TY - BOOK

T1 - Characterising the CRISPR immune system in Archaea using genome sequence analysis

AU - Shah, Shiraz Ali

PY - 2013

Y1 - 2013

N2 - Archaea, a group of microorganisms distinct from bacteria andeukaryotes, are equipped with an adaptive immune system calledthe CRISPR system, which relies on an RNA interference mechanismto combat invading viruses and plasmids. Using a genomesequence analysis approach, the four components of archaealgenomic CRISPR loci were analysed, namely, repeats, spacers,leaders and cas genes. Based on analysis of spacer sequences itwas predicted that the immune system combats viruses and plasmidsby targeting their DNA. Furthermore, analysis of repeats,leaders and cas genes revealed that CRISPR systems exist as distinctfamilies which have key differences between themselves.Closely related organisms were seen harbouring different CRISPRsystems, while some distantly related species carried similarsystems, indicating frequent horizontal exchange. Moreover, itwas found that cas genes of Type I CRISPR systems could be dividedinto functionally independent modules which occasionallyexchange to form new combinations of Type I systems. Furthermore,Type III systems were found to be genomically associatedwith various combinations of accessory genes which may play arole in functionally extending the activity of the Type III interferencecomplexes. This dynamic nature of the CRISPR immunesystems may be a prerequisite for their continued efficacy againstthe ever changing threats they protect their hosts from.

AB - Archaea, a group of microorganisms distinct from bacteria andeukaryotes, are equipped with an adaptive immune system calledthe CRISPR system, which relies on an RNA interference mechanismto combat invading viruses and plasmids. Using a genomesequence analysis approach, the four components of archaealgenomic CRISPR loci were analysed, namely, repeats, spacers,leaders and cas genes. Based on analysis of spacer sequences itwas predicted that the immune system combats viruses and plasmidsby targeting their DNA. Furthermore, analysis of repeats,leaders and cas genes revealed that CRISPR systems exist as distinctfamilies which have key differences between themselves.Closely related organisms were seen harbouring different CRISPRsystems, while some distantly related species carried similarsystems, indicating frequent horizontal exchange. Moreover, itwas found that cas genes of Type I CRISPR systems could be dividedinto functionally independent modules which occasionallyexchange to form new combinations of Type I systems. Furthermore,Type III systems were found to be genomically associatedwith various combinations of accessory genes which may play arole in functionally extending the activity of the Type III interferencecomplexes. This dynamic nature of the CRISPR immunesystems may be a prerequisite for their continued efficacy againstthe ever changing threats they protect their hosts from.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122420225105763

M3 - Ph.D. thesis

BT - Characterising the CRISPR immune system in Archaea using genome sequence analysis

PB - Department of Biology, Faculty of Science, University of Copenhagen

ER -