Difference between revisions of "Part:BBa K1529797"

Latest revision as of 19:20, 2 November 2014

Plux-CmR-RhlI

We constructed this part by combining BBa_K395162, BBa_B0034 and BBa_C0070.

To characterize Plux-CmR-RhlI (BBa_K1529797), we introduced Plux-CmR-RhlI on pSB3K3 with Ptet-LuxR-Ptrc-RFP on pSB6A1 to E. coli as “3OC12HSL dependent CmR and C4HSL producer cell”.
In this E. coli, constitutively expressed LuxR activates the expression of CmR and RhlI in the presence of 3OC12HSL.

To confirm 3OC12HSL-dependent CmR production, we cultured Plux-CmR-RhlI cell in LB media with Amp, Kan and Cm.
Fig.1 shows OD590 by CmR producer cells dependent on different conditions.

Fig. 1. 3OC12HSL-dependent CmR expressionh in 100 microg / mL chloramphenicol

To confirm 3OC12HSL-dependent C4HSL production, we introduced Ptet-RhlR on pSB6A1 and Plux-GFP on pSB3K3 to E. coli as “Rhl reporter cell”.
Fig.2 shows fluorescence intensity by Rhl reporter cells dependent on different conditions.

Fig. 2. C4HSL production in the presence of 3OC12HSL

From these experiments, we confirmed that the part Plux-CmR-RhlI (BBa_K1529797) worked accurately.

Moreover, by co-culturing the cells containing this part with the cells containing C4HSL dependent 3OC12HSL producer part (Prhl(RL)-CmR-LasI:BBa_K1529302), we succeeded in constructing a positive feedback system.(Fig. 4.)

Fig. 3.Plasmids for the experiment of Co-culture.

Fig. 4. The growth of Campany(Prhl(RL)-CmR-LasI) and Customer(Plux-CmR-RhlI) when co-cultured for 6 hours.

Fig. 5.Increase of OD(co-culture) / OD(mono culture)

To see how the initial amount affect the growth, an additional experiment was conducted.
We conducted the experiment shown above at a smaller scale.
Increase of OD(co-culture) / OD(mono culture) was calculated by the equation shown below.
　　　OD590 of the co-cultured sample / OD590 of the mono cultured sample
　　　　*OD was measured after 4h incubation
　　　　*The ratio of customer and company in co-cultured sample is Customer : Company = 30 : 13

Sample condition is as follows.

　　　　*(Initial cell concentration of Customer[microL], Initial cells concentration of Company[microL])

When the initial amount is enough, the increase of OD(co-culture) / OD(mono culture) is high because of the mutualism between Customer and Company.
On the contrary, the ratio is low when the initial amount is small (Fig. 5).


We operated three independent co-culture assays. First, we confirmed whether mutualism was achievable. This result shows that the final OD of co-cultured cells was more than the final OD of both mono-cultured cells combined, when the initial OD of Company (Prhl(RL)-CmR-LasI:BBa_K1529302) was 0.05 (Fig. 6).

Fig. 6.First Co-culture Assay

Secondly, we specified the range of the initial OD of Customer (Plux-CmR-RhlI:BBa_K1529797) that can achieve mutualism. This result shows that the best condition for mutualism is when the initial OD of Company (Prhl(RL)-CmR-LasI:BBa_K1529302) and Customer (Plux-CmR-RhlI:BBa_K1529797) were 0.05 and 0.02 (Fig. 7).

Fig. 7.Second Co-culture Assay

Thirdly, we confirmed whether we can achieve mutualism if the initial OD became lower. This result shows that the lower the initial OD was, the less possible the mutualism could be achieved (Fig. 8).

Fig. 8.Third Co-culture Assay

For more information, see [http://2014.igem.org/Team:Tokyo_Tech/Project our work in Tokyo_Tech 2014 wiki].

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