Long-term Sabbatical
Lateral gene transfer is a major force in the evolution of microorganisms. The ability to obtain genetic novelty can accelerate adaptation to new niches and speeds up evolutionary transitions and speciation events. However, exposure to foreign DNA is also harmful for microbes, mostly because the vectors of gene transfer such as plasmids and viruses are parasitic and often lethal for their hosts. Microorganisms have therefore developed several defense mechanisms to degrade foreign DNA. In prokaryotes CRISPR (Clustered, Regularly, Interspaced, Short, Palindromic Repeats) - based systems digest invading DNA or RNA, thus preventing not only viral infections but also the acquisition of potentially beneficial traits such as antibiotic resistance. CRISPR systems acquire new invader-derived sequences and thus establish immune memory, and also a record of past infections by selfish mobile elements.
Active CRISPR systems will mean a decrease in genomic evolvability, since fewer new genes and functions from plasmids and lysogenic phages will enter the genome, but this would be offset by an increase in the fitness of cells that do not have to replicate additional plasmids. This cost/benefit balance may be the reason that only 40-50% of bacterial species and 90% of archaeal species carry those systems.
I will use computational tools to investigate the effects that CRISPR systems have on the evolution of prokaryotic genomes, and estimate their activity in resistance to viruses. The results will further our understanding of how the dynamic interactions between lateral gene transfer and the host-parasite arms race together shape microbial genomes.
Do microbial immune systems reduce lateral gene transfer in prokaryotic genomes?
| PI(s): | Uri Gophna (Tel Aviv University (ISRAEL)) |
| Start Date: | 18-Aug-2013 |
| End Date: | 17-Aug-2014 |
| Keywords: | selfish genes, genomics, evolutionary genetics, evolutionary novelty |
Lateral gene transfer is a major force in the evolution of microorganisms. The ability to obtain genetic novelty can accelerate adaptation to new niches and speeds up evolutionary transitions and speciation events. However, exposure to foreign DNA is also harmful for microbes, mostly because the vectors of gene transfer such as plasmids and viruses are parasitic and often lethal for their hosts. Microorganisms have therefore developed several defense mechanisms to degrade foreign DNA. In prokaryotes CRISPR (Clustered, Regularly, Interspaced, Short, Palindromic Repeats) - based systems digest invading DNA or RNA, thus preventing not only viral infections but also the acquisition of potentially beneficial traits such as antibiotic resistance. CRISPR systems acquire new invader-derived sequences and thus establish immune memory, and also a record of past infections by selfish mobile elements.Active CRISPR systems will mean a decrease in genomic evolvability, since fewer new genes and functions from plasmids and lysogenic phages will enter the genome, but this would be offset by an increase in the fitness of cells that do not have to replicate additional plasmids. This cost/benefit balance may be the reason that only 40-50% of bacterial species and 90% of archaeal species carry those systems.
I will use computational tools to investigate the effects that CRISPR systems have on the evolution of prokaryotic genomes, and estimate their activity in resistance to viruses. The results will further our understanding of how the dynamic interactions between lateral gene transfer and the host-parasite arms race together shape microbial genomes.
