R-plasmid transfer in soil and water.

R-plasmid transfer in Escherichia coli was investigated in nutrient broth, sterile soil, and sterile stream water. Plasmid transfer occurred in broth cultures at 30 and 22 degrees C, but not at 15 degrees C. R-plasmid transfer was not observed at 30, 22, and 15 degrees C in nonamended sterile soil and stream water. The addition of nutrients to sterile stream water and soil allowed plasmid transfer to occur at temperatures ranging from 15 to 30 degrees C. R-plasmid transfer was also observed in soil adjusted from 20 to 100% of its water-holding capacity.