Difference between revisions of "Part:BBa K540001"

Revision as of 17:14, 21 September 2011

rcn, cobalt-sensitive promoter

Rcn is a promoter that is activated by cobalt. A repressor is fixed to the promoter by default, and cobalt binds to this repressor, which activates the gene under control of this promoter.

Rcn is also activated by nickel, but we have not characterized this aspect.

Characterization

Kinetic Mesurement

Important : this characterization hasn't been done with this biobrick and an iGEM Gfp. It has been done with the promoter before that the silent mutation to remove the PstI site was made. The GFP used here, is a stable GFP.

In order to determine wether rcn promoter is inducible by cobalt or not, a kinetic of the fluorescence (excitation 490nm, emission 510nm) of the two following strains has been done:
NM522+p157 where p157 is a plasmid containing a stable GFP under the control of rcn promoter.
NM522+p115 where p115 is the p157 corresponding control plasmid.

Both strain are cultivated without cobalt and with 25µM of cobalt. 1ml of bacteria is added to 100ml of M63G medium and 1ml of spectinomycin in a 250ml erlen. The four erlens are put in a 37°C bath with a 270rpm agitation. Every hour, a 3mL and 1mL culture sampling are done for a fluorescence measurement and a OD(600nm) measurement respectively. Near an OD(600nm) of 1, samplings are done every half hour. The measurements are stopped when the OD reaches 1. A last sampling is done after an overnight growth.

The experiment has been performed in triplicate and the results shown below are the mean values obtained from the 3 operators.

It is shown out from these two graphics that the strain NM522+p115 (carrying a control plasmid) doesn't have any fluorescent activity and does not respond at all to cobalt. Whereas the strain NM522+p157 (carrying a plasmid with GFP under the control of rcn promoter) responds well to cobalt. A fluorescent activity is detected even without cobalt. This could be linked to a leaky nature of the promoter rcn. However this activity is at least two times lower than the one obtained in presence of cobalt.

The standard deviation concerning the values for NM522+p157 + 25µM Cobalt looks big while the one of the other strain is equivalent. The grow state for this strain for each operator is similar as shown bellow so the standard deviation's difference can't be linked to this.

Conclusion

Our characterisation of rcn promoter shows that this promoter is inducible by cobalt. Kinetic analysis of the promoter allowed us to establish that an OD(600nm) of 0,2 was optimum for rcn promoter activation.

To conclude, this work shows that this promoter can be used with efficiency in a cobalt sensitive system.

Safety

This part is not toxic by itself. However, when using this part, you will probably need to handle cobalt. Cobalt is toxic in all its forms ( ionic or metallic ) by inhalation, ingestion or contact. Wear adapted personal protection equipment ( labcoat, safety glasses, safety gloves ) and dispose of it in appropriate waste containers.

Sequence and Features