • A logarithmic scale is used because of the huge difference in initial numbers and total population.
• • Lag phase = Slow growth. Not all bacteria reproducing.
  • Log phase = Exponential growth. Without limiting factors bacteria are doubling at the maximum rate.
  • Stationary phase = Waste build up is killing bacteria but those that die are replaced evenly.
  • Death phase = Waste build up makes conditions unviable. All bacteria eventually die.

  
• • Log numbers tell us what exponent (or power) is needed to make a certain number
  • Common log = Log-10
  • Natural log = Log-e (appears on your calculator as ln)
• • Bacterial growth is often rapid. Bacteria divide by binary fission which means the population can double every generation
  • We can use the equation N = N0 x 2n
  • Where N is the population number
  • Where n is the number of generations
  • Where N0 is the initial number of bacteria.