Team:Tokyo Tech/Projects/making-rain/index.htm
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Revision as of 22:55, 27 October 2011
Making it Rain
Playing RPS with E. coli during summer was fun, but,
even if humans won, celebrations did not last long
since we soon returned to complaining about the hot weather.
As a prize for humans who win in our RPS game, we designed an
E. coli that can make it rain, making the hot summer more
fun and refreshing (let alone applications in agriculture).
1. Introduction
To make it rain we focus on the substance isoprene. It has been observed that trees in tropical rainforests contribute to the formation of photo-smog aerosol in the lower atmosphere by releasing isoprene (Paulson and Seinfeld, 1992). The photo-oxidized isoprene acts as a condensation nucleus [2], may cause shower (make it rain) even if it is present in very low concentrations.
![Fig.1](https://static.igem.org/mediawiki/2011/7/79/Isoprene-aerosol.png)
It is known that the enzyme isoprene synthase can catalyze the conversion of dimethylallyl diphosphate(DMAPP) to isoprene. DMAPP is normally synthesized by E. coli, so the only thing we need to make our bacteria synthetize isoprene is isoprene synthase. The isoprene synthase coding gene (ispS) is isolated from the tree poplar (Barbara Miller et al, 2001). E. coli introduced this gene released isoprene into the air by diffusion [1]
![Fig.3](https://static.igem.org/mediawiki/2011/c/cd/TokyoTech_rain_fig2.png)
In this study, we tried to make E. coli synthesize isoprene by introducing ispS.
2. Isoprene by E. coli
To measure the amount of isoprene produced by E. coli introduced ispS, we constructed negative control PlacIQ and sample PlacIQ-rbs-ispS, using the PlacIQ promoter (BBa_I14032) and ispS. Gene ispS is extracted from the pMK backbone vector. (see more about our constructions)
![Fig.3](https://static.igem.org/mediawiki/2011/0/08/Rain-const.png)
We used Gas Chromotrography-Mass Spectrometry (GC-MS) to measure the amount of isoprene from E. coli. When using GC-MS, we injected a series of chloroform-diluted liquid isoprene to draw the calibration curve. To confirm that liquid isoprene produced by E. coli would be released as a gas, we diluted liquid isoprene in water and also in LB medium. In both cases, we could confirm isoprene was evaporated into the air (see more about these experiments).
According to the calibration curve, we detected 4×10-5 mg/L isoprene produced by E. coli BL21 (DE3) introduced isoprene synthase, while negative control (PlacIQ) produced one tenth of our new E. coli. (see more about GC-MS)
3.Aerosol by Isoprene
The reaction between isoprene and ozone has been studied to examine physical and chemical characteristics of the secondary organic aerosol formed. An aerosol is a suspension of fine solid particles or liquid droplets in a gas. By far the most common aerosols in the atmosphere are clouds, which normally consist of suspensions of water droplets or ice particles of greater or lesser density, which can later cause rain. According to those information, we designed an easy indoor experiment of reaction between isoprene and ozone, and confirmed that isoprene can make aerosol. (see more...)
4.Conclusion
We confirmed that E. coli introduced ispS produces isoprene and that isoprene makes aerosol. So our E. coli will make it rain!
[1] Yaru zhao, et al., Biosynthesis of isoprene in Escherichia coli via methylerythritol phosphate (MEP) pathway, Appl Microbiol Biothechnol(2011) 90:1915-1922
[2] Leonardo Silva Santos, et al., Mimicking the atmospheric OH-radical-mediated photooxidation of isoprene: formation of cloud-condensation nuclei polyols monitored by electrospray ionization mass spectrometry, Rapid Communication in Mass Spectrometry, 2006