An evolutionary arms race occurs when species interact, and each is under strong evolutionary pressure to compensate for evoluationary advances made by the other. The classic example for microbes is the phage-host arms race. A high ratio of non-synonymous to synonymous substitutions in protein-coding genes, taken to indicate strong positive selection, is one of several possible bioinformatics signatures for an arms race.

Microbial evoluationary arms race systems include:

  • the phage-host arms race
  • bacteriocin systems
  • syntrophic partnership optimization in complex communities