Team:Tokyo Tech/BlackenedEcoli

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Revision as of 15:51, 21 October 2009

Achievement

Melanin production pathway

Quantitative analysis of Darkness

We created Blackened E.coli by the melA gene.

Introduction ~Why do we need a Blackened E.coli~

One of the famous black pigment is a Melanin which was utilized in a number of organisms. Previously, it’s noted that the body color of E.coli was changed from white to black by a large amount of Melanin. Melanin was made by the melA gene. The melA gene code for a Tyrosinase (EC 1.14.18.1). Tyrosinase catalyze the first step of Melanin production pathway to make Dopaquinone. After production of Dopaquinone, Melanin is generated by nonenzymatical chain reaction. So, overexprssion of tyrosinase in E.coli cause a large amount of Melanin. Therefore, we consider these mechanisms enable us to control the Mars temperature, get the heat energy that helps bacteria grow and protect DNA from UV on the mars surface. Because melanin has a high efficiency heat absorption and absorbs Ultra Violet.

Increase Mars temperature

According to　Stefan-Boltzmann law, blackbody emit per surface in unit time is calculated as

σT⁴,

where T is the temperature of the black body and σ = 5.67 * 10 ^{− 8}(W / m²K⁴) is constant value. The total energy that comes from the sun is calculated as

S(1 − A)πr²,

where S = 597(W / m²) is the energy which actually reaches Mars from the sun, A is the albedo of Mars and r = 3.3972 * 10⁶(m) is the radius of Mars. Albedo is a ratio at which a planet reflect the sun light. Regarding Mars as blackbody, the radiative equilibrium temperature of Mars is estimated as

T= .

If we succeeded in decreasing the albedo by making Mars black, the temperature will change as the graph shows. x axis is year and y axis is temperature.

temperature estimation

We assume that the albedo decreases as

A = 0.15 * exp( − x).

If we could change the albedo from 0.15 to 0.05, the temperature of Mars would increase by about 6 Celsius degree.

Increase Reserving thermal energy

E.coli can get thermal energy, even if it is a little, by changing the body-color to black and uses the energy for its metabolism.

Protection from UV ray

UV strength on the Mars’ surface is weakened by initial energy supply of our project. But it can be easily changed by the convection of the atmosphere. So, we think it significant to blacken E.coli, which can protect them from variable UV ray.

Utilize Melanin production pathway

Melanin was made by Tyrosinase (EC 1.14.18.1). Tyrosinase catalyze the first step of Melanin production pathway to make Dopaquinone. After production of Dopaquinone, Melanin is generated by nonenzymatical chain reaction. So, Overexprssion of tyrosinase in E.coli cause a large amount of Melanin.

Melanin production pathway

Materials and Methods

Bacterial strains and cultivation

Escherichia coli K-12 JM109 was cultivated in Casein medium during melA expressing analysis. Casein medium used for melA expressing analysis contained, per liter, 1g glucose, 5g NaCl, 0.1g CaCl2, 10g bactotryptone, 15g agar, 5g casein, 0.4mg CuSO4 and 2g l-tyrosine.

Construction of the melA gene

The coding sequence of melA gene from Rhizobium etli CFN42, which was synthesized and optimized sewuence by GENEART.

melA expressing analysis

We transformed respectively BBa_K193602(placIQ-RBS-melA on pSB4A5) and control(placIQ-RBS on pSB4A5) into JM109 strain, and cultured them. Then we dispersed cultured strains on Casein medium. After 72 hour, we took a picture of these medium and measured darkness of these medium. Darkness was quantified with ImageJ softwere.

Result

As observed for Fig? , colony expressing melA was 10-folds blacker than control.　 As a result, blackness of colony expressing melA and control was showed marked difference.

Quantitative analysis of Darkness

Discussion and Future vision

Conclusion we could build melA into BioBricks, and create blackened E.coli by melanin.

Further blackened E.coli

Please, look under figure. This pathway is very simplified Phe and Tyr biosynthesis pathway. In previous study, forced expression of aroG and TyrA induced large accumulation of Tyrosine in E.coli. So, we will be planning to construct new igem parts to expressing aroG and tyrA.

Control mars temperature by temperature regulated response color change

Finally, we will want to create temperature-regulated genetic circuit using LacI_ts. This protein is temperature-sensitive. It inhibit LacI promoter at conventional temperature. Though, this protein isn’t inhibit promoter when environment temperature reach high.

If this plan is completely execution, E.coli is black to heat the mars during the cold. But, color of E.coli body change for white when the Mars is warmed.

This Genetic Circuit will can controls mars temperature?

References

• Natividad Cabrera-Valladares, Alfredo Mart´ınez, Silvia Pi˜nero, Victor H. Lagunas-Mu˜noz,Raunel Tinoco, Ram´on de Anda, Rafael V´azquez-Duhalt,Francisco Bol´ıvar, Guillermo Gosset. Expression of the melA gene from Rhizobium etli CFN42 in Escherichia coli and characterization of the encoded tyrosinase. Enzyme and Microbial Technology 38 (2006) 772–779
  
  
• Christine Nicole S. Santos and Gregory Stephanopoulos. Melanin-Based High-Throughput Screen for L-Tyrosine Production in Escherichia coli. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Feb. 2008, p. 1190–1197
• New Mars • View topic - Terraforming with a Broom [http://www.newmars.com/forums/viewtopic.php?t=5316]
• Dim Martian Surface May Fuel Global Warming [http://www.scientificamerican.com/article.cfm?id=more-heat-than-light-dim]

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