Hypervariation and phase variation in the bacteriophage ‘resistome’

Most bacteria encode proteins for defence against infection by bacteriophages. The mechanisms that bring about phage defence are extremely diverse, suggesting frequent independent evolution of novel processes. Phage defence determinants are often plasmid or phage-encoded and many that are chromosoma...

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Bibliographic Details
Published in:Current opinion in microbiology 2007-08, Vol.10 (4), p.396-400
Main Authors: Hoskisson, Paul A, Smith, Margaret CM
Format: Article
Language:English
Subjects:
Bacteria
Bacteria - enzymology
Bacteria - virology
Bacterial Physiological Phenomena
Bacteriophages - genetics
Bacteriophages - physiology
Biological and medical sciences
DNA Restriction-Modification Enzymes
Evolution, Molecular
Fundamental and applied biological sciences. Psychology
Microbiology
Pathology
Replicative cycle, interference, host-virus relations, pathogenicity, miscellaneous strains
Virology
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Summary:Most bacteria encode proteins for defence against infection by bacteriophages. The mechanisms that bring about phage defence are extremely diverse, suggesting frequent independent evolution of novel processes. Phage defence determinants are often plasmid or phage-encoded and many that are chromosomal show evidence of lateral transfer. Recent studies on restriction–modification (R–M) systems show that these genes are amongst the most rapidly evolving. Some bacteria have contingency genes that encode alternative target specificity determinants for Type I or Type III R–M systems, thus expanding the range of phages against which the host population is immune. The most counter-intuitive observation, however, is the prevalence of phase variation in many restriction systems, but recent arguments suggest that switching off expression of R–M systems can aid phage defence.
ISSN:1369-5274
1879-0364
DOI:10.1016/j.mib.2007.04.003