|Virus-host interactions in the thermophilic archaeon Sulfolobus with a focus on the CRISPR defense system|
Le Moine Bauer, S. (2011). Virus-host interactions in the thermophilic archaeon Sulfolobus with a focus on the CRISPR defense system. MSc Thesis. University of Copenhagen. Danish Archaea Centre: Copenhagen. 70 pp.
Archaea; Sulfolobus; Thermophilic microorganisms; Virussen; Marien
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Since the early times of life, hosts and viruses have been fighting in an endless arms race which has lead to the development of different defense mechanisms in cells. The most recently discovered is the CRISPR defense system (Clustered Regularly Interspaced Short Palindromic Repeats). This system incorporates copies of small sequences (spacers) from invading DNA (virus, plasmid) into the genome of the cell. These copies are then used as a probe to guide a defensive protein complex against the invading DNA. While the second part of the system is rather well known, the molecular mechanisms leading to the acquisition of new spacers is poorly understood. In the first part of this work, we tried to induce spacer acquisition by challenging different Sulfolobus hosts with STSV2 (not published yet) under several conditions (Optimal conditions, UV stress, temperature stress, minimal medium, low concentration stress, reinfection). Results were analyzed by amplifying and sequencing the upstream region of the different CRISPR loci but no spacer acquisition was observed under any of the conditions used. In the second part of this work, we studied the virus-host interactions between STSV2 and its Sulfolobus hosts. The different growth curves and plaque assays performed showed no significant impact of the infection. Although different morphological features were observed by electron microscopy in STSV2 particles depending on the host, we could not find any genomic differences neither by enzyme restriction digestion with EcoNI and EcoRI nor by sequencing the STSV2 ORF 131 structural protein.