Regulatory

Part:BBa_I13453:British Columbia

Designed by: jkm   Group: MIT   (2005-05-25)


Name: pBAD wild type
Input: L-arabinose
Output: PoPS

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All characterization of BBa_I13453 was done using BW27783 cells carrying the construct BBa_K206004.

Transfer Function

We attempted to find the transfer function relating input concentration of arabinose to PoPS by measuring RFP production in response to varying arabinose concentration.

Figure 1. Transfer function of BBa_I13453. Points represent individual measurements. The line is of a Hill equation fitted to our data.

We fit a Hill equation to the data from our experiment and used it to determine the values listed in our datasheet.


Expression Rate

We measured the development of RFP over time, in response to intermediate concentrations of arabinose.

Figure 2. Fluorescence development after induction with arabinose. Points represent means of 3 separate measurements. Error bars represent the standard deviation. Control measurements were of BW27783 cells lacking the construct.

Specificity

We investigated the specificity of BBa_I13453 for its ligand, arabinose, by testing it against several other aldopentoses (except rhamnose, a methyl-pentose).

Figure 3. Sugar specificity of BBa_I13453. Bars represent individual measurements. Sugars were present at 0.05% w/v except for lyxose which was 0.01% w/v.

Summary Datasheet

Experiment1 Characteristic1 Value1
Transfer Function Hill coefficient 2.19
Switch Point 4.08E-6 M L-arabinose, exogenous
Rate of Expression Response Time ~10 hours
Input compatibility Strong response to L-arabinose
No response to Ribose, xylose, lyxose, rhamnose

1Measured by the UBC iGEM Team 2009

General Characterization Protocols

  1. Inoculate 5mL LB-Chlor medium in a sterile test tube with a colony from a streak plate of pSB1C3-K206004-transformed BW27783 cells.
  2. Grow overnight at 37C, shaking at 210rpm.
  3. Measure OD600 and dilute to OD600=0.25A in 15mL of LB-Chlor with added arabinose (or other sugars).
  4. Grow at 37C, shaking at 210rpm.
  5. At appropriate timepoints (~24 hours for Transfer Function and Specificity experiments), remove samples for measuring OD600 (1/10 dilution) and fluorescence (fluorescence samples were frozen at -80C as cell pellets and measured together).

Sugars were made up to 10% w/v or 500uM stock solutions in water and filter sterilized with a 0.45um filter. RFP fluorescence was measured by pelleting 500uL of cells and resuspending in PBS, then collecting 50000 events on a Becton-Dickinson Influx flow cytometer. Fluorescence was calculated by finding the mean of the RFP histogram for each sample, normalized to OD600 (when possible).