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1.  CRISPR/Cas systems in archaea 
Mobile Genetic Elements  2012;2(1):63-64.
CRISPR (Clustered, Regularly, Interspaced, Short, Palindromic Repeats) loci have been shown to provide prokaryotes with an adaptive immunity against viruses and plasmids. CRISPR arrays are transcribed and processed into small CRISPR RNA molecules, which base-pair with invading DNA or RNA and lead to its degradation by CRISPR-associated (Cas) protein complexes. New spacers can be acquired by active CRISPR/Cas systems, and thus the sequences of these spacers provide a record of the past “infection history” of the organism. Recently we used spacer sequences from archaeal genomes to infer gene exchange events among archaeal species and genera and to demonstrate that at least in this domain of life CRISPR indeed has an anti-viral role.
doi:10.4161/mge.19907
PMCID: PMC3383453  PMID: 22754756
CRISPR; Lateral Gene Transfer; archaea; horizontal gene transfer; viruses
2.  CRISPR loci reveal networks of gene exchange in archaea 
Biology Direct  2011;6:65.
Background
CRISPR (Clustered, Regularly, Interspaced, Short, Palindromic Repeats) loci provide prokaryotes with an adaptive immunity against viruses and other mobile genetic elements. CRISPR arrays can be transcribed and processed into small crRNA molecules, which are then used by the cell to target the foreign nucleic acid. Since spacers are accumulated by active CRISPR/Cas systems, the sequences of these spacers provide a record of the past "infection history" of the organism.
Results
Here we analyzed all currently known spacers present in archaeal genomes and identified their source by DNA similarity. While nearly 50% of archaeal spacers matched mobile genetic elements, such as plasmids or viruses, several others matched chromosomal genes of other organisms, primarily other archaea. Thus, networks of gene exchange between archaeal species were revealed by the spacer analysis, including many cases of inter-genus and inter-species gene transfer events. Spacers that recognize viral sequences tend to be located further away from the leader sequence, implying that there exists a selective pressure for their retention.
Conclusions
CRISPR spacers provide direct evidence for extensive gene exchange in archaea, especially within genera, and support the current dogma where the primary role of the CRISPR/Cas system is anti-viral and anti-plasmid defense.
Open peer review
This article was reviewed by: Profs. W. Ford Doolittle, John van der Oost, Christa Schleper (nominated by board member Prof. J Peter Gogarten)
doi:10.1186/1745-6150-6-65
PMCID: PMC3285040  PMID: 22188759
CRISPR; Lateral Gene transfer; Horizontal gene transfer; viruses; archaea; competence

Results 1-2 (2)