Genomic traces of the coevolution of archaea and viruses

The tug-of-war between Bacteria and Archaea on one side and viruses and other mobile elements on the other leaves its traces in the genomes of the involved parties and thus can be analysed in respect of their co-evolution. We identified several unusual processing steps during the maturation of transfer RNAs and hypothesize that these represent protection mechanisms against viral attacks (Heinemann, I.U. et al., 2010, Randau, L. et al., 2009). One example is the splitting of transfer RNA genes resulting in the elimination of potential viral attachments sites.

Other recently discovered defence mechanisms against viruses are the different CRISPR/Cas systems found in Bacteria and nearly all Archaea (Marakova, K.S. et al., 2011). These systems generate small crRNAs that contain sequences derived from viruses and together with a set of Cas proteins mediate the interference of repeated viral attacks. We perform functional analyses of the CRISPR/Cas subtype that is prevalent in methanogens and Clostridia. An unusual crRNA processing enzyme was identified.