Team:Austin UTexas


Congratulations to the Austin UTexas 2019 iGEM team for their achievements!

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Team representatives receive the 2019 special award for Best Measurement!
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Austin UTexas tied with the Grand Prize Winner!
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Members of the team during the poster session
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The team stands proudly with their achievements
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The team strikes a pose for the 2019 Jamboree


Metabolic burden is often overlooked when designing genetic devices.


A major obstacle in the progress of synthetic biology is that of metabolic burden exceeding a bacterial host’s cellular capacity. When a part is burdensome, it experiences evolutionary instability as loss-of-function mutations accumulate. This is problematic for synthetic biologists that rely on their constructs to last, whether they are for small-scale lab projects, or for high-stake industrial applications.

Metabolic Burden

Burden is the degree to which a construct slows cellular replication and prevents conservation of the part in the host cell. Any part that is introduced to a host cell will redirect cellular resources towards itself, imposing a high level of stress on the cell, and creating an abnormal environment for the host. As a result, the evolutionary stability of the transformed cell is compromised, and burdensome pathways tend to break fairly quickly.

We use modeling to determine how big of a metabolic burden would lead to evolutionary instability.

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Evolutionary Stability

The “lifespan” of a genetic device is brief, because the unstable cellular environment will eventually force the cell to undergo evolutionary changes to relieve it of metabolic burden. Once loss-of-function mutations are introduced and genetic parts break, the mutant cells, which now experience significantly less burden, quickly outcompete the non-mutated cells.

How Do We Measure Burden?

Burdensome parts are identified by measuring and analyzing the growth rates of each part. The burdensome parts are further analyzed to determine the types of burden that they produce, which is achieved by observing GFP expression rates.

We have measured the burden of 330 parts from iGEM distribution kits

Impact on Synthetic Biology Community

We measured 330 parts from iGEM distribution kits, which includes frequently used promoters, coding regions, terminators, ribosome binding sites, and many other types of BioBricks. Synthetic biologists and iGEM students rely on the constructs within the iGEM registry without knowing if those parts are reliable. With our “Burdenometer," researchers can now assess the burden associated with those parts and choose more evolutionarily stable constructs. This information is important if a specific type of output is expected, maximizing productivity is a priority, or long-term propagation is pursued. It is also useful when troubleshooting cultivation failure. However, we are not confined to just these 330 parts! Synthetic biologists can now use our standardized measurement system to determine the burden of any genetic part that interests them.

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