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The rise and fall of CRISPRs – dynamics of spacer acquisition and loss
Author(s) -
Westra Edze R.,
Brouns Stan J. J.
Publication year - 2012
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2012.08170.x
Subject(s) - crispr , biology , sulfolobus solfataricus , plasmid , genetics , horizontal gene transfer , mobile genetic elements , population , crispr interference , sulfolobus , computational biology , dna , cas9 , archaea , gene , genome , demography , sociology
Summary Bacteria and Archaea are continuously exposed to mobile genetic elements (MGE), such as viruses and plasmids. MGEs may provide a selective advantage, may be neutral or may cause cell damage. To protect against invading DNA, prokaryotes utilize a number of defence systems, including the CRISPR/Cas system. CRISPR/Cas systems rely on integration of invader sequences (spacers) into CRISPR loci that act as a genetic memory of past invasions. Processed CRISPR transcripts are utilized as guides by Cas proteins to cleave complementary invader nucleic acids. In this issue, two groups report on spacer acquisition and turnover dynamics of CRISPR loci in a thermoacidophilic archeon and a pathogenic bacterium. Erdmann and Garrett (2012) demonstrate that three of the six CRISPR loci of Sulfolobus solfataricus rapidly acquire new spacer sequences from a conjugative plasmid present in a virus mixture. Intriguingly, two distinct mechanisms of spacer integration are utilized: leader adjacent and internal CRISPR spacer acquisition. Lopez‐Sanchez et al. (2012) studied the type II system of Streptococcus agalactiae and observe heterogeneity in the bacterial population. A fraction of the population lost one or more anti‐mobilome spacer sequences during its cultivation, allowing the transfer of a MGE in this subpopulation and a rapid response to altering selection pressures.