Defense Against Viruses and Other Genetic Parasites in Prokaryotes

Kira S.Makarova, Yuri I.Wolf, Eugene V.Koonin

National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD, United States.

Abstract

Archaea and bacteria employ the full range of defense mechanisms against genetic parasites, from passive virus entry evasion to suppressing viral infection via elaborate immunity system based on self versus nonself recognition, to programmed cell death. Components of microbial antiviral defense are among the fastest-evolving and most mobile genes. The dynamic evolution of defense systems is supported by their association with mobile genetic elements and a variety of diversity-generating mechanisms. In this article, we discuss classification, genetic organization and evolution of microbial defense systems.

Key words: Arms race, CRISPR-Cas, Defense islands, Defense systems, Gene shuffling, Immunity, Programmed cell death, Restriction-modification, Toxin-antitoxin systems.