STUDIES ON THE COBALT-RESISTANCE IN ESCHERICHfA COLI

II. GENETIC TRANSFER OF COBALT-RESISTANCE IN E. COLI K-12

Abstract

Studies were made on the genetic analysis of cobalt-resistant mutant of E. coli K-12 isolated in the author's laboratory. In this report studies on the genetic transfer were described. The transfer experiments were performed either on a cobalt-containing synthetic agar or in a liquid medium supplemented with UV-induced cell-free lysate of the resistant mutant.
1. Cobalt resistance was transferred from the resistant strains to the sensitive strain of E. coli K-12, by streaking the donor and the recipient organisms parallel to each other on a cobalt-containing synthetic agar.
2. Resistance was also transferred from cobalt-resistant strains to sensitive strains of E. coli K-12 in an UV-irradiated cellular lysate. Resistance was not transferred to the E. coli B strain. Using the streptomycin-resistant strain of E. coli K-12 as the recipient, this organism became cobalt resistant and it also retained its streptomycin resistance.
3. The genetic transfer of cobalt resistance in E. coli K-12 was also accomplished from cobalt-resistant mutants, which became cobalt resistant according to the above transfer experiments, to sensitive strains of E. coli K-12, and this transferring activity is maintained even after 10 to 20 subcultures in cobalt free medium.
From these results it is evident that the genetic transfer of cobalt-resistance in E. coli K-12 was possible by the use of UV-induced cellular lysate. Presumably it may be transferred by vectors, namely phage particles, liberated from the donor cells. Precise studies on the nature of the transducing agent will be described in another publication.