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Team:Tokyo Tech/BlackenedEcoli
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Contents |
Achievement
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 organism. 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 considered these mechanism enable us to control the Mars temperature, get the heat energy that help to grow bacteria and, protect DNA from UV on the mars surface. Because of Melanin has a high efficiency heat absorption and absorb 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 the mars from the sun, A is the albedo of the Mars and r = 3.3972 * 106(m) is the radius of the Mars. Albedo is a ratio at which a planet reflect the sun light. Regarding the Mars as blackbody, the radiative equilibrium temperature of the Mars is estimated as
T=
.
If we succeeded in decreasing the albedo by making the Mars black, the temperature will change as the graph shows. x axis is year and y axis is temperature.
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 the 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.
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
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.
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
