Promiscuous restriction is a cellular defense strategy that confers fitness advantage to bacteria

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 109; no. 20; pp. E1287 - E1293
• Main Authors: Vasu, Kommireddy, Nagamalleswari, Easa, Nagaraja, Valakunja
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 15.05.2012; National Acad Sciences
• Series: PNAS Plus
• Subjects: Bacteria; bacteriophages; Bacteriophages - genetics; Bacteriophages - metabolism; Biological Evolution; Biological Sciences; Cells; Chromosomes; Deoxyribonucleases, Type II Site-Specific; Deoxyribonucleases, Type II Site-Specific - genetics; Deoxyribonucleases, Type II Site-Specific - metabolism; Deoxyribonucleic acid; DNA; DNA Restriction-Modification Enzymes; DNA Restriction-Modification Enzymes - metabolism; Electrophoresis, Polyacrylamide Gel; enzymology; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Fitness; Genetic Fitness; Genetic Fitness - genetics; genetics; genome; Genomes; Host-Pathogen Interactions; Klebsiella pneumoniae; Klebsiella pneumoniae - enzymology; Klebsiella pneumoniae - virology; metabolism; Oligonucleotides; Oligonucleotides - genetics; Parasites; Phages; PNAS Plus; Races; Restriction-modification; Self; virology
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1119226109

Most bacterial genomes harbor restriction–modification systems, encoding a REase and its cognate MTase. On attack by a foreign DNA, the REase recognizes it as nonself and subjects it to restriction. Should REases be highly specific for targeting the invading foreign DNA? It is often considered to be the case. However, when bacteria harboring a promiscuous or high-fidelity variant of the REase were challenged with bacteriophages, fitness was maximal under conditions of catalytic promiscuity. We also delineate possible mechanisms by which the REase recognizes the chromosome as self at the noncanonical sites, thereby preventing lethal dsDNA breaks. This study provides a fundamental understanding of how bacteria exploit an existing defense system to gain fitness advantage during a host–parasite coevolutionary "arms race."