Abstract
Publisher Summary This chapter focuses on bacterial inserted sequence (IS) elements and discusses their influence on genetic stability and evolution. Escherichia coli ( E. coli ) carries a number of different IS elements in its chromosome. These elements may transpose to new locations at frequencies estimated to be of the order of 10 -5 to 10 -6 per IS element and per generation of the host cell. The overall transposition frequency in E. coli can then be estimated to be around 10 -4 per generation, or perhaps even ten times higher. But often these processes are lethal and may, therefore, escape detection. A transposon flanked by IS elements resident in E. coli usually transposes at a considerably lower frequency than the single IS element. In contrast, some transposons active in E. coli , but whose flanking IS elements are not resident in E. coli , are known to transpose with rather high frequencies in the order of 10 -3 per generation, which may reflect the dependence of IS elements and transposons on the bacterial host strain. Such a high transposition rate may not be desirable to a bacterial strain because it may affect the overall stability of the strain, and therefore represent an evolutionary disadvantage. On the other hand, the presence of a number of different IS elements each in a certain number of copies in bacteria might suggest that IS elements act as desirable agents in evolution.
Published Version
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