How often does bacterial transformation happen?

Question

I have been reading:>M. Dröge, A. Pühler, W. Selbitschka, "Horizontal gene transfer among bacteria in terrestrial and aquatic habitats as assessed by microcosm and field studies", Biol. Fertil. Soils (1999) **29** pp221–245 [[PDF]](http://molecol.ifas.ufl.edu/education/webctvista/lectures/lgenetic/bsf29-3.pdf)I am not a biologist and am trying to get a feeling for how often prokaryotes make changes to their chromosomal DNA. **How often is plasmid DNA successfully incorporated into chromosomal DNA?** I would like to estimate either the number of gene changes (or, failing this, base pair changes) that a bacterium makes per unit time. Or, equivalently, the mean time between such changes.

Answer 1

This depends on the prokaryote and the environmental conditions at the time. Usually, the chance and amount of transformation increases when the prokaryote is under stress conditions. The sharing of genetic material has both risk of gaining deleterious mutations and helps increase chances of survival if they gain a useful gene, such as heat or desiccation resistance. When prokaryotes are under stress, the risk of gene transfer is worth the possible improvement in chances of survival.

Some species of bacteria will do gene transfer under good conditions, but this is usually with very specific plasmids and certain transport systems.

Under either condition, the DNA integration tends to be quite low. Most commonly, integration into DNA tends to happen at spontaneous break sites in the chromosomal DNA.

To find out the transformation efficiency, overall or over time, you'd need to test that particular species by using a marker to track the DNA transfer or track changes with genome sequencing.