Difference between revisions of "Part:BBa K733012"

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xylR+PxylA+RBS+ydcE+Ptms+RBS+ydcD: Cell Growth Inhibition Device

This construct is for the characterization of the cell growth inhibition device. pTms+RBS+ydcD is for the stabilization of the cell growth inhibition system. By this stabilizer, under low level of induction, YdcD will counteract EndoA to protect cell from being sick. (Pellegrini et al., 2005) However, as long as the induction level is strong enough and reaches a threshold, the amount of EndoA accumulated in the cell can inhibit the growth of the bacteria.

Ptms+RBS+ydcD: BBa_K733010

Xylose inducible promoter with ydcE gene: BBa_K733011

Characterization

Objective

The objective of this characterization is to find out what is the minimal concentration of xylose to inhibit the growth of our B. hercules.

Method

I. Construct.

xylR: The transcriptional regulator for the xylose inducible promoter.

PxylA: The xylose inducible promoter.

ydcE (ndoA): The toxin gene encoding EndoA.

Ptms: The low efficient constitutive promoter.

ydcD (endB): The antitoxin gene encoding YdcD.

II. Culture Medium.

Supplemented M9 minimal medium (M9 salt, 1 mM thiamine hydrochloride, 0.2% casamino acids, 0.1 M MgSO4, 0.5 M CaCl2, 0.4% glycerol) was used for our characterization. The reason for this medium and 0.4% glycerol as the carbon source is that glucose can repress the induction of xylose. (Kim, Mogk & Schumann,. 1996) 25 mg/mL chloramphenicol was diluted 100 times and added to the medium to select the bacteria with our intended vectors. The final concentration gradient of xylose in the supplemented M9 minimal medium is: 0.05%, 0.10%, 0.15%, 0.20% and 0.25%.

III. Control and Experiment Group.

Control Group: E. coli DH10β without any vector was engaged in characterization as control. It was inoulated into the supplemented M9 minimal medium with xylose concentration: 0.00%, 0.05%, 0.10%, 0.15%, 0.20%, 0.25%. Note that in the control group, the medium was not added with chloramphenicol.

Experiment Group: E. coli DH10β with our cell growth inhibition device were inoculated in the supplemented M9 minimal medium with xylose concentration: 0.00%, 0.05%, 0.10%, 0.15%, 0.20%, 0.25%. The total volume of the culture was 2mL for each test tube.

IV. Experiment.

The bacteria cultures were incubated in 37 degree Celsius, shaked with 200 rpm for exactly 16 hours. After 16-hour incubation, the turbidity of the cultures were checked and photographed. Later, 50uL culture from one set of the experiments were taken and be spread on chloramphenicol 25 ug/mL LB plate for overnight incubation.

Result

Note that after spreading the culture on the plates, there were bacteria growing for all the tubes in the experiment groups. Admittedly, there were distinguishable difference between the concentration of 0.00%, 0.05% and 0.10% and the concentration of 0.15%, 0.20% and 0.25%: for the left three groups, the number of bacteria was much more than that in the right three ones. This result indicated that our E. coli did not die for the xylose induction, but its growth was inhibited.

Sequence and Features

Reference

Pellegrini O, Mathy N, Gogos A, Shapiro L, and Condon C. "The Bacillus subtilis ydcDE operon encodes an endoribonuclease of the MazF/PemK family and its inhibitor.." Molecular microbiology. 56.5 (2005): 1139-1148. Print.

Kim, L., Mogk, A., & Schumann, W. (1996). A xylose-inducible Bacillus subtilis integration vector and its application.. Gene, 181(1-2), 71-76.