Team:Chiba/Project/Experiments:Sender Crosstalk

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Revision as of 04:25, 30 October 2008

Sender Crosstalk

Design

Fig.1 Sender switch

Fig.2 AHL varieties

Each species has their own LuxI-type proteins,which synthesize their specific autoinducers,AHLs.AHLs produced by different LuxI-type proteins differ only in the length of the acyl-chain moiety and substitution at position C-3.LuxR,which is original for Vibrio fischeri,is activated by its cognate autoinducer,3OC6HSL.However,LuxR is also activated by non-endogenous molecules,C4HSL,C6HSL,and 3OC12HSL.Activation by non-endogenous molecules requires a higher signal concentration(2).This results in slower activation of receivers,when AHL concentration is increasing.

Experiments

The purpose of this experiment was to create delays in communication time using cross-talk between non-specific signals. We used the following genes for this experiment.

Details

Method

To characterize quorum sensing crosstalk, constitutive AHL senders were mixed with constitutive receivers and measure fluorescence intensity.

1. Transformed Senders into E.coli strains(XL10Gold) and Receiver into E.coli strain(JW1908).
2. Inoculated them independently in liquid media. Incubated at 37°C for 12hours.
3. Mixed them.
4. Incubated at 30°C.
5. Measured intensity of green fluorescence(485 nm(excitation) and 527 nm(emission)) at regular time intervals.

more details...

Results & Discussion

Fig.3 senders crosstalk test.senders strain XL10Gold,Receiver strain JW1908.Reaction temparature was 30°C.All measurements are averages from three replicate cultures with error bars representing standard deviations.Labeling:LuxI,RhlI,LasI means fluorescence induced by AHLs synthesized by LuxI,RhlI,LasI respectively.

Senders(XL10Gold), T9002(JW1908)@30°C, Sender(μL):Receiver(μL)=500：500, 100:1000, 10:1000

• 37°Cで行った実験と比べ、LasIが活性。（intensity of green fluorescence of Eight hours later 37°C：30°C=163：245）
• LasとLux(Plac)１：１で蛍光強度200に達するまでの時間に2．5時間の時差がみられた。
• Rhlのタグなしとタグ付きの差は、８ｈ後の最終強度にしか現れなかった。

また、差が一番でたのが30°Cで行ったこの実験で、タグなし：タグつき＝507：456。

3OC6HSL,3OC12HSLに対する、LuxRの応答時間に、二時間の差ができた（3OC12HSLの場合、3OC6HSLに比べて二時間遅れて応答する）。 (そのときの条件は、培養温度30°C、genelatorの株はXL10Gold,Receiverの株はJW1908のとき、であった。) <??

• LasI is more activated @30°C than @37°C(After 8 hours fuluorecence intensity 37°C：30°C=163：245)
• The time to achieve 200 of fuluorecence intensity with LasI and LuxR(pLac)(=1:1) was delayed 2.5 hours.
• RhlI and RhlI(with LVA tag)made a difference of the latest intensities after 8 hours.

And,this conbination(@30°C) made a greatest differences.(no LVA tag):(LVA tag)=507:456.

When we used the cross-talk strategy using 3OC12HSL instead of 3OC6HSL, the delayed switch worked 2 hours after the original switch worked. Futher variation of delayed switches will be realized:

Future plans

• Reduce quantity of expression of an enzyme composing AHL

1. Replace medium RBS with weak one.
2. Alter the copy number of plasmids in the sender into low.

• To make the slope of transfer curve of our device to be steep:

1. Introduce Positive Feedback Loop into our gene circuit.

Other Experiments

Visual Judgement

• Fluorescence intensity was from 150 to 200 when the 2 mL of reaction culture in a test tube.

Senders(JW1908), T9002(JW1908)@37°C, Sender(μL):Receiver(μL)=500：500, 100:1000, 10:1000

• Among RhlI, LasI, and CinI+LVA, RhlI+LVA is the easist to cross-talk with LuxR
• Delay time by cross-talk among senders are generated only a range of one hour to amount

to 200 of fluorescence intensity.

Senders(JW1908),T9002(JW1908)@30°C,Sender(μL):Receiver(μL)=500：500,100:1000,10:1000

Senders(XL10Gold),T9002(JW1908)@37°C, Sender(μL):Receiver(μL)=500：500,100:1000,10:1000

Senders(XL10Gold), T9002(JW1908)@25°C, Sender(μL):Receiver(μL)=500：500, 100:1000, 10:1000

Demo ~Senders~

We experimentally tested the sender genes LuxI and LasI which produce the greatest time difference. We mixed bacteria(XL10G) transformed with either the LuxI or LasI genes and bacteria (of the BW strain) transformed with the LuxR gene at a 1:1 ratio and visually observed GFP fluorescence.

Results

Fig.4 Demo

0 h

4 h (Lux I GFP detected)

8 h (Lux I GFP and Las I GFP detected)

-->more about Demo experiments detail

references

1. M.K Winson et al.:Construction and analysis of luxCDABE-based plasmid sensors　for investigating N-acyl homoserine lactone-mediated quorum sensing.FEMS Microbiology Letters 163 (1998) 185-192
2. BBa_F2620:Specificity
3. Paul Williams.:Quorum sensing, communication and cross-kingdom signalling in the bacterial world.Microbiology 153 (2007), 3923-3938

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