UNalphabeting the Central Dogma of Life

This proposal aims to construct a bacterial strain LIFE-19 which relies solely on 19 amino acids to build all its proteins.

While all living cells known to human beings produce proteins from the same 20 coded amino acids, the study of origins of life imply that earlier cells may have functioned with a smaller alphabet. This is thought-provoking in the present biological context, wherein each of the 20 serves a distinct and vital role.

Although many scientists have engaged in theoretical exercises involving the reduction of this amino acid alphabet, the inherent biological intricacy and a lack of suitable tools have impeded experiments on an organismal level. This project seeks to mutate all the tryptophan (Trp) protein sites in a minimal Mycoplasma genome template.

Trp stands out as both one of the scarcest and one of the evolutionary youngest members of the protein alphabet. Here, we will engineer Trp out of a minimal genome in a 2-stage process.

Initially, semi-automated gene editing will target all individual Mycoplasma Trp-sites concurrently, using broad randomization schemes (capitalizing on the PIs expertise).

This will allow us to compare Trp dispensability across the proteome and select the most viable Trp-substituted protein variants. Second, the selected mutations will be combined to write a new LIFE-19 genome using a bottom-up synthesis. LIFE-19 will lay the next steppingstone to our understanding of lifes limits.

We will be able to get a glimpse into what cells probably went through billions of years ago, when they teetered on the border between life and nonlife.

With the reduced number of building blocks, LIFE-19 will also generate an important step towards a cellular chassis with minimal energetic demands and therefore key inventory in Synthetic Biology research.

Overall, this project will challenge the textbook knowledge that life depends on the 20 canonical amino acids, by effectively UNalphabeting the Central Dogma of biology.