Abstract
We report here that certain kinds of foods can act as media that induce genetic competency of Escherichia coli. Of 42 food samples tested, more than 10 showed an ability to induce competency. Among them, tofu supernatant showed the highest activity, corresponding to about one half of the activity obtained with 100 mM CaCl2. These results suggest that some populations of E. coli in food environments exist as "competent cells". There were no clear correlations between transformation frequencies and the chemical indices of foods (Ca2+ or Mg2+ concentrations and pH), suggesting that complex factors in foods affect competency development.
