Specific Role of Sex Pili in the Effective Eliminatory Action of Sodium Dodecyl Sulfate on Sex and Drug Resistance Factors in Escherichia coli

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Abstract
Evidence is presented for the specific role of sex pili in the eliminatory action of sodium dodecyl sulfate (SDS) on sex (F) and drug resistance (R) factors in Escherichia coli K-12 strains leading to their loss. SDS at 0.03% concentration lysed JE3100 F8+ (F-gal)/gal−fla−pil− in Penassay broth after they had grown exponentially and reached maximum growth to the extent that the agent at concentrations higher than 1% did. However, the agent was only effective in eliminating sex factors from JE3100 in high frequencies at concentrations higher than 1%. Increase of osmotic pressure of the culture with SDS at concentrations as low as 0.03 to 0.1% by addition of sucrose led to the substantial increase of elimination efficiency. Reconstruction experiments between F8+ and F− cells in the SDS culture revealed the selective growth of F− cells as well as a delay of maximum growth of F− variants derived from F8+ cells, compared with those of F8+ cells, as well as F− cells originally added to the culture. The agent was not very effective in eliminating sex factors from JE3427 F8m+5/fla−pil− cells which lack the function of production of F pili. F8m+5 cells showed a sensitivity toward SDS intermediate between those of F8+ and F− cells. SDS was further effective in eliminating R factors from KE132 R100-1+/fla−pil− cells in high efficiency; however, the action was not efficient with KE133 F100+ cells possibly with fewer sex pili than R100-1+. Action of acridine orange on these F+ or R+ strains was found to be different in some aspects from that of SDS.