Specific Action of Sodium Dodecyl Sulfate on the Sex Factor of Escherichia coli K-12 Hfr Strains

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RESUMO

A specific action of sodium dodecyl sulfate (SDS) on the sex (F) factor in the integrated state of Escherichia coli K-12 Hfr H strain is reported. Growth of Hfr cells in Penassay Broth containing SDS results in the elimination of part or all of the F factor, yielding low and nonfertile variants of defective Hfr type and F+ cells and also F− derivatives. Appearance of such variants was generally observed after the culture reached stationary phase. The frequencies of F− cells then increased. F− cells were usually isolated as the major population among survivors. Some defective variants of Hfr cells with an intermediate fertility between standard Hfr and F+ cells had lost sensitivity toward the male-specific ribonucleic acid phage M12. Other defective Hfr variants with as much or less fertility than standard F+ cells had also all lost sensitivity to phage M12. On single-colony isolation, they segregated nonfertile female H cells which, when infected with F, could restore high fertility with oriented transfer of the chromosome the same as that of the original Hfr H. Also, sensitivity to phage M12 was regained. Female H cells were characterized as those lacking fertility but still retaining a small segment of F or sfa locus at the original part of the chromosome, where newly infected F could attach. Similar results were obtained with two other Hfr strains. A possible mechanism of the specific action of SDS is discussed.

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