Effect of Metallic Cations on the Viability of Phenol-treated Escherichia coli

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RESUMO

Five metallic cations (Fe3+, Cr3+, Ca2+, Mg2+, Mn2+; concentration range, 1.85 × 10-4 to 37 × 10-4m) were incorporated individually as chlorides into nutrient broth and agar media used for the recovery of phenol-treated Escherichia coli. The effects observed varied with the concentration and the ionic species. In nutrient agar, Fe3+ and Cr3+ were generally beneficial but were toxic at 37 × 10-4m. Of the divalent ions tested, Ca2+ and Mg2+ usually gave higher counts in nutrient broth, except at a concentration of 9.25 × 10-4m, whereas the effect of Mn2+ was rather variable. Two possible explanations are suggested to explain these effects. Toxic materials may be removed from the media by the precipitates formed on the addition of Fe3+ or Cr3+, or, in the case of the divalent ions, the integrity of the bacterial cell membranes may be maintained.

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