Influence of Alkylating Agents on the Structure of the Bacterial Nucleoid
Alkylating agents such as methyl methane sulfonate (MMS) and mitomycin C cause large changes in the nucleoid structure of Escherichia coli. In the presence of high concentrations of these compounds, 25 and 0.1 mM respectively, relaxation of the supercoiled structure takes place. This can be demonstrated both by centrifugation studies as well as by phase contrast microscopy of the cells. Low concentrations of mitomycin C, 1–10 μM, on the other hand Cause a rec A dependent increase in the nucleoid mass. During repair, in the absence of the alkylating agents, the number of breaks decreases and supercoiling is introduced again into the nucleoid. The data suggest that consideration of the 3-dimensional structure may be important both during mutagenesis and repair.
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