Auxotrophy

The complex pattern of evolution of vitamin auxotrophy across the eukaryotic tree of life is intimately connected with the interdependence between organisms.

[7] A chemical is considered positive for Ames test if it causes mutations increasing the observed reversion rate and negative if presents similar to the control group.

There is a normal, but small, number of revertant colonies expected when an auxotrophic bacteria is plated on a media without the metabolite it needs because it could mutate back to prototrophy.

It is suggested that if a mutation can arise in bacterial DNA under presence of a mutagen then the same effect would occur for larger organisms causing cancer.

[6] A negative Ames test result could suggest that the substance is not a mutagen and would not cause tumor formation in living organisms.

[8] A large number of unnatural amino acids, which are similar to their canonical counterparts in shape, size and chemical properties, are introduced into the recombinant proteins by means of auxotrophic expression hosts.

[9] For example, methionine (Met) or tryptophan (Trp) auxotrophic Escherichia coli strains can be cultivated in a defined minimal medium.

In this experimental setup it is possible to express recombinant proteins whose canonical Trp and Met residues are completely substituted with different medium-supplemented related analogs.

For example, the first clearly successful attempt to evolve Escherichia coli that can survive solely on the unnatural amino acid thieno[3,2-b]pyrrolyl) alanine as the only substitute for tryptophan was made in 2015.

[13] The 1993 film Jurassic Park (based on the 1990 Michael Crichton novel of the same name) features dinosaurs that were genetically altered so that they could not produce the amino acid lysine.