Variation in spontaneous deletion rates at different locations of the Salmonella typhimurium chromosome
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
How and at what rates spontaneous deletions form is still a partly unresolved question. Here we have constructed a genetic tool that can be used to determine spontaneous chromosomal deletion rates at any chromosomal location. We measured deletion rates at 12 chromosomal locations and identified the deletable region as the largest deletion found at each location. Our data shows that spontaneous deletion rates can at least vary 100-fold between the different chromosomal locations when normalized to the size of the deletable region. The isolated deletions ranged in size from 1-200 kbp and the highest deletion rates were found around 2 Mbp of the S. typhiumurium chromosome, suggesting a potential hotspot for deletion formation. No long repeat sequences were found in this region that could explain the high deletion rate. Furthermore, no obvious correlation between fitness (measured as exponential growth rate) and deletion size could be seen. Surprisingly, since deletions are commonly considered deleterious certain deletions (ranging from 18- to 38 kbp in size) increased the growth rate of the cells with ~5% in both rich and poor growth media. These results suggest that the bacterial chromosome is heterogeneous with respect to the rate of deletion formation and that some deletions could become fixed as a consequence of natural selection rather than by drift and/or mutational biases.
bacteria, gene loss, chromosome
Microbiology in the medical area Microbiology in the medical area
Research subject Evolutionary Genetics; Microbiology
IdentifiersURN: urn:nbn:se:uu:diva-111427OAI: oai:DiVA.org:uu-111427DiVA: diva2:281153