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Revision as of 17:17, 19 September 2012

Bacillus BioBrick Box - Promoters

Eleven of the nineteen promoters of the [http://partsregistry.org/Part:BBa_J23100 Anderson collection] (J23100,J23101, J23102, J23103, J23106, J23107, J23113, J23114, J23115, J23117, J23118) were evaluated in the reporter vector pSB_Bs3C-luxABCDE from the BioBrickBox containing the lux operon as a reporter for promoter activity. The gene expression which correlates to the promoter activity leads to the expression of the lux operon with the luciferase. The luminescence which is produced by the luciferase can be measured with the plate reader (BioTek). Data derive from three undependant measurements (Fig. 1). Curves were fitted over each other (t=0, OD₆₀₀=0,3) and smoothed by taking average of three neighboring values. OD₆₀₀ values shown are plate reader units and about one third of the usual OD₆₀₀ values. All clones show a usual growth curves. The activity of the promoters raises during the pass from the transition to the stationary phase. This maximum (t=1h) reaches from 200Lumi/OD₆₀₀ (promoter J23115) to a maximum of 1500 Lumi/OD₆₀₀ for the strongest promoter (J23101). Afterwards the activity goes down to the beginning level (t=2h). The oscillation of luminescence (Lumi/ OD₆₀₀ in the beginning of the curves are due to the small OD₆₀₀ and do not mean a high promoter activity. The luminescence of one clone of the promoters J23107 and J23114 do not show activity where in future a second clone with promoter activity should be measured. In comparison to all the other evaluated Bacillus promoters these Anderson promoters showed a very low acitivity in B. subtilis.

To measure the activity not only with the lux reporter operon, four promoters of the Anderson collection were cloned into the reporter vector pSB_Bs1C-lacZ to do β galactosidase assays and then to compare the results of the strength of these promoters in B. subtilis. (Fig. 2)

The constitutive promoters P_liaG and P_lepA were evaluated in the reporter vector pSB_Bs3C-luxABCDE which contains the lux operon. Data derive from three undependant measurements (Fig. 3). Curves were fitted over each other (t=0, OD₆₀₀=0,3) and smoothed by taking average of three neighboring values. OD₆₀₀ values shown are plate reader units and about one third of the usual OD values. All clones show a usual growth curves. The activity of the promoters raises during the pass from the transition to the stationary phase. The second clone of the promoters P_lepA and P_liaG did not show any luminescence activity. In the beginning of the growth curve the activity of both promoters raise to their maximum. They show a similar behaviour in pertaining to the groth curve. P_liaG has an activity maximum of about 100.000 Lumi/OD₆₀₀ during the pass from logarithmic to the stationary phase. P_lepA shows an maximum of about 400.000 Lumi/OD₆₀₀. Comparing these two constitutive promoters the activity of P_lepA is about four times higher than the activity of P_liaG. In the late stationary phase the activity completely disappears.

The β galactosidase assay of the constitutive Bacillus promoters Pveg and P_liaG was repeated three times. Data show one representative result. Two undependant clones of B. subtilis with the same construct were measured and their mean with standard deviation is show in the graph. In the beginning of the growth curve both promoters show a small activity. But then it raises to a maximum before it decreases to the begininng level after about seven hours (Data not shown). Summing up the course of activity of both promoters P_veg and P_liaG is very similar based on the growth curve. The highest beta galactosidase activity and therefore the highest activity of the promoter Pveg can with an maximum of 65 Miller units be found during the transfer from the logarithmic to the stationary phase. This is about five times higher than the acitivity of the promoter P_liaG with an maximum activity of about 12 Miller Units.