IGEM:IMPERIAL/2008/New/Major Results/Calibration Curve1

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Calibration Curve - O.D.600 vs Colony Forming Units

In order for us to convert the non standardised fluorescence data from the promoter characterisation into the standardized units of rate of GFPmut3b Synthesis per second per colony forming unit, we have constructed a calibration curve to convert O.D.600 to colony forming units. Using this calibration curve fluorescence data can be normalised based upon the number of colony forming units which approximates to the number of cells.

O.D.600 vs Cell Number Protocol

Click this link for the full protocol

Brief Descrption of protocol

  • Prepare an Overnight Culture of B.subtilis
  • Measure the O.D.600
  • Carry out a series of dilutions to give a range of O.D.600 e.g. 0.5, 1, 1.5, 2, 2.5, 3.
  • Carry out dilution plating with each O.D.600,
  • Grow overnight at 37oC ,
  • Count the number of Colony Forming Units,
  • Multiply the dilutions from the dilution plating,


  • We performed the protocol with 8 repeats for each O.D.600 across two dilutions. Examples of the density of plates we counted are shown below.
  • The results of the protocol are summarised in the graph below. To convert from O.D.600 we
Here are two examples of the dilution plates
Here are two examples of the dilution plates
Here is the Graph
Here is the Graph
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