Introduction

Bacteria and their phages have co-existed for billions of years. The pressure of phage infection is thought to be a major driver of bacterial evolution and has favored the development of a diversity of anti-phage weapons. These weapons, namely anti-phage defense systems can be defined as single genes or groups of genes that partially or fully inhibit phage infection. For reviews on anti-phage systems, see : (, , , ) .

A brief history of anti-phage systems

The first discovered anti-phage system, a Restriction-Modification (RM) system, was described in the early 1950s (, ) . In the following decades, a handful of other systems were discovered () . In 2007, CRISPR-Cas systems were discovered to be anti-phage systems () . As CRISPR-Cas systems and RM systems are extremely prevalent in bacteria, it was thought for some years that the antiviral immune system of bacteria had been mostly elucidated.

Following these two major breakthroughs, knowledge of anti-phage systems remained scarce for some years. Yet, in 2011, it was revealed that anti-phage systems tend to colocalize on the bacterial genome in defense-islands () . This led to a guilt-by-association hypothesis: if a gene or a set of genes is frequently found in bacterial genomes near known defense systems, such as RM or CRISPR-Cas systems, then it might constitute a new defense system. This hypothesis was tested systematically in a landmark study in 2018 () leading to the discovery of 10 novel anti-phage systems. This started the uncovering of an impressive diversity of defense systems in a very short amount of time () .

To date over 150 types of defense systems have been described, unveiling an unsuspected diversity of molecular mechanisms. The antiviral immune systems of bacteria therefore appear much more complex than previously envisioned, and new discoveries do not seem to be slowing down.

Introducing the defense finder wiki

The fast pace of discoveries in the field can be intimidating to newcomers and can make it difficult for all to keep track of new discoveries. For this reason, we decided to implement a collaborative knowledge base for the community. This wiki is divided in two sections:

This wiki is only a first version and is intended to evolve based on the ideas and needs of the people using it. Whether it is to suggest new pages or to edit existing ones, all contributions are more than welcome: please do not hesitate to contact us to participate!