Synthetic biology is an exciting area of research that aims to genetically improve organisms to make them more efficient and hopefully more useful to us as well. The human population in 1950 was 2.5 billion, yet it is predicted to surpass 9 billion by 2050. Even with population growth slowing, increasing life spans and standards of living will soon tax our natural resources. One of the most concerning is our food supply. The agriculture industry needs a revolution in order to keep up with our expected growth rates. Currently about 80% of chemically fixated nitrogen is used as agricultural fertilizers, the majority in developed lands. Intracellular nitrogen fixation in crops could help to sustain the burgeoning world population, especially in areas with less fertile soil without taxing the planet’s waterways. The exponential increase in nitrogen fertilizer has led to more runoff into rivers and oceans. Fertilizers then provide nutrition for algal blooms that result in hypoxia and form oceanic dead zones. These dead zones lead to the death of marine species and have potentially large economic consequences.

The ramifications of nitrogen fertilizer runoff can be averted by genetically engineering plant crops to fix their own nitrogen. Some cyanobacteria fix nitrogen for nutritional needs, while most organisms can only acquire it from the food it consumes. Synthetic biology allows us to transfer this ability to fix nitrogen to a heterologous host that has many genetic tools, Escherichia coli, so that we can learn how to give single cell organisms, and eventually chloroplasts the ability to create their own nitrogen fertilizer.

Diazotrophic (organisms that fix nitrogen) cyanobacteria such Nostoc Punctiforme or Anabaena use heterocysts (specialized nitrogen fixing cells) to create a mini-anaerobic environment to aid nitrogen fixation. However, Cyanothece 51142, a non-heterocyst, fixes nitrogen in the same cell as photosynthesis by relying on a circadian metabolic process, when there is less oxygen byproduct from photosynthesis. Our goal this summer is to engineer the regulation of the proteins necessary for nitrogen fixation so that they are highly repressed when activated by broad spectrum light (such as the sun), and are highly active when there is no light around, mimicking the cycle where photosynthesis occurs during the day and nitrogen fixation occurs at night.