Bacteria are essentially haploid, that is they only contain one copy of their genome. Consequently, unlike higher organisms which are usually diploid, and which containing two copies of the genome, changes in the DNA sequence of the genome (mutations) usually result directly in measurable phenotypes. There is no blending or filtering of the genome’s informational content as is the case with higher organisms and mutations or glitches in the genetic code can become readily visible.
The bacterium Serratia marcescens usually grows as a distinctive and red pigmented colony. However, if it is exposed to agents which cause DNA mutation, and these genetic changes occur in pathway that gives rise to the red pigment, then the bacterium will become white.
In this process here, I have dramatically increased the natural mutation rate of the genome of this bacterium by exposing it to radiation. The damage to its DNA can clearly been seen in the emergence of many non-pigmented white mutants, amongst the red-pigment parent strain.
It strikes me that this system could be used as a living biological ink which would record exposure to radiation, and perhaps form the basis of a biological radiation detector. Maybe it’s already sniffing out and detecting the legacies of Chernobyl and Fukushima.