Revision as of 09:01, 19 October 2019

E. coli chromosomal ars promoter with arsR repressor gene

This part consists of the promoter of the E. coli JM109 chromosomal arsenic detoxification operon (ars operon), including the ArsR repressor binding site and the arsR gene encoding the arsR repressor protein, together with its ribosome binding site. Addition of any other genes to the 3' end of this part will result in their expression being dependent on the presence of sodium arsenate or sodium arsenite. Arsenite or arsenite anion binds to the repressor protein ArsR, resulting in inability to repress the promoter. Based on our experiments, a concentration of 1 micromolar sodium arsenate in LB is sufficient for essentially full expression, though this will vary according to conditions.

Sequence and Features

Supplementary material offered by other groups

The following is from TJU-China 2018. We used the part:Bba-J33201 saved in plate3 and wanted to build a new arsenic induction loop through it. Therefore, we first added 10μlddH2O to the corresponding hole, and then took PCR was performed at 1μl, and the corresponding DNA fragment was obtained.

Figure1. The result of nucleic acid gel electrophoresis of Bba-J33201 after PCR. Lane M, Marker. Lane 1-6，Bba-J33201

Then we performed PCR on the promoter fragment and ArsR fragment in this fragment, and the results are as follows.

Figure2. The result of nucleic acid gel electrophoresis of Ars Promoter after PCR. lane M, Marker. Lane 1-4, Ars Promoter.

Figure 3. The result of nucleic acid gel electrophoresis of ArsR Protein after PCR. Lane M, Marker. Line1, ArsR Protein.

Characterization

Worldshaper-Wuhan 2019's Characterization

Detail information please check our wiki website

http://2019.igem.org/Team:Worldshaper-Wuhan-A/Measurement

Aim of experiment

Based on J33201 part, a biosensor pSB1C3-pArsR-RBS-GFP(K3153000) was constructed to detect arsenite(As3+) in water and contributed to this well-characterized part.

Methods

1. Growth curve of E.coli containing part K577881 in different concentrations of arsenite(As3+)

Constructed plasmid pSB1C3-pArsR-GFP containing J33201 part was transformed into E.coli DH5α strain. Single colony was selected to inoculate LB broth containing chloramphenicol and cultured overnight. Then overnight culture was inoculated in the fresh LB medium containing chloramphenicol 34μg/ml at a ratio of 1:100, mixed well and divide into tubes. Different concentrations of arsenite(As3+) solutions were added into the test tubes, respectively, so that the final concentration of arsenic was (0, 5ppb, 10ppb, 50ppb, 100ppb, 500ppb, 1ppm, 5ppm, 10ppm, 50ppm and 100ppm). Samples were taken at different time points of 0h, 1h, 2h…8h and overnight (16h) at one hour interval and OD600 value were measured with a Multiskan Spectrum Microplate Reader.

2. GFP expression of E.coli under the control of J33201 induced by different concentration of arsenite (As3+)

Overnight cultured bacterial solution was inoculated in LB broth containing chloramphenicol at 1:50 to expand the culture, and the experiment was started when OD600 reached 0.4-0.6. Different concentrations of arsenite solutions were added into the test tube, respectively, so that the final concentration of arsenic was (0,5ppb, 10ppb, 50ppb, 100ppb, 500ppb, 1ppm, 5ppm, 10ppm, 50ppm, 100ppm).

(1) Samples were taken at overnight (16h). GFP fluorescence intensity (485 nm excitation/ 528 nm emission) and OD600 value were measured at the same time. The bacteria were centrifuged, and the pellets were was observed and photographed under Blue Light Gel Imager.

(2)Samples were taken at different time points of 0h, 2h, 4h, 6h and overnight (16h). GFP fluorescence intensity (485 nm excitation/ 528 nm emission) and OD600 value were measured at the same time.

Results

Fig.1 showed that bacteria growth was not affected in the range of 5ppb-10ppm of arsenite solution (As3+). However, as the concentration of arsenite increased to 50ppm, the growth of the bacteria was seriously inhibited, suggesting the toxictity to cells at this level.

Fig.1 Growth curve of E.coli in different concentration of arsenic (As3+).

As shown in Fig.2, our constructed biosensor based on J33201 part is very sensitive to arsenite(As3+) and the fluoresence signal can be detected at 50ppb arsenite. Significant dose-dependent effect was observed at the range of 50ppb-1ppm arsenite. The threshold of this biosensor is 10ppm. As the arsenite concentration increased to 50ppm, it does’t work due to the toxicity to cell at this level.

(Fig.2a)

(Fig.2b)

Fig.2 GFP expression of E.coli under the control of J33201 in different concentration of arsenite (As3+).

As it is shown in Fig.3, our constructed biosensor by J33201 reacted rapidly in arsenite solution. Afrer adding arsenite for 4 hours, the corresponding fluorescence signal can be detected at 100ppb. As time increases, a weak signal can be detected at 50ppb, indicating that the biosensor can work within 4 hours.

Fig.3 GFP expression of E.coli in different concentration of arsenite (As3+) at different time points under the control of J33201.

Summary

our biosensor constructed on the basis of J33201 is sensitive and fast. The biosensor can detect 100ppb-10ppm arsenite (As3+) in water within 4 hours. With the extension of time, the minimum detection limit can reach 50ppb.

Reference:

Anal Bioanal Chem. 2011 May;400(4):1031-9. Epub 2011 Mar 27.