Spectra of spontaneous growth-dependent and adaptive mutations at ebgR.

A comparison of the spectra of spontaneous growth-dependent and adaptive mutations in ebgR shows that both spectra are dominated by insertion sequence (IS)-mediated mutations. The difference between growth-dependent mutations (61% IS mediated) and adaptive mutations (80% IS mediated) is highly significant (P < 0.0001). In contrast, the spectra of growth-dependent and adaptive non-IS-mediated mutations do not differ from each other and therefore do not provide support for the hypothesis that adaptive and growth-dependent mutations arise by substantially different mechanisms.