Team:Tokyo Tech/AHL Assay/Only Assay

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3-2-2 AHL only of final genetic circuits assay

Contents

1. Introduction

2. Summary of the experiment

3. Results

4. Discussion

5. Materials and methods

   5-1. Construction

   5-2. Assay protocol

6. Reference

1. Introduction

　This section is an extension of the previous section (3-2-1 AHL reporter assay), and the point of Quorum Sensing was further evaluated. Specifically, production of AHLs and AHL-mediated communication between the Snow White coli and Queen coli were analyzed.

Fig. 3-2-2-1 Our final genetic circuits

2. Summary of the experiment

The reporter (Queen-like coli and Snow White-like coli) and sender (Queen-like coli) E. coli cells were prepared which carried rhlR and luxR genes, respectively. Then,(a) C4 was added into Queen-like coli, and (b) C4 was added into a co-culture of Queen-like coli and Snow White-like coli. The Relative Fluorescent Unit (RFU) of GFP was measured. The results indicated that Prhl(BBa_I14017) activity was so low that our final genetic circuits would not work with a wild type Prhl.(BBa_R0071)

-Plasmids

A. Pcon-rbs-rhlR-LVA(BBa_C0071)(pSB6A1)
, Prhl(BBa_I14017)-rbs-lasI(BBa_C0078)-rbs-gfp-LVA (pSB3K3) (Fig. 3-2-2-2-1)

Fig. 3-2-2-2-1 Pcon-rbs-rhlR-LVA(pSB6A1), Prhl-rbs-lasI-rbs-gfp-ssrA (pSB3K3)

B. Pcon-rbs-luxR(BBa_C0062)(pSB6A1)
, Plux(BBa_R0062)-rbs-rhlI(BBa_I19026)-rbs-rfp-ssrA (pSB3K3) (Fig. 3-2-2-2-2)

Fig. 3-2-2-2-2 Pcon-rbs-luxI(pSB6A1), Plux-rbs-rhlI-rbs-rfp-ssrA (pSB3K3)

C. pSB6A1
, pSB3K3…Negative (Fig. 3-2-2-2-3)

Fig. 3-2-2-2-3 pSB6A1, pSB3K3

3. Results

RFU of GFP / Turbidity was almost the same though adding C4 or DMSO (negative control; note that C4 was dissolved with DMSO) into Queen-like coli or the co-culture (Fig.3-2-2-3). The leak of Prhl(BBa_I14017) was high and the cause is explained Rhl system assay page.

Fig. 3-2-2-3 RFU of GFP / Turbidity of Only Assay

4. Discussion

The expression level of Prhl(BBa_I14017) was so weak and the leak was so high that Queen-like coli could not influence Snow White-like coli; in other words, our final genetic circuits did not work. Taken together the results, we again recognized that we have to improve Prhl activity to operate our final circuits.

5. Materials and methods

5-1. Construction

-Strain
All the plasmids were prepared in XL1-Blue strain.

-Medium
LB medium AK:
LB medium containing ampicillin (50 microg/ mL) and kanamycin (50 microg/ mL)

5-2. Assay protocol

The following experiments are performed at 37℃ unless otherwise stated.

1) Prepare the overnight cultures in LB medium AK with vigorous shaking.

2) Dilute the overnight cultures to 1 / 60 in fresh LB medium AK with vigorous shaking for 1 h.

3) Add C4 (100 microM) to Queen-like coli and C12 to Snow White-like coli, and incubate them with vigorous shaking for 4 h.

4) Measure RFU of GFP at 490nm as an exciting wavelength, 525nm as a measurement wavelength.

6. Reference

(1) Bo Hu et al. (2010) An Environment-Sensitive Synthetic Microbial Ecosystem. PLoS ONE 5(5): e10619
(2) Chen M. Zhang et al (2014) Distributed implementation of the genetic double-branch structure in Escherichia coli. Chinese Science Bulletin 59: 4625-4630