The arms race between bacteria and phages

Bacteria, the most abundant organisms on the planet, are outnumbered by a factor of 10 to 1 by phages that infect them. Faced with the rapid evolution and turnover of phage particles, bacteria have evolved various mechanisms to evade phage infection and killing, leading to an evolutionary arms race. We study this arms race in order to understand how the extensive co-evolution of both phage and host shapes the huge diversity of the microbial world. For example, we found how bacterial genomes evolve in response to phage attacks (Avrani et al, Nature 2011).

As part of our reserach, we study the CRISPR system, an adaptive immunity system widespread in prokaryotes that uses RNAi-like mechanisms to destroy infecting viruses. We also used genomics and molecular evolution techniques to search for novel anti-phage defense systems in microbial genomes. The arms race between phages and bacteria residing in the human gut is also studied in our lab. We identified almost 1000 phages the infect bacteria that inhabit the human gut, and showed that these phages are shared among geographically distant human populations, possibly affecting human health (Stern, Mick et al 2012).