Estimating the fitness effect of an insertion sequence
Manuel Bichsel1, A D Barbour, Andreas Wagner
1Institute of Evolutionary Biology and Environmental Studies, University of Zürich, Zuerich, Switzerland. manuel.bichsel@ieu.uzh.ch
Journal of Mathematical Biology
|January 19, 2012
Summary
Mobile DNA, specifically insertion sequences (IS) in prokaryotes, persist due to low fitness costs and horizontal gene transfer. Beneficial effects may accelerate the spread of IS like IS5.
Area of Science:
- Microbiology
- Genetics
- Evolutionary Biology
Background:
- Mobile DNA, particularly insertion sequences (IS), are prevalent in prokaryotic genomes.
- The persistence of IS is debated, with hypotheses including occasional benefits versus horizontal gene transfer (HGT) overcoming detrimental effects.
Purpose of the Study:
- To model the long-term population dynamics of prokaryotes infected with insertion sequences.
- To investigate the factors influencing the persistence and distribution of IS, using IS5 as a case study.
Main Methods:
- Development of a mathematical model simulating prokaryote cell populations with IS infections.
- Analysis of IS5 distribution data from 525 sequenced proteobacterial genomes.
- Comparison of model predictions with empirical data regarding IS prevalence and spread.
Main Results:
- Insertion sequences exhibit minimal fitness costs, behaving as neutral or slightly detrimental elements.
- IS infections can persist and reach observed distributions if HGT rates are comparable to fitness costs.
- The computed fitness cost and HGT rate suggest unrealistically long times to reach observed IS5 prevalence, implying a role for beneficial effects.
Conclusions:
- The low fitness cost of IS supports their persistence through HGT, provided HGT rates are sufficiently high.
- Observed IS prevalence, particularly for IS5, may be influenced by occasional beneficial effects that accelerate their spread.
- Further research is needed to fully elucidate the evolutionary dynamics of mobile DNA in prokaryotes.
