CAGEN: Competitive Gene Expression Challenge

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Synopsis: This challenge is to engineer a cell that maximizes production of a reporter molecule, while competing for resources with a cell lacking the engineered circuit. Equally-sized inoccula of the engineered strain and the wild-type strain are added to a batch culture and grown to saturation. The winning team has the highest reporter yield.

Motivation: Synthetic biosynthesis of protein and small molecule targets is often limited by genetic instability of engineered strains and competition for resources with non-producing mutants. This is particularly true for valuable but cytotoxic molecules (for example, antibiotics such as carbapenems). Costly fermentation processes might become more reliable if we could engineer strains that i) make more efficient use of resources, or ii) can actively inhibit accumulation of non-producers.

Impact: This challenge could impact the practice of industrial biotechnology by providing new tools and strategies for maximizing heterologous product yield in batch fermentation. Indirectly, development of these tools would be useful to the broader community of biological engineers interested in genetic stability, control of diverse populations, and circuit design.

Metric(s): The product will be fixed for a given edition of the challenge; for the 2011-2012 CAGEN challenge, the reporter molecule will be GFP. (In subsequent editions, the product could have greater significance or level of public recognition [e.g. a flu drug].) Product yield across three replicate batch flasks will be measured for each group, normalized to some limiting nutrient. The overall winner will be determined by a jury consisting of the CAGEN steering committee, based on the highest yield. The jury may award additional prizes for novel mechanisms.

Contact: To provide feedback on this challenge, send e-mail to Richard Murray (murray-at-caltech-dot-edu).