Escherichia coli adapts metabolically to 6- and 7-fluoroindole, enabling proteome-wide fluorotryptophan substitution

Nature has scarcely evolved a biochemistry around fluorine. However, modern science proved fluorinated organic molecules to be suitable building blocks for biopolymers, from peptides and proteins up to entire organisms. Here, we conducted adaptive laboratory evolution (ALE) experiments to introduce fluorine into living microorganisms. By cultivating Escherichia coli with fluorinated indole analogues, we successfully evolved microbial cells capable of utilizing either 6-fluoroindole or 7-fluoroindole for growth. Our improved ALE protocols enabled us to overcome previous challenges and achieve consistent and complete adaptation of microbial populations to these unnatural molecules. In the ALE experiments, we supplied fluoroindoles to auxotrophic E. coli bacteria, exerting strong selective pressure that led to microbial adaptation and growth on monofluorinated indoles. Within the cells, these indoles were converted into corresponding amino acids (6- and 7-fluorotryptophan) and incorporated into the proteome at tryptophan sites. This study is a first step and establishes a strong foundation for further exploration of the mechanisms underlying fluorine-based life and how a formerly stressor (fluorinated indole) becomes a vital nutrient. ![Figure][1] ### Competing Interest Statement The authors have declared no competing interest. [1]: pending:yes