Experimental results：

Response to nickel ions：

We added nickel ions in the medium of strain K2304002. After 2h (200rpm, 37 ℃, LB), we centrifuged the culture medium at 12000 r / min. The red precipitate appeared at the bottom of the centrifuge tube，while the blank control group produced very little, or none of the red precipitation. This indicates that KL2304002 can be induced by Ni ions to produce RFP.

Specific response:

In order to detect whether strain K2304002 is also induced by other ions,

We mixed samples using Cd^{2 +}, Co^{2 +}, Cu^{2 +}, Fe^{3 +}, and Ni^{2 +in LB medium, with a concentration of 0.01 mmol / L .}

We cultured the samples at 250rpm, 37 ℃ overnight.

The next day we observed them with a fluorescence microscope. Excitation light is Blue background light.

Clearly, only the sample with Ni ions showed red fluorescence, the other groups had no red fluorescence. Note that the iron ions reacted with the supstance in the culture medium，so that there is an impurity in the field of view.

Qualitative testing：

K304002 was cultured at different concentrations of nickel ions, and the fluorescence intensity was measured every hour. We found that different concentrations of nickel ions caused inconclusive differences in fluorescence intensity.

Therefore, we tried to find a way to perform qualitative testing. We used different concentrations of nickel ions to induce the strain in OD0.8, and detected the fluorescence intensity every other hour by fluorescence spectrophotometer. And finally we found with a nickel ion concentration of 10-6mmol / L to 10-4mmol / L, that the correlation between fluorescence intensity and nickel ion concentration is the highest. So it has the application value of qualitative detection.

Modeling results：

In the process of modeling, we present some basic assumptions.

Assumptions:

• The degradation of other supstances are linear.

• Each cell has the same state.

• The reaction in the process satisfies the first-order kinetic reaction.

Then we reached some conclusions through modeling.

Transcription Repression： Release Repression： Total Model： https://2017.igem.org/Team:HBUT-China/Model