These days, more and more artists implement biological living systems in their work, such as recently colored yeasts. Indeed, researchers achieved to create from the Saccharomyces cerevisiae
wild-type strain, 10 mutated strains which express 10 different colors.
Main properties and behaviors of this unicellular-fungus microorganism
remain the same. The pigment
in charge of the color expression is embedded in the cell via a
plasmid, a circular DNA molecule which is separated from chromosomal DNA
so that it can replicate independently. Unexpectedly, seekers only
resort to 3 types of pigments. The most incredible are Carotene pigments whom rate expression modulates the visible color of yeasts from light yellow to pink. On the contrary, Violacein could be toxic to yeast cells at high concentration.
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| Picture representing cultures of 9th yeast strain from Yeast Art |
As
pigment could put in danger future art production, we would like to
analyze how far these mutated strain could resist to environment
shiftings. Indeed, creation intends to touch people with aesthetic
representations implying this works to be easily and sustainably
sharable. Thus, they need to resist to Museum’s environment: light
overexposure, a continuous flow of bystanders, and temperature changes
between night and day. So how could we manage to preserve pigment
intensity knowing that optimal temperature for yeast growth rate is 30°C
and Violacein is synthesized by an enzymatic reaction?
We made an overnight culture
in a 96-wells plate incubated at 30°C in a plate spectrophotometer.
The 11 colored strains were replicated in 8 wells each. So that we could
save time determining the most efficient strain -rapid and uniform
growth - and making a first comparison between strains’ growth rates.
During
day 1 we compared the growth rate of wild-type and purple strain at
different temperature (28°C and 35°C) using 3 replicates of each strain
culture in YPD medium and Kova slide to count at a precise time number
of divided cells in samples. We could study the influence of temperature
on cells expansion.
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| 13 hours |
We
can see from this graph that the red strain didn’t grow up. The strain
which grew rapidly is the white one (~3.7x10⁻4 cells/min) (non-mutant).
The slowest is the pink one (~1.5x10⁻4 cells/min). We think that the red
didn’t grow up because of a lack of adenine in the medium. Yeast needs
sugar, oxygen and some amino acids to grow. We used a simple medium
without specific nutrients so maybe yeast consumes in a quick way all
the nutrient from the medium.
 | ||
| 4869.1 secondes |
We
can see on the graph that the white strain has a growth rate of
7.5x10-5 and the purple strain has a growth rate of 4.8x10-5. So at 35
degrees the white strain grow almost twice as fast than the purple.
 | |||
| 4500 secondes |
Then,
at 30 degrees, the white strain (W) grows also twice as fast as the purple one (P). The white strain has a
growth rate of ~6.0x10-5 and the purple strain has a growth rate of
~2.7x10-5.
Our
teacher said these different strains of yeast are originally the same.
But with our experiment, we discovered that the mutant strains have
different behaviors. The induced mutations to create pigment expression
drive changes in yeast's metabolisms: colored strains grow slowly and
not as the same way.
So if you want to do a picture with yeast to expose in a museum take the white strain.
We
notice that each strain has different characteristics regarding the
growth rate: each color strains had a specific trend (comparing the 8
wells together) that differs from others and mainly the wild-type one.
We must stay vigilant as we studied small samples and plate
spectrophotometer doesn't allow us to measure growth rate precisely
mostly if we don’t wait enough time or don’t use blank samples to
compare with.
Thus as a future project, we would like to analyze the viability of colonies over time at extreme temperatures to determine which is the optimal growth range for each.
We
were also curious to mate two mutated strains together and analyze
pigment’s prevalences resorting to a sporulated medium and tetrad
dissection to analyze produced colonies.
Yeast
Art opens impressive perspectives and represents more over another way
to promote collaboration between artists and scientific.
Here are additional resources for incorrigible curious.
- YeastArt applications from biopointillism to genetical engineering: This website presents all the steps of these artistic developments.
- Boeke Lab from NYU school of Medecine where colored yeast were produced
- Painting with yeast, 9 Mar. 2017, Posted by Jeffrey Perkel
- Article presenting pigment insertion in yeasts and characteristics of different pigments
Mitchell,
L. A., Chuang, J., Agmon, N., Khunsriraksakul, C., Phillips, N. A.,
Cai, Y., ... & Blomquist, P. (2015). Versatile genetic assembly
system (VEGAS) to assemble pathways for expression in S. cerevisiae. Nucleic acids research, gkv466.
- To learn more about new genetic engineering on yeast :
Sc2.0 project hits new milestone: 5 additional chromosomes completed!
Posted on March 9, 2017 by kyang
Posted on March 9, 2017 by kyang
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