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Experimental adaptation of Salmonella typhimurium to mice
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
Karolinska Institute, Microbiology and Tumor Biology Center, S-171 77 Stockholm, Sweden.
2004 (Swedish)In: Genetics, ISSN 0016-6731, E-ISSN 1943-2631, Vol. 168, 1119-1130 p.Article in journal (Refereed) Published
Abstract [en]

Experimental evolution is a powerful approach to study the dynamics and mechanisms of bacterial niche specialization. By serial passage in mice, we evolved 18 independent lineages of Salmonella typhimurium LT2 and examined the rate and extent of adaptation to a mainly reticuloendothelial host environment. Bacterial mutation rates and population sizes were varied by using wild-type and DNA repair-defective mutator (mutS) strains with normal and high mutation rates, respectively, and by varying the number of bacteria intraperitoneally injected  into mice. After <200 generations of adaptation all lineages showed an increased fitness as measured by a faster growth rate in mice (selection coefficients 0.11–0.58). Using a generally applicable mathematical model we calculated the adaptive mutation rate for the wild-type bacterium to be >10−6/cell/generation, suggesting that the majority of adaptive mutations are not simple point mutations. For the mutator lineages, adaptation to mice was associated with a loss of fitness in secondary environments as seen by a reduced metabolic capability. During adaptation there was no indication that a high mutation rate was counterselected. These data show that S. typhimurium can rapidly and extensively increase its fitness in mice but this niche specialization is, at least in mutators, associated with a cost.                 

Place, publisher, year, edition, pages
2004. Vol. 168, 1119-1130 p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-70294DOI: 10.1534/genetics.104.030304OAI: oai:DiVA.org:uu-70294DiVA: diva2:98205
Available from: 2006-05-05 Created: 2006-05-05 Last updated: 2011-07-22Bibliographically approved

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Nilsson, AnnikaBerg, OttoAndersson, Dan I.
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